Involved in the assembly of lipopolysaccharide (LPS). Required for the translocation of LPS from the inner membrane to the outer membrane. May form a bridge between the inner membrane and the outer membrane, via interactions with LptC and LptD, thereby facilitating LPS transfer across the periplasm. Component of the lipopolysaccharide transport and assembly complex. Can form head-to-tail homodimers and oligomers. Interacts with LptC, LptD and with the lipid A domain of LPS. Associates with both the inner membrane and the outer membrane. Transcriptionally regulated by sigma-E factor. The N-terminal domain interacts with LptC, at the inner membrane, and the C-terminal domain interacts with LptD, at the outer membrane. Results in an earlier growth arrest and onset of cell lethality. Belongs to the LptA family.