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2exo

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{{STRUCTURE_2exo| PDB=2exo | SCENE= }}
{{STRUCTURE_2exo| PDB=2exo | SCENE= }}
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'''CRYSTAL STRUCTURE OF THE CATALYTIC DOMAIN OF THE BETA-1,4-GLYCANASE CEX FROM CELLULOMONAS FIMI'''
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===CRYSTAL STRUCTURE OF THE CATALYTIC DOMAIN OF THE BETA-1,4-GLYCANASE CEX FROM CELLULOMONAS FIMI===
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==Overview==
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beta-1,4-Glycanases, principally cellulases and xylanases, are responsible for the hydrolysis of plant biomass. The bifunctional beta-1,4-xylanase/glucanase Cex from the bacterium Cellulomonas fimi, one of a large family of cellulases/xylanases, depolymerizes oligosaccharides and releases a disaccharide unit from the substrate nonreducing end. Hydrolysis occurs with net retention of the anomeric configuration of the sugar through a double-displacement mechanism involving a covalent glycosyl-enzyme intermediate. The active site nucleophile, Glu233, has been unambiguously identified by trapping of such an intermediate [Tull et al. (1991) J. Biol. Chem. 266, 15621-15625] and the acid/base catalyst, Glu127, by detailed kinetic analysis of mutants [MacLeod et al. (1994) Biochemistry 33, 6371-6376]. However, little is known about the enzyme's overall folding and its active site architecture. We report here the high-resolution crystal structure of the catalytic domain of Cex. The atomic structure refinement results in a model that includes 2400 protein atoms and 45 water molecules, with an R-factor of 0.217 for data extending to 1.8-A resolution. The protein forms an eight-parallel-stranded alpha/beta-barrel, which is a novel folding pattern for a microbial beta-glycanase. The active site, inferred from the location of Glu233, Glu127, and other conserved residues, is an open cleft on the carboxy-terminal end of the alpha/beta-barrel. An extensive hydrogen-bonding network stabilizes the ionization states of the key residues; in particular, the Asp235-His205-Glu233 hydrogen-bonding network may play a role in modulating the ionization state of Glu233 and in controlling local charge balance during the reaction.
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{{ABSTRACT_PUBMED_7918478}}
==About this Structure==
==About this Structure==
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[[Category: White, A.]]
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[[Category: Withers, S G.]]
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''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Sun Jul 27 12:28:44 2008''

Revision as of 09:28, 27 July 2008

Image:2exo.png

Template:STRUCTURE 2exo

CRYSTAL STRUCTURE OF THE CATALYTIC DOMAIN OF THE BETA-1,4-GLYCANASE CEX FROM CELLULOMONAS FIMI

Template:ABSTRACT PUBMED 7918478

About this Structure

2EXO is a Single protein structure of sequence from Cellulomonas fimi. Full crystallographic information is available from OCA.

Reference

Crystal structure of the catalytic domain of the beta-1,4-glycanase cex from Cellulomonas fimi., White A, Withers SG, Gilkes NR, Rose DR, Biochemistry. 1994 Oct 25;33(42):12546-52. PMID:7918478

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