LptD_NT relays LPS from LptA. Portion of LptD_NT of LptD likely resides in the outer membrane, and the LPS-conduit of the β-jellyroll is open to lipid phase (Fig. 1c). At the interface of LptD_NT domain and the β-barrel of LptD, the hydrophobic portion of LPS may directly enter into the lipid phase, whereas the hydrophilic moiety of LPS may enter into the barrel of LptD. The LPS molecules are inserted into the outer leaflet of the outer membrane upon dislocation of strands β1 and β2. LptE is a lipoprotein, and probably binds to the hydrophilic head groups of LPS in the process.