Involved in the assembly of lipopolysaccharide (LPS). Required for the translocation of LPS from the inner membrane to the outer membrane. Facilitates the transfer of LPS from the inner membrane to the periplasmic protein LptA. Could be a docking site for LptA. Component of the lipopolysaccharide transport and assembly complex. Interacts with LptA and the LptBFG transporter complex. When overexpressed, can form homodimers in vivo. Leads to irreversible cell damage, growth arrest and an extreme sensitivity to SDS. Interacts with the LptBFG ABC transporter complex, but does not affect its ATPase activity. Belongs to the LptC family.