1ut9

STRUCTURAL BASIS FOR THE EXOCELLULASE ACTIVITY OF THE CELLOBIOHYDROLASE CBHA FROM C. THERMOCELLUM

spinqualitylabelsall models 1ut9, resolution 2.10Å Show:Asymmetric Unit Biological Assembly Drag the structure with the mouse to rotate   Export Animated Image   Print3D Structural highlights 1ut9 is a 1 chain structure with sequence from Clostridium thermocellum. Full crystallographic information is available from OCA. For a guided tour on the structure components use FirstGlance. Activity: Cellulase, with EC number 3.2.1.4 Resources: FirstGlance, OCA, RCSB, PDBsum Evolutionary Conservation Check, as determined by ConSurfDB. You may read the explanation of the method and the full data available from ConSurf. Publication Abstract from PubMed Numerous bacterial and fungal organisms have evolved elaborate sets of modular glycoside hydrolases and similar enzymes aimed at the degradation of polymeric carbohydrates. Presently, on the basis of sequence similarity catalytic modules of these enzymes have been classified into 90 families. Representatives of a particular family display similar fold and catalytic mechanisms. However, within families distinctions occur with regard to enzymatic properties and type of activity against carbohydrate chains. Cellobiohydrolase CbhA from Clostridium thermocellum is a large seven-modular enzyme with a catalytic module belonging to family 9. In contrast to other representatives of that family possessing only endo- and, in few cases, endo/exo-cellulase activities, CbhA is exclusively an exocellulase. The crystal structures of the combination of the immunoglobulin-like module and the catalytic module of CbhA (Ig-GH9_CbhA) and that of an inactive mutant Ig-GH9_CbhA(E795Q) in complex with cellotetraose (CTT) are reported here. The detailed analysis of these structures reveals that, while key catalytic residues and overall fold are conserved in this enzyme and those of other family 9 glycoside hydrolases, the active site of GH9_CbhA is blocked off after the -2 subsite. This feature which is created by an extension and altered conformation of a single loop region explains the inability of the active site of CbhA to accommodate a long cellulose chain and to cut it internally. This altered loop region is responsible for the exocellulolytic activity of the enzyme. Structural basis for the exocellulase activity of the cellobiohydrolase CbhA from Clostridium thermocellum.,Schubot FD, Kataeva IA, Chang J, Shah AK, Ljungdahl LG, Rose JP, Wang BC Biochemistry. 2004 Feb 10;43(5):1163-70. PMID:14756552 From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See Also Cellobiohydrolase Glucanase

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