Characterization of the Mycobacterial MSMEG-3762/63 Efflux Pump in Drug Efflux.

Multi-drug resistant tuberculosis (MDR-TB) represents a major health problem worldwide. Drug efflux and the activity of efflux transporters likely play important roles in the development of drug-tolerant and drug-resistant mycobacterial phenotypes. This study is focused on the action of a mycobacterial efflux pump as a mechanism of drug resistance. Previous studies demonstrated up-regulation of the TetR-like transcriptional regulator in and its ortholog in () in acid-nitrosative stress conditions. MSMEG-3765 regulates the expression of the operon, and of the orthologous region in (). MSMEG-3762 and Rv1687c are annotated as ATP-binding proteins, while MSMEG-3763 and Rv1686c are annotated as trans-membrane polypeptides, defining an ABC efflux pump in both and . The two putative efflux systems share a high percentage of identity. To examine the role of the putative efflux system MSMEG-3762/63, we constructed and characterized a deletion mutant in (∆). By comparative analysis of wild type, knockout, and complemented strains, together with structural modeling and molecular docking bioinformatics analyses of the MSMEG-3763 trans-membrane protein, we define the protein complex MSMEG-3762/63 as an efflux pump. Moreover, we demonstrate involvement of this pump in biofilm development and in the extrusion of rifampicin and ciprofloxacin (CIP), antimicrobial drugs used in first- and second-line anti-TB therapies.