This domain is involved in cellulose binding [(PUBMED:1490597)] and is found associated with a wide range of bacterial glycosyl hydrolases. The structure for this domain is known [(PUBMED:8918451)]; it forms a beta sandwich.
Crystal structure of a bacterial family-III cellulose-binding domain: ageneral mechanism for attachment to cellulose.
EMBO J. 1996; 15: 5739-51
Display abstract
The crystal structure of a family-III cellulose-binding domain (CBD) fromthe cellulosomal scaffoldin subunit of Clostridium thermocellum has beendetermined at 1.75 A resolution. The protein forms a nine-stranded betasandwich with a jelly roll topology and binds a calcium ion. conserved,surface-exposed residues map into two defined surfaces located on oppositesides of the molecule. One of these faces is dominated by a planar linearstrip of aromatic and polar residues which are proposed to interact withcrystalline cellulose. The other conserved residues are contained in ashallow groove, the function of which is currently unknown, and which hasnot been observed previously in other families of CBDs. On the basis ofmodeling studies combined with comparisons of recently determined NMRstructures for other CBDs, a general model for the binding of CBDs tocellulose is presented. Although the proposed binding of the CBD tocellulose is essentially a surface interaction, specific types andcombinations of amino acids appear to interact selectively with glucosemoieties positioned on three adjacent chains of the cellulose surface. Themajor interaction is characterized by the planar strip of aromaticresidues, which align along one of the chains. In addition, polar aminoacid residues are proposed to anchor the CBD molecule to two otheradjacent chains of crystalline cellulose.
Identification of the cellulose-binding domain of the cellulosome subunitS1 from Clostridium thermocellum YS.
FEMS Microbiol Lett. 1992; 78: 181-6
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The 3' region of a gene designated cipB, which shows strong homology withcipA that encodes the cellulosome SL subunit of Clostridium thermocellumATCC 27405, was isolated from a gene library of C. thermocellum strain YS.The truncated S1 protein encoded by the cipB derivative bound tightly tocellulose. The cellulose-binding domain in this polypeptide consisted of aC-terminal proximal 167 residue sequence which showed complete identitywith residues 337-503 of mature SL from C. thermocellum strain ATCC 27405.The cellulose-binding domain interacted with both crystalline andamorphous cellulose, but not with xylan.
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