The sigma(E) and Cpx regulatory pathways: overlapping but distinct envelope stress responses

The Cpx and sigma(E) extracytoplasmic stress responses sense and respond to misfolded proteins in the bacterial envelope. Recent studies have highligh ted differences between these regulatory pathways in terms of activating si gnals, mechanisms of signal transduction and the nature of the responses. C umulatively, the findings suggest distinct physiological roles for these pa rtially overlapping envelope stress responses. The sigma(E) pathway is esse ntial for survival and is primarily responsible for monitoring and respondi ng to alterations in outer membrane protein folding. Mounting evidence sugg ests that the Cpx regulon may have been adapted to ensure properly timed ex pression and assembly of adhesive organelles.