Participates in the development of tolerance to both isoniazid and ethambutol. May function through a MDR-pump like mechanism, although it does not appear to directly transport isoniazid from the cell. Forms multimeric structures containing a central pore. Specifically induced by a broad range of inhibitors of cell wall biosynthesis, including antibiotics that inhibit the synthesis of peptidoglycan (ampicillin), arabinogalactam (ethambutol), mycolic acids (isoniazid, ethionamide) and fatty acids (5-chloropyrazinamide). Down-regulated by the nucleoid-associated protein Lsr2. Deletion results in increased susceptibility to isoniazid and accumulation of intracellular ethidium bromide.