Regulation of multidrug resistance genes by transcription factors of the BltR subfamily

BltR protein is a MerR family transcription factor experimentally characterized in Bacillus subtilis . It activates the transcription of genes encoding the multidrug transporter Blt and spermine/spermidine acetyltransferase BltD. Comparative genomics methods were applied to BltR-dependent regulons in 25 bacterial genomes. The structure of the promoter regions of the regulated genes is typical of MerR family activators: their binding sites are located in long spacers between promoter boxes. The regulated genes usually form divergons with the regulator genes. The transcription factors under consideration regulate the transcription of multidrug transporter and spermine/spermidine acetyltransferase genes. These transporters can be either secondary or ATP-dependent. The conservative function of both types as multidrug transporters is confirmed by phylogenetic analysis.