Part of the tripartite efflux system EmrYK-TolC, which confers resistance to various drugs. Part of the tripartite efflux system EmrYK-TolC, which is composed of an inner membrane transporter, EmrY, a membrane fusion protein, EmrK, and an outer membrane component, TolC. The complex forms a large protein conduit and can translocate molecules across both the inner and outer membranes (By similarity). Growth phase-dependent transcription is induced by tetracycline. Expression may be controlled by both RpoS and the Mar system. Mutants are more sensitive to nalidixic acid, mitomycin C and other stresses such as hydrogen peroxide or UV irradiation. Belongs to the major facilitator superfamily. EmrB family.