Detailed studies have shown that LmrP mediates the transbilayer movement of the amphiphilic cationic substrate TMA-DPH (1-(4-(trimethylamino)phenyl)-6-phenylhexa-1,3,5-triene) from the inner leaflet of the cytoplasmic membrane to the external side of the cell [5 ], thus effectively facilitating the transbilayer efflux of substrate across a permeability barrier at a rate that exceeds the rate of passive substrate influx.
Source: wiktionary