title: The role of rRNA bases in the interaction of peptidyltransferase inhibitors with bacterial ribosomes.
abstract: Synergism of streptogramins A (virginiamycin M, VM) and B (virginiamycin S, VS), peptidyltransferase inhibitors, was explored in EM4/pLC7-21 (wild type) and EM4/pERY (VS-resistant). These bacterial strains contained multicopy plasmids carrying an rrnH operon with wild type (pLC7-21) or mutated (A2058----U transversion) 23 S rRNA gene. Ribosomes with wild type and mutated rRNA were both present in EM4/pERY. The latter particles did not bind VS; in the presence of VM, however, high affinity VS binding occurred. As shown previously, VS protected against chemical reagents certain bases in domain V rRNA and VM in the stems flanking this loop. Differences between wild type and mutant ribosomes were observed: A2058, A2059, A2062, and G2505, protected by VS and ERY in EM4/pLC7-21, were unshielded in EM4/pERY. A2062 was shielded by VM in EM4/pERY, not in EM4/pLC7-21, and G2505 of mutant ribosomes became protected by VS when VM was simultaneously present. Induction by VM of a high affinity VS binding site in VS-sensitive and -resistant ribosomes indicates A2058 mutation to entail a conformational change of this site, which is counteracted by VM fixation. Accessibility of A2062 to chemical reagents (unlike behavior of EM4/pERY and EM4/pLC7-21 in the presence of VM) implies different conformations for wild type and mutant ribosomes.
authors.affiliation: Microbiology and Genetics Unit, University of Louvain Medical School, Brussels, Belgium.
authors.forename: P
authors.initials: P
authors.lastname: Vannuffel
authors.forename: M
authors.initials: M
authors.lastname: Di Giambattista
authors.forename: C
authors.initials: C
authors.lastname: Cocito
mesh_terms: D001483:Base Sequence; D007700:Kinetics; D008433:Mathematics; D008962:Models, Theoretical; D008969:Molecular Sequence Data; D009690:Nucleic Acid Conformation; D009838:Oligodeoxyribonucleotides; D010458:Peptidyl Transferases / Q000037:antagonists & inhibitors*; D012335:RNA, Ribosomal / Q000235:genetics / Q000378:metabolism*; D012338:RNA, Ribosomal, 23S / Q000235:genetics / Q000378:metabolism*; D012270:Ribosomes / Q000187:drug effects / Q000378:metabolism*; D014769:Virginiamycin / Q000494:pharmacology*
chemical_list: D009838:Oligodeoxyribonucleotides; D012335:RNA, Ribosomal; D012338:RNA, Ribosomal, 23S; D014769:Virginiamycin; D010458:Peptidyl Transferases