ANATOAnaphylatoxin homologous domain
|SMART accession number:||SM00104|
|Description:||C3a, C4a and C5a anaphylatoxins are protein fragments generated enzymatically in serum during activation of complement molecules C3, C4, and C5. They induce smooth muscle contraction. These fragments are homologous to a three-fold repeat in fibulins.|
|Interpro abstract (IPR000020):|
Complement components C3, C4 and C5 are large glycoproteins that have important functions in the immune response and host defence [(PUBMED:1431125)]. They have a wide variety of biological activities and are proteolytically activated by cleavage at a specific site, forming a- and b-fragments [(PUBMED:2777798)]. A-fragments form distinct structural domains of approximately 76 amino acids, coded for by a single exon within the complement protein gene. The C3a, C4a and C5a components are referred to as anaphylatoxins [(PUBMED:2777798), (PUBMED:3081348)]: they cause smooth muscle contraction, histamine release from mast cells, and enhanced vascular permeability [(PUBMED:3081348)]. They also mediate chemotaxis, inflammation, and generation of cytotoxic oxygen radicals [(PUBMED:3081348)]. The proteins are highly hydrophilic, with a mainly alpha-helical structure held together by 3 disulphide bridges [(PUBMED:3081348)].
Fibulins are secreted glycoproteins that become incorporated into a fibrillar extracellular matrix when expressed by cultured cells or added exogenously to cell monolayers [(PUBMED:2269669), (PUBMED:12778127)]. The five known members of the family share an elongated structure and many calcium-binding sites, owing to the presence of tandem arrays of epidermal growth factor-like domains. They have overlapping binding sites for several basement-membrane proteins, tropoelastin, fibrillin, fibronectin and proteoglycans, and they participate in diverse supramolecular structures. The amino-terminal domain I of fibulin consists of three anaphylatoxin-like (AT) modules, each approximately 40 residues long and containing four or six cysteines. The structure of an AT module was determined for the complement-derived anaphylatoxin C3a, and was found to be a compact alpha-helical fold that is stabilised by three disulphide bridges in the pattern Cys1-4, Cys2-5 and Cys3-6 (where Cys is cysteine). The bulk of the remaining portion of the fibulin molecule is a series of nine EGF-like repeats [(PUBMED:8245130)].
|GO component:||extracellular region (GO:0005576)|
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