Mediates resistance to long-chained antibacterial fatty acids (FAs) (PubMed:10447892). Function is dependent on the MtrE outer membrane protein (PubMed:10447892). Probably part of a tripartite efflux system FarAB-MtrE, which is composed of an inner membrane transporter, FarB, a periplasmic membrane fusion protein, FarA, and an outer membrane component, MtrE. Expression is positively regulated by MtrR (PubMed:10447892, PubMed:14645274). MtrR acts by modulating the expression of the regulatory protein FarR, which directly controls the expression of the farAB operon (PubMed:14645274). Belongs to the membrane fusion protein (MFP) (TC 8.A.1) family.