1xbd
From Proteopedia
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INTERNAL XYLAN BINDING DOMAIN FROM CELLULOMONAS FIMI XYLANASE D, NMR, 5 STRUCTURES
Overview
BACKGROUND: Many enzymes that digest polysaccharides contain separate, polysaccharide-binding domains. Structures have been previously determined, for a number of cellulose-binding domains (CBDs) from cellulases. RESULTS:, The family IIb xylan-binding domain 1 (XBD1) from Cellulomonas fimi, xylanase D is shown to bind xylan but not cellulose. Its structure is, similar to that of the homologous family IIa CBD from C. fimi Cex, consisting of two four-stranded beta sheets that form a twisted 'beta, sandwich'. The xylan-binding site is a groove made from two tryptophan, residues that stack against the faces of the sugar rings, plus several, hydrogen-bonding polar residues. CONCLUSIONS: The biggest difference, between the family IIa and IIb domains is that in the former the, solvent-exposed tryptophan sidechains are coplanar, whereas in the latter, they are perpendicular, forming a twisted binding site. The binding sites, are therefore complementary to the secondary structures of the ligands, cellulose and xylan. XBD1 and CexCBD represent a striking example of two, proteins that have high sequence similarity but a different function.
About this Structure
1XBD is a Single protein structure of sequence from Cellulomonas fimi. Active as Endo-1,4-beta-xylanase, with EC number 3.2.1.8 Full crystallographic information is available from OCA.
Reference
A family IIb xylan-binding domain has a similar secondary structure to a homologous family IIa cellulose-binding domain but different ligand specificity., Simpson PJ, Bolam DN, Cooper A, Ciruela A, Hazlewood GP, Gilbert HJ, Williamson MP, Structure. 1999 Jul 15;7(7):853-64. PMID:10425686
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