Involved in peptidoglycan biosynthesis. Transports lipid-linked peptidoglycan precursors from the inner to the outer leaflet of the cytoplasmic membrane. May serve as a defense mechanism against naturally occurring MurJ antagonists. Cell wall biogenesis; peptidoglycan biosynthesis. Transcribed under partial control of SigM ECF sigma factor (PubMed:17434969, PubMed:25918422). Expression is up-regulated in the absence of MurJ (PubMed:25918422). Mutants lacking both murJ and amj have a lethal defect in cell wall synthesis. Belongs to the Amj family.