title: The beta-lactam-sensitive D,D-carboxypeptidase activity of Pbp4 controls the L,D and D,D transpeptidation pathways in Corynebacterium jeikeium.
abstract: Corynebacterium jeikeium is an emerging nosocomial pathogen responsible for vascular catheters infections, prosthetic endocarditis and septicemia. The treatment of C. jeikeium infections is complicated by the multiresistance of clinical isolates to antibiotics, in particular to beta-lactams, the most broadly used class of antibiotics. To gain insight into the mechanism of beta-lactam resistance, we have determined the structure of the peptidoglycan and shown that C. jeikeium has the dual capacity to catalyse formation of cross-links generated by transpeptidases of the d,d and l,d specificities. Two ampicillin-insensitive cross-linking enzymes were identified, Ldt(Cjk1), a member of the active site cysteine l,d-transpeptidase family, and Pbp2c, a low-affinity class B penicillin-binding protein (PBP). In the absence of beta-lactam, the PBPs and the l,d-transpeptidase contributed to the formation of 62% and 38% of the cross-links respectively. Although Ldt(Cjk1) and Pbp2C were not inhibited by ampicillin, the participation of the l,d-transpeptidase to peptidoglycan cross-linking decreased in the presence of the drug. The specificity of Ldt(Cjk1) for acyl donors containing a tetrapeptide stem accounts for this effect of ampicillin since the essential substrate of Ldt(Cjk1) was produced by an ampicillin-sensitive d,d-carboxypeptidase (Pbp4(Cjk)). Acquisition and mutational alterations of pbp2C accounted for high-level beta-lactam resistance in C. jeikeium.
authors.affiliation: Centre de Recherche des Cordeliers, LRMA, Université Pierre et Marie Curie - Paris 6, UMR S 872, Paris, F-75006 France.
authors.forename: Marie
authors.initials: M
authors.lastname: Lavollay
authors.forename: Michel
authors.initials: M
authors.lastname: Arthur
authors.forename: Martine
authors.initials: M
authors.lastname: Fourgeaud
authors.forename: Lionel
authors.initials: L
authors.lastname: Dubost
authors.forename: Arul
authors.initials: A
authors.lastname: Marie
authors.forename: Philippe
authors.initials: P
authors.lastname: Riegel
authors.forename: Laurent
authors.initials: L
authors.lastname: Gutmann
authors.forename: Jean-Luc
authors.initials: JL
authors.lastname: Mainardi
mesh_terms: D000595:Amino Acid Sequence; D000667:Ampicillin / Q000378:metabolism / Q000494:pharmacology; D000900:Anti-Bacterial Agents / Q000378:metabolism / Q000494:pharmacology*; D001426:Bacterial Proteins / Q000737:chemistry / Q000378:metabolism / Q000494:pharmacology; D002268:Carboxypeptidases / Q000378:metabolism*; D020134:Catalytic Domain; D002473:Cell Wall / Q000378:metabolism; D003352:Corynebacterium / Q000187:drug effects / Q000201:enzymology*; D004926:Escherichia coli / Q000378:metabolism; D008969:Molecular Sequence Data; D009169:Mycobacterium tuberculosis / Q000378:metabolism; D009842:Oligopeptides / Q000378:metabolism / Q000494:pharmacology; D046915:Penicillin-Binding Proteins / Q000378:metabolism; D010457:Peptidoglycan / Q000737:chemistry / Q000378:metabolism / Q000494:pharmacology; D010458:Peptidyl Transferases / Q000378:metabolism*; D011506:Proteins / Q000378:metabolism; D013379:Substrate Specificity; D020713:Vancomycin Resistance / Q000187:drug effects; D018440:beta-Lactam Resistance / Q000187:drug effects; D047090:beta-Lactams / Q000737:chemistry / Q000378:metabolism / Q000494:pharmacology*
chemical_list: D000900:Anti-Bacterial Agents; D001426:Bacterial Proteins; D009842:Oligopeptides; D046915:Penicillin-Binding Proteins; D010457:Peptidoglycan; D011506:Proteins; D047090:beta-Lactams; D000667:Ampicillin; D010458:Peptidyl Transferases; D002268:Carboxypeptidases; C094315:metallocarboxypeptidase D