title: Substitutions in PBP2b from β-Lactam-resistantStreptococcus pneumoniaeHave Different Effects on Enzymatic Activity and Drug Reactivity.
abstract: Pneumococcus resists β-lactams by expressing variants of its target enzymes, the penicillin-binding proteins (PBPs), with many amino acid substitutions. Up to 10% of the sequence can be modified. These altered PBPs have a much reduced reactivity with the drugs but retain their physiological activity of cross-linking the peptidoglycan, the major constituent of the bacterial cell wall. However, because β-lactams are chemical and structural mimics of the natural substrate, resistance mediated by altered PBPs raises the following paradox: how PBPs that react poorly with the drugs maintain a sufficient level of activity with the physiological substrate. This question is addressed for the first time in this study, which compares the peptidoglycan cross-linking activity of PBP2b from susceptible and resistant strains with their inhibition by different β-lactams. Unexpectedly, the enzymatic activity of the variants did not correlate with their antibiotic reactivity. This finding indicates that some of the numerous amino acid substitutions were selected to restore a viable level of enzymatic activity by a compensatory molecular mechanism.
authors.affiliation: From the Institut de Biologie Structurale, Université Grenoble Alpes, CEA, CNRS, 38044 Grenoble, France.
authors.forename: Philippe
authors.initials: P
authors.lastname: Calvez
authors.affiliation: the Department of Chemical Biology and Organic Chemistry, Institute of Biomembranes, Bijvoet Center for Biomolecular Research, Utrecht University, Utrecht 3584 CH, The Netherlands, and.
authors.forename: Eefjan
authors.initials: E
authors.lastname: Breukink
authors.affiliation: the School of Life Sciences, University of Warwick, Coventry CV4 7AL, United Kingdom.
authors.forename: David I
authors.initials: DI
authors.lastname: Roper
authors.affiliation: From the Institut de Biologie Structurale, Université Grenoble Alpes, CEA, CNRS, 38044 Grenoble, France.
authors.forename: Mélanie
authors.initials: M
authors.lastname: Dib
authors.affiliation: From the Institut de Biologie Structurale, Université Grenoble Alpes, CEA, CNRS, 38044 Grenoble, France.
authors.forename: Carlos
authors.initials: C
authors.lastname: Contreras-Martel
authors.affiliation: From the Institut de Biologie Structurale, Université Grenoble Alpes, CEA, CNRS, 38044 Grenoble, France, andre.zapun@ibs.fr.
authors.forename: André
authors.initials: A
authors.lastname: Zapun
mesh_terms: D000595:Amino Acid Sequence; D002511:Cephalosporins / Q000378:metabolism; D024881:Drug Resistance, Bacterial / Q000187:drug effects*; D046915:Penicillin-Binding Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D011489:Protein Denaturation; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D017386:Sequence Homology, Amino Acid; D013296:Streptococcus pneumoniae / Q000187:drug effects* / Q000378:metabolism; D047090:beta-Lactams / Q000494:pharmacology*
chemical_list: D002511:Cephalosporins; D046915:Penicillin-Binding Proteins; D011994:Recombinant Proteins; D047090:beta-Lactams; C021720:nitrocefin
keywords: Streptococcus; antibiotic resistance; cell wall; enzyme kinetics; peptidoglycan