2bvd: Difference between revisions

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[[Image:2bvd.gif|left|200px]]
{{Seed}}
[[Image:2bvd.png|left|200px]]


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{{STRUCTURE_2bvd|  PDB=2bvd  |  SCENE=  }}  
{{STRUCTURE_2bvd|  PDB=2bvd  |  SCENE=  }}  


'''HOW FAMILY 26 GLYCOSIDE HYDROLASES ORCHESTRATE CATALYSIS ON DIFFERENT POLYSACCHARIDES. STRUCTURE AND ACTIVITY OF A CLOSTRIDIUM THERMOCELLUM LICHENASE, CTLIC26A'''
===HOW FAMILY 26 GLYCOSIDE HYDROLASES ORCHESTRATE CATALYSIS ON DIFFERENT POLYSACCHARIDES. STRUCTURE AND ACTIVITY OF A CLOSTRIDIUM THERMOCELLUM LICHENASE, CTLIC26A===




==Overview==
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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.
The line below this paragraph, {{ABSTRACT_PUBMED_15987675}}, adds the Publication Abstract to the page
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{{ABSTRACT_PUBMED_15987675}}


==About this Structure==
==About this Structure==
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[[Category: Taylor, E J.]]
[[Category: Taylor, E J.]]
[[Category: Lichenase,beta-1 4 beta-1 3 glucanase,glycoside hydrolase family 26]]
[[Category: Lichenase,beta-1 4 beta-1 3 glucanase,glycoside hydrolase family 26]]
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Revision as of 05:13, 28 July 2008

File:2bvd.png

Template:STRUCTURE 2bvd

HOW FAMILY 26 GLYCOSIDE HYDROLASES ORCHESTRATE CATALYSIS ON DIFFERENT POLYSACCHARIDES. STRUCTURE AND ACTIVITY OF A CLOSTRIDIUM THERMOCELLUM LICHENASE, CTLIC26A

Template:ABSTRACT PUBMED 15987675

About this Structure

2BVD is a Single protein structure of sequence from Clostridium thermocellum. Full crystallographic information is available from OCA.

Reference

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

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