1nlr

From Proteopedia

Revision as of 14:38, 5 November 2007

ENDO-1,4-BETA-GLUCANASE CELB2, CELLULASE, NATIVE STRUCTURE

Overview

Cellulases are the glycoside hydrolases responsible for the enzymatic, breakdown of the structural plant polymer cellulose. Together with, xylanases they counteract the lmitless accumulation of plant biomass in, nature and are of considerable fundamental and biotechnological interest., Endoglucanase CelB from Streptomyces lividans performs hydrolysis of the, beta-1,4-glycosidic bonds of cellulose, with net retention of anomeric, configuration. The enzyme is a member of glycoside hydrolase family 12, [Henrissat, B., and Bairoch, A. (1996) Biochem. J. 316, 695-696], which, had previously eluded detailed structural analysis. A truncated, but, cataytically competent form of CelB, locking the flexible linker region, and cellulose-binding domain, has been constructed and overexpressed in a, S. lividans expression system. The three-dimensional X-ray structure of, the resulting catalytic domain, CelB2, has been solved by conventional, multiple isomorphous replacement methods and refined to an R factor of, 0.187 at 1.75 A resolution. The overall fold of the enzyme shows a, remarkable similarity to that of family 11 xylanases, as previously, predicted by hydrophobic clustering analysis [Torronen, A., Kubicek, C.P., and Henrissat, B. (1993) FEBS Lett. 321, 135-139]. The 23 kDa protein, presents a jelly-roll topology, built up mainly by antiparallel, beta-sheets arranged in a sandwich-like manner. A deep substrate-binding, cleft runs across the surface, as has been observed in other endoglucanase, structures, and is potentially able to accommodate up to five binding, subsites. The likely catalytic nucleophile and Bronsted acid/base, residues Glu 120 and Glue 203, respectively, have their carboxylate groups, separated by a distance of approximately 7.0 A and are located, approximately 15 A from one end of the cleft, implying a -3 to +2 active, site.

About this Structure

1NLR is a Single protein structure of sequence from Streptomyces lividans. Active as Cellulase, with EC number 3.2.1.4 Structure known Active Sites: GAB and NF. Full crystallographic information is available from OCA.

Reference

The Streptomyces lividans family 12 endoglucanase: construction of the catalytic cre, expression, and X-ray structure at 1.75 A resolution., Sulzenbacher G, Shareck F, Morosoli R, Dupont C, Davies GJ, Biochemistry. 1997 Dec 23;36(51):16032-9. PMID:9440876

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