In association with lipoprotein LprG probably transports triacylglycerides (TAG) across the inner cell membrane into the periplasm; TAG probably regulates lipid metabolism and growth regulation and plays a structural role in the outer membrane. TAG (and maybe other lipids) enters the central cavity of the P55 transporter from within the cell inner membrane via clefts on the cytoplasmic face of P55 between TM5-TM8 and TM2-TM11. From there the lipid is probably transferred to the hydrophobic cavity of LprG. Probably does not function as a bona fide drug efflux pump, but instead plays a role in outer membrane biogenesis. Probably required with LprG for normal surface localization of lipoarabinomannan (LAM)