Mercury-type transcriptional regulators (MerR-transcriptional regulator) and major facilitator superfamily (MFS) transporters usually form an important sensor-response transport system in many microorganisms. This system has been shown to be involved in the regulation and transport (efflux) of a wide and diverse array of secondary metabolites including antimicrobial agents, dyes, chemicals, metals and evem harmful oxygen radicals. Inhibition or inactivation of this transport system is considered a promising approach for controlling microbial resistance, and thus may become a promising target of therapeutics particularly for the clinically relevant pathogens. However, the genetic and proteomics of this system have not been fully studied. In this work, a DNA segment (1.926 kb) from Bacillus circulans ATCC 21588 harboring the two genes, bciR and bciT arranged in an operon was amplified using PCR, analyzed and submitted into the GenBank database (accession code, KR049081). A two open reading frames (ORFs), namely BciR and BciT were found to encode a putative MerR-transcriptional regulator (BciR; 153 aa) and a putative MFS transporter (BciT; 392 aa), respectively. Analysis of the conserved domains and modeled tertiary structures revealed that, BciR possesses an N-terminal H-T-H motive (HTH type) region with possible transcriptional related activity and a conserved metal binding site at the C-terminal end. BciT was likely an MFS protein with nine transmembrane helices. This is the first report about detection of a bciR/bciT operon that putatively encode a sensor-response transport system in Bacillus circulans ATCC 12588.

 

Key words: MerR-type transcription regulator, multidrug efflux protein, major facilitator superfamily MFS, Bacillus circulans ATCC 21588.