title: 23S ribosomal RNA mutations in halobacteria conferring resistance to the anti-80S ribosome targeted antibiotic anisomycin.
abstract: Halobacterium (H.) halobium and H. cutirubrum mutants resistant to the anti-80S ribosome targeted inhibitor anisomycin were isolated. Three classes of mutants were obtained: Class I displayed a minimal inhibitory concentration (MIC) to anisomycin of 10 micrograms/ml, class II of 25 micrograms/ml and class III of at least 400 micrograms/ml. In vitro polyphenylalanine synthesis assays demonstrated that in those cases tested resistance was a property of the large ribosomal subunit. By primer extension analysis, each mutation class could be correlated with a distinct base change within the peptidyltransferase loop of 235 rRNA. In class I A2472 was changed to C, in class II G2466 was changed to C and in the high-level resistant class III C2471 was replaced by U. A. double mutant - obtained by selection of a class I mutant for high-level anisomycin resistance - acquired the C2471 to U replacement of class III in addition to the class I mutation. The results provide information on the action of a eukaryotic protein synthesis inhibitor on archaebacterial ribosomes and demonstrate the suitability of organisms with a single rRNA transcriptional unit on the chromosome for direct selection of mutations in ribosomal RNA.
mesh_terms: D000841:Anisomycin / Q000494:pharmacology*; D001483:Base Sequence; D003001:Cloning, Molecular; D004247:DNA / Q000378:metabolism; D004352:Drug Resistance, Microbial; D006217:Halobacterium / Q000187:drug effects / Q000235:genetics*; D007700:Kinetics; D009154:Mutation; D009690:Nucleic Acid Conformation; D011072:Poly U / Q000235:genetics; D014176:Protein Biosynthesis; D011759:Pyrrolidines / Q000494:pharmacology*; D012335:RNA, Ribosomal / Q000235:genetics*; D012270:Ribosomes / Q000187:drug effects*
chemical_list: D011759:Pyrrolidines; D012335:RNA, Ribosomal; D011072:Poly U; D000841:Anisomycin; D004247:DNA