1cem | pdb_00001cem
ENDOGLUCANASE A (CELA) CATALYTIC CORE, RESIDUES 33-395
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Overview
BACKGROUND. Cellulases, which catalyze the hydrolysis of glycosidic bonds, in cellulose, can be classified into several different protein families., Endoglucanase CelA is a member of glycosyl hydrolase family 8, a family, for which no structural information was previously available. RESULTS. The, crystal structure of CelA was determined by multiple isomorphous, replacement and refined to 1.65 A resolution. The protein folds into a, regular (alpha/alpha)6 barrel formed by six inner and six outer alpha, helices. Cello-oligosaccharides bind to an acidic cleft containing at, least five D-glucosyl-binding subsites (A-E) such that the scissile, glycosidic linkage lies between subsites C and D. The strictly conserved, residue Glu95, which occupies the center of the substrate-binding cleft, and is hydrogen bonded to the glycosidic oxygen, has been assigned the, catalytic role of proton donor. CONCLUSIONS. The present analysis provides, a basis for modeling homologous family 8 cellulases. The architecture of, the active-site cleft, presenting at least five glucosyl-binding subsites, explains why family 8 cellulases cleave cello-oligosaccharide polymers, that are at least five D-glycosyl subunits long. Furthermore, the, structure of CelA allows comparison with (alpha/alpha)6 barrel, glycosidases that are not related in sequence, suggesting a possible, albeit distant, evolutionary relationship between different families of, glycosyl hydrolases.
About this Structure
1CEM is a Single protein structure of sequence from Clostridium thermocellum. Active as Cellulase, with EC number 3.2.1.4 Full crystallographic information is available from OCA.
Reference
The crystal structure of endoglucanase CelA, a family 8 glycosyl hydrolase from Clostridium thermocellum., Alzari PM, Souchon H, Dominguez R, Structure. 1996 Mar 15;4(3):265-75. PMID:8805535
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