SMART MODE:

NORMAL GENOMIC

• Mold C, Gresham HD, Du Clos TW
• Serum amyloid P component and C-reactive protein mediate phagocytosis through murine Fc gamma Rs.
• J Immunol. 2001; 166: 1200-5
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• The pentraxins, serum amyloid P component (SAP) and C-reactive protein (CRP) are acute-phase serum proteins in mice and humans, respectively. Although SAP binds to DNA and chromatin and affects clearance of these autoantigens, no specific receptor for SAP has been identified. CRP is an opsonin, and we have shown that it binds to FcgammaR. Mice deficient in FcgammaR were used to assess the role of these receptors in phagocytosis by pentraxins using zymosan as a ligand. Phagocytosis of zymosan by bone marrow macrophages (BMM) was enhanced by opsonization with SAP or CRP. BMM from mice deficient in all three FcgammaR or in gamma-chain ingested unopsonized zymosan, but phagocytosis of SAP- or CRP-opsonized zymosan was not enhanced. SAP binding to BMM from gamma-chain-deficient mice was also greatly reduced, indicating little or no binding of SAP to FcgammaRII. SAP and CRP opsonized zymosan for phagocytosis by BMM from mice deficient in FcgammaRII or FcgammaRIII. SAP, but not CRP, opsonized zymosan for uptake by neutrophils that express only low levels of FcgammaRI. Together these results indicate that FcgammaRI and FcgammaRIII are receptors for SAP in the mouse. Opsonization of zymosan by CRP is mediated through FcgammaRI. Pentraxins are major proteins of the innate immune system and arose earlier in evolution than Igs. The use of FcgammaR by the pentraxins links innate and adaptive immunity and may have important consequences for processing, presentation, and clearance of the self-Ags to which these proteins bind.

• Coker AR, Purvis A, Baker D, Pepys MB, Wood SP
• Molecular chaperone properties of serum amyloid P component.
• FEBS Lett. 2000; 473: 199-202
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• The selective binding of serum amyloid P component (SAP) to proteins in the pathological amyloid cross-beta fold suggests a possible chaperone role. Here we show that human SAP enhances the refolding yield of denatured lactate dehydrogenase and protects against enzyme inactivation during agitation of dilute solutions. These effects are independent of calcium ions and are not inhibited by compounds that block the amyloid recognition site on the B face of SAP, implicating the A face and/or the edges of the SAP pentamer. We discuss the possibility that the chaperone property of SAP, or its failure, may contribute to the pathogenesis of amyloidosis.

• Vorum H, Jacobsen C, Honore B
• Calumenin interacts with serum amyloid P component.
• FEBS Lett. 2000; 465: 129-34
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• We recently reported the identification of human calumenin, a novel Ca(2+) binding, transformation-sensitive and secreted protein [Vorum et al. (1998) Biochim. Biophys. Acta 1386, 121-131; Vorum et al. (1999) Exp. Cell Res. 248, 473-481] belonging to the family of multiple EF-hand proteins of the secretory pathway that include reticulocalbin, ERC-55, Cab45 and crocalbin. In order to further investigate the extracellular functions of calumenin we immobilized the recombinant protein to a column. After application of a placental tissue extract we were able to elute one protein that interacts with calumenin in the presence of Ca(2+). Amino acid sequencing identified this protein as serum amyloid P component (SAP). Furthermore, we verified and characterized the calumenin-SAP interaction by the surface plasmon resonance technique. The findings indicate that calumenin may participate in the immunological defense system and could be involved in the pathological process of amyloidosis that leads to formation of amyloid deposits seen in different types of tissues.

• Hutchinson WL, Hohenester E, Pepys MB
• Human serum amyloid P component is a single uncomplexed pentamer in whole serum.
• Mol Med. 2000; 6: 482-93
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• BACKGROUND: Serum amyloid P component (SAP) is a universal constituent of amyloid deposits and contributes to their pathogenesis. SAP also has important normal functions in the handling of chromatin in vivo and resistance to bacterial infection. The atomic resolution crystal structure of SAP is known, but its physiological oligomeric assembly remains controversial. In the absence of calcium, isolated human SAP forms stable decamers composed of two cyclic disk-like pentamers interacting face to face. However, in the presence of its specific low molecular weight ligands and calcium, SAP forms stable pentamers. In the presence of calcium, but without any ligand, isolated human SAP aggressively autoaggregates and precipitates, imposing severe constraints on methods for molecular mass determination. MATERIALS AND METHODS: Gel filtration chromatography and density gradient ultracentrifugation were used to compare SAP with the closely related molecule, C-reactive protein (CRP; which is known to be a single pentamer) and the effect of human serum albumin on SAP autoaggregation was investigated. RESULTS: In most physiological buffers and with the necessary absence of calcium, SAP, whether isolated or from whole serum samples, eluted from gel filtration columns clearly ahead of CRP. This is consistent with the existence of a monodisperse population of SAP decamers, as previously reported. However, in Tris/phosphate buffer, SAP was pentameric, suggesting that decamerization involved ionic interactions. On density gradients formed in undiluted normal human serum, SAP sedimented as single pentamers not complexed with any macromolecular ligand, regardless of the presence or absence of calcium. The calcium-dependent autoaggregation of isolated SAP was completely inhibited by physiological concentrations of albumin and the SAP remained pentameric. CONCLUSIONS: Human SAP exists within serum as single uncomplexed pentamers in the presence or absence of calcium. This oligomeric assembly, thus, does not require a calcium-dependent small molecule interaction. The usual >2000-fold molar excess of albumin over SAP in plasma is apparently sufficient to keep SAP in its physiological conformation.

• Ochrietor JD, Harrison KA, Zahedi K, Mortensen RF
• Role of STAT3 and C/EBP in cytokine-dependent expression of the mouse serum amyloid P-component (SAP) and C-reactive protein (CRP) genes.
• Cytokine. 2000; 12: 888-99
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• Inflammation is accompanied by a rapid increase in blood levels of acute phase proteins synthesized by hepatocytes in response to cytokines. Although C-reactive protein (CRP) levels increase dramatically in most mammals, the major acute phase protein in the mouse is the homologous pentraxin, serum amyloid P-component (SAP), whereas CRP is a minor acute phase reactant. The molecular basis for the pronounced difference in SAP and CRP gene expression in the mouse is unknown. Transfection of ++/Li mouse hepatoma cells with CAT-reporter constructs containing the 5'-flanking region of the mouse CRP gene indicated that transcription was stimulated by either IL-6, or IL-6 plus IL-1, when > or =360 bp of the 5'-proximal DNA was present. Examination of the 5'-flanking region of the mouse SAP gene revealed that the region between -433 and -397 from the transcription start site responded to IL-1 and IL-6 by binding both STAT3 and C/EBPbeta. This responsive region consisted of two adjacent C/EBPbeta consensus sites that overlap with two STAT3 consensus sites and was found to bind C/EBPbeta at an upstream site of -427 to -409 and STAT3 at a downstream site of -415 to -397. By contrast, the 360 bp promoter of the CRP gene was bound only by STAT3 at consensus sites at -93, -142, -173, and -287 from the start site; however, a single consensus site for C/EBP at -75 was not recognized. STAT3 appears to be necessary for both mouse SAP and CRP gene transcription since overexpression of an inactive, deletion mutant of STAT3 inhibited transcription of both genes. The results indicate that both STAT3 and C/EBPbeta participate in mouse SAP gene expression, whereas only STAT3 is involved in mouse CRP gene expression. The findings for mouse SAP gene expression are consistent with the reported interaction between these two transcription factors for human CRP gene transcription.

• Thompson D, Pepys MB, Wood SP
• The physiological structure of human C-reactive protein and its complex with phosphocholine.
• Structure Fold Des. 1999; 7: 169-77
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• BACKGROUND: Human C-reactive protein (CRP) is the classical acute phase reactant, the circulating concentration of which rises rapidly and extensively in a cytokine-mediated response to tissue injury, infection and inflammation. Serum CRP values are routinely measured, empirically, to detect and monitor many human diseases. However, CRP is likely to have important host defence, scavenging and metabolic functions through its capacity for calcium-dependent binding to exogenous and autologous molecules containing phosphocholine (PC) and then activating the classical complement pathway. CRP may also have pathogenic effects and the recent discovery of a prognostic association between increased CRP production and coronary atherothrombotic events is of particular interest. RESUTLS: The X-ray structures of fully calcified C-reactive protein, in the presence and absence of bound PC, reveal that although the subunit beta-sheet jellyroll fold is very similar to that of the homologous pentameric protein serum amyloid P component, each subunit is tipped towards the fivefold axis. PC is bound in a shallow surface pocket on each subunit, interacting with the two protein-bound calcium ions via the phosphate group and with Glu81 via the choline moiety. There is also an unexpected hydrophobic pocket adjacent to the ligand. CONCLUSIONS: The structure shows how large ligands containing PC may be bound by CRP via a phosphate oxygen that projects away from the surface of the protein. Multipoint attachment of one planar face of the CRP molecule to a PC-bearing surface would leave available, on the opposite exposed face, the recognition sites for C1q, which have been identified by mutagenesis. This would enable CRP to target physiologically and/or pathologically significant complement activation. The hydrophobic pocket adjacent to bound PC invites the design of inhibitors of CRP binding that may have therapeutic relevance to the possible role of CRP in atherothrombotic events.

• Shrive AK, Metcalfe AM, Cartwright JR, Greenhough TJ
• C-reactive protein and SAP-like pentraxin are both present in Limulus polyphemus haemolymph: crystal structure of Limulus SAP.
• J Mol Biol. 1999; 290: 997-1008
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• C-reactive protein and serum amyloid P component are members of the pentraxin family of oligomeric serum proteins which has been conserved through evolution. In humans both have pentameric structures and both play complex roles in the immune response, C-reactive protein being the classical acute-phase reactant produced in response to tissue damage and inflammation. An invertebrate SAP-like pentraxin has not previously been identified and it has been postulated that C-reactive protein and serum amyloid P component are products of a gene duplication event within vertebrate evolution. We have isolated serum amyloid P component from the haemolymph of the phylogenetically ancient "living fossil", the horseshoe crab Limulus polyphemus and determined the three-dimensional structure by X-ray crystallography. The structure of the previously undiscovered Limulus serum amyloid P component, the first invertebrate lectin structure to be determined, reveals the pentraxin fold and a novel doubly stacked octameric ring. The crystal structure and the discovery that both prototypic pentraxins are present in Limulus raises the possibility that both were present in the common ancestors of arthropods and chordates over 500 million years ago. The impact of the results on our understanding of the origins and evolution of pentraxins and innate immunity is discussed.

• Mold C, Gewurz H, Du Clos TW
• Regulation of complement activation by C-reactive protein.
• Immunopharmacology. 1999; 42: 23-30
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• C-reactive protein (CRP) is an acute-phase serum protein and a mediator of innate immunity. CRP binds to microbial polysaccharides and to ligands exposed on damaged cells. Binding of CRP to these substrates activates the classical complement pathway leading to their uptake by phagocytic cells. Complement activation by CRP is restricted to C1, C4, C2 and C3 with little consumption of C5-9. Surface bound CRP reduces deposition of and generation of C5b-9 by the alternative pathway and deposition of C3b and lysis by the lectin pathway. These activities of CRP are the result of recruitment of factor H resulting in regulation of C3b on bacteria or erythrocytes. Evidence is presented for direct binding of H to CRP. H binding to CRP or C3b immobilized on microtiter wells was demonstrated by ELISA. Attachment of CRP to a surface was required for H binding. H binding to CRP was not inhibited by EDTA or phosphocholine, which inhibit ligand binding, but was inhibited by a 13 amino acid CRP peptide. The peptide sequence was identical to the region of CRP that showed the best alignment to H binding peptides from Streptococcus pyogenes (M6) and Neisseria gonorrhoeae (Por1A). The results suggest that CRP bound to a surface provides secondary binding sites for H resulting in greater regulation of alternative pathway amplification and C5 convertases. Complement activation by CRP may help limit the inflammatory response by providing opsonization with minimal generation of C5a and C5b-9.

• Coe JE, Vomachka AJ, Ross MJ
• Effect of hamster pregnancy on female protein, a homolog of serum amyloid P component.
• Proc Soc Exp Biol Med. 1999; 221: 369-75
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• Pentraxins such as human serum amyloid P component (SAP) and C reactive protein (CRP) represent an ancient family of proteins that are ubiquitous in nature and have evolved with little change in structure or regulation. The pentraxin in the Syrian hamster (Mesocricetus auratus) is unique because it is preferentially expressed in the female at high constitutive levels and accordingly called female protein (FP) or FP(SAP) due to its close homology with human SAP. The high levels of FP in female serum (100-fold greater than male serum) suggested its role in hamster pregnancy, one of the shortest of any eutherian mammal. We determined the serum FP concentration in pregnant Syrian hamsters and found a marked decrease (>80%) at term with the nadir at parturition with subsequent increase. A similar downregulation of FP was found in the normal female Syrian hamster after injury (acute phase response), so in both cases the assumed beneficial effects were achieved with less, rather than more pentraxin, a paradoxical pentraxin response. The fall in serum FP concentration could represent a response to protect the fetus from the high and potentially toxic level of FP normally found in the female, that is harmful because of its association with amyloidosis. An FP that is 97.5% identical to Syrian hamster FP is found in the Turkish hamster (Mesocricetus brandti), although serum levels in females are much lower, and amyloid is very rare. During pregnancy/parturition of Turkish hamsters, the serum level of FP remained remarkably constant. In a more distantly related hamster, the Armenian hamster (Cricetulus migratorius), serum FP actually increased during pregnancy and at parturition in a manner similar to that found in the Armenian hamster during an acute phase response. The heterogeneity of FP kinetics during pregnancy in these three species of hamster indicates pleomorphic gene structure for regulation of their similar FPs, and suggests that this protein may have a different function in the pregnancy of each species.

• de Haas CJ
• New insights into the role of serum amyloid P component, a novel lipopolysaccharide-binding protein.
• FEMS Immunol Med Microbiol. 1999; 26: 197-202
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• Serum amyloid P component (SAP) is a highly preserved plasma protein named for its ubiquitous presence in amyloid deposits. Although SAP is described to bind many ligands, no clear biological function has been ascribed to it as yet. This review summarizes the current knowledge about the protein SAP, its ligands and functional properties. Finally, the author focuses on the recent finding of the binding of SAP to lipopolysaccharide (LPS) and Gram-negative bacteria and the possible functional consequences of these interactions.

• Nelsestuen GL, Ostrowski BG
• Membrane association with multiple calcium ions: vitamin-K-dependent proteins, annexins and pentraxins.
• Curr Opin Struct Biol. 1999; 9: 433-7
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• Peripheral membrane association with high calcium stoichiometry is shared by three families of proteins: annexins, pentraxins and vitamin-K-dependent proteins. Recent crystal structure determinations, biophysical studies of membrane binding and analyses of protein electrostatic properties offer striking and different concepts for membrane association by each of these protein families.

• Lund V, Olafsen JA
• A comparative study of pentraxin-like proteins in different fish species.
• Dev Comp Immunol. 1998; 22: 185-94
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• Pentraxins are a family of pentameric serum proteins that have been conserved in evolution and share sequence homology, similar subunit assembly and the capacity for calcium-dependent ligand binding. The classical pentraxins are human C-reactive protein (CRP) and serum amyloid P component (SAP). The sequence homology and gene organization indicate that they arose from a gene duplication of an ancestral pentraxin gene. They are usually isolated based on their affinity for phosphorylcholine and agarose, respectively. We have used this method for isolation of pentraxin-like proteins from normal serum of Atlantic salmon (Salmo salar), common wolffish (Anarhichas lupus), cod (Gadus morhua) and halibut (Hippoglossus hippoglossus). Although pentraxin structures have not been verified, the isolated proteins all appear to be pentraxin-like based on their binding specificity, molecular weight of subunits, cross-reactivity with antibodies to human pentraxins and N-terminal amino acid sequences. However, with the described method only one pentraxin-like protein was detected in each of the fish species.

• Heegaard NH
• Capillary electrophoresis for the study of affinity interactions.
• J Mol Recognit. 1998; 11: 141-8
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• Molecular recognition may be characterized both qualitatively and quantitatively by electrophoretic methods if complexed molecules differ in electrophoretic mobility from unbound ones. The use of capillary zone electrophoresis (CE) for the characterization of affinity interactions is advantageous because of the high resolution, reproducibility and wide applicability of the technique and because of the mild conditions, i.e., physiological buffers without additions of organics or detergents, that are often sufficient for highly efficient separations. CE gives the ability to characterize binding between small amounts of unlabelled reactants in solution, has few requirements for special characteristics of the interacting molecules and is also applicable to the study of interactions of individual components in mixtures, as detection of binding and analytical separation are achieved in one step. This is unique compared with other techniques for the study of non-covalent interactions. The advantages and disadvantages of using CE to demonstrate molecular interactions, to screen for specific ligand binding in complex mixtures and to calculate binding constants will be discussed.

• Heegaard NH
• A heparin-binding peptide from human serum amyloid P component characterized by affinity capillary electrophoresis.
• Electrophoresis. 1998; 19: 442-7
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• Affinity capillary electrophoresis (CE) was used for a detailed characterization of the binding between heparin and a peptide isolated from the heparin-binding serum protein amyloid P component (SAP). The peptide corresponds to a tryptic fragment (T3) comprising amino acids 14-38 of SAP. By including ligands in the electrophoresis buffer various glycosaminoglycans could be screened for binding of T3 using one sample aliquot. The binding was found to be highly specific for heparin and heparin fragments down to tetramers and appeared strongest at a slightly alkaline pH while no binding could be demonstrated with heparan sulfate, chondroitin sulfate, desulfated heparin, mannose 6-phosphate and phosphotyrosine. The T3-heparin complexes were sufficiently stable to perform quantitative measurements of the binding using preequilibration of samples prior to a CE-mediated separation of bound and free T3-peptide. Plots based on quantitation of analyte peaks corresponding to free and complexed T3 yielded a dissociation constant of 1.5 microM for the interaction with heparin. The results indicate that a specific subfraction of the heparin molecules is active in binding interactions with the peptide. The affinity CE approach proved to be useful for these studies because of its sensitivity to complex formation involving charged ligands and the possibility of achieving separations under native conditions. Also advantageous is the low sample consumption and the ability to analyze unlabeled reactants in solution.

• Duong T, Acton PJ, Johnson RA
• The in vitro neuronal toxicity of pentraxins associated with Alzheimer's disease brain lesions.
• Brain Res. 1998; 813: 303-12
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• Serum amyloid P component (AP) and C-reactive protein (CRP) are normal serum components which belong to the pentraxin family of proteins. These proteins have been previously localized by immunohistochemical method to the brain lesions of Alzheimer's disease (AD). AP is a constant constituent of amyloid deposits including those found in AD. Both AP and CRP have been localized to AD neurofibrillary tangles. An indirect role for these proteins has been previously suggested in the etiology of AD. We studied the effects of serum AP and CRP on a human-derived neuronal cell line (hNT). In treated cell cultures, AP and CRP were detected immunohistochemically within hNT neurons, indicating cellular uptake of these proteins. Serum AP at the lowest serum physiological concentration (8 microgram/ml) showed a marked toxicity to hNT neurons. CRP also displayed toxicity to the hNT neurons but at a level compatible with inflammatory states (50 microgram/ml). These results suggest a more direct role for serum AP and CRP in the pathogenesis of AD.

• Jensen LE, Hiney MP, Shields DC, Uhlar CM, Lindsay AJ, Whitehead AS
• Acute phase proteins in salmonids: evolutionary analyses and acute phase response.
• J Immunol. 1997; 158: 384-92
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• Inflammation induces dramatic changes in the biosynthetic profile of the liver, leading to increased serum concentrations of positive acute phase (AP) proteins and decreased concentrations of negative AP proteins. Serum amyloid A (SAA) and the pentraxins C-reactive protein (CRP) and serum amyloid P component (SAP) are major AP proteins: their serum levels can rise by 1000-fold, indicating that they play a critical role in defense and/or the restoration of homeostasis. We have cloned SAA and a SAP-like pentraxin from salmonid fish species. The salmonid SAA shares approximately 70% amino acid identity with mammalian AP SAA. When salmonids are challenged with an AP stimulus, i.e., Aeromonas salmonicida, SAA responds dramatically as a major AP reactant. The salmonid pentraxin shows approximately 40% amino acid identity to both mammalian SAP and CRP. Evolutionary analysis suggests the presence of only a single such protein in teleosts and lower animal species. Surprisingly, the salmonid pentraxin behaves as a negative AP reactant, reminiscent of the SAP-like Syrian hamster female protein, in that hepatic mRNA concentrations decline to 50% of prestimulus levels. This study reinforces the hypothesis that SAA induction is an essential and universal feature of the vertebrate AP response and that it represents part of an ancient host defense system. Conversely, the species-dependent heterogeneity of pentraxin expression during the vertebrate AP response supports the possibility that its most important ancestral (and perhaps present) function is not related to its AP behavior.

• Agrawal A, Lee S, Carson M, Narayana SV, Greenhough TJ, Volanakis JE
• Site-directed mutagenesis of the phosphocholine-binding site of human C-reactive protein: role of Thr76 and Trp67.
• J Immunol. 1997; 158: 345-50
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• We have reported previously that residues Lys57, Arg58, and Trp67 of human C-reactive protein (CRP) contribute to the structure of the phosphocholine (PCh)-binding site. In this study, based on the three-dimensional structures of human CRP and serum amyloid P, we constructed an additional mutant, T76Y, to probe the structural determinants of the PCh-binding site of CRP. Binding properties of four mutant CRPs, K57Q/R58G, W67K, K57Q/R58G/W67K, and T76Y were compared. Wild-type (wt) and all mutant CRPs were purified by affinity chromatography on PCh-, pneumococcal C-polysaccharide (PnC)-, or phosphoethanolamine-conjugated agarose columns. Purified mutant CRPs, K57Q/R58G/W67K and T76Y failed to bind to solid phase, PCh-substituted BSA. They did, however, bind to immobilized PnC, although with substantially decreased avidity compared with wt CRP. W67K, K57Q/R58G/W67K, and T76Y CRP required a 10-fold higher Ca2+ concentration than wt CRP to bind PnC and exhibited decreased avidity for mAb EA4.1, which recognizes a Ca2+-dependent epitope. We conclude that Thr76 is a determinant of the PCh-binding site, probably interacting with the choline group. This conclusion is supported by recent crystallographic data indicating that this residue participates in the formation of a hydrophobic pocket that constitutes the binding site for choline. Trp67, Lys57, and Arg58 do not directly contact PCh, but appear to be required for the proper conformation of the binding site.

• Danielsen B, Sorensen IJ, Nybo M, Nielsen EH, Kaplan B, Svehag SE
• Calcium-dependent and -independent binding of the pentraxin serum amyloid P component to glycosaminoglycans and amyloid proteins: enhanced binding at slightly acid pH.
• Biochim Biophys Acta. 1997; 1339: 73-8
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• Serum amyloid P component (SAP), a member of the pentraxin family of proteins, binds calcium-dependently to several ligands including glycosaminoglycans (GAG's). We have investigated the influence of pH on the Ca2(+)-dependent binding of SAP to solid phase GAG's and amyloid fibril proteins (AA and beta2M) by ELISA. An increase in the dose-dependent binding of SAP to heparan sulfate, AA-protein and beta2M was observed as the pH decreased from 8.0 to 5.0. Furthermore, a lower, but significant Ca2(+)-independent binding of SAP to heparan sulfate, dermatan sulfate, AA protein and the amyloid precursor protein beta2M was observed. This binding was also enhanced at slightly acid pH, most pronounced at pH 5.0. The results of this study indicate that SAP can exhibit both Ca2(+)-dependent and -independent binding to ligands involved in amyloid fibril formation and that the binding is enhanced under conditions of slightly lowered pH.

• Coe JE, Ross MJ
• Electrophoretic polymorphism of a hamster pentraxin, female protein (amyloid P component).
• Scand J Immunol. 1997; 46: 180-6
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• Serum amyloid P protein (SAP) is a ubiquitous vertebrate protein distinguished by its conservative evolution and paucity of polymorphic forms. The SAP homologue in the Syrian hamster (Mesocricetus auratus), called Female Protein [FP(SAP)] is unique because its synthesis is controlled by sex hormones. These observations were limited to the commercially available standard Syrian hamsters that are descendants of three littermates captured in Syria in 1930. The authors examined FP(SAP) expression in nine inbred lines of Syrian hamsters that were derived from 12 wild hamsters captured in 1971. In general, regulation of FP(SAP) was similar in the new wild hamster strains, although a novel electrophoretically slower FP(SAP) was found in three of the strains. The slow FP(SAP) was not distinguished by size, antigenicity, binding capacity, or regulation. The electrophoretic difference was still apparent after deglycosylation. Hybrid offspring coexpressed both fast and slow FP monomers and formed a unique hybrid pentamer that had a new mobility between the fast and slow parent FP(SAP). The origin of this unusual polymorphism could be related to the amyloidogenesis associated with expression of FP(SAP) in the standard Syrian hamster.

• Coe JE, Cieplak W, Hadlow WJ, Ross MJ
• Female protein, amyloidosis, and hormonal carcinogenesis in Turkish hamster: differences from Syrian hamster.
• Am J Physiol. 1997; 273: 93441-93441
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• The Syrian hamster (Mesocricetus auratus) has been widely used as an experimental animal and is a unique model for three sex hormone-regulated events: 1) estrogen-initiated renal carcinogenesis, 2) sex-limited expression of amyloidosis, a ubiquitous disease, and 3) sex hormone control of a serum amyloid P component (SAP) called female protein (FP). In this study, we evaluated the closely related Turkish hamster (Mesocricetus brandti) for these three events and found some very different responses: 1) estrogen-initiated renal carcinogenesis was not found in Turkish hamster, 2) amyloidosis was not sex limited and actually was a rare disease in the Turkish hamster, and 3) Turkish hamsters did express a sex-limited SAP-FP in serum that was antigenically identical and structurally very similar (97.5%) to Syrian hamster SAP-FP. However, acute phase regulation of SAP-FP synthesis was different, and serum levels of this pentraxin were much lower than those found in the Syrian hamster. On the other hand, in contrast to findings in the Syrian hamster, hepatic tumors were relatively common in normal and especially in estrogen-treated Turkish hamsters. Therefore, although they are closely related, these two Mesocricetus hamster species have markedly dissimilar responses to sex hormones.

• Siebert HC, Andre S, Reuter G, Kaptein R, Vliegenthart JF, Gabius HJ
• Comparison between intact and desialylated human serum amyloid P component by laser photo CIDNP (chemically induced dynamic nuclear polarization) technique: an indication for a conformational impact of sialic acid.
• Glycoconj J. 1997; 14: 945-9
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• The human pentraxin serum amyloid P component (SAP) exhibits no microheterogeneity in its complex di-antennary glycan. To elucidate whether the removal of sialic acids from this glycoprotein might affect the accessibility of certain amino acid residues of the protein we employed the laser photo CIDNP approach as a sensitive tool. The CIDNP effect is generated by the interaction of a photoexcited dye with reactive amino acids and results in enhanced absorption- or emission-signals which can be observed for the three aromatic amino acids histidine, tryptophan, and tyrosine if they are accessible to the dye. Therefore, this technique can be applied to explore surface exposure of these amino acid residues. The respective spectra of SAP and enzymatically desialylated SAP were determined. Six tryptophan/histidine signals and one tyrosine signal are present in the aromatic part of the CIDNP difference spectrum of SAP. The corresponding spectrum of desialylated SAP shows remarkable alterations. The chemical shift of one Trp/His-characteristic signal is decreased by 0.1 ppm. One Trp/His-signal disappeared and a new one was formed in the CIDNP difference spectrum of desialylated SAP, while the other signals were unaffected. The Tyr signal has a clearly enhanced intensity in desialylated SAP. Therefore, the removal of sialic acid moieties from the single N-glycan of each monomer apparently affects surface presentation of distinct CIDNP-reactive amino acids of SAP [1]. A conformational change of the protein part of SAP in relation with a different orientation of the desialylated oligosaccharide chain in comparison to the complete one is a possible explanation of our CIDNP results.

• Zahedi K
• Characterization of the binding of serum amyloid P to laminin.
• J Biol Chem. 1997; 272: 2143-8
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• Serum amyloid P (SAP) is a member of the pentraxin family. These are evolutionarily conserved proteins made up of five noncovalently bound identical subunits that are arranged in a flat pentameric disc. Although a variety of activities have been attributed to SAP and other pentraxins, their biological functions remain unclear. In humans SAP is a constitutive serum protein that is synthesized by hepatocytes. It is encoded by a single copy gene on chromosome 1. SAP is a component of all amyloid plaques and is also a normal component of a number of basement membranes including the glomerular basement membrane. The association and distribution of SAP within the glomerular basement membrane are altered or completely disrupted in a number of nephritides (e.g. Alport's Syndrome, type II membranoproliferative glomerulonephritis, and membranous glomerulonephritis). In the present study the binding of SAP to laminin was characterized. SAP binds to human laminin and merosin as well as mouse and rat laminins. The binding of SAP to mouse laminin is saturable and calcium-dependent. The Kd of this interaction is 2. 74 x 10(-7) M, with a SAP/laminin molar ratio of 1:7.1. Competition binding assays indicate that the binding of SAP to laminin is inhibited by both SAP and its analog, C-reactive protein, as well as phosphatidylethanolamine. In turbidity assays SAP enhanced the polymerization of laminin in a concentration-dependent manner. However, SAP did not alter the ability of laminin to serve as a cell adhesion substrate. Previous observations indicating that SAP binds to extracellular matrix components such as type IV collagen, proteoglycans, and fibronectin in concert with the data presented here suggest that SAP may play an important role in determining the structure of those basement membranes with which it is associated.

• Szalai AJ, Agrawal A, Greenhough TJ, Volanakis JE
• C-reactive protein: structural biology, gene expression, and host defense function.
• Immunol Res. 1997; 16: 127-36
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• Over the past few years substantial insight was gained into the biology and biochemistry of human C-reactive protein (CRP). X-ray crystallography in conjunction with mutational analyses, generated the three-dimensional structure of the protein and indicated the topology and structure of ligand-binding sites. Using human CRP transgenic mice infected with Streptococcus pneumoniae, we obtained data that clearly established CRP as an important host defense molecule. Studies using the same mice revealed a previously unknown testosterone-dependence of constitutive expression of human CRP. In this article we provide a brief overview of these recent findings.

• Hohenester E, Hutchinson WL, Pepys MB, Wood SP
• Crystal structure of a decameric complex of human serum amyloid P component with bound dAMP.
• J Mol Biol. 1997; 269: 570-8
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• Serum amyloid P component (SAP) is a glycoprotein that binds in a calcium-dependent fashion to a variety of ligands including other proteins, glycosaminoglycans and DNA. SAP is universally associated with the amyloid deposits in all forms of amyloidoses including Alzheimer's disease. Small-molecule ligands that displace SAP from amyloid fibrils and thereby expose the fibrils to proteolytic clearance mechanisms hold potential as drugs for the prevention and treatment of amyloidosis. We have carried out a screen for novel SAP ligands and have identified 2'-deoxyadenosine-5'-monophosphate (dAMP) as a ligand. The crystal structure of the SAP-dAMP complex determined at 2.8 A resolution (R = 0.232, R(free) = 0.252) reveals a decamer in which all interactions between SAP pentamers are mediated by the ligand. The stability of the decamer in solution has been demonstrated by gel filtration chromatography. The two calcium ions of SAP are bridged by the dAMP phosphate group and five hydrogen bonds are formed between the protein and the ligand, including specific interactions made by the adenine base. This mode of dAMP binding is not compatible with the nucleotide being part of double-helical DNA. The SAP-dAMP decamer is stabilized mainly by base-stacking of adjacent ligand molecules and possibly by electrostatic interactions involving the dAMP phosphate groups; decamerization buries 1000 A2 (2.6%) of the pentamer solvent-accessible surface. Ligand-induced decamerization of SAP, which utilizes the high cooperativity of a multiple-site interaction, may be a strategy to overcome the problems for drug design associated with the rather modest affinities of SAP for small-molecule ligands.

• Barbashov SF, Wang C, Nicholson-Weller A
• Serum amyloid P component forms a stable complex with human C5b6.
• J Immunol. 1997; 158: 3830-5
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• A 30,000 m.w. protein bound tightly to C5b6, which was formed by activating C7-depleted human serum with zymosan. The protein remained bound to the C5b6 complex during the isolation procedure for C5b6, including chromatography on lysine-Sepharose and an anion exchange resin. Following electrophoresis and electroblotting of the C5b6 complex to a polyvinylidene difluoride transfer membrane, the 30,000 m.w. protein was microsequenced. The 24 N-terminal amino acid sequence was determined and showed identity of the 30,000 m.w. protein with the serum amyloid P (SAP) component. The C5b6-SAP complex did not dissociate in the presence of 10 mM EDTA, which distinguishes SAP-C5b6 binding from SAP's usual Ca2+-dependent binding to other molecules. SAP, which was isolated from serum by chromatography, was able to bind to preformed C5b6, which had been assembled and isolated from purified components. Functionally, the C5b6-SAP could bind C7, and the resulting C5b67-SAP complex had only moderately lower specific hemolytic activity than that of C5b67. In addition, hemolytically inactive C5b67-SAP, such as hemolytically inactive C5b67, was chemotactically active for neutrophils, while isolated SAP had no effect on cell mobility. Because SAP reacts with other serum proteins and with cells, it is likely that the addition of SAP to terminal complement complexes may affect the fate of these complexes.

• Kilpatrick DC
• Isolation of human mannan binding lectin, serum amyloid P component and related factors from Cohn fraction III.
• Transfus Med. 1997; 7: 289-94
• Display abstract

• Cohn Fraction III, a waste product of plasma fractionation, is a source of several proteins involved in host defence as part of the innate immune system. Here a procedure is described for purifying mannan binding lectin and serum amyloid P component to virtual homogeneity from Cohn Fraction I + III, and their separation from other mannan-binding factors and from C-reactive protein. It is suggested that products derived from Cohn Fraction III could have therapeutic potential, either for specific substitution therapy or as a combined package of innate immune factors.

• Du Clos TW
• The interaction of C-reactive protein and serum amyloid P component with nuclear antigens.
• Mol Biol Rep. 1996; 23: 253-60
• Display abstract

• The pentraxins are a family of proteins characterized by cyclic pentameric structure, calcium-dependent ligand binding and sequence homology. The two main representatives of this family are the serum proteins, C-reactive protein (CRP) and serum amyloid P component (SAP). In man CRP is an acute phase reactant which increases up to 1,000 fold during the acute phase response whereas SAP is a constitutive protein expressed at about 30 micrograms/ml. These proteins activate complement through the classical pathway and participate in opsonization of particulate antigens and bacteria. In the past several years it has been determined that both of these pentraxins interact with nuclear antigens including chromatin and small nuclear ribonucleoproteins (snRNPs). Both CRP and SAP have nuclear transport signals which facilitate their entry into the nuclei of intact cells. Furthermore, these pentraxins have been shown to affect the clearance of nuclear antigens in vivo. It is now believed that one of the major functions of the pentraxins could be to interact with the nuclear antigens released from apoptotic or necrotic cells. This interaction could mitigate against deposition of these antigens in tissue and autoimmune reactivity.

• Shrive AK et al.
• Three dimensional structure of human C-reactive protein.
• Nat Struct Biol. 1996; 3: 346-54
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• The structure of the classical acute phase reactant human C-reactive protein provides evidence that phosphocholine binding is mediated through calcium and a hydrophobic pocket centred on Phe 66. The residue Glu 81 is suitably positioned to interact with the choline group. A cleft on the pentameric face opposite to that containing the calcium site may have an important functional role. The structure provides insights into the molecular mechanisms by which this highly conserved plasma protein, for which no polymorphism or deficiency state is known, may exert its biological role.

• Zahedi K
• Characterization of the binding of serum amyloid P to type IV collagen.
• J Biol Chem. 1996; 271: 14897-902
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• Serum amyloid P (SAP), a member of the evolutionarily conserved pentraxin family, is a normal component of a number of basement membranes, including glomerular and alveolar. In vitro SAP binds to a variety of proteins including fibronectin, proteoglycans, and the collagen-like region of the complement component C1q. In these studies, binding of SAP to type IV collagen, a major component of basement membrane, was examined. Purified SAP binds to human and mouse type IV collagen but not type I, II, or III collagens. Binding of SAP to type IV collagen is dependent on the presence of Ca2+. This binding is saturable with a Kd approximately 1.2 x 10(-7) M based on solid phase binding and 4 x 10(-8) M based on the IC50 value from fluid phase binding data. Binding of SAP to type IV collagen was inhibited by both SAP and C-reactive protein (CRP). However, a 5-fold molar excess of CRP as compared with SAP was required to inhibit the SAP binding by 50%. Binding of SAP to type IV collagen was inhibited by both collagen IV and C1q but not by phosphatidylethanolamine or bovine serum albumin. The inhibition data indicate that SAP may bind to the triple helical region of type IV collagen via a site distinct from its galactan binding site. The most likely site of SAP involved in its interaction with type IV collagen may be the region spanning amino acid residues 108-120, which shows a great deal of sequence homology (60% strict identity) with the CRP region implicated in its binding to the collagen-like region of the C1q molecule.

• Heegaard NH, Heegaard PM, Roepstorff P, Robey FA
• Ligand-binding sites in human serum amyloid P component.
• Eur J Biochem. 1996; 239: 850-6
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• Amyloid P component (AP) is a naturally occurring glycoprotein that is found in serum and basement membranes. AP is also a component of all types of amyloid, including that found in individuals who suffer from Alzheimer's disease and Down's syndrome. Because AP has been found to bind strongly and specifically to certain glycosaminoglycans that are components of amyloid deposits, AP may play an important role in the maintenance of amyloid. In the present work, we isolated and identified two proteolytic fragments of AP that are responsible for its heparin-binding activity. Neither fragment corresponds to published heparin-binding sequences. The structural requirements for activity of the peptides (amino acid residues 27-38 and 192-203 of AP) were examined by means of solid-phase inhibition assays with synthetic peptides. AP-(192-203)-peptide inhibits the Ca(2+)-dependent binding of AP to heparin with an IC50 of 25 microM, while the IC50 of AP-(27-38)-peptide and AP-(33-38)-peptide are 10 microM and 2 microM, respectively. The understanding of the structure and function of active AP peptides will be useful for development of amyloid-targeted diagnostics and therapeutics.

• Adachi T, Mogi M, Harada M, Kojima K
• Selective removal of human serum amyloid P component from rat blood by use of an immunoaffinity membrane in an extracorporeal circulation system.
• J Chromatogr B Biomed Appl. 1996; 682: 47-54
• Display abstract

• We examined the suitability of an immunoaffinity membrane (IAM) bearing specific antibody as a ligand for removing human serum amyloid P component (hSAP) from blood passed through a simple extracorporeal circulation system established in rats. The specific antibody was the most effective of the various ligands tested for removing hSAP from human blood. To determine the value of the hSAP in human or rat plasma, we also developed a simple ELISA. In the rat extracorporeal circulation system, the hSAP level in the inlet blood to the IAM module decreased to 49% of the initial concentration within 60 min. In contrast, the hSAP remained at the initial concentration throughout the study in the module without the IAM. The use of this extracorporeal circulation system in this case allows preclinical evaluation of the ex vivo removal of a human plasma component in an animal model. Biocompatibility of the IAM was also examined. No change in blood cell counts or activation of the coagulation system occurred after contact with the IAM. Non-specific adsorption was not observed, since there was no statistically significant difference in IgG, complement C3, or albumin level between the pre- and post-treatment with this module. The immunological effects of the IAM were also examined using this system. Four weeks after the termination of the extracorporeal circulation, the rats examined showed no detectable antibody titer to the ligand.

• Polevshchikov AV, Nazarov PG, Kozlov SV, Galkina EV, Berestova LK
• [The regulation of blood neutrophil functions by C-reactive protein and serum amyloid P]
• Fiziol Zh Im I M Sechenova. 1996; 82: 67-72
• Display abstract

• The effect of C-reactive protein on oxygen metabolism and lysosomal activity of the human blood neutrophils was found to depend on its ability to conform and to render both the pro- and anti-inflammatory results. The serum amyloid P exerted mostly a consistent anti-inflammatory effect.

• Burlingame RW, Volzer MA, Harris J, Du Clos TW
• The effect of acute phase proteins on clearance of chromatin from the circulation of normal mice.
• J Immunol. 1996; 156: 4783-8
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• The clearance of nucleosome core particles and H1-stripped chromatin from the circulation of mice was examined. Radiolabeled chromatin preparations were injected into mice, and blood samples were obtained over 60 min. The animals were then killed, and the selected organs were collected and radioactivity was measured. The acute phase response (APR) was induced by i.p. injections of casein before some clearance studies. Serum amyloid P component, the major acute phase protein in mice, increased from 27 microg/ml to 339 microg/ml during the acute phase. The rate of chromatin clearance decreased during the acute phase in C57BL/10J mice. At 5 min, 18% +/- 3% of the originally measured radioactivity remained in control animals compared with 49% +/- 2% in acute phase animals (p < 0.001). Co-injection of either serum amyloid P component or C-reactive protein, the major acute phase protein in humans, caused a decrease in the rate of chromatin clearance similar to that observed following the induction of the APR. APR induction also caused a higher percentage of the chromatin to localize in the liver compared with the spleen, with the ratio changing from 10.2 +/- 0.7 to 16.1 +/- 1.9 (p < 0.004). In addition, the APR caused a decrease in the percentage of chromatin localized in the kidney. The lack of radioactivity associated with cells in the circulation indicates that complement is not a major factor in the clearance mechanism of chromatin. These findings suggest that the APR produces major changes in the rate and path of chromatin clearance. These changes may protect against deposition of chromatin in target organs of systemic lupus erythematosus.

• Sorensen IJ, Nielsen EH, Andersen O, Danielsen B, Svehag SE
• Binding of complement proteins C1q and C4bp to serum amyloid P component (SAP) in solid contra liquid phase.
• Scand J Immunol. 1996; 44: 401-7
• Display abstract

• Serum amyloid P component (SAP), a member of the conserved pentraxin family of plasma proteins, binds calcium dependently to its ligands. The authors investigated SAPs interaction with the complement proteins C4b binding protein (C4bp) and C1q by ELISA, immunoelectrophoresis and electron microscopy. Binding of these proteins to SAP was demonstrated when SAP was immobilized using F(ab')2 anti-SAP, but not when SAP reacted with these proteins in liquid phase; thus the binding to human SAP was markedly phase state dependent. Presaturation of solid phase SAP with heparin, which binds SAP with high affinity, did not interfere with the subsequent binding of C4bp or C1q to SAP. In contrast, collagen I and IV showed partial competition with the binding of C1q to SAP. Using fresh serum, immobilized native SAP bound C4bp whereas binding of C1q/C1 could not be demonstrated. Altogether the results indicate that firm binding of C1q and C4bp to SAP requires that SAP is presented on a solid phase, that C1q and C4bp react with sites distinct from the heparin binding site, and that C1q and collagen I share binding sites on SAP. Immobilized native SAP, aggregated SAP and SAP-heparansulphate complexes induced no detectable complement activation.

• Introna M et al.
• Cloning of mouse ptx3, a new member of the pentraxin gene family expressed at extrahepatic sites.
• Blood. 1996; 87: 1862-72
• Display abstract

• Pentraxins, which include C reactive protein (CRP) and serum amyloid P component (SAP), are prototypic acute phase reactants that serve as indicators of inflammatory reactions. Here we report genomic and cDNA cloning of mouse ptx3 (mptx3), a member of the pentraxin gene family and characterize its extrahepatic expression in vitro and in vivo. mptx3 is organized into three exons on chromosome 3: the first (43 aa) and second exon (175 aa) code for the signal peptide and for a protein portion with no high similarity to known sequences the third (203 aa) for a domain related to classical pentraxins, which contains the "pentraxin family signature." Analysis of the N terminal portion predicts a predominantly alpha helical structure, while the pentraxin domain of ptx3 is accommodated comfortably in the tertiary structure fold of SAP. Normal and transformed fibroblasts, undifferentiated and differentiated myoblasts, normal endothelial cells, and mononuclear phagocytes express mptx3 mRNA and release the protein in vitro on exposure to interleukin-1beta (IL-1beta) and tumor necrosis factor (TNF)alpha. mptx3 was induced by bacterial lipopolysaccharide in vivo in a variety of organs and, most strongly, in the vascular endothelium of skeletal muscle and heart. Thus, mptx3 shows a distinct pattern of in vivo expression indicative of a significant role in cardiovascular and inflammatory pathology.

• Schwalbe RA, Coe JE, Nelsestuen GL
• Association of rat C-reactive protein and other pentraxins with rat lipoproteins containing apolipoproteins E and A1.
• Biochemistry. 1995; 34: 10432-9
• Display abstract

• C-Reactive protein (CRP) is a member of the pentraxin family of proteins, ubiquitous components of animal serum. This study suggests that, in serum, rat CRP is complexed with lipoprotein and may interact directly with apolipoprotein E. When mixed with diluted rat serum, radiolabeled rat CRP showed a slightly higher sedimentation coefficient (about 15%) than that of the free protein. Elimination of calcium or addition of O-phosphorylethanolamine (O-PE), a low molecular weight compound that binds tightly to rat CRP in a calcium-dependent manner, abolished this difference. Adsorption of rat serum on a rat CRP affinity gel and elution with PE resulted in the isolation of material containing high levels of apolipoproteins E and A1. The affinity-purified preparation interacted with rat CRP and altered the sedimentation coefficient of the latter to the value observed in whole serum. Conversely, rat CRP increased the sedimentation coefficient of the major component of the affinity-purified material or to diluted rat serum, human serum amyloid P (SAP) and hamster female protein (FP), two other members of the pentraxin protein family, also had slightly higher sedimentation coefficients. In contrast, human CRP showed no evidence of an interaction in rat serum or with the affinity-purified proteins. This selectivity coincided with the ability of these pentraxins to bind to O-PE with high affinity. The sedimentation properties of serum lipoproteins, radiolabeled with [3H]cholesterol, also suggested an interaction with rat CRP.(ABSTRACT TRUNCATED AT 250 WORDS)

• Jensen LE, Petersen TE, Thiel S, Jensenius JC
• Isolation of a pentraxin-like protein from rainbow trout serum.
• Dev Comp Immunol. 1995; 19: 305-14
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• Serum amyloid P-component (SAP) is a glycoprotein consisting of five or ten noncovalently associated identical subunits of molecular weight 19,000-30,000. Herein we report the isolation and partial characterization of a SAP-like protein from rainbow trout serum. The protein was isolated by calcium-dependent binding to Sepharose followed by ion-exchange and size-exclusion chromatography. Rabbit antibody against human SAP reacted with the trout protein and the NH2-terminal sequence of 16 amino acids showed 60% identity with the first 15 residues of human SAP. SDS-PAGE and endoglycosidase treatment indicated that the trout protein is a glycoprotein in which five or six subunits are linked by disulphide bonds. The subunits have a molecular weight of 37,000 of which approximately 13% is due to carbohydrate. We propose to name the trout protein sulphide linked SAP (SL-SAP).

• Li XA, Hatanaka K, Ishibashi-Ueda H, Yutani C, Yamamoto A
• Characterization of serum amyloid P component from human aortic atherosclerotic lesions.
• Arterioscler Thromb Vasc Biol. 1995; 15: 252-7
• Display abstract

• Serum amyloid P component (SAP) is a glycoprotein in human plasma. We recently showed the localization of SAP in human atherosclerotic lesions by immunohistochemical staining. In this study, the presence of SAP in atherosclerotic lesions was confirmed, and the biochemical character of SAP in atherosclerotic intima was investigated and compared with that of native SAP. Atherosclerotic intima was sequentially extracted with 2 mmol/L CaCl2-Tris-buffered saline (TBS), 10 mmol/L EDTA-TBS, 3 mol/L guanidine-TBS, and collagenase digestion. The character of SAP in each extract was studied with double immunodiffusion, electroimmunoassay, crossed immunoelectrophoresis, and Western immunoblotting. The total amount of SAP in atherosclerotic intima was 190 +/- 64 micrograms/g wet tissue with an SAP-albumin ratio of 1:22.7, which is 44 times higher than the relative plasma ratio of 1:1000. This suggests that SAP is specifically localized in atherosclerotic lesions. SAP from the intima was indistinguishable from plasma or purified SAP with respect to immunological character and molecular weight. However, electrophoretic mobility and the binding of SAP to atherosclerotic intima appeared heterogeneous. Of total extractable SAP, about 43% appeared in the CaCl2-TBS fraction, 25% in the EDTA-TBS fraction, and 32% in the collagenase digestion fraction. SAP is one of the two pentraxins in human plasma; the other is C-reactive protein, which has also been reported to locate in atherosclerotic lesions. Our findings suggest a role for SAP in atherogenesis and encourage efforts to determine more precisely the physiological contributions of the pentraxin family to the development of atherosclerosis.

• Evans TC Jr, Nelsestuen GL
• Dissociation of serum amyloid P from C4b-binding protein and other sites by lactic acid: potential role of lactic acid in the regulation of pentraxin function.
• Biochemistry. 1995; 34: 10440-7
• Display abstract

• Serum amyloid P (SAP) and C-reactive protein (CRP) are two members of the pentraxin family of proteins. These proteins associate with a variety of other materials that are found in serum under normal or pathological circumstances. This study showed that carboxylated compounds, especially lactic acid, were capable of dissociating pentraxins from several macromolecular binding sites. When measured by sucrose density gradient ultracentrifugation, complete dissociation of the complex of hSAP (human SAP) with C4b-binding protein (C4BP) occurred at > or = 5 mM lactate. Lactate dissociated the hSAP-membrane complex and prevented hSAP self-association. The only interaction that was not dissociated by 10 mM lactate was the hSAP-heparin complex. The relative efficacies of several dissociating agents were O-phosphorylethanolamine > lactate > succinate > carbonate > epsilon-amino-n-caproic acid. This suggested that the carboxyl group plus a hydrogen-bonding site on the hydrocarbon chain was important, but a charged amino group was not a contributor to function when the anion was provided by a carboxyl group. The concentration of lactic acid needed to dissociate hSAP from C4BP was dependent on protein concentration in a manner suggesting the cooperative binding of lactate (coefficient = 2) to hSAP. Pure proteins, at concentrations found in normal serum, required about 12 mM lactate for half-dissociation of the hSAP-C4BP complex. Other pentraxins also interacted with lactic acid, but with lower affinities. An important observation was that lactic acid was capable of dissociating rat CRP from lipoproteins in rat serum. Human CRP bound very weakly to lactate, so that lactate probably is not a significant regulator of this pentraxin.(ABSTRACT TRUNCATED AT 250 WORDS)

• Gewurz H, Zhang XH, Lint TF
• Structure and function of the pentraxins.
• Curr Opin Immunol. 1995; 7: 54-64
• Display abstract

• Over the past two years, the three-dimensional structure of the serum amyloid P component was defined by X-ray diffraction, the first such visualization of a pentraxin. Binding sites for calcium, ligands and complement were identified. New fusion proteins with amino acid sequence homology to the pentraxins were described, and new insights were gained into pentraxin phylogeny, biosynthesis, ligands, complement activation, leukocyte reactivity and biological functions in vivo.

• Sorensen IJ, Andersen O, Nielsen EH, Svehag SE
• Multiple isoforms of the human pentraxin serum amyloid P component.
• Int Arch Allergy Immunol. 1995; 106: 25-31
• Display abstract

• Human serum amyloid P component (SAP) isolated from 20 healthy individuals was analyzed by anion exchange chromatography and isoelectric focusing (IEF) in order to investigate the existence of multiple forms of SAP and interindividual structural differences. Anion exchange chromatography showed one major and several minor subpopulations of SAP. IEF of all SAP isolates showed a previously unreported degree of heterogeneity with six isoelectric forms (pKi range 5.5-6.1) and with minor interindividual differences in respect of isoelectric points. Total enzymatic deglycosylation of SAP reduced the number of bands in IEF to two indicating the existence of two types of polypeptide chains.

• Marshall GE
• Human scleral elastic system: an immunoelectron microscopic study.
• Br J Ophthalmol. 1995; 79: 57-64
• Display abstract

• An immunocytochemical study was conducted on elastic components in the sclera of seven aged human eyes. By conventional electron microscopy, elastic tissue consists of three distinct fibre types--elastic fibres, elaunin fibres, and oxytalan fibres. The distribution of six components associated with the elastic system (elastin, amyloid P component, laminin, fibronectin, gp 115, and vitronectin) were studied by immunogold transmission electron microscopy. The codistribution of amyloid P component and laminin was further studied by double immunolabelling. Both elastic and elaunin fibres contained elastin. The microfibrillar sheaths of elastic fibres labelled for amyloid P component, those of elaunin fibres for amyloid P and laminin, and those of oxytalan fibres for laminin only. No labelling was observed for fibronectin, gp 115, and vitronectin. In terms of the proteins investigated, the biochemical profile of the three fibre types was not completely identical and was manifest as different affinities in the binding of serum amyloid P component and an association with laminin.

• Garcia de Frutos P, Hardig Y, Dahlback B
• Serum amyloid P component binding to C4b-binding protein.
• J Biol Chem. 1995; 270: 26950-5
• Display abstract

• Human C4b-binding protein (C4BP), which is a regulator of the classical complement pathway C3 convertase, forms high affinity complexes with anticoagulant protein S and with the pentraxin serum amyloid P component (SAP). SAP is a plasma protein present in all amyloid deposits. Recently, SAP was shown to inhibit the complement regulatory functions of C4BP. In this investigation, we have studied the structural requirements for the C4BP-SAP interaction. C4BP was subjected to chymotrypsin digestion, which yielded two major fragments corresponding to the central core (160 kDa) and to the cleaved-off tentacles (48 kDa). SAP-Sepharose specifically bound the 160-kDa fragment, suggesting that the central core of C4BP contains the binding site for SAP. In a quantitative affinity chromatography assay, the dissociation constants for binding of intact C4BP and of the 160-kDa central core fragment to SAP were found to be 30 and 70 nM, respectively. Recombinant C4BP composed of only alpha-chains bound SAP with similar affinity (Kd = 22 nM), whereas nonglycosylated recombinant alpha-chain C4BP (synthesized in the presence of tunicamycin) bound SAP with lower affinity (Kd = 126 nM). This suggests that the carbohydrate moiety of the central core of C4BP is important for binding of C4BP to SAP in contrast to the C4BP beta-chain, which is not required. EDTA, heparin, and phosphorylethanolamine as well as a peptide comprising amino acids 27-39 of SAP were found to completely displace C4BP from the SAP matrix. Moreover, the immobilized SAP peptide bound C4BP in a reaction that, in contrast to the C4BP-SAP interaction, was not dependent on calcium.

• Schlimgen AK, Helms JA, Vogel H, Perin MS
• Neuronal pentraxin, a secreted protein with homology to acute phase proteins of the immune system.
• Neuron. 1995; 14: 519-26
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• We have identified, by affinity chromatography, a binding protein for the snake venom toxin taipoxin. The sequence of this 47 kDa protein is unique, is characteristic of a secreted protein, and has homology to the acute phase proteins serum amyloid P protein and C-reactive protein of the pentraxin family. We have named this protein neuronal pentraxin (NP), as Northern analysis and in situ hybridization demonstrate high message levels in neurons of cerebellum, hippocampus, and cerebral cortex. Because NP may be released synaptically and has homology to immune proteins potentially involved in uptake of lipidic, toxic, or other antigenic material, we suggest that NP may be involved in a general uptake of synaptic macromolecules.

• Sorensen IJ, Andersen O, Nielsen EH, Svehag SE
• Native human serum amyloid P component is a single pentamer.
• Scand J Immunol. 1995; 41: 263-7
• Display abstract

• Serum amyloid P component (SAP) and C-reactive protein (CRP) are members of the pentraxin protein family. SAP is the precursor protein to amyloid P component present in all forms of amyloidosis. The prevailing notion is that SAP in circulation has the form of a double pentameric molecule (decamer) whereas CRP is a single pentameric molecule. We have investigated by gel permeation chromatography the M(r) of SAP in freshly collected human serum and of SAP purified by carbohydrate affinity chromatography and anion exchange chromatography. SAP was monitored by quantitative immunoelectrophoresis and ELISA, and SAP peak fractions were analysed by use of SDS-PAGE, Western blotting, and electron microscopy. The results indicate that native SAP circulates as a single pentamer, a part of which forms complexes with C4b-binding protein. The properties of SAP changed during purification as indicated by rocket immunoelectrophoresis and electron microscopy. Thus, electron micrographs of purified SAP showed a predominance of decamers. However, the decamer form of SAP reversed to single pentamers when purified SAP was incorporated into SAP-depleted serum.

• Quigley J, Misquith S, Surolia A, Srimal S, Armstrong P
• Preliminary investigation of the molecular basis for the functional differences between the two pentraxins limulin and C-reactive protein from the plasma of the American horseshoe crab, Limulus polyphemus.
• Biol Bull. 1994; 187: 229-30

• Landsmann P et al.
• Binding of human serum amyloid P component (hSAP) to human neutrophils.
• Eur J Biochem. 1994; 223: 805-11
• Display abstract

• Human serum amyloid P component (hSAP) and human C-reactive protein (hCRP) are normal serum constituents related to the pentraxin family of plasma proteins. hSAP has morphological and immunochemical identity and extensive sequence similarity to the amyloid P (AP) component found in normal tissues and particularly in amyloid deposits. hCRP and its proteolytic products have been previously shown to bind and to interact with various types of human leukocytes. Binding-displacement experiments with 125I-labeled hSAP and hCRP show that both proteins have specific high-affinity binding sites on normal human polymorphonuclear leukocytes (PMN) and each can compete efficiently with the binding of the other. Scatchard analysis of hSAP-displacement curves reveals a heterogeneous population of hSAP-binding sites existing on the PMN cells, among them about 300,000 low-affinity binding sites with Kd < or = 5 x 10(-6) M and about 30,000 high-affinity binding sites with Kd < or = 5 x 10(-8) M. hAP was found to be degraded by enzymes from human neutrophils to yield a mixture of low-molecular-mass peptides, similarly to the case of CRP reported previously. The binding of hSAP can be efficiently inhibited by this peptide mixture. The results suggest that both hCRP and hSAP, together with related peptides, may participate in vivo in an unknown mechanism of regulation of human neutrophils.

• Christner RB, Mortensen RF
• Specificity of the binding interaction between human serum amyloid P-component and immobilized human C-reactive protein.
• J Biol Chem. 1994; 269: 9760-6
• Display abstract

• C-reactive protein (CRP) and serum amyloid P-component (SAP) are two members of a group of plasma proteins termed pentraxins, which are composed of five identical noncovalently linked subunits that display Ca(2+)-dependent binding to a wide variety of substrates. Purified human SAP binds to CRP, only when the latter is immobilized, in a Ca(2+)-dependent manner under physiological conditions. Externally labeled SAP rapidly binds to two distinct forms of immobilized CRP (direct and phosphorylcholine captured) with a relatively high affinity (KD = 5 nM) at a molar ratio of specifically bound SAP/CRP = 0.3. Studies of binding inhibition using monoclonal antibodies to CRP or synthetic peptides of CRP revealed that residues 134-148 and the COOH-terminal region (residues 191-206) were recognized by SAP. A fragment of CRP consisting of the COOH-terminal 60 residues within each subunit was also selectively bound by SAP. The ability of immobilized CRP to bind SAP was distinguished from CRP's lectin-like binding reactivity since deglycosylated SAP retained its binding reactivity for CRP and sugars that inhibit CRP's lectin-like binding activity failed to inhibit binding. A peptide from trypsin digested SAP composed of residues 144-199 retained CRP binding activity, implicating the COOH-terminal region of SAP as the CRP recognition site.

• Pepys MB et al.
• Human serum amyloid P component is an invariant constituent of amyloid deposits and has a uniquely homogeneous glycostructure.
• Proc Natl Acad Sci U S A. 1994; 91: 5602-6
• Display abstract

• Human serum amyloid P component (SAP) is a normal plasma protein and the precursor of amyloid P component (AP), a universal constituent of the abnormal tissue deposits in amyloidosis, including Alzheimer disease. We show here that its single N-linked biantennary oligosaccharide does not display the microheterogeneity usually characteristic of glycoproteins. The protein and the glycan structures of AP were also invariant, their resistance to degradation suggesting a role in persistence of amyloid deposits. Asialo-SAP was rapidly cleared from the circulation in mice by a mechanism dependent on terminal galactose residues and was catabolized in hepatocytes. However blockade of this pathway did not affect the clearance of native SAP. Rapid hepatic uptake and catabolism of human asialo-SAP in man were also directly demonstrated. The protein and glycan homogeneity of SAP and the integrity of AP suggest that the complete glycoprotein structure is important for the normal and the pathophysiological functions of this molecule.

• Dong A, Caughey WS, Du Clos TW
• Effects of calcium, magnesium, and phosphorylcholine on secondary structures of human C-reactive protein and serum amyloid P component observed by infrared spectroscopy.
• J Biol Chem. 1994; 269: 6424-30
• Display abstract

• The secondary structures of human C-reactive protein (CRP) and serum amyloid P component (SAP) in D2O-based solutions in the presence or absence of calcium, magnesium, and phosphorylcholine have been investigated using Fourier transform infrared spectroscopy. Quantitative analysis provided estimations of about 50% beta-sheet, 12% alpha-helix, 24% beta-turn, and 14% unordered structure for CRP and about 54% beta-sheet, 12% alpha-helix, 25% beta-turn, and 9% unordered structure for SAP. With both proteins significant calcium-dependent changes were observed in conformation-sensitive amide I regions assigned to each type of structure. The CRP spectrum was also affected by magnesium, but the changes differed from those induced by calcium. The SAP spectrum was not affected by magnesium. Phosphorylcholine in the presence of calcium also affected the spectrum of CRP but not the spectrum of SAP. Our present study provides the first direct comparison of the secondary structures of the pentraxins human CRP and SAP and hamster female protein (Dong, A., Caughey, B., Caughey, W. S., Bhat, K. S., and Coe, J. E. (1992) Biochemistry 32, 9364-9370). These findings suggest that the three pentraxins have similar secondary structure compositions and calcium-dependent conformational changes, but differ significantly in their responses to phosphorylcholine and magnesium. Such properties are expected to be relevant to the incompletely understood roles of these highly conserved proteins including binding to nuclear proteins, complement activation, and association with amyloids.

• Lee GW, Goodman AR, Lee TH, Vilcek J
• Relationship of TSG-14 protein to the pentraxin family of major acute phase proteins.
• J Immunol. 1994; 153: 3700-7
• Display abstract

• TNF-stimulated gene-14 (TSG-14) encodes a secreted glycoprotein with significant sequence homology to C-reactive protein (CRP) and serum amyloid P component (SAP), members of the pentraxin family of acute phase proteins. TSG-14 mRNA was elevated in human FS-4 fibroblasts by treatment with TNF, IL-1, or bacterial LPS, and weakly by dexamethasone. Abs to recombinant TSG-14 immunoprecipitated a 42-kDa protein from the culture supernatants of TNF- or IL-1-stimulated FS-4 cells. TSG-14 protein was also inducible in the Hep3B human hepatoma cell line by TNF, IL-1, IL-6, or dexamethasone. CRP protein, identified by immunoprecipitation of a 25-kDa band with Abs to CRP, was induced in Hep3B cells by IL-1, IL-6, or dexamethasone. Immunoprecipitations with polyclonal Abs to TSG-14 and CRP suggested that the two proteins are immunologically cross-reactive. Appearance of TSG-14 protein was demonstrated in the serum of mice after injection with LPS. No TSG-14 mRNA was detected in the liver of LPS-injected mice, suggesting that hepatocytes are not the major site of TSG-14 synthesis. Thus, in the intact organism the main cellular sources of TSG-14 and classical acute phase proteins appear to be different.

• Hutchinson WL, Noble GE, Hawkins PN, Pepys MB
• The pentraxins, C-reactive protein and serum amyloid P component, are cleared and catabolized by hepatocytes in vivo.
• J Clin Invest. 1994; 94: 1390-6
• Display abstract

• The cellular sites of clearance and degradation of the pentraxin plasma proteins, C-reactive protein, the classical acute phase reactant, and serum amyloid P component (SAP), a universal constituent of amyloid deposits, were sought using the ligand 125I-tyramine cellobiose (TC) which is substantially retained within the cells in which catabolism takes place. Pentraxins labeled with 125I-TC showed the same in vitro and in vivo ligand binding and the same in vivo plasma t1/2 as the directly iodinated proteins and the native unlabeled pentraxins, indicating that their mode of clearance was likely to be physiological. After intravenous injection into mice and rabbits of human C-reactive protein, human SAP, and mouse SAP, each labeled with 125I-TC, most of the radioactivity remaining in the body at 24 h was located in hepatocytes. None was detected in other liver cells, and only traces were present in other viscera; the rest was in the carcass, representing intact pentraxins in the blood and extravascular compartment, and escaped label which had not yet been excreted. Hepatocytes are thus the single major site of pentraxin clearance and catabolism in vivo. This is consistent with the observation that SAP that has localized to amyloid deposits persists there and is not degraded.

• Christner RB, Mortensen RF
• Binding of human serum amyloid P-component to phosphocholine.
• Arch Biochem Biophys. 1994; 314: 337-43
• Display abstract

• Human serum amyloid P-component (SAP) and C-reactive protein (CRP) are structurally similar pentraxins composed of five identical subunits in a disc-like configuration and display Ca(2+)-dependent binding reactivity to a variety of unrelated ligands. CRP is generally classified and defined as a phosphocholine (PC)-binding protein, whereas SAP is identified as a polysaccharide-binding protein. We examined the PC-binding activity of human SAP and compared it to human CRP since many of the biological activities of CRP are triggered upon PC-binding. SAP was able to bind to immobilize PC in a saturable, Ca(2+)-dependent manner but with lower avidity than CRP in direct competitive binding assays. The affinity of the binding of SAP to soluble [14C]PC was slightly lower than the affinity of CRP; however, the valence of SAP was only one PC-binding site/pentraxin or 2/protein vs 5 such sites per CRP molecule. Both SAP and CRP displayed a similar binding preference for PC vs phosphoethanolamine (PE). Two monoclonal antibodies (mAb) generated against the PC-binding site of SAP also reacted with the PC-binding site of CRP and inhibited PC-binding by both pentraxins. A mAb specific for the PC-binding site on CRP also inhibited SAP binding to PC. SAP was also recognized by two anti-idiotypic mAb that shared reactivity with the TEPC-15 PC-binding myeloma protein and the PC-binding site of CRP. Both pentraxins could be isolated from human serum by affinity chromatography on either PC- or PE-substituted agarose beads. The findings indicate that SAP is also a PC-binding protein.

• Garcia de Frutos P, Dahlback B
• Interaction between serum amyloid P component and C4b-binding protein associated with inhibition of factor I-mediated C4b degradation.
• J Immunol. 1994; 152: 2430-7
• Display abstract

• Serum amyloid P component (SAP) is a member of the pentraxin protein family. Although present in all types of amyloid deposits, it is also a normal constituent of blood and extravascular tissues. In blood, SAP forms a calcium-dependent, noncovalent complex with C4b-binding protein (C4BP). C4BP regulates the classical complement pathway as it binds C4b and functions as cofactor in its degradation by factor I. Although SAP and C4b bind to distinct sites on C4BP, it is not known whether the SAP-C4BP interaction affects the function of C4BP. We report that in a fluid phase system, SAP inhibited degradation of C4(H2O) (which is C4b-like) in a dose-dependent manner. Phosphorylethanolamine was found to alleviate the inhibitory effect of SAP on C4(H2O) degradation. Because this compound is known to inhibit the SAP-C4BP interaction, this indicated direct binding of SAP to C4BP to be required for inhibition of C4(H2O) degradation. Even though C4BP, C4(H2O), and SAP form a multimolecular complex in fluid phase, SAP was found to inhibit binding of C4BP to immobilized C4(H2O). The inhibitory effect was calcium dependent and alleviated by phosphorylethanolamine. Heparin, which is known to inhibit the interaction between SAP and C4BP, was also found to counteract the inhibitory effect of SAP on C4BP binding to C4(H2O). However, the effect of heparin was biphasic because high concentrations of heparin directly inhibited binding of C4(H2O) to C4BP. The inhibition of C4BP function by SAP suggests that SAP may be involved in regulation of the classical complement pathway C3 convertase.

• Murata M, Onuma M, Kodama H
• Isolation and characterization of rainbow trout (Oncorhynchus mykiss) serum amyloid P component (SAP)
• J Vet Med Sci. 1994; 56: 661-5
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• We purified a Ca(2+)-dependent agarose-binding protein from rainbow trout (Oncorhynchus mykiss) sera. SDS-PAGE analysis showed the possibility that the purified protein was a polymer with a molecular weight of over 100,000 composed of covalently-bounded 32-kDa subunits. N-terminal twenty amino acid sequence of the 32-kDa protein showed partial homology with other known serum amyloid P components (SAPs) including plaice (Pleuronectes platessa) (indicated 40% homology), human (55%), hamster (45%), rat and mouse (40%) SAPs. In electron micrographs the 32-kDa protein was observed as pentameric disc-like structure. On the basis of the results, the 32-kDa agarose-binding protein of rainbow trout was concluded to belong to pentraxin family and to be a SAP homologue.

• Tennent GA, Pepys MB
• Glycobiology of the pentraxins.
• Biochem Soc Trans. 1994; 22: 74-9

• Steel DM, Whitehead AS
• The major acute phase reactants: C-reactive protein, serum amyloid P component and serum amyloid A protein.
• Immunol Today. 1994; 15: 81-8
• Display abstract

• Following an acute phase stimulus, such as infection or physical injury, many liver-derived plasma proteins are increased in concentration. These provide enhanced protection against invading micro-organisms, limit tissue damage and promote a rapid return to homeostasis. Diana Steel and Alexander Whitehead discuss the gene structure, regulation and possible clinical significance of the most dramatically induced acute phase reactants.

• Nielsen EH, Sorensen IJ, Vilsgaard K, Andersen O, Svehag SE
• Calcium-enhanced aggregation of serum amyloid P component and its inhibition by the ligands heparin and heparan sulphate. An electron microscopic and immunoelectrophoretic study.
• APMIS. 1994; 102: 420-6
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• Serum amyloid P component (SAP) is a pentraxin found in the circulation and in all forms of amyloid deposits. Its physiological and pathophysiological functions are largely unknown. Electron microscopy showed purified human SAP to consist of double pentameric discs compatible with the results of size chromatography. The formation of double pentamers did not require calcium ions. The outer diameter of the discs arranged face-to-face was 11.6 nm and the inner diameter 3.2 nm. The thickness of single and double pentamers was 4.1 and 8.7 nm, respectively. Quadruple pentamers were occasionally seen. The self-aggregation of human SAP molecules was investigated in the presence and absence of calcium ions at different concentrations. In calcium-free solutions few and mostly small SAP aggregates were seen. After addition of calcium at increasing concentration the aggregates grew in size and crystalline-like structures were formed already at 2 mM calcium. At 25 mM calcium, large aggregates with a crystalline array occasionally exhibiting cylinders predominated. Binding of the ligands heparin and heparan sulphate to SAP completely abolished the calcium-enhanced aggregation, but the distribution of the SAP molecules was affected, resulting in strands or groups of adjacent molecules. The electrophoretic mobility of SAP was moreover significantly altered after its calcium-dependent reaction with these ligands. We conclude that purified SAP has a tendency to double pentamer formation and self-aggregation also in the absence of calcium ions. However, aggregation is greatly enhanced even at low concentrations (2 mM) of calcium. SAP's tendency to self-aggregation is abolished after its binding to heparin or heparin sulphate. Furthermore, our TEM studies indicate that purified human SAP freed of its natural ligands has the double pentameric form, whereas the electrophoretic investigations suggest that SAP's interaction with low-molecular-weight natural ligands in serum prevents homodimerization and self-aggregation.

• Pepys MB, Booth SE, Tennent GA, Butler PJ, Williams DG
• Binding of pentraxins to different nuclear structures: C-reactive protein binds to small nuclear ribonucleoprotein particles, serum amyloid P component binds to chromatin and nucleoli.
• Clin Exp Immunol. 1994; 97: 152-7
• Display abstract

• Binding of the human pentraxin plasma proteins, C-reactive protein (CRP) and serum amyloid P component (SAP), to the nuclei of human cells was studied using whole acute phase serum as the source of the proteins and confocal immunofluorescence microscopy. CRP and SAP clearly bound to distinct, different structures. Double staining with MoAbs to the Sm D and Sm B/B' components of small nuclear ribonucleoproteins confirmed that CRP bound exclusively to these particles. As expected, SAP bound to chromatin and, in addition, binding to the nucleolus was observed for the first time. These interactions demonstrated under relatively physiological conditions, with native pentraxins unseparated from serum and with nuclear constituents in situ, are likely to be of functional importance in vivo.

• Rudnick CM, Dowton SB
• Serum amyloid-P component of the Armenian hamster: gene structure and comparison with structure and expression of the SAP gene from Syrian hamster.
• Scand J Immunol. 1993; 38: 445-50
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• Serum amyloid P (SAP), a phylogenetically conserved pentraxin, is an integral component of all amyloid deposits. Regulation of expression of SAP gene expression is quite different in two related hamster species. In Syrian hamsters, the resting serum levels of SAP are determined by gender, and the direction of alteration following inflammation is divergent. In Armenian hamsters, SAP is not a prominent acute-phase reactant and there is no gender dimorphism of expression. The structure and expression of the SAP gene of the Armenian hamsters was investigated by isolation of genomic clones, nucleotide sequence analysis, and RNA studies. The gene structure of Armenian hamster SAP is similar to the genes of all other pentraxins studied. While the upstream regions of the SAP genes of Syrian and Armenian hamsters are quite similar, important differences in potential enhancer sites have been recognized by comparing the corresponding sequences of SAP genes from both species. Little alteration in hepatic levels of transcripts encoding SAP or CRP, the other pentraxin, were noted following administration of lipopolysaccharide to Armenian hamsters. This relative lack of response occurred despite a marked acute phase reaction documented for serum amyloid A mRNA levels.

• Tennent GA et al.
• Studies of the structure and binding properties of hamster female protein.
• Immunology. 1993; 80: 645-51
• Display abstract

• We report here the characterization of hamster female protein (FP), a member of the pentraxin family of plasma proteins, as a molecule composed of glycosylated subunits of 25,655 MW containing a single intrachain disulphide bridge. In the presence of EDTA the subunits are non-covalently associated as pentamers of mass approximately 128,000 MW, and in the presence of calcium they aggregate further, probably to form decamers. This pentamer-decamer transition at physiological ionic strength has not been described in other pentraxins. As previously reported, FP shares the capacity of C-reactive protein (CRP) in other species to bind phosphocholine and we show here that it also resembles human CRP in binding only weakly to agarose, to human AA amyloid fibrils in vitro, and to mouse AA amyloid deposits in vivo. It thus differs markedly from human and mouse serum amyloid P component (SAP) but it is nevertheless deposited in hamster AA amyloid in vivo and clearly is the hamster counterpart of SAP in other species. These results illustrate the subtle diversity among members of the otherwise conserved pentraxin family of vertebrate plasma proteins.

• Rudnick CM, Dowton SB
• Serum amyloid P (female protein) of the Syrian hamster. Gene structure and expression.
• J Biol Chem. 1993; 268: 21760-9
• Display abstract

• The structure and expression of the gene encoding serum amyloid P (SAP) component of the Syrian hamster have been studied by isolation of cosmid clones, nucleotide sequence analyses, and quantitation of nuclear run-on transcripts, nuclear RNA, mRNA, and protein levels. Hamster SAP, originally identified as female protein (FP), is a unique pentraxin because pretranslational expression of this gene is modulated by mediators of inflammation and sex steroids. SAP(FP) levels are high in sera from female hamsters and low in males. The response to inflammation is divergent; SAP(FP) levels decrease in females and increase in males during an acute phase response. The SAP(FP) gene encodes a 211 amino acid residue mature polypeptide as well as a 22-residue signal peptide. The intron/exon organization is similar to that of other pentraxins, but additional transcripts are generated from alternate polyadenylation sites in the 3' region. Circulating levels of SAP(FP) and the corresponding hepatic transcript levels are augmented by estrogen, while testosterone, dexamethasone, and progesterone cause a decrease in these levels. In addition the cytokines interleukin-1, -6, and tumor necrosis factor mediate a decrease in hepatic SAP(FP) transcript levels in female hamsters but did not cause a significant elevation of SAP(FP) mRNA in livers of male hamsters. The differences in expression of the SAP(FP) gene between male and female hamsters and between unstimulated male hamsters and male hamsters stimulated with an injection of lipopolysaccharide are due, at least in part, to alterations in transcription.

• Ying SC, Gewurz AT, Jiang H, Gewurz H
• Human serum amyloid P component oligomers bind and activate the classical complement pathway via residues 14-26 and 76-92 of the A chain collagen-like region of C1q.
• J Immunol. 1993; 150: 169-76
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• Serum amyloid P component (SAP) was polymerized using the cleavable cross-linker 3,3'-dithio-bis-(sulfo-succinimidylpropionate) to study its interaction with the C system. Dimers and trimers, but no larger oligomers, were observed; the trimers retained native SAP immunoreactivity (except for one calcium-dependent epitope) without displaying neo-SAP epitopes. The SAP trimers bound strongly to C1q, at the level of the collagen-like region (CLR). SAP bound to synthetic C1q A chain peptides 14-26 and 76-92, and these peptides inhibited the binding of SAP trimers to the CLR. When incubated in dilute human serum, SAP trimers consumed total C and C4, but not alternative pathway, hemolytic activities. Consumption of C4 by SAP trimers was inhibited by C1q A chain peptide 14-26. Thus, SAP oligomers bind C1q and activate the classical C pathway via the collagen-like region of C1q, at sites located within residues 14-26 and/or 76-92 of the C1q A chain.

• Seery LT, Schoenberg DR, Barbaux S, Sharp PM, Whitehead AS
• Identification of a novel member of the pentraxin family in Xenopus laevis.
• Proc R Soc Lond B Biol Sci. 1993; 253: 263-70
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• Pentraxins are a family of acute phase reactants. Two family members, C-reactive protein (CRP) and serum amyloid P component (SAP), are known in a range of mammalian species. CRP and SAP are both about 200 residues long, and arose from a gene duplication event, apparently before the divergence of the mammalian orders. To elucidate the origins of mammalian pentraxins, we have searched for pentraxin-coding genes in the amphibian Xenopus laevis. We have identified a gene determining a protein (XL-PXN1) which is about twice the size expected: the XL-PXN1 gene appears to be a fusion between regions encoding an amino-terminal peptide of unknown function and a carboxy-terminal pentraxin. The pentraxin domain is more divergent from CRP and SAP than they are from each other: it provides an outgroup for analysis of the evolution of mammalian pentraxins and confirms that putative CRP and SAP proteins partly characterized in non-vertebrate species cannot be true homologues of the mammalian proteins.

• Rubio N, Sharp PM, Rits M, Zahedi K, Whitehead AS
• Structure, expression, and evolution of guinea pig serum amyloid P component and C-reactive protein.
• J Biochem (Tokyo). 1993; 113: 277-84
• Display abstract

• The structure and expression of the pentraxins, serum amyloid P component (SAP), and C-reactive protein (CRP), have been investigated in the guinea pig. Northern blot analysis of hepatic RNA from animals in which acute inflammation had been induced by intraperitoneal injection of thioglycollate established that neither SAP or CRP is a major acute phase reactant in the guinea pig. Genomic clones of SAP and CRP were isolated and sequenced, and the gene and the derived protein sequences were compared with other mammalian homologues. Both genes have organizations typical of the pentraxin genes of other species, but some differences were defined in the regions that potentially determine the capacity of the pentraxin gene to be induced during acute inflammation. Nucleotide substitutions in coding regions have occurred at similar rates in the two pentraxin genes. Nonsynonymous substitution rates indicate that SAP and CRP are subject to similar, relatively low levels of constraint; at the amino acid sequence level the rate of evolution is approximately two replacements per site per 10(9) years. An estimate of the phylogenetic relationship among the pentraxin genes suggests that SAP and CRP arose as the result of a gene duplication event that occurred very early in mammalian evolution, but subsequent to the divergence of the reptilian ancestors of the mammalian and avian lineages. This raises doubts about the identity of proteins from fish, which have been previously characterized as CRP and SAP.

• Kinoshita CM et al.
• A protease-sensitive site in the proposed Ca(2+)-binding region of human serum amyloid P component and other pentraxins.
• Protein Sci. 1992; 1: 700-9
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• Serum amyloid P component (SAP) is a decamer of 10 identical 25.5-kDa subunits. Limited proteolysis of SAP with alpha-chymotrypsin cleaves the subunit into two fragments of 18 and 7.5 kDa, although the fragments stay together in the decamer under nondenaturing conditions. Proteolysis does not occur in the presence of Ca2+ (10 mM). Cleavage with alpha-chymotrypsin prevents the Ca(2+)-dependent binding of SAP to zymosan extract, nucleosomes, and DNA. The alpha-chymotrypsin cleavage site identified is in a region of SAP that is highly conserved in members of the human C-reactive protein (CRP) family of proteins (pentraxins) to which SAP belongs and is similar to the Ca(2+)-binding site in calmodulin and related Ca(2+)-binding proteins (Nguyen, N.Y., Suzuki, A., Boykins, R.A., & Liu, T.-Y., 1986, J. Biol. Chem. 261, 10456-10465). Treatment of SAP with other proteases (trypsin, Pronase, and Nagarse protease) yields fragmentation patterns upon sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) that are similar to those obtained with alpha-chymotrypsin. Two other members of the pentraxin family of proteins, hamster female protein and rabbit CRP, also exhibit similar fragmentation patterns on SDS-PAGE when treated with the various proteases. Recently, it has been shown that the homologous protein, human CRP, is cleaved in the same homologous position as cleavage of SAP by alpha-chymotrypsin, resulting in the loss of Ca(2+)-binding (as shown by equilibrium dialysis) and Ca(2+)-dependent binding reactivities (Kinoshita, C.M., Ying, S.-C., Hugli, T.E., Siegel, J.N., Potempa, L.A., Jiang, H.J., Houghten, R.A., & Gewurz, H., 1989, Biochemistry 28, 9840-9848).(ABSTRACT TRUNCATED AT 250 WORDS)

• Schwalbe RA, Dahlback B, Coe JE, Nelsestuen GL
• Pentraxin family of proteins interact specifically with phosphorylcholine and/or phosphorylethanolamine.
• Biochemistry. 1992; 31: 4907-15
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• Pentraxins are a family of serum proteins characterized by five identical subunits that are noncovalently linked. The two major types of pentraxins are C-reactive protein (CRP) and serum amyloid P component (SAP). CRP proteins are identified by their calcium-dependent interaction with phosphorylcholine. This study showed that SAP also bound to phosphorylated compounds but had a high specificity for phosphorylethanolamine. Thus, human CRP and SAP show high specificity that is complementary for the related compounds, phosphorylcholine and phosphorylethanolamine, respectively. This relationship suggests a complementary and/or related function for the pentraxins. Pentraxins from other species were also examined. Mouse SAP showed binding interactions and specificity similar to human SAP. Female protein (FP) from hamster and rat CRP showed a hybrid specificity and bound to both phosphorylethanolamine and phosphorylcholine. All of the proteins that bound phosphorylethanolamine also associated with human C4b-binding protein (C4BP). With the exception of human and rat CRP, all the proteins also bound to vesicles containing acidic phospholipids. All of these binding interactions were calcium-dependent and mutually exclusive, suggesting that they involved the same site on the protein. These findings suggest possible ways to examine the function of the pentraxins.

• Swanson SJ, Christner RB, Mortensen RF
• Human serum amyloid P-component (SAP) selectively binds to immobilized or bound forms of C-reactive protein (CRP).
• Biochim Biophys Acta. 1992; 1160: 309-16
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• The two homologous human pentraxins, C-reactive protein (CRP) and serum amyloid P-component (SAP), specifically bind to each other only when the CRP is in an immobilized form bound to one of its ligands or to an antibody. CRP did not bind to immobilized SAP. The binding of SAP to immobilized forms of CRP was Ca(2+)-dependent and of sufficient affinity to occur in the presence of serum or purified serum proteins. SAP bound preferentially to a synthetic peptide corresponding to the Ca(2+)-binding region of CRP. Monoclonal antibodies to a synthetic peptide corresponding to the Ca(2+)-binding region selectively inhibited the binding interaction. Proteolytic cleavage of CRP between residues 146 and 147 within the Ca2+ binding region abolished the SAP-binding site; however, the intact subunits of the pentameric CRP were capable of binding SAP. The significance of the binding interaction is that it may serve as the basis for localization of SAP to sites of tissue damage or repair, sites where CRP is selectively deposited.

• Hicks PS, Saunero-Nava L, Du Clos TW, Mold C
• Serum amyloid P component binds to histones and activates the classical complement pathway.
• J Immunol. 1992; 149: 3689-94
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• Two members of the pentraxin family of proteins, C-reactive protein (CRP) and serum amyloid P component (SAP), bind to chromatin and may be involved in the solubilization and clearance of nuclear material. Previous studies demonstrated that CRP binding to chromatin is mediated by histones. SAP differs from CRP in being able to bind to DNA, but SAP binding to histones has not been reported. CRP is an activator of the classical C pathway, and C-dependent cleavage of chromatin in the presence of CRP and serum has been shown. Oligomers of SAP have recently been found to bind to C1q and consume total C and C4, indicating that SAP can activate C as well. The present study examined CRP and SAP binding to histones H1 and H2A and C activation after binding. SAP binding to histones H1 and H2A was observed as well as SAP binding to chromatin. In contrast to CRP, SAP binding to chromatin did not require H1. SAP partially inhibited CRP binding to chromatin and to H1. However, neither pentraxin inhibited binding of the other to H2A. Binding of either CRP or SAP to H2A activated C in SAP-depleted serum leading to the deposition of C4 and C3. C activation required C1q and produced C4d indicating that it occurred through the classical pathway. These findings demonstrate that CRP and SAP share histone as well as chromatin binding, and that both pentraxins can activate the classical C pathway after ligand binding.

• Fernandez MC, Mullenix MC, Christner RB, Mortensen RF
• A cell attachment peptide from human C-reactive protein.
• J Cell Biochem. 1992; 50: 83-92
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• The serum acute phase reactant, C-reactive protein (CRP), is selectively deposited at sites of tissue damage and degraded by neutrophils into biologically active peptides. A synthetic peptide corresponding to residues 27-38 present in each of the five identical subunits of CRP mediated cell attachment activity in vitro. Although the CRP-derived peptide contains a Tuftsin (TKPR)-like sequence at its amino-terminus, the Tuftsin tetrapeptide itself, as well as several synthetic peptides of CRP, failed to inhibit the cell-attachment activity to the CRP-derived peptide. Peptides containing the sequences responsible for the cell attachment activity of the extracellular matrix proteins, fibronectin (Fn) and laminin, failed to inhibit the CRP-derived peptide cell attachment activity. However, the addition of the RGDS and RGDSPASSLP cell-binding peptides of Fn to cells enhanced attachment to the active peptide from CRP. In the converse experiment, the cell-binding peptide of CRP did not influence cell attachment to Fn or laminin. A peptide corresponding to the same stretch of amino acid residues within the homologous Pentraxin, serum amyloid P-component (SAP), displayed nearly identical cell-attachment activity. Several monoclonal antibodies (mAb) specific for the CRP-derived cell-binding peptide neutralized its cell-attachment activity. These mAbs reacted with intact CRP and neutralized the cell-binding activity of CRP itself. The findings suggest that a peptide with cell-binding activity could be generated from the breakdown of CRP and then contribute directly to cellular events leading to tissue repair.

• Saunero-Nava L, Coe JE, Mold C, Du Clos TW
• Hamster female protein binding to chromatin, histones and DNA.
• Mol Immunol. 1992; 29: 837-45
• Display abstract

• Hamster female protein (FP) is a member of the family of proteins known as pentraxins which share amino acid sequence homology, cyclic pentameric structure and calcium-dependent binding to ligands. Other members of this family include C-reactive protein (CRP) and serum amyloid P component (SAP), and most species synthesize both CRP and SAP. FP is unusual in that it is apparently the only pentraxin produced in hamsters, it is under hormonal control and it shares binding characteristics with both CRP and SAP. CRP has been defined and isolated by its calcium-dependent binding to pneumococcal C-polysaccharide via phosphocholine (PC) residues. SAP has been isolated by calcium-dependent binding to agarose. FP binds to both PC and agarose. Recently, both SAP and CRP have been found to bind to chromatin in a calcium-dependent manner and involvement of these proteins in the clearance of nuclear material has been proposed. In this paper we test whether FP shares the ability to bind to chromatin and histones, and compare its relative avidities for these ligands. Similar to CRP, FP bound to histones H1 and H2A, and chromatin. FP shared with SAP the ability to bind to DNA. However, FP binding was inhibited by PC for all ligands, whereas SAP binding was not. FP and SAP also failed to compete with each other for binding to DNA. By cross-inhibition FP bound much less well to PC than CRP, but was a very effective inhibitor of CRP binding to H2A. These studies demonstrate that chromatin and histone binding are conserved among these pentraxins. The role of the proposed PC binding site in these binding reactions is discussed.

• Ying SC et al.
• Reactivity of anti-human C-reactive protein (CRP) and serum amyloid P component (SAP) monoclonal antibodies with limulin and pentraxins of other species.
• Immunology. 1992; 76: 324-30
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• Limulus polyphemus C-reactive protein (CRP) (limulin) has approximately 30% amino acid sequence homology and shares at least one idiotypic determinant associated with ligand-binding activity with human CRP (hCRP); limulin also shares amino acid sequence homology and lectin activity with human serum amyloid P component (hSAP). In the present study panels of 14 anti-hCRP monoclonal antibodies (mAb) directed to distinct hCRP epitopes and 11 anti-hSAP mAb directed to distinct epitopes of hSAP were tested for reactivity with limulin and pentraxins of other species including rabbit CRP (raCRP), rat CRP and hamster female protein (FP) by ELISA and Western blot analyses. None of the anti-human pentraxin mAb showed strong cross-reactivity with limulin; only five mAb reacted with limulin at all, and cross-reactivities of these mAb with the other pentraxins, when present, also were weak. Cross-reactivity of limulin with hCRP and hSAP was similar, and in light of comparable amino acid sequence homology, suggests this molecule can be considered the limulus SAP as well as the limulus CRP. Several anti-hCRP mAb cross-reacted strongly with rabbit CRP and rat CRP; a few anti-hSAP cross-reacted strongly with FP; and weak cross-reactions were observed between hCRP and hSAP, but cross-reactivities between the pentraxins generally were limited and weak. A rabbit polyclonal antibody raised to highly conserved limulin peptide 141-156 and strongly reactive with limulin reacted weakly with hCRP and raCRP but failed to react with rat CRP, hSAP or FP. These studies emphasize a limited but distinct antigenic similarity between limulin, hCRP and other pentraxins, and identify mAb reactive with potential regions of shared structure and/or function between pentraxins of different species.

• Schade R, Burger W, Ladhoff AM, Pfister C, Nugel E
• The rat female protein, a pentraxin with lectinic properties.
• Agents Actions. 1991; 34: 358-68
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• The C-reactive protein is the major acute phase protein (APP) in humans which binds lectin-like to different membraneous structures and exerts an important function in non-specific defense. Because of a pentameric molecular symmetry CRP as well as serum amyloid P component (SAP) and hamster female protein (FP) was merged into a special protein family named pentraxins. In rats a protein was found referred to as rat FP which was close related to hamster FP with respect to hormonal regulation and APP nature as well. Based on this conformity the molecular structure of rat FP was analyzed and as the results a pentameric structure could be demonstrated for rat FP, too. Furthermore, the response of rat CRP and FP on injection of adrenal hormones, agents being involved in acute phase reaction, was investigated. Epinephrine administration led to an increase in CRP and a decrease in FP serum concentration. Dexamethasone has the same effect in case of FP and changed the CRP concentration in a biphasic way with a maximum at about 0.01 mg/kg, a minimum at 0.6 mg/kg and a return to control values at 1.8 mg/kg. Thus, the results indicate a neuroendocrine control of CRP and FP but probably in a different way. Using FITC-labelled lectin the exposition of galactose-containing membraneous structures could be demonstrated in carbon tetrachloride-injured liver tissue in contrast to controls. These binding sites are in accordance with increased FP-binding shown by immunofluorescence histochemistry. Thus, lectin-like properties may be ascribed to rat FP comparable to CRP and SAP activity. The results are discussed with respect to findings from literature that also the acetylcholine receptor seems to have a pentameric structure.

• Du Clos TW, Mold C, Stump RF
• Identification of a polypeptide sequence that mediates nuclear localization of the acute phase protein C-reactive protein.
• J Immunol. 1990; 145: 3869-75
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• C-reactive protein (CRP) is the prototypic human acute phase serum protein. CRP binds to several nuclear Ag including chromatin, histones, and small nuclear ribonucleoproteins. Binding to sites of tissue inflammation and the nuclei of inflammatory cells has been demonstrated in vivo. We also noticed significant similarity between CRP and nucleoplasmin, a molecule with nuclear localization activity. We therefore decided to test whether CRP was capable of nuclear localization. CRP and the control protein human serum albumin were FITC-conjugated and microinjected into living VERO cells. The cells were incubated at 37 degrees C for 15 min and then examined by fluorescence microscopy. Nuclear localization of CRP but not albumin was rapid and a high nuclear to cytoplasmic ratio was seen, consistent with active nuclear transport. Incubation at reduced temperature inhibited nuclear uptake by CRP. A synthetic peptide, RKSLKK, from the CRP sequence, when coupled to FITC-albumin, also mediated nuclear localization. Nuclear localization of the related protein, serum amyloid P component, was also seen and a homologous nuclear localization signal was identified. Because CRP was previously demonstrated to inhibit RNA transcription and enhance chromatin degradation it is proposed that CRP may play a unique role in injured cells to alter processing of damaged nuclei. Biochemical, structural and sequence comparisons between the CRP/serum amyloid P component family of proteins (pentraxins) and the nucleoplasmin/B23 family of proteins showed regions of sequence homology that may be related to their shared cyclic pentameric structure.

• Whitehead AS, Rits M
• Characterization of the gene encoding mouse serum amyloid P component. Comparison with genes encoding other pentraxins.
• Biochem J. 1989; 263: 25-31
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• A CBA/J-strain mouse serum amyloid P component (SAP) genomic clone was isolated and analysed. The clone contains the entire SAP gene and specifies a primary transcript of 1065 nucleotide residues. This comprises a first exon of 206 nucleotide residues containing the mRNA 5'-untranslated region and sequence encoding the pre-SAP leader peptide and the first two amino acid residues of mature SAP separated by a single 110-base intron from a 749-nucleotide-residue second exon containing sequence encoding the bulk of the mature SAP and specifying the mRNA 3'-untranslated region. The overall organization is similar to that of the human SAP gene, and the coding region and intron sequences are highly conserved. The SAP RNA cap site was defined by primer extension analysis of polyadenylated acute-phase liver RNA. The 5'-region of the mouse SAP gene contains modified CAAT and TATA promoter elements preceded by a putative hepatocyte-nuclear-factor-1-recognition site; these structures are in a region that is highly homologous to the corresponding region of the human SAP gene. Comparisons of the mouse SAP gene structure and derived amino acid sequence with those of other mammalian pentraxins were made.

• Ohnishi S, Maeda S, Nishiguchi S, Arao T, Shimada K
• Structure of the mouse C-reactive protein gene.
• Biochem Biophys Res Commun. 1988; 156: 814-22
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• A genomic DNA clone corresponding to the mouse C-reactive protein (CRP) has been isolated and characterized. The mouse CRP gene is 1.9-kilobase pairs in length and contains a single intron of 213-base pairs which interrupts the codon for the 2nd amino acid residue of the mature CRP protein. We compared nucleotide sequences of the mouse and human CRP genes and discussed structures of possible regulatory sequences. With this characterization, the isolation and sequence analyses of a set of mouse and human pentraxin genes, i.e. CRP and serum amyloid P component genes is not complete.

• Coe JE, Ross MJ
• Hamster female protein, a pentameric oligomer capable of reassociation and hybrid formation.
• Biochemistry. 1987; 26: 704-10
• Display abstract

• Syrian hamster female protein (SFP), a serum oligomer composed of five identical subunits, was reassociated in vitro from monomer subunits. The reconstituted pentamer was genuine by morphologic, antigenic, and structural criteria. Another female protein (FP), a homologue from Armenian hamsters (AFP), also reassociated into a pentamer after dissociation with 5 M guanidine hydrochloride. These two FP's hybridized when a mixture of them was dissociated and then reassociated. Differences between the parent FP's were used to show that the recombinant pentamer contained monomer subunits from both SFP and AFP. Reassociation of both FP's was enhanced by increasing FP concentration and also by adding Ca2+ during reassembly. The two FP's differed in their reassociation profile in that SFP was especially efficient in reassembly, whereas AFP was more dependent upon Ca2+. Female protein is a homologue of C-reactive protein and amyloid P component, and all of these proteins (pentraxins) share a similar structure. The in vitro dissociation-reassociation of female protein described herein may reflect an in vivo dissociation-reassociation which is functionally important and a common metabolic feature within this family of proteins.

• Maudsley S et al.
• Identification and isolation of two pentraxins from bovine serum.
• Clin Exp Immunol. 1987; 67: 662-73
• Display abstract

• Two distinct pentraxin proteins were isolated from bovine serum by calcium-dependent affinity chromatography on high pyruvate agarose gel. One of these proteins cross-reacted specifically with certain rabbit anti-human CRP antisera and was therefore designated as bovine CRP. The other cross-reacted specifically with a sheep anti-human SAP antiserum and was therefore designated as bovine SAP. Although the mixture of these two pentraxins was not resolved by gel filtration chromatography, they were separated by solid phase absorption of the CRP with immobilized rabbit anti-human CRP antibodies. Their identity as pentraxins was confirmed by their electron microscopic appearance. Bovine CRP was composed of a single type of non-glycosylated subunit whilst bovine SAP contained two major types of glycosylated subunits and a minor polypeptide, the glycosylation of which was not determined. Serum concentrations were in the range of 5-40 mg/l and neither protein behaved as an acute phase reactant. No bovine serum protein undergoing calcium-dependent binding to phosphoryl choline or pneumococcal C-polysaccharide was obtained.

• Maudsley S, Pepys MB
• Immunochemical cross-reactions between pentraxins of different species.
• Immunology. 1987; 62: 17-22
• Display abstract

• Monospecific antisera were raised by immunization with pentraxins, C-reactive protein (CRP) or serum amyloid P component (SAP), that had been isolated from man and a number of different vertebrate species. These antisera were used to test sera or serous fluids from a range of other vertebrate species and also some invertebrates. Cross-reactions between species were comparatively rare but were seen among primates and among ruminants. There was also cross-reactivity between these two groups. Antisera to plaice pentraxins did not react with sera from higher vertebrates but did recognize antigens in sera from other flat fish. No cross-reactivity was observed between CRP and SAP either within or between species despite the known homologies of amino acid sequence and similarities of structure within the family. Several reactions occurred with sera in which either CRP or SAP had previously not been sought or in which only preliminary investigations had been performed. The proteins detected were: CRP in goat, cow, sheep, cat and lemon sole; SAP in monkey and dab. These findings significantly extend the range of species in which pentraxins are known to be present.

• Ishikawa N, Shigemoto K, Maruyama N
• The complete nucleotide and deduced amino acid sequence of mouse serum amyloid P component.
• Nucleic Acids Res. 1987; 15: 7186-7186

• Ohnishi S, Maeda S, Shimada K, Arao T
• Isolation and characterization of the complete complementary and genomic DNA sequences of human serum amyloid P component.
• J Biochem (Tokyo). 1986; 100: 849-58
• Display abstract

• Complementary and genomic DNA clones corresponding to the human serum amyloid P component (SAP) mRNA have been isolated and analyzed. The nucleotide sequences of the cDNA and the corresponding regions of the genomic SAP DNA reported here were identical, and revealed that after coding for a signal peptide of 19 amino acids and the first two amino acids of the mature SAP protein, there is one small intron of 115-base pairs (bp), followed by a nucleotide sequence coding for the remaining 202 amino acid residues. The SAP gene has an ATATAAA sequence 29-bp upstream from the cap site, but there is no CAAT box-like sequence. A possible polyadenylation signal sequence, ATTAAA, was found to be located 28-bp upstream from the polyadenylation site. A comparison of the genomic SAP DNA sequence with that of human C-reactive protein (CRP) revealed a striking overall homology which was not uniform: several highly conserved regions were bounded by non-homologous regions. This comparison provides further support for the hypothesis that SAP and CRP are products of a gene duplication event.

• Maudsley S, Hind CR, Munn EA, Buttress N, Pepys MB
• Isolation and characterization of guinea-pig serum amyloid P component.
• Immunology. 1986; 59: 317-22
• Display abstract

• A pentraxin was isolated from acute-phase guinea-pig serum by calcium-dependent affinity chromatography on agarose. It was immunochemically identical to guinea-pig amyloid P component and therefore has been called guinea-pig serum amyloid P component (SAP). Guinea-pig SAP has an apparent MW of between 265,000 and 300,000 by different techniques, and is composed of 10 noncovalently associated subunits arranged in two pentameric annular discs interacting face-to-face. It is apparently composed of two types of subunit, which run as a closely spaced doublet on reduced sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE). At least one type of subunit is glycosylated. The serum concentration was 16 +/- 4 mg/l in outbred animals, rising to 25 +/- 4 mg/l in an acute-phase response. Binding to agarose correlated with the agarose pyruvate content and was completely abolished by diazomethane treatment of the agarose, which methylates the pyruvate carboxylic moiety. Binding was also inhibited in the presence of free methyl 4,6-o-(carboxyethylidine)-beta-D-galactopyranoside. No protein resembling C-reactive protein (CRP) was obtained by calcium-dependent affinity chromatography of acute-phase guinea-pig serum on phosphorylcholine (PC)-Sepharose, and it not clear whether a counterpart of CRP exists in this species.

• Nguyen NY, Suzuki A, Boykins RA, Liu TY
• The amino acid sequence of Limulus C-reactive protein. Evidence of polymorphism.
• J Biol Chem. 1986; 261: 10456-65
• Display abstract

• The amino acid sequence, the positions of the disulfide bonds, and the site of glycosylation for the three subunits of Limulus C-reactive proteins (CRPs) 1.1, 1.4, and 3.3 have been established. The three subunits were shown to exist approximately in equimolar amount and are tightly associated. The hexagonal structure of Limulus CRP, as revealed by electron microscopic studies of Fernandez-Moran et al. (Fernandez-Moran, H., Marchalonis, J., and Edelman, G. M. (1968) J. Mol. Biol. 32, 467-469) might consist of two each of the subunits. The three subunits share an identical amino-terminal sequence of 44 residues and a carboxyl-terminal sequence from residues 206 to 218. Microheterogeneity exists to the extent of 10 to 11% for the entire protein. The positions of 6 half-cystines that form the three disulfide bonds and the site of glycosylation are constant in all subunits. Sequence analyses of peptides derived from enzymatic and chemical cleavages of affinity purified Limulus CRP indicate that subunits other than the three mentioned above exist in the hemolymph. Limulus CRP is therefore polymorphic. Topological analyses of Limulus CRPs, human CRP, rabbit CRP, human amyloid P-component, and Syrian hamster female protein indicate that the seven proteins may originate from the same ancestral gene. Using the topological data generated from the amino acid sequences of the proteins, we calculate that human and Limulus CRPs diverged about 500 million years ago. This figure is in general agreement with the evolutionary distance postulated by anthropological estimation of 400-500 million years.

• Floyd-Smith G, Whitehead AS, Colten HR, Francke U
• The human C-reactive protein gene (CRP) and serum amyloid P component gene (APCS) are located on the proximal long arm of chromosome 1.
• Immunogenetics. 1986; 24: 171-6
• Display abstract

• The genes encoding two pentraxins, C-reactive protein (CRP) and serum amyloid P component (SAP), are located on the proximal long arm of human chromosome 1. Mapping of the CRP and SAP genes between the centromere and band q32 was achieved by Southern blot analysis of DNA from a panel of human X Chinese hamster somatic cell hybrids carrying defined fragments of human chromosome 1. Both genes were localized more precisely between bands q12 and q23 by in situ hybridization to human metaphase chromosomes.

• Woo P, Korenberg JR, Whitehead AS
• Characterization of genomic and complementary DNA sequence of human C-reactive protein, and comparison with the complementary DNA sequence of serum amyloid P component.
• J Biol Chem. 1985; 260: 13384-8
• Display abstract

• Complementary and genomic DNA clones corresponding to the human C-reactive protein (CRP) mRNA and structural gene have been analyzed and compared. Nucleotide sequencing of the coding regions of both cDNA and genomic DNA revealed an additional 19 amino acid peptide not described in the published CRP amino acid sequence. The CRP gene contains a single 278 base pair intron within the codon specifying the third residue of mature CRP. The intron contains a repetitive sequence (GT)15G(GT)3 which is similar to structures capable of adopting the Z-DNA form. A comparison of CRP coding and amino acid sequences with those of serum amyloid P component revealed striking overall homology which was not uniform: a region of limited conservation is bounded by two highly conserved regions.

• Prelli F, Pras M, Frangione B
• The primary structure of human tissue amyloid P component from a patient with primary idiopathic amyloidosis.
• J Biol Chem. 1985; 260: 12895-8
• Display abstract

• The amino acid sequence of human tissue amyloid P component (AP) extracted by a modified method from the spleen of a patient with primary idiopathic amyloidosis was determined. AP is a glycoprotein composed of a pair of noncovalently bound pentameric discs with a subunit size of 23-25 kDa. Each subunit consists of 204 residues, a single disulfide bridge linking Cys 36 to Cys 95, and a carbohydrate moiety attached to Asn 32. The precursor of AP is the serum amyloid protein (SAP). The primary structure of AP presented here differs from the amino acid sequence of SAP previously reported, but is identical to the amino acid sequence of mature SAP deduced from the nucleotide sequence of complementary DNA clones. It shares 52% homology with the amended sequence of human C-reactive protein, an acute phase protein, and 68% homology with the Syrian hamster "female protein," another acute phase protein whose response is modulated by sex steroids. AP/SAP, C-reactive protein, and female protein belong to a family of plasma proteins called pentraxins and their considerable sequence homology is probably the result of gene duplication. Neither the physiological function of AP nor its possible pathological role in amyloidosis are yet known.

• Taylor JA et al.
• Amino acid sequence homology between rat and human C-reactive protein.
• Biochem J. 1984; 221: 903-6
• Display abstract

• The rat serum protein that undergoes Ca2+-dependent binding to pneumococcal C-polysaccharide and to phosphocholine residues, and that is evidently a member of the pentraxin family of proteins by virtue of its appearance under the electron microscope, has been variously designated as rat C-reactive protein (CRP) [de Beer, Baltz, Munn, Feinstein, Taylor, Bruton, Clamp & Pepys (1982) Immunology 45, 55-70], 'phosphoryl choline-binding protein' [Nagpurkar & Mookerjea (1981) J. Biol. Chem. 256, 7440-7448] and rat serum amyloid P component (SAP) [Pontet, D'Asnieres, Gache, Escaig & Engler (1981) Biochim. Biophys. Acta 671, 202-210]. The partial amino acid sequence (45 residues) towards the C-terminus of this protein was determined, and it showed 71.7% identity with the known sequence of human CRP but only 54.3% identity with human SAP. Since human CRP and SAP are themselves approximately 50% homologous, the level of identity between the rat protein and human SAP is evidence only of membership of the pentraxin family. In contrast, the much greater resemblance to human CRP confirms that the rat C-polysaccharide-binding/phosphocholine-binding protein is in fact rat CRP.

• Weinstein PS, Skinner M, Sipe JD, Lokich JJ, Zamcheck N, Cohen AS
• Acute-phase proteins or tumour markers: the role of SAA, SAP, CRP and CEA as indicators of metastasis in a broad spectrum of neoplastic diseases.
• Scand J Immunol. 1984; 19: 193-8
• Display abstract

• Two hundred and seventy-seven patients with a broad spectrum of neoplastic diseases, including 10 classes of solid tumours and three classes of haematologic malignancies, were retrospectively surveyed, and from the same sample of plasma or serum their concentrations of serum amyloid A (SAA), serum amyloid P component (SAP), C-reactive protein (CRP), and carcinoembryonic antigen (CEA) were measured. SAA levels varied from 105 ng/ml to 105,000 ng/ml, and mean SAA levels were higher in patients with metastatic tumours than in those with limited disease (P less than 0.001). Similarly, CRP levels varied from less than 8 micrograms/ml to 328 micrograms/ml and were significantly higher in the metastatic disease category. In contrast, SAP levels varied from 32 micrograms/ml to 120 micrograms/ml and showed no difference in patients with limited or metastatic disease, although an overall slight elevation was present. CEA levels were available in 150 patients and were significantly higher in patients with advanced lung or breast cancer than in patients with limited disease. The correlation between mean SAA and CRP levels was significant (r = 0.74, P less than 0.001), suggesting that SAA originates as an acute-phase protein rather than as a tumour cell product. However, the consistent elevation of SAA in all tumour types and the more marked elevation in metastatic disease may make its measurement useful in malignancy.

• Robey FA, Tanaka T, Liu TY
• Isolation and characterization of two major serum proteins from the dogfish, Mustelus canis, C-reactive protein and amyloid P component.
• J Biol Chem. 1983; 258: 3889-94
• Display abstract

• Two major serum components from the dogfish, Mustelus canis, have been isolated using affinity chromatography. Both proteins bind to an AH-Sepharose 4B-phosphorylcholine affinity matrix in the presence of Ca2+ and are eluted from the column by EDTA. Upon readdition of Ca2+ to the eluted proteins, the two proteins can be separated by passage through a column of Sepharose CL-4B. The first protein, C-reactive protein, passes through the Sepharose CL-4B column in the presence of Ca2+ whereas the second protein, serum amyloid P component, remains bound. The serum amyloid P component is then eluted from the Sepharose CL-4B in pure form by EDTA. The dogfish C-reactive protein isolated by the phosphorylcholine affinity matrix precipitates with pneumococcal C-polysaccharide and with a synthetic derivative of bovine serum albumin to which phosphorylcholine is covalently attached. The precipitation is inhibited by either EDTA or by phosphorylcholine. Dogfish C-reactive protein has a molecular weight of approximately 250,000 with dimeric subunits of Mr = 50,000. Upon addition of beta-mercaptoethanol these dimeric subunits dissociate to two identical monomeric subunits of Mr = 25,000. The protein cross-reacts immunologically with goat antisera prepared against rabbit C-reactive protein. The dogfish serum amyloid P component has a molecular weight of at least 250,000 with monomeric subunits of Mr = 25,000. Cross-reactivity of the amyloid P component with the C-reactive protein could not be shown. However, NH2-terminal sequence analysis of the first 20 amino acids showed some homology. The relationship of dogfish C-reactive protein to the C-reactive proteins in Limulus polyphemus and in rabbits and humans is discussed.

• Fiedel BA, Ku CS, Izzi JM, Gewurz H
• Selective inhibition of platelet activation by the amyloid P-component of serum.
• J Immunol. 1983; 131: 1416-9
• Display abstract

• One component of amyloid, protein AP, has a characteristic pentameric structure and is identical with a 9.5s serum alpha 1-globulin designated serum amyloid P-component or SAP. Another pentameric molecule, the acute-phase reactant C-reactive protein (CRP), shares major amino acid sequence homology with SAP although, in man, SAP is not an acute-phase reactant. Recently, we demonstrated that heat-aggregated CRP (H-CRP), like heat-aggregated IgG, activates platelets to reactions of aggregation, secretion, and generation of thromboxane A2. We report here that physiologic concentrations of SAP inhibit platelet aggregation stimulated by H-CRP. SAP must be present before platelet challenge with H-CRP to be effective. Native (unaggregated) CRP does not inhibit platelet activation induced by H-CRP, and the platelet inhibitory effect of SAP is restricted because platelet responses to each heat-aggregated IgG, acid-soluble collagen, DNA, ADP, and thrombin remain unaltered in the presence of SAP. Thus, human SAP seems to selectively modulate platelet reactivity to modified CRP, and as such to down-regulate at least one aspect of the biologic capacity of its acute-phase homologue.

• White A, Fletcher TC, Pepys MB
• Serum concentrations of C-reactive protein and serum amyloid P component in plaice (Pleuronectes platessa L.) in relation to season and injected lipopolysaccharide.
• Comp Biochem Physiol B. 1983; 74: 453-8
• Display abstract

• 1. Mean monthly serum levels of total protein, C-reactive protein (CRP) and serum amyloid P component (SAP) in plaice, showed no significant difference between the sexes. 2. Highest values for CRP and protein were found between June and September, with no significant seasonal variation in SAP. 3. There was no change in CRP concentration in plaice maintained for 7 days at a higher temperature of 18.5 degrees C. 4. Injection of lipopolysaccharide caused the highest value for CRP on day 1 and for the spleen index on day 5 after injection. 5. Phagocytic stimulation with carbon had no significant effect on the CRP response to endotoxin.

• Coe JE
• Homologs of CRP: a diverse family of proteins with similar structure.
• Contemp Top Mol Immunol. 1983; 9: 211-38

• de Beer FC et al.
• Isolation and characterization of C-reactive protein and serum amyloid P component in the rat.
• Immunology. 1982; 45: 55-70
• Display abstract

• C-reactive protein (RP) and serum amyloid P component (SAP) have been identified for the first time in rat serum and isolated by calcium-dependent affinity chromatography. Rat CRP closely resembled human CRP in its amino acid composition, in having five subunits per molecule and in its electron microscopic appearance as a pentameric annular disc. It differed, however, from all other mammalian CRP's characterised hitherto in being a glycoprotein bearing a single complex oligosaccharide on each polypeptide subunit. Furthermore one pair of tis subunits per molecule was linked by a interchain disulphide bridges whereas in other animals the subunits of both CRP and SAP are all non-covalently associated. The serum concentration of CRP in normal healthy laboratory rats and in specific pathogen-free rats was 300-600 micrograms/ml which is much greater than has been described in any other species and exceeds even maximal acute phase levels of CRP in man. Following injections of casein or croton oil, serum CRP levels rose to a maximum of about 900 micrograms/ml. Rat CRP bound to pneumococcal C-polysaccharide (CPS( but, in marked contrast to the behaviour of CRP from man, rabbit and marine teleost fish, it did not precipitate with CPS solutions, agglutinate CPS-coated sheep erythrocytes or initiate complement activation. Rat SAP, like SAP of other species, was a glycoprotein but unlike them it was composed only of a single pentameric disc not two such discs interacting face-to-face. The normal level of SAP in rat serum was 20-50 micrograms/ml, very similar to the levels seen in man, and it did not behave as an acute phase reactant in response to casein or croton-oil injections. In this respect it resembled human SAP but differed from murine SAP which is a major acute phase reactant.

• De Beer FC, Pepys MB
• Isolation of human C-reactive protein and serum amyloid P component.
• J Immunol Methods. 1982; 50: 17-31
• Display abstract

• Procedures are described for the isolation in high yield of consistent, highly purified preparations of human C-reactive protein (CRP) and serum amyloid P component (SAP). CRP was obtained from malignant ascitic and pleural fluids by calcium-dependent affinity chromatography on pneumococcal C-polysaccharide covalently coupled to cyanogen bromide-activated Sepharose. It was then gel filtered on Ultrogel AcA44 (acrylamide-agarose beads) in the presence of calcium ions, combining molecular sieve chromatography with removal of contaminating SAP by its affinity of agarose. Residual trace contaminants were removed by immunoabsorption with anti-normal human serum and anti-SAP antibodies insolubilised on Sepharose and/or by absorption with Sepharose-Con A to remove glycoproteins and Blue-Sepharose to remove albumin. After a final gel filtration step on Sephacryl S-300 35-45% of the initial CRP was recovered in pure form according to biochemical and immunochemical criteria. SAP was isolated from normal serum by calcium-dependent affinity chromatography on unsubstituted Sepharose beads, followed by solid-phase immunoabsorption of contaminants and finally gel filtration on Sephacryl S-300. At least 50% of the SAP in the starting material was recovered in pure form according to biochemical and immunochemical criteria. Ready availability of such preparations facilitates biochemical, biophysical and particularly biological studies of these plasma proteins.

• Jensson O, Bjornsson OG, Arnason A, Birgisdottir B, Pepys MB
• Serum amyloid P-component and C-reactive protein in serum of healthy Icelanders and members of an Icelandic family with macroglobulinaemia.
• Acta Med Scand. 1982; 211: 341-5
• Display abstract

• Serum levels of amyloid P-component (SAP) and C-reactive protein (CRP) were determined in 260 asymptomatic Icelanders of both sexes and various age groups and in 60 members of a family with macroglobulinaemia. In the normal group the SAP levels were normally distributed but slightly higher than in a comparable British group. Elevated levels of SAP and CRP were found in four elderly sibs of the macroglobulinaemia family. Two of them had benign monoclonal macroglobulinaemia (BMM), one had Waldenstrom's macroglobulinaemia and one increased polyclonal IgA. In addition, a notable small increase (2-20 micrograms/ml) in the levels of CRP was found in 6 children and 3 grandchildren of two elderly sibs with BMM. This increase in serum CRP levels was also found in five of six family members when investigated four years later. The HLA haplotypes present in the family members, including B7, are not closely associated with the various abnormal protein changes detected in the elderly sibs of the second generation or their descendents. Likewise, the increased levels of SAP, CRP or IgM are not associated with any particularly type of the genetic protein markers of blood group systems tested.

• Pepys MB et al.
• C-reactive protein and serum amyloid P component in the plaice (Pleuronectes platessa L.), a marine teleost, are homologous with their human counterparts.
• Biochim Biophys Acta. 1982; 704: 123-33
• Display abstract

• C-reactive protein and serum amyloid P component were isolated from serum of the plaice (Pleuronectes platessa L.), a murine teleost. The isolation was based on their calcium-dependent binding affinity for pneumococcal C-polysaccharide and for agarose, respectively. These specificities are the same as those of human C-reactive protein and serum amyloid P component, respectively, and we have previously reported that the plaice molecules resemble human C-reactive protein and serum amyloid P component in their electron microscopic appearance. We describe here estimation of the molecular weights of plaice C-reactive protein and serum amyloid P component and their subunits, and analysis of their amino acid composition, glycosylation and partial amino-terminal amino acid sequences. The results establish that plaice C-reactive protein and serum amyloid P component are homologous with each other and with their human counterparts and indicate that there has been stable conservation of this protein family throughout vertebrate evolution.

• White A, Fletcher TC
• The effects of adrenal hormones, endotoxin and turpentine on serum components of the plaice (Pleuronectes platessa L.).
• Comp Biochem Physiol C. 1982; 73: 195-200
• Display abstract

• 1. Within 24 hr of injection into plaice, cortisol, deoxycorticosterone, adrenalin or endotoxin cause an increase (P less than 0.001) in circulating C-reactive protein (CRP). Turpentine and soluble dexamethasone have no effect. 2. The increase in CRP with endotoxin is not enhanced with adrenalin or deoxycorticosterone, and in conjunction with cortisol the increase is additive. 3. Changes in CRP are independent of the amounts of serum amyloid P-component or total protein. 4. Turpentine, cortisol and adrenalin cause a rapid increase in circulating glucose. 5. It is concluded that some adrenal hormones stimulate the CRP acute phase response in plaice, without an apparent provoking agent.

• Baltz ML et al.
• Phylogenetic aspects of C-reactive protein and related proteins.
• Ann N Y Acad Sci. 1982; 389: 49-75

• Gewurz H, Mold C, Siegel J, Fiedel B
• C-reactive protein and the acute phase response.
• Adv Intern Med. 1982; 27: 345-72
• Display abstract

• Since its discovery approximately fifty years ago, CRP has been recognized as the prototype acute phase reactant. Now appreciated as a trace serum protein that elevates markedly in concentration in association with inflammation and tissue necrosis, CRP also has been found deposited at sites of cell injury. Together with its long appreciated ability to initiate precipitation, agglutination, and capsular swelling reactions, these considerations early led to the surmise that CRP may play a role in the host adaptive response. Studies of its binding specificities have indicated that CRP has reactivity with (a) phosphocholine and phosphate esters, and hence with lipids widely distributed in mammalian and microbial cells; and (b) with multiple widely distributed polycations, including those derived from leukocyte granules. Interaction with either of these ligands has been shown to alter CRP in such a way that it can bring about activation of the complement system with generation of all the known C-dependent reactivities, including component consumption, adherence, phagocytosis, and cytolysis. Similarly, modified CRP has been shown to react with the FcR or a closely related receptor of monocytes and lead to phagocytosis, to react with certain FcR-bearing lymphocytes, and to activate the platelet. Thus, CRP shares with immunoglobulins the ability to initiate multiple effector functions that have been associated with the inflammatory response, as well as to bring about primary recognition reactions. Obviously CRP-ligand reactions would be favored during intervals of acute inflammation and tissue necrosis, when larger amounts of CRP are available. Therefore, in addition to serving as a diagnostic aid for the presence of inflammatory and necrotic processes, elevated levels of CRP may well provide an important component of the nonspecific host mechanisms, particularly in the early stages following inflammatory stimuli. Inquiries into the structure and function of CRP indicated an unexpected relationship of this molecule to an amyloid-related protein. The amyloid P component shows remarkable structural similarity to CRP and also exhibits calcium-dependent reactivity with widely distributed ligands; those appreciated to date have mainly involved polysaccharides derived from fungi and natural products. While the only relationship of SAP to an immune-related effector system found to date is reactivity with altered C3, it nonetheless seems plausible that SAP, which like CRP recognizes certain microbial and altered host molecules and has the potential of activating a host effector system at the recognition site. Further inquiry into the structure and functional relationships of these molecules, which are broadly distributed through the vertebrates, should help to reveal the role that CRP and other acute phase proteins have in the body economy and provide additional insights to the understanding of body defense mechanisms in inflammatory, repair, and defense processes generally.

• Anderson JK, Mole JE
• Large scale isolation and partial primary structure of human plasma amyloid P-component.
• Ann N Y Acad Sci. 1982; 389: 216-34

• Hutchcraft CL, Gewurz H, Hansen B, Dyck RF, Pepys MB
• Agglutination of complement-coated erythrocytes by serum amyloid P-component.
• J Immunol. 1981; 126: 1217-9
• Display abstract

• Serum amyloid P-component (SAP) is a normal plasma glycoprotein apparently identical with the P-component associated with amyloid deposits. SAP shows extensive amino acid sequence homology with the C-reactive protein, and both have a similar molecular configuration. SAP undergoes calcium-dependent binding to zymosan, agarose, and amyloid fibrils, but its functional properties are not yet known. We report here that SAP agglutinates complement-(C) coated antibody-sensitized erythrocytes by a calcium-dependent reaction. SAP was found to interact predominantly with a modified form of bound C3b. This modification was achieved by prolonged treatment of EAC43 with heated normal human serum or with isolated C3bINA and beta 1H, and reactivity was reduced upon treatment of the cells with trypsin. SAP thus seems to react with fixed C3 in a manner similar to the reaction of C3 with bovine conglutinin, a molecule that also undergoes calcium-dependent binding to zymosan and agarose. These studies identify a new reactivity for SAP and demonstrate an interaction between an amyloid protein and the C system. The close similarity between the calcium-dependent binding specificities of SAP and of bovine conglutinin may assist in characterization of these molecules and in investigation of their function.

• Coe JE, Margossian SS, Slayter HS, Sogn JA
• Hamster female protein. A new Pentraxin structurally and functionally similar to C-reactive protein and amyloid P component.
• J Exp Med. 1981; 153: 977-91
• Display abstract

• Female protein (FP), a serum protein present in normal female hamsters was found to be similar to acute-phase reactant, C-reactive protein (CRP) and serum amyloid P component (SAP) in the following ways: (a) hamster FP complexed with phosphorylcholine (PC) in a Ca++-dependent fashion as shown by its isolation from serum by affinity chromatography with PC-Sepharose and selective elution with free PC or EDTA; (b) electron microscopy of FP indicated a pentameric structure similar in size and appearance to other pentraxins; (c) the parent molecule of FP (150,000 mol wt) was composed of five noncovalantly assembled subunits of 30,000 mol wt; and (d) the amino acid analysis and terminal NH2 sequence of FP clearly showed homology with SAP-CRP. Although FP evolved from an ancestral gene common to SAP and CRP, and shares functional, morphological and structural properties with these acute-phase proteins, the biological homology of FP appears quite diverse as this protein is a prominent serum constituent (1-2 mg/ml) of normal female hamsters and under hormonal control (testosterone suppression) in males.

• Uhlenbruck G, Solter J, Janssen E
• [New reaction mechanisms of C-reactive protein (CRP) and related proteins (author's transl)]
• J Clin Chem Clin Biochem. 1981; 19: 1201-8

• Levo Y, Frangione B, Franklin EC
• Amino acid sequence similarities between amyloid P component C1t and CRP.
• Nature. 1977; 268: 56-7

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