Periplasmic stress and ECF sigma factors

Annu Rev Microbiol. 2001;55:591-624. doi: 10.1146/annurev.micro.55.1.591.


Envelope stress responses play important physiological roles in a variety of processes, including protein folding, cell wall biosynthesis, and pathogenesis. Many of these responses are controlled by extracytoplasmic function (ECF) sigma factors that respond to external signals by means of a membrane-localized anti-sigma factor. One of the best-characterized, ECF-regulated responses is the sigma(E) envelope stress response of Escherichia coli. The sigma(E) pathway ensures proper assembly of outer-membrane proteins (OMP) by controlling expression of genes involved in OMP folding and degradation in response to envelope stresses that disrupt these processes. Prevailing evidence suggests that, in E. coli, a second envelope stress response controlled by the Cpx two-component system ensures proper pilus assembly. The sensor kinase CpxA recognizes misfolded periplasmic proteins, such as those generated during pilus assembly, and transduces this signal to the response regulator CpxR through conserved phosphotransfer reactions. Phosphorylated CpxR activates transcription of periplasmic factors necessary for pilus assembly.

Publication types

  • Review

MeSH terms

  • Bacterial Outer Membrane Proteins / metabolism
  • Bacterial Physiological Phenomena*
  • Bacterial Proteins / metabolism*
  • Escherichia coli Proteins*
  • Fimbriae, Bacterial / metabolism
  • Heat-Shock Proteins / metabolism
  • Periplasm / metabolism
  • Periplasm / physiology*
  • Protein Folding
  • Protein Kinases / metabolism
  • Sigma Factor / metabolism*
  • Signal Transduction


  • Bacterial Outer Membrane Proteins
  • Bacterial Proteins
  • Escherichia coli Proteins
  • Heat-Shock Proteins
  • Sigma Factor
  • CpxR protein, Bacteria
  • Protein Kinases
  • CpxA protein, E coli
  • CpxA protein, bacteria