title: Mutations in conserved helix 69 of 23S rRNA of Thermus thermophilus that affect capreomycin resistance but not posttranscriptional modifications.
abstract: Translocation during the elongation phase of protein synthesis involves the relative movement of the 30S and 50S ribosomal subunits. This movement is the target of tuberactinomycin antibiotics. Here, we describe the isolation and characterization of mutants of Thermus thermophilus selected for resistance to the tuberactinomycin antibiotic capreomycin. Two base substitutions, A1913U and mU1915G, and a single base deletion, DeltamU1915, were identified in helix 69 of 23S rRNA, a structural element that forms part of an interribosomal subunit bridge with the decoding center of 16S rRNA, the site of previously reported capreomycin resistance base substitutions. Capreomycin resistance in other bacteria has been shown to result from inactivation of the TlyA methyltransferase which 2'-O methylates C1920 of 23S rRNA. Inactivation of the tlyA gene in T. thermophilus does not affect its sensitivity to capreomycin. Finally, none of the mutations in helix 69 interferes with methylation at C1920 or with pseudouridylation at positions 1911 and 1917. We conclude that the resistance phenotype is a consequence of structural changes introduced by the mutations.
authors.affiliation: Department of Molecular Biology, Cell Biology and Biochemistry, Brown University, Providence, RI 02912, USA.
authors.forename: Tanakarn
authors.initials: T
authors.lastname: Monshupanee
authors.forename: Steven T
authors.initials: ST
authors.lastname: Gregory
authors.forename: Stephen
authors.initials: S
authors.lastname: Douthwaite
authors.forename: Wipa
authors.initials: W
authors.lastname: Chungjatupornchai
authors.forename: Albert E
authors.initials: AE
authors.lastname: Dahlberg
mesh_terms: D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D001483:Base Sequence; D002207:Capreomycin / Q000494:pharmacology*; D017124:Conserved Sequence; D024881:Drug Resistance, Bacterial / Q000235:genetics*; D020868:Gene Silencing; D008745:Methylation; D009154:Mutation; D009690:Nucleic Acid Conformation; D009876:Operon; D010641:Phenotype; D012323:RNA Processing, Post-Transcriptional / Q000235:genetics*; D012338:RNA, Ribosomal, 23S / Q000235:genetics / Q000378:metabolism*; D016963:Thermus thermophilus / Q000187:drug effects* / Q000378:metabolism
chemical_list: D000900:Anti-Bacterial Agents; D012338:RNA, Ribosomal, 23S; D002207:Capreomycin