3k4z | pdb_00003k4z

Crystal Structure of the Cellulosomal CBM4 from Clostridium thermocellum Cellulase CbhA

spinqualitylabelsall models 3k4z, resolution 2.11Å Show:Asymmetric Unit Biological Assembly Drag the structure with the mouse to rotate   Export Animated Image   Print3D Structural highlights 3k4z is a 1 chain structure with sequence from Acetivibrio thermocellus JW20. Full crystallographic information is available from OCA. For a guided tour on the structure components use FirstGlance. Method: X-ray diffraction, Resolution 2.11Å Ligands: BGC, MG, NI, OXL, PRD_900005, XGP Resources: FirstGlance, OCA, PDBe, RCSB, PDBsum, ProSAT 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 The crystal structure of the carbohydrate-binding module (CBM) 4 Ig fused domain from the cellulosomal cellulase cellobiohydrolase A (CbhA) of Clostridium thermocellum was solved in complex with cellobiose at 2.11 A resolution. This is the first cellulosomal CBM4 crystal structure reported to date. It is similar to the previously solved noncellulosomal soluble oligosaccharide-binding CBM4 structures. However, this new structure possesses a significant feature-a binding site peptide loop with a tryptophan (Trp118) residing midway in the loop. Based on sequence alignment, this structural feature might be common to all cellulosomal clostridial CBM4 modules. Our results indicate that C. thermocellum CbhA CBM4 also has an extended binding pocket that can optimally bind to cellodextrins containing five or more sugar units. Molecular dynamics simulations and experimental binding studies with the Trp118Ala mutant suggest that Trp118 contributes to the binding and, possibly, the orientation of the module to soluble cellodextrins. Furthermore, the binding cleft aromatic residues Trp68 and Tyr110 play a crucial role in binding to bacterial microcrystalline cellulose (BMCC), amorphous cellulose, and soluble oligodextrins. Binding to BMCC is in disagreement with the structural features of the binding pocket, which does not support binding to the flat surface of crystalline cellulose, suggesting that CBM4 binds the amorphous part or the cellulose "whiskers" of BMCC. We propose that clostridial CBM4s have possibly evolved to bind the free-chain ends of crystalline cellulose in addition to their ability to bind soluble cellodextrins. The unique binding mode of cellulosomal CBM4 from Clostridium thermocellum cellobiohydrolase A.,Alahuhta M, Xu Q, Bomble YJ, Brunecky R, Adney WS, Ding SY, Himmel ME, Lunin VV J Mol Biol. 2010 Sep 17;402(2):374-87. Epub 2010 Jul 21. PMID:20654622 From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.

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