title: A novel metallo-beta-lactamase, Mbl1b, produced by the environmental bacterium Caulobacter crescentus.
abstract: Caulobacter crescentus 101123 possesses a gene (Mbl1b) encoding a metallo-beta-lactamase with 32% amino acid identity to the L1 metallo-beta-lactamase from Stenotrophomonas maltophilia. The gene was cloned into an expression vector and the enzyme, Mbl1b, was expressed in Escherichia coli. Mbl1b was purified. Catalytic properties for several antibiotics were determined. The enzyme exhibits Michaelis-Menten kinetics for imipenem, meropenem and nitrocefin but substrate inhibition kinetics with cefoxitin, cefaloridine, penicillin G and ampicillin. A homology model predicts Mbl1b has the same structural fold as other metallo-beta-lactamases with a detailed structure very similar to L1 but whereas L1 is a homotetramer, Mbl1b is monomeric. The main differences between Mbl1 and L1 are in the N-terminal region.
authors.affiliation: Department of Pathology and Microbiology, University of Bristol, University Walk, UK. a.m.simm@bristol.ac.uk
authors.forename: A M
authors.initials: AM
authors.lastname: Simm
authors.forename: C S
authors.initials: CS
authors.lastname: Higgins
authors.forename: S T
authors.initials: ST
authors.lastname: Pullan
authors.forename: M B
authors.initials: MB
authors.lastname: Avison
authors.forename: P
authors.initials: P
authors.lastname: Niumsup
authors.forename: O
authors.initials: O
authors.lastname: Erdozain
authors.forename: P M
authors.initials: PM
authors.lastname: Bennett
authors.forename: T R
authors.initials: TR
authors.lastname: Walsh
mesh_terms: D000595:Amino Acid Sequence; D001665:Binding Sites; D016935:Caulobacter crescentus / Q000201:enzymology*; D003001:Cloning, Molecular; D007700:Kinetics; D008958:Models, Molecular; D008969:Molecular Sequence Data; D011487:Protein Conformation; D017386:Sequence Homology, Amino Acid; D013379:Substrate Specificity; D015032:Zinc / Q000378:metabolism; D001618:beta-Lactamases / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*
chemical_list: D001618:beta-Lactamases; D015032:Zinc