title: Methyltransferase Erm(37) slips on rRNA to confer atypical resistance in Mycobacterium tuberculosis.
abstract: Members of the Mycobacterium tuberculosis complex possess a resistance determinant, erm(37) (also termed ermMT), which is a truncated homologue of the erm genes found in a diverse range of drug-producing and pathogenic bacteria. All erm genes examined thus far encode N(6)-monomethyltransferases or N(6),N(6)-dimethyltransferases that show absolute specificity for nucleotide A2058 in 23 S rRNA. Monomethylation at A2058 confers resistance to a subset of the macrolide, lincosamide, and streptogramin B (MLS(B)) group of antibiotics and no resistance to the latest macrolide derivatives, the ketolides. Dimethylation at A2058 confers high resistance to all MLS(B) and ketolide drugs. The erm(37) phenotype fits into neither category. We show here by tandem mass spectrometry that Erm(37) initially adds a single methyl group to its primary target at A2058 but then proceeds to attach additional methyl groups to the neighboring nucleotides A2057 and A2059. Other methyltransferases, Erm(E) and Erm(O), maintain their specificity for A2058 on mycobacterial rRNA. Erm(E) and Erm(O) have a full-length C-terminal domain, which appears to be important for stabilizing the methyltransferases at their rRNA target, and this domain is truncated in Erm(37). The lax interaction of the M. tuberculosis Erm(37) with its rRNA produces a unique methylation pattern and confers resistance to the ketolide telithromycin.
authors.affiliation: Department of Biochemistry and Molecular Biology, University of Southern Denmark, DK-5230 Odense M, Denmark.
authors.forename: Christian Toft
authors.initials: CT
authors.lastname: Madsen
authors.forename: Lene
authors.initials: L
authors.lastname: Jakobsen
authors.forename: Karolina
authors.initials: K
authors.lastname: Buriánková
authors.forename: Florence
authors.initials: F
authors.lastname: Doucet-Populaire
authors.forename: Jean-Luc
authors.initials: JL
authors.lastname: Pernodet
authors.forename: Stephen
authors.initials: S
authors.lastname: Douthwaite
mesh_terms: D000900:Anti-Bacterial Agents / Q000494:pharmacology; D001483:Base Sequence; D024881:Drug Resistance, Bacterial / Q000235:genetics; D015870:Gene Expression; D005798:Genes, Bacterial; D048628:Ketolides / Q000494:pharmacology; D008780:Methyltransferases / Q000235:genetics / Q000378:metabolism*; D008969:Molecular Sequence Data; D020102:Mycobacterium smegmatis / Q000235:genetics / Q000378:metabolism; D009169:Mycobacterium tuberculosis / Q000187:drug effects / Q000235:genetics* / Q000378:metabolism*; D009690:Nucleic Acid Conformation; D012329:RNA, Bacterial / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D012335:RNA, Ribosomal / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization
chemical_list: D000900:Anti-Bacterial Agents; D048628:Ketolides; D012329:RNA, Bacterial; D012335:RNA, Ribosomal; D008780:Methyltransferases; C035181:rRNA (adenosine-O-2'-)methyltransferase; C106791:telithromycin