title: Clinical inhibitor-resistant mutants of the beta-lactamase TEM-1 at amino-acid position 69. Kinetic analysis and molecular modelling.
abstract: The kinetic parameters of three IRT (Inhibitor-Resistant-TEM-derived-) beta-lactamases (IRT-5, IRT-6 and IRT-I69) were determined for substrates and the beta-lactamase inhibitors: clavulanic acid, sulbactam and tazobactam, and compared with those of TEM-1 beta-lactamase. The catalytic behaviour of the beta-lactamases towards substrates and inhibitors was correlated with the properties of the amino acid at position ABL69. The three IRT beta-lactamases contain at that position a residue Ile, Leu and Val, amino acids whose side-chain are branched. Molecular modelling shows that the methyl groups of Ile-69 (C gamma 2) and Val-69 (C gamma 1) produced steric constraints with the side chain of Asn-170 as well as the main chain nitrogen of Ser-70, a residue contributing to the oxyanion hole. We suggest that hydrophobicity could be the main factor responsible for the kinetic properties of Met69Leu (IRT-5), as no steric effects could be detected by molecular modelling. Hydrophobicity and steric constraints are combined in Met69Ile and Met69Val, IRT-I69 and IRT-6, respectively.
authors.affiliation: Museum National d'Histoire Naturelle, CNRS URA 401, Paris, France.
authors.forename: E B
authors.initials: EB
authors.lastname: Chaibi
authors.forename: J
authors.initials: J
authors.lastname: Péduzzi
authors.forename: S
authors.initials: S
authors.lastname: Farzaneh
authors.forename: M
authors.initials: M
authors.lastname: Barthélémy
authors.forename: D
authors.initials: D
authors.lastname: Sirot
authors.forename: R
authors.initials: R
authors.lastname: Labia
mesh_terms: D000900:Anti-Bacterial Agents / Q000737:chemistry* / Q000494:pharmacology*; D019818:Clavulanic Acid / Q000737:chemistry / Q000494:pharmacology; D004352:Drug Resistance, Microbial; D004926:Escherichia coli / Q000187:drug effects* / Q000201:enzymology; D007700:Kinetics; D008958:Models, Molecular; D008968:Molecular Conformation; D010397:Penicillanic Acid / Q000031:analogs & derivatives / Q000737:chemistry / Q000494:pharmacology; D011487:Protein Conformation; D013407:Sulbactam / Q000737:chemistry / Q000494:pharmacology; D000078142:Tazobactam; D065093:beta-Lactamase Inhibitors; D001618:beta-Lactamases / Q000737:chemistry* / Q000145:classification
chemical_list: D000900:Anti-Bacterial Agents; D065093:beta-Lactamase Inhibitors; D019818:Clavulanic Acid; D010397:Penicillanic Acid; D001618:beta-Lactamases; C034413:beta-lactamase TEM-1; D013407:Sulbactam; D000078142:Tazobactam