Translocates 4-amino-4-deoxy-L-arabinose-phosphoundecaprenol (alpha-L-Ara4N-phosphoundecaprenol) from the cytoplasmic to the periplasmic side of the inner membrane. Bacterial outer membrane biogenesis; lipopolysaccharide biosynthesis. Heterodimer of ArnE and ArnF. Belongs to the ArnF family.