Part of the ABC transporter complex MlaFEDB, which is involved in a phospholipid transport pathway that maintains lipid asymmetry in the outer membrane by retrograde trafficking of phospholipids from the outer membrane to the inner membrane. Responsible for energy coupling to the transport system. The complex is composed of two ATP-binding proteins (MlaF), two transmembrane proteins (MlaE), two cytoplasmic solute-binding proteins (MlaB) and six periplasmic solute-binding proteins (MlaD). Belongs to the ABC transporter superfamily. MlaF family.