Involved in peptidoglycan biosynthesis. Transports lipid-linked peptidoglycan precursors from the inner to the outer leaflet of the cytoplasmic membrane. Cell wall biogenesis; peptidoglycan biosynthesis. Essential for growth, it cannot be deleted. Under non-permissive conditions, conditional mutant shows growth arrest, dramatic morphological changes and cell lysis. Depletion causes accumulation of peptidoglycan precursors in the cytoplasm. Belongs to the MurJ/MviN family.