Part of the tripartite efflux system EmrAB-TolC, which confers resistance to antibiotics such as CCCP, FCCP, 2,4-dinitrophenol and nalidixic acid. EmrA is a drug-binding protein that provides a physical link between EmrB and TolC. Homodimer and homotrimer. 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 EmrB. EmrAB complex forms a dimer in vitro. Belongs to the membrane fusion protein (MFP) (TC 8.A.1) family.