1uy0
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CARBOHYDRATE BINDING MODULE (CBM6CM-2) FROM CELLVIBRIO MIXTUS LICHENASE 5A IN COMPLEX WITH GLC-1,3-GLC-1,4-GLC-1,3-GLC
OverviewOverview
Glycoside hydrolases that release fixed carbon from the plant cell wall, are of considerable biological and industrial importance. These hydrolases, contain non-catalytic carbohydrate binding modules (CBMs) that, by, bringing the appended catalytic domain into intimate association with its, insoluble substrate, greatly potentiate catalysis. Family 6 CBMs (CBM6), are highly unusual because they contain two distinct clefts (cleft A and, cleft B) that potentially can function as binding sites. Henshaw et al., (Henshaw, J., Bolam, D. N., Pires, V. M. R., Czjzek, M., Henrissat, B., Ferreira, L. M. A., Fontes, C. M. G. A., and Gilbert, H. J. (2003) J., Biol. Chem. 279, 21552-21559) show that CmCBM6 contains two binding sites, that display both similarities and differences in their ligand, specificity. Here we report the crystal structure of CmCBM6 in complex, with a variety of ligands that reveals the structural basis for the ligand, specificity displayed by this protein. In cleft A the two faces of the, terminal sugars of beta-linked oligosaccharides stack against Trp-92 and, Tyr-33, whereas the rest of the binding cleft is blocked by Glu-20 and, Thr-23, residues that are not present in CBM6 proteins that bind to the, internal regions of polysaccharides in cleft A. Cleft B is solvent-exposed, and, therefore, able to bind ligands because the loop, which occludes this, region in other CBM6 proteins, is much shorter and flexible (lacks a, conserved proline) in CmCBM6. Subsites 2 and 3 of cleft B accommodate, cellobiose (Glc-beta-1,4-Glc), subsite 4 will bind only to a, beta-1,3-linked glucose, whereas subsite 1 can interact with either a, beta-1,3- or beta-1,4-linked glucose. These different specificities of the, subsites explain how cleft B can accommodate beta-1,4-beta-1,3- or, beta-1,3-beta-1,4-linked gluco-configured ligands.
About this StructureAbout this Structure
1UY0 is a Single protein structure of sequence from Cellvibrio mixtus with , , and as ligands. Known structural/functional Site: . Full crystallographic information is available from OCA.
ReferenceReference
The crystal structure of the family 6 carbohydrate binding module from Cellvibrio mixtus endoglucanase 5a in complex with oligosaccharides reveals two distinct binding sites with different ligand specificities., Pires VM, Henshaw JL, Prates JA, Bolam DN, Ferreira LM, Fontes CM, Henrissat B, Planas A, Gilbert HJ, Czjzek M, J Biol Chem. 2004 May 14;279(20):21560-8. Epub 2004 Mar 8. PMID:15010454
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