2bvd

HOW FAMILY 26 GLYCOSIDE HYDROLASES ORCHESTRATE CATALYSIS ON DIFFERENT POLYSACCHARIDES. STRUCTURE AND ACTIVITY OF A CLOSTRIDIUM THERMOCELLUM LICHENASE, CtLIC26A

spinqualitylabelsall models 2bvd, resolution 1.60Å Show:Asymmetric Unit Biological Assembly Drag the structure with the mouse to rotate   Export Animated Image   Print3D Structural highlights 2bvd is a 1 chain structure with sequence from Acetivibrio thermocellus. Full crystallographic information is available from OCA. For a guided tour on the structure components use FirstGlance. Method: X-ray diffraction, Resolution 1.6Å Ligands: ISX Resources: FirstGlance, OCA, PDBe, RCSB, PDBsum, ProSAT Function GUNH_ACET2 This enzyme catalyzes the endohydrolysis of 1,4-beta-glucosidic linkages in cellulose, lichenin and cereal beta-D-glucans. Evolutionary Conservation Check, as determined by ConSurfDB. You may read the explanation of the method and the full data available from ConSurf. Publication Abstract from PubMed One of the most intriguing features of the 90 glycoside hydrolase families (GHs) is the range of specificities displayed by different members of the same family, whereas the catalytic apparatus and mechanism are often invariant. Family GH26 predominantly comprises beta-1,4 mannanases; however, a bifunctional Clostridium thermocellum GH26 member (hereafter CtLic26A) displays a markedly different specificity. We show that CtLic26A is a lichenase, specific for mixed (Glcbeta1,4Glcbeta1,4Glcbeta1,3)n oligo- and polysaccharides, and displays no activity on manno-configured substrates or beta-1,4-linked homopolymers of glucose or xylose. The three-dimensional structure of the native form of CtLic26A has been solved at 1.50-A resolution, revealing a characteristic (beta/alpha)8 barrel with Glu-109 and Glu-222 acting as the catalytic acid/base and nucleophile in a double-displacement mechanism. The complex with the competitive inhibitor, Glc-beta-1,3-isofagomine (Ki 1 microm), at 1.60 A sheds light on substrate recognition in the -2 and -1 subsites and illuminates why the enzyme is specific for lichenan-based substrates. Hydrolysis of beta-mannosides by GH26 members is thought to proceed through transition states in the B2,5 (boat) conformation in which structural distinction of glucosides versus mannosides reflects not the configuration at C2 but the recognition of the pseudoaxial O3 of the B2,5 conformation. We suggest a different conformational itinerary for the GH26 enzymes active on gluco-configured substrates. How family 26 glycoside hydrolases orchestrate catalysis on different polysaccharides: structure and activity of a Clostridium thermocellum lichenase, CtLic26A.,Taylor EJ, Goyal A, Guerreiro CI, Prates JA, Money VA, Ferry N, Morland C, Planas A, Macdonald JA, Stick RV, Gilbert HJ, Fontes CM, Davies GJ J Biol Chem. 2005 Sep 23;280(38):32761-7. Epub 2005 Jun 28. PMID:15987675 From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See Also Glucanase 3D structures

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