The 3-D structure of a zinc metallo-beta-lactamase from Bacillus cereus reveals a new type of protein fold.
Carfi, A., Pares, S., Duee, E., Galleni, M., Duez, C., Frere, J.M., Dideberg, O.(1995) EMBO J 14: 4914-4921
- PubMed: 7588620 
- DOI: https://doi.org/10.1002/j.1460-2075.1995.tb00174.x
- Primary Citation of Related Structures:  
1BMC - PubMed 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.
Organizational Affiliation: 
Institut de Biologie Structurale Jean-Pierre Ebel (CEA-CNRS), Laboratoire de Cristallographie Macromoléculaire, Grenoble, France.