Part of the tripartite efflux system EmrAB-TolC, which confers resistance to antibiotics such as CCCP, FCCP, 2,4-dinitrophenol and nalidixic acid. Part of the tripartite efflux system EmrAB-TolC, which is composed of an inner membrane transporter, EmrB, a periplasmic membrane fusion protein, EmrA, and an outer membrane component, TolC. The complex forms a large protein conduit and can translocate molecules across both the inner and outer membranes. Interacts with EmrA. EmrAB complex forms a dimer in vitro. Belongs to the major facilitator superfamily. EmrB family.