Cau-1, a subclass B3 metallo-β-lactamase of low substrate affinity encoded by an ortholog present in the Caulobacter crescentus chromosome

Jean Denis Docquier, Fabrizio Pantanella, Francesco Giuliani, Maria Cristina Thaller, Gianfranco Amicosante, Moreno Galleni, Jean Marie Frère, Karen Bush, Gian Maria Rossolini

Research output: Contribution to journalArticle

Abstract

The sequenced chromosome of Caulobacter crescentus CB15 encodes a hypothetical protein that exhibits significant similarity (30 to 35% identical residues) to metallo-β-lactamases of subclass B3. An allelic variant of this gene (divergent by 3% of its nucleotides) was cloned in Escherichia coli from C. crescentus type strain DSM4727. Expression studies confirmed the metallo-β-lactamase activity of its product, CAU-1. The enzyme produced in E. coli was purified by two ion-exchange chromatography steps. CAU-1 contains a 29.kDa polypeptide with an alkaline isoelectric pH (> 9), and unlike the L1 enzyme of Stenotrophomonas maltophilia, the native form is monomeric. Kinetic analysis revealed a preferential activity toward penicillins, carbapenems, and narrow-spectrum cephalosporins, while oxyimino cephalosporins were poorly or not hydrolyzed. Affinities for the various β-lactams were poor overall (Km values were always > 100 μM and often > 400 μM). The interaction with divalent ion chelators appeared to occur by a mechanism similar to that prevailing in other members of subclass B3. In C. crescentus, the CAU-1 enzyme is produced independently of β-lactam exposure and, interestingly, the blaCAU determinant is bracketed by three other genes, including two genes encoding enzymes involved in methionine biosynthesis and a gene encoding a putative transcriptional regulator, in an operon-like structure. The CAU-1 enzyme is the first example of a metallo-β-lactamase in a member of the α subdivision of the class Proteobacteria.

Original languageEnglish
Pages (from-to)1823-1830
Number of pages8
JournalAntimicrobial Agents and Chemotherapy
Volume46
Issue number6
DOIs
Publication statusPublished - 2002

ASJC Scopus subject areas

  • Pharmacology (medical)

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    Docquier, J. D., Pantanella, F., Giuliani, F., Thaller, M. C., Amicosante, G., Galleni, M., Frère, J. M., Bush, K., & Rossolini, G. M. (2002). Cau-1, a subclass B3 metallo-β-lactamase of low substrate affinity encoded by an ortholog present in the Caulobacter crescentus chromosome. Antimicrobial Agents and Chemotherapy, 46(6), 1823-1830. https://doi.org/10.1128/AAC.46.6.1823-1830.2002