1eqc
From Proteopedia
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EXO-B-(1,3)-GLUCANASE FROM CANDIDA ALBICANS IN COMPLEX WITH CASTANOSPERMINE AT 1.85 A
Overview
A group of fungal exo-beta-(1,3)-glucanases, including that from the human, pathogen Candida albicans (Exg), belong to glycosyl hydrolase family 5, that also includes many bacterial cellulases (endo-beta-1, 4-glucanases)., Family members, despite wide sequence variations, share a common mechanism, and are characterised by possessing eight invariant residues making up the, active site. These include two glutamate residues acting as nucleophile, and acid/base, respectively. Exg is an abundant secreted enzyme possessing, both hydrolase and transferase activity consistent with a role in cell, wall glucan metabolism and possibly morphogenesis. The structures of Exg, in both free and inhibited forms have been determined to 1.9 A resolution., A distorted (beta/alpha)8 barrel structure accommodates an active site, which is located within a deep pocket, formed when extended loop regions, close off a cellulase-like groove. Structural analysis of a covalently, bound mechanism-based inhibitor (2-fluoroglucosylpyranoside) and of a, transition-state analogue (castanospermine) has identified the binding, interactions at the -1 glucose binding site. In particular the carboxylate, of Glu27 serves a dominant hydrogen-bonding role. Access by a 1,3-glucan, chain to the pocket in Exg can be understood in terms of a change in, conformation of the terminal glucose residue from chair to twisted boat., The geometry of the pocket is not, however, well suited for cleavage of, 1,4-glycosidic linkages. A second glucose site was identified at the, entrance to the pocket, sandwiched between two antiparallel phenylalanine, side-chains. This aromatic entrance-way must not only direct substrate, into the pocket but also may act as a clamp for an acceptor molecule, participating in the transfer reaction.
About this Structure
1EQC is a Single protein structure of sequence from Candida albicans with CTS as ligand. Active as Glucan 1,3-beta-glucosidase, with EC number 3.2.1.58 Full crystallographic information is available from OCA.
Reference
The structure of the exo-beta-(1,3)-glucanase from Candida albicans in native and bound forms: relationship between a pocket and groove in family 5 glycosyl hydrolases., Cutfield SM, Davies GJ, Murshudov G, Anderson BF, Moody PC, Sullivan PA, Cutfield JF, J Mol Biol. 1999 Dec 3;294(3):771-83. PMID:10610795
Page seeded by OCA on Tue Nov 20 14:13:40 2007
