title: The crystal structure of beta-glucosidase from Bacillus circulans sp. alkalophilus: ability to form long polymeric assemblies.
abstract: Family 1 of glycosyl hydrolases is a large and biologically important group of enzymes. A new three-dimensional structure of this family, beta-glucosidase from Bacillus circulans sp. alkalophilus is reported here. This is the first structure of beta-glucosidase from an alkaliphilic organism. The model was determined by the molecular replacement method and refined to a resolution of 2.7 A. The quaternary structure of B. circulans sp. alkalophilus beta-glucosidase is an octamer and subunits of the octamer show a similar (beta/alpha)(8) barrel fold to that previously reported for other family 1 enzymes. The crystal structure suggested that Cys169 in the active site is substituted. The Cys169 is located near the putative acid/base catalyst Glu166 and it may contribute to the high pH optimum of the enzyme. The crystal structure also revealed that the asymmetric unit contains two octamers which have a clear binding interaction with each other. The ability of the octamers to link with each other suggested that beta-glucosidase from Bacillus circulans sp. alkalophilus is able to form long polymeric assemblies, at least in the crystalline state.
authors.affiliation: Department of Chemistry, University of Joensuu, Joensuu, 80101, Finland.
authors.forename: N
authors.initials: N
authors.lastname: Hakulinen
authors.forename: S
authors.initials: S
authors.lastname: Paavilainen
authors.forename: T
authors.initials: T
authors.lastname: Korpela
authors.forename: J
authors.initials: J
authors.lastname: Rouvinen
mesh_terms: D000595:Amino Acid Sequence; D001407:Bacillus / Q000201:enzymology*; D001426:Bacterial Proteins / Q000737:chemistry*; D001665:Binding Sites; D001704:Biopolymers; D003460:Crystallization; D018360:Crystallography, X-Ray; D008958:Models, Molecular; D008969:Molecular Sequence Data; D011487:Protein Conformation; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid; D001617:beta-Glucosidase / Q000737:chemistry*
chemical_list: D001426:Bacterial Proteins; D001704:Biopolymers; D001617:beta-Glucosidase