1z3t
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Structure of Phanerochaete chrysosporium cellobiohydrolase Cel7D (CBH58) in complex with cellobiose
OverviewOverview
The cellobiohydrolase Pc_Cel7D is the major cellulase produced by the, white-rot fungus Phanerochaete chrysosporium, constituting approximately, 10% of the total secreted protein in liquid culture on cellulose. The, enzyme is classified into family 7 of the glycoside hydrolases and, like, other family members, catalyses cellulose hydrolysis with net retention of, the anomeric carbon configuration. Previous work described the apo, structure of the enzyme. Here we investigate the binding of the product, cellobiose, and several inhibitors, i.e. lactose, cellobioimidazole, Tris/HCl, calcium and a thio-linked substrate analogue, methyl, 4-S-beta-cellobiosyl-4-thio-beta-cellobioside (GG-S-GG). The three, disaccharides bind in the glucosyl-binding subsites +1 and +2, close to, the exit of the cellulose-binding tunnel/cleft. Pc_Cel7D binds to lactose, more strongly than cellobiose, while the opposite is true for the, homologous Trichoderma reesei cellobiohydrolase Tr_Cel7A. Although both, sugars bind Pc_Cel7D in a similar fashion, the different preferences can, be explained by varying interactions with nearby loops. Cellobioimidazole, is bound at a slightly different position, displaced approximately 2 A, toward the catalytic centre. Thus the Pc_Cel7D complexes provide evidence, for two binding modes of the reducing-end cellobiosyl moiety; this, conclusion is confirmed by comparison with other available structures. The, combined results suggest that hydrolysis of the glycosyl-enzyme, intermediate may not require the prior release of the cellobiose product, from the enzyme. Further, the structure obtained in the presence of both, GG-S-GG and cellobiose revealed electron density for Tris at the catalytic, centre. Inhibition experiments confirm that both Tris and calcium are, effective inhibitors at the conditions used for crystallization.
About this StructureAbout this Structure
1Z3T is a Single protein structure of sequence from Phanerochaete chrysosporium with CBI and NAG as ligands. Active as Cellulose 1,4-beta-cellobiosidase, with EC number 3.2.1.91 Full crystallographic information is available from OCA.
ReferenceReference
Structures of Phanerochaete chrysosporium Cel7D in complex with product and inhibitors., Ubhayasekera W, Munoz IG, Vasella A, Stahlberg J, Mowbray SL, FEBS J. 2005 Apr;272(8):1952-64. PMID:15819888
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