Regulation of the Escherichia coli σE‐dependent envelope stress response

Abstract

Summary: The Escherichia coli σ E‐dependent stress response pathway controls the expression of genes encoding periplasmic folding catalysts, proteases, biosynthesis enzymes for lipid A (a component of lipopolysaccharide or LPS) and other proteins known or predicted to function in or produce components of the envelope. When E. coli is subjected to heat or other stresses that generate unfolded envelope proteins, σ E activity is induced. Four key players in this signal transduction pathway have been identified: RseA, an inner membrane σ E antisigma factor; RseB, a periplasmic protein that binds to the periplasmic face of RseA; and the DegS and YaeL proteases. The major point of regulation, the interaction between σ E and RseA, is primarily controlled by the stability of RseA. Envelope stress promotes RseA degradation, which occurs by a proteolytic cascade initiated by DegS. There is evidence that one σ E‐inducing stress (OmpC overexpression) directly activates DegS to cleave RseA. Secondarily, envelope stress may relieve RseB‐mediated enhancement of RseA activity. Additional levels of control upon σ E activity may become evident upon further study of this stress response pathway.