title: The 3-D structure of a zinc metallo-beta-lactamase from Bacillus cereus reveals a new type of protein fold.
abstract: The 3-D structure of Bacillus cereus (569/H/9) beta-lactamase (EC 3.5.2.6), which catalyses the hydrolysis of nearly all beta-lactams, has been solved at 2.5 A resolution by the multiple isomorphous replacement method, with density modification and phase combination, from crystals of the native protein and of a specially designed mutant (T97C). The current model includes 212 of the 227 amino acid residues, the zinc ion and 10 water molecules. The protein is folded into a beta beta sandwich with helices on each external face. To our knowledge, this fold has never been observed. An approximate internal molecular symmetry is found, with a 2-fold axis passing roughly through the zinc ion and suggesting a possible gene duplication. The active site is located at one edge of the beta beta sandwich and near the N-terminal end of a helix. The zinc ion is coordinated by three histidine residues (86, 88 and 149) and a water molecule. A sequence comparison of the relevant metallo-beta-lactamases, based on this protein structure, highlights a few well-conserved amino acid residues. The structure shows that most of these residues are in the active site. Among these, aspartic acid 90 and histidine 210 participate in a proposed catalytic mechanism for beta-lactam hydrolysis.
authors.affiliation: Institut de Biologie Structurale Jean-Pierre Ebel (CEA-CNRS), Laboratoire de Cristallographie Macromoléculaire, Grenoble, France.
authors.forename: A
authors.initials: A
authors.lastname: Carfi
authors.forename: S
authors.initials: S
authors.lastname: Pares
authors.forename: E
authors.initials: E
authors.lastname: Duée
authors.forename: M
authors.initials: M
authors.lastname: Galleni
authors.forename: C
authors.initials: C
authors.lastname: Duez
authors.forename: J M
authors.initials: JM
authors.lastname: Frère
authors.forename: O
authors.initials: O
authors.lastname: Dideberg
mesh_terms: D000595:Amino Acid Sequence; D001409:Bacillus cereus / Q000201:enzymology*; D001483:Base Sequence; D001665:Binding Sites; D018360:Crystallography, X-Ray; D008667:Metalloproteins / Q000737:chemistry* / Q000378:metabolism; D008958:Models, Molecular; D008969:Molecular Sequence Data; D017433:Protein Structure, Secondary; D015203:Reproducibility of Results; D017386:Sequence Homology, Amino Acid; D015032:Zinc / Q000737:chemistry*; D001618:beta-Lactamases / Q000737:chemistry* / Q000378:metabolism
chemical_list: D008667:Metalloproteins; D001618:beta-Lactamases; D015032:Zinc