Identification and in vivo functional analysis of a virginiamycin S resistance gene (varS) from Streptomyces virginiae.
BarA of Streptomyces virginiae is a specific receptor protein for virginiae butanolide (VB), one of the gamma-butyrolactone autoregulators of the Streptomyces species, and acts as a transcriptional regulator controlling both virginiamycin production and VB biosynthesis. The downstream gene barB, the transcription of which is under the tight control of the VB-BarA system, was found to be transcribed as a polycistronic mRNA with its downstream region, and DNA sequencing revealed a 1,554-bp open reading frame (ORF) beginning at 161 bp downstream of the barB termination codon. The ORF product showed high homology (68 to 73%) to drug efflux proteins having 14 transmembrane segments and was named varS (for S. virginiae antibiotic resistance). Heterologous expression of varS with S. lividans as a host resulted in virginiamycin S-specific resistance, suggesting that varS encoded a virginiamycin S-specific transport protein. Northern blot analysis indicated that the bicistronic transcript of barB-varS appeared 1 to 2 h before the onset of virginiamycin M1 and S production, at which time VB was produced, while exogenously added virginiamycin S apparently induced the monocistronic varS transcript.
D015107:4-Butyrolactone / Q000031:analogs & derivatives / Q000096:biosynthesis; D000595:Amino Acid Sequence; D000900:Anti-Bacterial Agents / Q000096:biosynthesis / Q000378:metabolism / Q000494:pharmacology*; D001426:Bacterial Proteins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D001483:Base Sequence; D001692:Biological Transport; D015152:Blotting, Northern; D004352:Drug Resistance, Microbial / Q000235:genetics*; D015964:Gene Expression Regulation, Bacterial / Q000187:drug effects; D005796:Genes / Q000235:genetics; D005798:Genes, Bacterial; D008565:Membrane Proteins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D008969:Molecular Sequence Data; D016366:Open Reading Frames / Q000235:genetics; D011401:Promoter Regions, Genetic / Q000235:genetics; D012333:RNA, Messenger / Q000032:analysis / Q000235:genetics; D011994:Recombinant Proteins / Q000096:biosynthesis / Q000378:metabolism; D017386:Sequence Homology, Amino Acid; D013302:Streptomyces / Q000187:drug effects* / Q000235:genetics / Q000378:metabolism; D013997:Time Factors; D014169:Transformation, Bacterial; D014769:Virginiamycin / Q000096:biosynthesis / Q000378:metabolism / Q000494:pharmacology*