(Left) σE inhibition. σE is held inactive by RseA in the inner membrane. DegS, a protease, can cleave RseA if activated, but RseA cleavage is prevented by RseB. (Right) σE activation. When concomitant defects in OMP assembly and LPS assembly occur, σE is activated. Periplasmic LPS dissociates RseB from RseA, and periplasmic OMPs activate DegS to cleave RseA. This leads to a proteolytic cascade that degrades RseA, releasing and activating σE.