The 3-D structure of a zinc metallo-beta-lactamase from Bacillus cereus reveals a new type of protein fold

EMBO J. 1995 Oct 16;14(20):4914-21.

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.

Publication types

  • Comparative Study
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Acid Sequence
  • Bacillus cereus / enzymology*
  • Base Sequence
  • Binding Sites
  • Crystallography, X-Ray
  • Metalloproteins / chemistry*
  • Metalloproteins / metabolism
  • Models, Molecular
  • Molecular Sequence Data
  • Protein Structure, Secondary*
  • Reproducibility of Results
  • Sequence Homology, Amino Acid
  • Zinc / chemistry*
  • beta-Lactamases / chemistry*
  • beta-Lactamases / metabolism

Substances

  • Metalloproteins
  • beta-Lactamases
  • Zinc