AcrA-AcrB-AcrZ-TolC is a drug efflux protein complex with broad substrate specificity that uses the proton motive force to export substrates. This subunit may act as an adapter protein that links AcrB and TolC stably together (By similarity). Monomeric in solution. Homotrimeric; interacts independently with AcrB and TolC as well as AcrZ. Part of the AcrA-AcrB-TolC efflux pump (By similarity). Belongs to the membrane fusion protein (MFP) (TC 8.A.1) family.