title: A novel peptidoglycan cross-linking enzyme for a beta-lactam-resistant transpeptidation pathway.
abstract: The beta-lactam antibiotics remain the most commonly used to treat severe infections. Because of structural similarity between the beta-lactam ring and the d-alanyl(4)-d-alanine(5) extremity of bacterial cell wall precursors, the drugs act as suicide substrates of the dd-transpeptidases that catalyze the last cross-linking step of cell wall assembly. Here, we show that this mechanism of action can be defeated by a novel type of transpeptidase identified for the first time by reverse genetics in abeta-lactam-resistant mutant of Enterococcus faecium. The enzyme, Ldt(fm), catalyzes in vitro the cross-linking of peptidoglycan subunits in a beta-lactam-insensitive ld-transpeptidation reaction. The specificity of Ldt(fm) for the l-lysyl(3)-d-alanine(4) peptide bond of tetrapeptide donors accounts for resistance because the substrate does not mimic beta-lactams in contrast to d-alanyl(4)-d-alanine(5) in the pentapeptide donors required for dd-transpeptidation. Ldt(fm) homologues are encountered sporadically among taxonomically distant bacteria, indicating that ld-transpeptidase-mediated resistance may emerge in various pathogens.
authors.affiliation: INSERM, U655-Laboratoire de Recherche Moléculaire sur les Antibiotiques, Université Pierre et Marie Curie, Paris, France. jlmainar@bhdc.jussieu.fr
authors.forename: Jean-Luc
authors.initials: JL
authors.lastname: Mainardi
authors.forename: Martine
authors.initials: M
authors.lastname: Fourgeaud
authors.forename: Jean-Emmanuel
authors.initials: JE
authors.lastname: Hugonnet
authors.forename: Lionel
authors.initials: L
authors.lastname: Dubost
authors.forename: Jean-Paul
authors.initials: JP
authors.lastname: Brouard
authors.forename: Jamal
authors.initials: J
authors.lastname: Ouazzani
authors.forename: Louis B
authors.initials: LB
authors.lastname: Rice
authors.forename: Laurent
authors.initials: L
authors.lastname: Gutmann
authors.forename: Michel
authors.initials: M
authors.lastname: Arthur
mesh_terms: D000409:Alanine / Q000737:chemistry; D000595:Amino Acid Sequence; D000667:Ampicillin / Q000494:pharmacology; D000818:Animals; D000900:Anti-Bacterial Agents / Q000494:pharmacology; D001921:Brain / Q000382:microbiology; D002384:Catalysis; D002473:Cell Wall / Q000378:metabolism; D002845:Chromatography; D002852:Chromatography, Ion Exchange; D003432:Cross-Linking Reagents / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D024881:Drug Resistance, Bacterial; D016984:Enterococcus faecium / Q000201:enzymology* / Q000378:metabolism; D004926:Escherichia coli / Q000378:metabolism; D013058:Mass Spectrometry; D008954:Models, Biological; D008956:Models, Chemical; D008957:Models, Genetic; D008969:Molecular Sequence Data; D010455:Peptides / Q000737:chemistry; D010457:Peptidoglycan / Q000737:chemistry*; D010458:Peptidyl Transferases / Q000737:chemistry; D011485:Protein Binding; D013379:Substrate Specificity; D047090:beta-Lactams / Q000737:chemistry / Q000494:pharmacology
chemical_list: D000900:Anti-Bacterial Agents; D003432:Cross-Linking Reagents; D010455:Peptides; D010457:Peptidoglycan; D047090:beta-Lactams; D000667:Ampicillin; D010458:Peptidyl Transferases; D000409:Alanine