title: Structures of exoglucanase from Clostridium cellulovorans: cellotetraose binding and cleavage.
abstract: Exoglucanase/cellobiohydrolase (EC 3.2.1.176) hydrolyzes a β-1,4-glycosidic bond from the reducing end of cellulose and releases cellobiose as the major product. Three complex crystal structures of the glycosyl hydrolase 48 (GH48) cellobiohydrolase S (ExgS) from Clostridium cellulovorans with cellobiose, cellotetraose and triethylene glycol molecules were solved. The product cellobiose occupies subsites +1 and +2 in the open active-site cleft of the enzyme-cellotetraose complex structure, indicating an enzymatic hydrolysis function. Moreover, three triethylene glycol molecules and one pentaethylene glycol molecule are located at active-site subsites -2 to -6 in the structure of the ExgS-triethylene glycol complex shown here. Modelling of glucose into subsite -1 in the active site of the ExgS-cellobiose structure revealed that Glu50 acts as a proton donor and Asp222 plays a nucleophilic role.
authors.affiliation: Molecular Science and Engineering, National Taipei University of Technology, 1, Section 3, Chung-Hsiao E. Road, Taipei 10608, Taiwan.
authors.forename: Li Chu
authors.initials: LC
authors.lastname: Tsai
authors.affiliation: Institute of Biological Chemistry, Academia Sinica, 128 Academia Road, Section 2, Taipei 11529, Taiwan.
authors.forename: Imamaddin
authors.initials: I
authors.lastname: Amiraslanov
authors.affiliation: Molecular Science and Engineering, National Taipei University of Technology, 1, Section 3, Chung-Hsiao E. Road, Taipei 10608, Taiwan.
authors.forename: Hung Ren
authors.initials: HR
authors.lastname: Chen
authors.affiliation: Institute of Biological Chemistry, Academia Sinica, 128 Academia Road, Section 2, Taipei 11529, Taiwan.
authors.forename: Yun Wen
authors.initials: YW
authors.lastname: Chen
authors.affiliation: Institute of Molecular Biology, Academia Sinica, 128 Academia Road, Section 2, Taipei 11529, Taiwan.
authors.forename: Hsiao Lin
authors.initials: HL
authors.lastname: Lee
authors.affiliation: Institute of Molecular Biology, Academia Sinica, 128 Academia Road, Section 2, Taipei 11529, Taiwan.
authors.forename: Po Huang
authors.initials: PH
authors.lastname: Liang
authors.affiliation: Institute of Biological Chemistry, Academia Sinica, 128 Academia Road, Section 2, Taipei 11529, Taiwan.
authors.forename: Yen Chywan
authors.initials: YC
authors.lastname: Liaw
mesh_terms: D055162:Biocatalysis; D002118:Calcium / Q000378:metabolism; D020134:Catalytic Domain; D044602:Cellulases / Q000737:chemistry* / Q000378:metabolism*; D002482:Cellulose / Q000031:analogs & derivatives* / Q000737:chemistry / Q000378:metabolism; D046974:Clostridium cellulovorans / Q000201:enzymology*; D003460:Crystallization; D018360:Crystallography, X-Ray; D062105:Molecular Docking Simulation; D017433:Protein Structure, Secondary; D013780:Tetroses / Q000737:chemistry / Q000378:metabolism*
chemical_list: D013780:Tetroses; C048468:cellotetraose; D002482:Cellulose; D044602:Cellulases; D002118:Calcium
keywords: (α/α)6 fold; Clostridium cellulovorans; GH48 exoglucanase; glycoside hydrolase; oligosaccharide binding and cleavage; reducing end of cellulose; β-1,4-glycosidic bonds