Protein misfolding in the cell envelope of Escherichia coli: new signaling pathways.

Depending on their cellular localization, misfolded proteins in Escherichia coli trigger two different heat-shock responses. Cytoplasmic proteins induce the 'classical' heat-shock regulon transcribed by the E sigma 32 polymerase. By contrast, misfolding of proteins in the cell envelope induces the newly described E sigma E-dependent regulon. This implies that there is an inducible transduction machinery in the inner membrane. The response to protein misfolding in the cell envelope is a finely tuned system regulated by a cascade of phosphorylation and dephosphorylation reactions.