title: Identification of the cellulose-binding domain of a Bacillus subtilis endoglucanase distinct from its catalytic domain.
abstract: The endoglucanase (BSC) from Bacillus subtilis IFO 3034, which shows no ability to hydrolyze microcrystalline cellulose, was found to bind to Avicel. Ninety-eight amino acids-truncation at the COOH-terminus of BSC did not abolish the carboxymethyl cellulose (CMC)-hydrolyzing ability, but removed the Avicel-binding ability. These data suggested the presence of an Avicel-binding domain at the COOH-terminus of BSC, despite its inability to hydrolyze crystalline cellulose. A mutant enzyme with Phe at the 131st His, generated by site-directed mutagenesis, had no enzymatic activity with CMC as the substrate, as predicted from hydrophobic cluster analysis, while the cellulose-binding ability of the mutant enzyme still remained. Similarly, the mutation at the 169th Glu severely affected the enzyme activity, but not the cellulose-binding ability. All these data clearly show that BSC is composed of the catalytic domain at its NH2-terminal portion and the cellulose-binding domain at its COOH-terminal portion, and that the two domains are independently functional in the absence of the other.
authors.affiliation: Department of Agricultural Chemistry, Faculty of Agriculture, University of Tokyo, Japan.
authors.forename: J S
authors.initials: JS
authors.lastname: Park
authors.forename: A
authors.initials: A
authors.lastname: Nakamura
authors.forename: S
authors.initials: S
authors.lastname: Horinouchi
authors.forename: T
authors.initials: T
authors.lastname: Beppu
mesh_terms: D001412:Bacillus subtilis / Q000201:enzymology* / Q000235:genetics; D001483:Base Sequence; D002266:Carboxymethylcellulose Sodium / Q000378:metabolism; D002384:Catalysis; D002480:Cellulase / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D002482:Cellulose / Q000378:metabolism*; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D009154:Mutation; D010957:Plasmids; D011485:Protein Binding
chemical_list: D002482:Cellulose; D002480:Cellulase; D002266:Carboxymethylcellulose Sodium