Kinetic characterization of GES-22 β-lactamase harboring the M169L clinical mutation

• Published in: Journal of antibiotics 2016-12, Vol.69 (12), p.858-862
• Main Authors: Saral, Aysegul, Leonard, David A, Duzgun, Azer Ozad, Cicek, Aysegul Copur, June, Cynthia M, Sandalli, Cemal
• Format: Article
• Language: English
• Subjects: 631/45/607; 631/45/607/1164; 82; 82/16; 82/80; 82/83; Acinetobacter baumannii - enzymology; Acinetobacter baumannii - genetics; Amino Acid Sequence; Amino Acid Substitution; Anti-Bacterial Agents - chemistry; Anti-Bacterial Agents - pharmacology; Aztreonam - pharmacology; Bacteriology; beta-Lactamase Inhibitors - pharmacology; beta-Lactamases - chemistry; beta-Lactamases - genetics; beta-Lactamases - pharmacology; Biomedical and Life Sciences; Bioorganic Chemistry; Carbapenems - pharmacology; Ceftazidime - pharmacology; Cephalosporins - pharmacology; Clavulanic Acid - pharmacology; Drug Resistance, Bacterial - genetics; Hydrolysis; Life Sciences; Medicinal Chemistry; Microbiology; Mutation; Organic Chemistry; original-article; Penicillins - pharmacology; Plasmids - genetics; Protein Conformation; Substrate Specificity; Turkey
• ISSN: 0021-8820; 1881-1469
• DOI: 10.1038/ja.2016.48

The class A β-lactamase GES-22 has been identified in Acinetobacter baumannii isolates in Turkey, and subsequently shown to differ from GES-11 by a single substitution (M169L). Because M169 is part of the omega loop, a structure that is known to have major effects on substrate selectivity in class A β-lactamases, we expressed, purified and kinetically characterized this novel variant. Our results show that compared with GES-11 6 × His , GES-22 6 × His displays more efficient hydrolysis of penicillins, and aztreonam, but a loss of efficiency against ceftazidime. In addition, the M169L substitution confers on GES-22 more efficient hydrolysis of the mechanistic inhibitors clavulanic acid and sulbactam. These effects are highly similar to other mutations at the homologous position in other class A β-lactamases, suggesting that this methionine has a key structural role in aligning active site residues and in substrate selectivity across the class.