4b4f

Thermobifida fusca Cel6B(E3) co-crystallized with cellobiose

spinqualitylabelsall models 4b4f, resolution 2.20Å Show:Asymmetric Unit Biological Assembly Drag the structure with the mouse to rotate   Export Animated Image   Print3D Structural highlights 4b4f is a 2 chain structure with sequence from Thermobifida fusca. Full crystallographic information is available from OCA. For a guided tour on the structure components use FirstGlance. Method: X-ray diffraction, Resolution 2.2Å Ligands: BGC, CA, PRD_900011, PRD_900020 Resources: FirstGlance, OCA, PDBe, RCSB, PDBsum, ProSAT Function Q60029_THEFU Publication Abstract from PubMed Cellulases, glycoside hydrolases that catalyze the degradation of cellulose, are classified as either endoglucanases or cellobiohydrolases (CBHs) based on their architecture and mode of action on the cellulose. CBHs bind the cellulose chain in a more or less closed tunnel and cleave off cellobiose units processively from one end of the cellulosic polymer, while endoglucanases have their active sites in a more or less open cleft and show a higher tendency to cut bonds internally in the polymer. The CBH Cel6A (also called CBH2) from the ascomycete Hypocrea jecorina has a much shorter substrate-binding tunnel and seems less processive than the CBH Cel7A (CBH1), from the same fungus. Here, we present the X-ray crystal structure of the catalytic domain of the CBH Cel6B, also called E3, from the soil bacterium Thermobifida fusca, both in its apo form and co-crystallized with cellobiose. The enzyme structure reveals that the Cel6B enzyme has a much longer substrate-binding site than its fungal GH6 counterparts. The tunnel is comparable in length to that of GH7 CBHs. In the ligand structure with cellobiose, the tunnel exit is completely closed by a 13-residue loop not present in fungal GH6 enzymes. The loop needs to be displaced to allow cellobiose product release for a processive action by the enzyme. When ligand is absent, seven of these residues are not visible in the electron density and the tunnel exit is open. The Structure of a Bacterial Cellobiohydrolase: The Catalytic Core of the Thermobifida fusca Family GH6 Cellobiohydrolase Cel6B.,Sandgren M, Wu M, Karkehabadi S, Mitchinson C, Kelemen BR, Larenas EA, Stahlberg J, Hansson H J Mol Biol. 2013 Feb 8;425(3):622-35. doi: 10.1016/j.jmb.2012.11.039. Epub 2012, Dec 5. PMID:23220193 From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.

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