title: Kinetic characterization of GES-22 β-lactamase harboring the M169L clinical mutation.
abstract: 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-116 × His, GES-226 × Hisdisplays 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.
authors.affiliation: Department of Nutrition and Dietetics, Faculty of Health Sciences, Artvin Coruh University, Artvin, Turkey.|Microbiology and Molecular Biology Research Laboratory, Department of Biology, Faculty of Arts and Sciences, Recep Tayyip Erdogan University, Rize, Turkey.
authors.forename: Aysegul
authors.initials: A
authors.lastname: Saral
authors.affiliation: Department of Chemistry, Grand Valley State University, Allendale, MI, USA.
authors.forename: David A
authors.initials: DA
authors.lastname: Leonard
authors.affiliation: Department of Genetics and Bioengineering, Faculty of Engineering and Natural Sciences, Gümüşhane University, Gumushane, Turkey.
authors.forename: Azer Ozad
authors.initials: AO
authors.lastname: Duzgun
authors.affiliation: Department of Medical Microbiology, Faculty of Medicine, Recep Tayyip Erdogan University, Rize, Turkey.
authors.forename: Aysegul Copur
authors.initials: AC
authors.lastname: Cicek
authors.affiliation: Department of Chemistry, Grand Valley State University, Allendale, MI, USA.
authors.forename: Cynthia M
authors.initials: CM
authors.lastname: June
authors.affiliation: Microbiology and Molecular Biology Research Laboratory, Department of Biology, Faculty of Arts and Sciences, Recep Tayyip Erdogan University, Rize, Turkey.
authors.forename: Cemal
authors.initials: C
authors.lastname: Sandalli
mesh_terms: D040981:Acinetobacter baumannii / Q000201:enzymology / Q000235:genetics*; D000595:Amino Acid Sequence; D019943:Amino Acid Substitution; D000900:Anti-Bacterial Agents / Q000737:chemistry / Q000494:pharmacology; D001398:Aztreonam / Q000494:pharmacology; D015780:Carbapenems / Q000494:pharmacology; D002442:Ceftazidime / Q000494:pharmacology; D002511:Cephalosporins / Q000494:pharmacology; D019818:Clavulanic Acid / Q000494:pharmacology; D024881:Drug Resistance, Bacterial / Q000235:genetics*; D006868:Hydrolysis; D009154:Mutation; D010406:Penicillins / Q000494:pharmacology; D010957:Plasmids / Q000235:genetics; D011487:Protein Conformation; D013379:Substrate Specificity; D014421:Turkey; D065093:beta-Lactamase Inhibitors / Q000494:pharmacology; D001618:beta-Lactamases / Q000737:chemistry / Q000235:genetics* / Q000494:pharmacology*
chemical_list: D000900:Anti-Bacterial Agents; D015780:Carbapenems; D002511:Cephalosporins; D010406:Penicillins; D065093:beta-Lactamase Inhibitors; D019818:Clavulanic Acid; D002442:Ceftazidime; D001618:beta-Lactamases; D001398:Aztreonam