Efflux pump that contributes to intrinsic antibiotic resistance. The pump uses the electrochemical gradient as a source of energy. Confers resistance to various antibiotics, including tetracycline, acriflavine, spectinomycin and p-aminosalicylate. May be involved in export of toxic by-products that accumulate during stationary phase when nutrients are limited. Efflux activity is inhibited by carbonyl cyanide m-chlorophenylhydrazone (CCCP). Disruption mutant shows changes in morphology, growth defects and a progressive loss of viability upon subcultivation in liquid medium. Disruption leads to an extensive change in gene expression patterns during stationary phase, with no changes during exponential growth. It also alters susceptibility to many antibiotics. Belongs to the major facilitator superfamily. Drug:H(+) antiporter-3 (DHA3) (TC 2.A.1.21) family.