Transports trehalose monomycolate (TMM) to the cell wall. Flips TMM across the inner membrane. Membrane potential is not required for this function. Transports probably phosphatidylethanolamine (PE) as well. Contributes to membrane potential, cell wall composition, antibiotic susceptibility and fitness. Belongs to the resistance-nodulation-cell division (RND) (TC 2.A.6) family. MmpL subfamily.