title: Oxazolidinone antibiotics target the P site on Escherichia coli ribosomes.
abstract: The oxazolidinones are a novel class of antimicrobial agents that target protein synthesis in a wide spectrum of gram-positive and anaerobic bacteria. The oxazolidinone PNU-100766 (linezolid) inhibits the binding of fMet-tRNA to 70S ribosomes. Mutations to oxazolidinone resistance in Halobacterium halobium, Staphylococcus aureus, and Escherichia coli map at or near domain V of the 23S rRNA, suggesting that the oxazolidinones may target the peptidyl transferase region responsible for binding fMet-tRNA. This study demonstrates that the potency of oxazolidinones corresponds to increased inhibition of fMet-tRNA binding. The inhibition of fMet-tRNA binding is competitive with respect to the fMet-tRNA concentration, suggesting that the P site is affected. The fMet-tRNA reacts with puromycin to form peptide bonds in the presence of elongation factor P (EF-P), which is needed for optimum specificity and efficiency of peptide bond synthesis. Oxazolidinone inhibition of the P site was evaluated by first binding fMet-tRNA to the A site, followed by translocation to the P site with EF-G. All three of the oxazolidinones used in this study inhibited translocation of fMet-tRNA. We propose that the oxazolidinones target the ribosomal P site and pleiotropically affect fMet-tRNA binding, EF-P stimulated synthesis of peptide bonds, and, most markedly, EF-G-mediated translocation of fMet-tRNA into the P site.
authors.affiliation: Banting and Best Department of Medical Research, Toronto, Ontario M5G 1L6, Canada.
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Aoki
authors.forename: Lizhu
authors.initials: L
authors.lastname: Ke
authors.forename: Susan M
authors.initials: SM
authors.lastname: Poppe
authors.forename: Toni J
authors.initials: TJ
authors.lastname: Poel
authors.forename: Elizabeth A
authors.initials: EA
authors.lastname: Weaver
authors.forename: Robert C
authors.initials: RC
authors.lastname: Gadwood
authors.forename: Richard C
authors.initials: RC
authors.lastname: Thomas
authors.forename: Dean L
authors.initials: DL
authors.lastname: Shinabarger
authors.forename: M Clelia
authors.initials: MC
authors.lastname: Ganoza
mesh_terms: D000081:Acetamides / Q000494:pharmacology; D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D001426:Bacterial Proteins / Q000096:biosynthesis; D018988:Bacterial Translocation / Q000235:genetics; D004926:Escherichia coli / Q000187:drug effects* / Q000648:ultrastructure; D007700:Kinetics; D000069349:Linezolid; D010080:Oxazoles / Q000494:pharmacology*; D023303:Oxazolidinones / Q000494:pharmacology; D010442:Peptide Chain Initiation, Translational / Q000187:drug effects; D020653:Peptide Elongation Factor G / Q000235:genetics; D010445:Peptide Elongation Factors / Q000187:drug effects* / Q000235:genetics; D010458:Peptidyl Transferases / Q000737:chemistry; D014176:Protein Biosynthesis / Q000235:genetics; D012358:RNA, Transfer, Met / Q000187:drug effects; D012270:Ribosomes / Q000737:chemistry / Q000187:drug effects*
chemical_list: D000081:Acetamides; D000900:Anti-Bacterial Agents; D001426:Bacterial Proteins; D010080:Oxazoles; D023303:Oxazolidinones; D020653:Peptide Elongation Factor G; D010445:Peptide Elongation Factors; D012358:RNA, Transfer, Met; C020746:factor EF-P; D010458:Peptidyl Transferases; D000069349:Linezolid