Open AccessThe Lys234Arg Substitution in the Enzyme SHV-72 Is a Determinant for Resistance to Clavulanic Acid Inhibition
Author(s) -
Nuno Mendonça,
Vera Manageiro,
Frédéric Robin,
Maria José Salgado,
Eugénia Ferreira,
Manuela Caniça,
Richard Bonnet
Publication year - 2008
Publication title -
antimicrobial agents and chemotherapy
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.07
H-Index - 259
eISSN - 1070-6283
pISSN - 0066-4804
DOI - 10.1128/aac.01381-07
Subject(s) - aztreonam , clavulanic acid , beta lactamase inhibitors , klebsiella pneumoniae , imipenem , ceftazidime , enzyme , chemistry , microbiology and biotechnology , antibacterial agent , stereochemistry , amoxicillin , biology , biochemistry , antibiotics , bacteria , antibiotic resistance , gene , escherichia coli , pseudomonas aeruginosa , genetics
The new β-lactamase SHV-72 was isolated from clinicalKlebsiella pneumoniae INSRA1229, which exhibited the unusual association of resistance to the amoxicillin-clavulanic acid combination (MIC, 64 μg/ml) and susceptibility to cephalosporins, aztreonam, and imipenem. SHV-72 (pI 7.6) harbored the three amino acid substitutions Ile8Phe, Ala146Val, and Lys234Arg. SHV-72 had high catalytic efficiency against penicillins (k cat /K m , 35 to 287 μM−1 ·s−1 ) and no activity against oxyimino β-lactams. The concentration of clavulanic acid necessary to inhibit the enzyme activity by 50% was 10-fold higher for SHV-72 than for SHV-1. Molecular-dynamics simulation suggested that the Lys234Arg substitution in SHV-72 stabilized an atypical conformation of the Ser130 side chain, which moved the Oγ atom of Ser130 around 3.5 Å away from the key Oγ atom of the reactive serine (Ser70). This movement may therefore decrease the susceptibility to clavulanic acid by preventing cross-linking between Ser130 and Ser70.