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The crystal structure of a 2-fluorocellotriosyl complex of the Streptomyces lividans endoglucanase CelB2 at 1.2 angstrom resolution

TitleThe crystal structure of a 2-fluorocellotriosyl complex of the Streptomyces lividans endoglucanase CelB2 at 1.2 angstrom resolution
Publication TypeJournal Article
Year of Publication1999
AuthorsSulzenbacher, G, Mackenzie, LF, Wilson, KS, Withers, SG, Dupont, C, Davies, GJ
JournalBiochemistry
Volume38
Pagination4826-4833
Date PublishedApr
Type of ArticleArticle
ISBN Number0006-2960
KeywordsACTIVE-SITE, CELLULOMONAS-FIMI, GLYCOSYL HYDROLASES, MACROMOLECULAR STRUCTURES, MOLECULAR REPLACEMENT, PROTEIN MODELS, REFINEMENT, SEQUENCE-BASED CLASSIFICATION, TRICHODERMA-REESEI, X-ray structure
Abstract

Glycoside hydrolases have been classified into over 66 families on the basis of amino acid sequence. Recently a number of these families have been grouped into "clans" which share a common fold and catalytic mechanism [Henrissat, B., and Bairoch, A. (1996) Biochem. J, 316, 695-696]. Glycoside hydrolase Clan GH-C groups family 11 xylanases and family 12 cellulases, which share the same jellyroll topology, with two predominantly antiparallel beta-sheets forming a long substrate-binding cleft, and act with net retention of anomeric configuration. Here we present the three-dimensional structure of a family 12 endoglucanase, Streptomyces lividans CelB2, in complex with a 2-deoxy-2-fluorocellotrioside. Atomic resolution (1.2 Angstrom) data allow clear identification of two distinct species in the crystal. One is the glycosyl-enzyme intermediate, with the mechanism-based inhibitor covalently linked to the nucleophile Glu 120, and the other a complex with the reaction product, 2-deoxy-2-fluoro-beta-D-cellotriose. The active site architecture of the complex provides insight into the double-displacement mechanism of retaining glycoside hydrolases and also sheds light on the basis of the differences in specificity between family 12 cellulases and family 11 xylanases.

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