RESUMO
cis-Acting RNA elements in the leaders of bacterial mRNA often regulate gene transcription, especially in the context of amino acid metabolism. We determined that the transcription of the auxiliary, antibiotic-resistant tryptophanyl-tRNA synthetase gene (trpRS1) in Streptomyces coelicolor is regulated by a ribosome-mediated attenuator in the 5' leader of its mRNA region. This regulatory element controls gene transcription in response to the physiological effects of indolmycin and chuangxinmycin, two antibiotics that inhibit bacterial tryptophanyl-tRNA synthetases. By mining streptomycete genome sequences, we found several orthologs of trpRS1 that share this regulatory element; we predict that they are regulated in a similar fashion. The validity of this prediction was established through the analysis of a trpRS1 ortholog (SAV4725) in Streptomyces avermitilis. We conclude that the trpRS1 locus is a widely distributed and self-regulating antibiotic resistance cassette. This study provides insights into how auxiliary aminoacyl-tRNA synthetase genes are regulated in bacteria.
Assuntos
Antibacterianos/farmacologia , Farmacorresistência Bacteriana/genética , Ribossomos/fisiologia , Streptomyces/metabolismo , Transcrição Gênica/fisiologia , Triptofano-tRNA Ligase/metabolismo , Sequência de Bases , Deleção de Genes , Regulação Bacteriana da Expressão Gênica/fisiologia , Dados de Sequência Molecular , Mutagênese , Mutação de Sentido Incorreto , RNA Bacteriano/genética , RNA Bacteriano/metabolismo , RNA Mensageiro/genética , RNA Mensageiro/metabolismo , Streptomyces/genética , Triptofano-tRNA Ligase/genéticaRESUMO
Chloramphenicol, florfenicol, and thiamphenicol are used as antibacterial drugs in clinical and veterinary medicine. Two efflux pumps of the major facilitator superfamily encoded by the cmlR1 and cmlR2 genes mediate resistance to these antibiotics in Streptomyces coelicolor, a close relative of Mycobacterium tuberculosis. The transcription of both genes was observed by reverse transcription-PCR. Disruption of cmlR1 decreased the chloramphenicol MIC 1.6-fold, while disruption of cmlR2 lowered the MIC 16-fold. The chloramphenicol MIC of wild-type S. coelicolor decreased fourfold and eightfold in the presence of reserpine and Phe-Arg-beta-naphthylamide, respectively. These compounds are known to potentiate the activity of some antibacterial drugs via efflux pump inhibition. While reserpine is known to potentiate drug activity against gram-positive bacteria, this is the first time that Phe-Arg-beta-naphthylamide has been shown to potentiate drug activity against a gram-positive bacterium.
Assuntos
Proteínas de Bactérias/fisiologia , Resistência ao Cloranfenicol , Streptomyces coelicolor/efeitos dos fármacos , Proteínas de Bactérias/genética , Dipeptídeos/farmacologia , Reserpina/farmacologiaRESUMO
Indolmycin, a potential antibacterial drug, competitively inhibits bacterial tryptophanyl-tRNA synthetases. An effort to identify indolmycin resistance genes led to the discovery of a gene encoding an indolmycin-resistant isoform of tryptophanyl-tRNA synthetase. Overexpression of this gene in an indolmycin-sensitive strain increased the indolmycin MIC 60-fold. Its transcription and distribution in various bacterial genera were assessed. The level of resistance conferred by this gene was compared to that of a known indolmycin resistance gene and to those of genes with resistance-conferring point mutations.
Assuntos
Antibacterianos/farmacologia , Farmacorresistência Bacteriana Múltipla/genética , Triptofano-tRNA Ligase/fisiologia , Sequência de Aminoácidos , Cromatografia Líquida , Indóis/farmacologia , Isoenzimas/química , Isoenzimas/genética , Isoenzimas/fisiologia , Espectrometria de Massas , Testes de Sensibilidade Microbiana , Dados de Sequência Molecular , Mutagênese Sítio-Dirigida , Reação em Cadeia da Polimerase Via Transcriptase Reversa , Homologia de Sequência de Aminoácidos , Streptomyces/efeitos dos fármacos , Streptomyces/enzimologia , Streptomyces/genética , Streptomyces coelicolor/efeitos dos fármacos , Streptomyces coelicolor/enzimologia , Streptomyces coelicolor/genética , Streptomyces griseus/efeitos dos fármacos , Streptomyces griseus/enzimologia , Streptomyces griseus/genética , Triptofano/farmacologia , Triptofano-tRNA Ligase/química , Triptofano-tRNA Ligase/genéticaRESUMO
Streptomyces coelicolor has two genes encoding tryptophanyl-tRNA synthetases, one of which (trpRS1) is resistant to and transcriptionally activated by indolmycin. We found that this gene also confers resistance to chuangxinmycin (another antibiotic that inhibits bacterial tryptophanyl-tRNA synthetases) and that its transcription is not absolutely dependent on either antibiotic.
