title: Crystal structure of beta-amylase from Bacillus cereus var. mycoides at 2.2 A resolution.
abstract: The crystal structure of beta-amylase from Bacillus cereus var. mycoides was determined by the multiple isomorphous replacement method. The structure was refined to a final R-factor of 0.186 for 102,807 independent reflections with F/sigma(F) > or = 2.0 at 2.2 A resolution with root-mean-square deviations from ideality in bond lengths, and bond angles of 0.014 A and 3.00 degrees, respectively. The asymmetric unit comprises four molecules exhibiting a dimer-of-dimers structure. The enzyme, however, acts as a monomer in solution. The beta-amylase molecule folds into three domains; the first one is the N-terminal catalytic domain with a (beta/alpha)8 barrel, the second one is the excursion part from the first one, and the third one is the C-terminal domain with two almost anti-parallel beta-sheets. The active site cleft, including two putative catalytic residues (Glu172 and Glu367), is located on the carboxyl side of the central beta-sheet in the (beta/alpha)8 barrel, as in most amylases. The active site structure of the enzyme resembles that of soybean beta-amylase with slight differences. One calcium ion is bound per molecule far from the active site. The C-terminal domain has a fold similar to the raw starch binding domains of cyclodextrin glycosyltransferase and glucoamylase.
authors.affiliation: Laboratory of Enzyme Chemistry, College of Agriculture, University of Osaka Prefecture, Sakai, Osaka, 599-8531, Japan. chicago@biochem. osakafu-u.ac.jp
authors.forename: T
authors.initials: T
authors.lastname: Oyama
authors.forename: M
authors.initials: M
authors.lastname: Kusunoki
authors.forename: Y
authors.initials: Y
authors.lastname: Kishimoto
authors.forename: Y
authors.initials: Y
authors.lastname: Takasaki
authors.forename: Y
authors.initials: Y
authors.lastname: Nitta
mesh_terms: D000595:Amino Acid Sequence; D001409:Bacillus cereus / Q000201:enzymology* / Q000235:genetics; D001665:Binding Sites; D002118:Calcium / Q000378:metabolism; D020134:Catalytic Domain; D018360:Crystallography, X-Ray; D019281:Dimerization; D004563:Electrochemistry; D008958:Models, Molecular; D008969:Molecular Sequence Data; D017510:Protein Folding; D020836:Protein Structure, Quaternary; D017433:Protein Structure, Secondary; D017386:Sequence Homology, Amino Acid; D013025:Glycine max / Q000201:enzymology / Q000235:genetics; D001614:beta-Amylase / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism
chemical_list: D001614:beta-Amylase; D002118:Calcium