DegP and BepA have functionally segregated roles in degrading LptD. Relative OMP levels were determined from whole-cell lysates from a wild-type strain and strains containing each of the chromosomal mutations listed, in a ΔsurA or Δskp ΔfkpA background, by SDS-PAGE and immunoblotting for the proteins indicated. The ΔsurA ΔdegP strain and all control strains were grown at 25°C, while the Δskp ΔfkpA ΔdegP strain and all control strains were grown at 30°C. Red, reduced; Ox, oxidized.