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| {{STRUCTURE_2pbo| PDB=2pbo | SCENE= }} | | {{STRUCTURE_2pbo| PDB=2pbo | SCENE= }} |
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| '''E27Q mutant of EXO-B-(1,3)-Glucanase from Candida Albicans at 1.85 A'''
| | ===E27Q mutant of EXO-B-(1,3)-Glucanase from Candida Albicans at 1.85 A=== |
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| ==Overview==
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| 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.
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| ==About this Structure== | | ==About this Structure== |
| 2PBO is a [[Single protein]] structure of sequence from [http://en.wikipedia.org/wiki/Candida_albicans Candida albicans]. Full crystallographic information is available from [http://oca.weizmann.ac.il/oca-bin/ocashort?id=2PBO OCA]. | | 2PBO is a 1 chain structure of sequence from [http://en.wikipedia.org/wiki/Candida_albicans Candida albicans]. Full crystallographic information is available from [http://oca.weizmann.ac.il/oca-bin/ocashort?id=2PBO OCA]. |
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| ==Reference== | | ==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:[http://www.ncbi.nlm.nih.gov/pubmed/10610795 10610795]
| | <ref group="xtra">PMID:10610795</ref><references group="xtra"/> |
| [[Category: Candida albicans]] | | [[Category: Candida albicans]] |
| [[Category: Glucan 1,3-beta-glucosidase]] | | [[Category: Glucan 1,3-beta-glucosidase]] |
| [[Category: Single protein]]
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| [[Category: Cutfield, J F.]] | | [[Category: Cutfield, J F.]] |
| [[Category: Cutfield, S M.]] | | [[Category: Cutfield, S M.]] |
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| [[Category: Exo-glucanase]] | | [[Category: Exo-glucanase]] |
| [[Category: Hydrolase]] | | [[Category: Hydrolase]] |
| ''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Sun May 4 12:47:37 2008'' | | |
| | ''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Tue Feb 17 06:53:31 2009'' |
