New components of protein folding in extracytoplasmic compartments of Escherichia coli SurA, FkpA and Skp/OmpH

Mol Microbiol. 1996 Aug;21(4):871-84. doi: 10.1046/j.1365-2958.1996.561412.x.


A global search for extracytoplasmic folding catalysts in Escherichia coli was undertaken using different genetic systems that produce unstable or misfolded proteins in the periplasm. The extent of misfolding was monitored by the increased activity of the sigma E regulon that is specifically induced by misfolded proteins in the periplasm. Using multicopy libraries, we cloned two genes, surA and fkpA, that decreased the sigma E-dependent response constitutively induced by misfolded proteins. According to their sequences and their biochemical activities, SurA and FkpA belong to two different peptidyl prolyl isomerase (PPI) families. Interestingly, surA was also selected as a multicopy suppressor of a defined htrM (rfaD) null mutation. Such mutants produce a defective lipopolysaccharide that is unable to protect outer membrane proteins from degradation during folding. The SurA multicopy suppression effect in htrM (rfaD) mutant bacteria was directly associated with its ability to catalyse the folding of outer membrane proteins immediately after export. Finally, Tn10 insertions were isolated, which led to an increased activity of the sigma E regulon. Such insertions were mapped to the dsb genes encoding catalysts of the protein disulphide isomerase (PDI) family, as well as to the surA, fkpA and ompH/skp genes. We propose that these three proteins (SurA, FkpA and OmpH/Skp) play an active role either as folding catalysts or as chaperones in extracytoplasmic compartments.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Bacterial Outer Membrane Proteins / analysis
  • Bacterial Outer Membrane Proteins / chemistry
  • Bacterial Outer Membrane Proteins / genetics
  • Bacterial Proteins / genetics*
  • Bacterial Proteins / physiology
  • Carbohydrate Epimerases / genetics
  • Carrier Proteins*
  • DNA-Binding Proteins / genetics*
  • Detergents / pharmacology
  • Escherichia coli / chemistry*
  • Escherichia coli / drug effects
  • Escherichia coli / genetics
  • Escherichia coli Proteins*
  • Gene Expression Regulation, Bacterial / physiology
  • Genetic Complementation Test
  • Heat-Shock Proteins*
  • Immunophilins*
  • Isomerases / genetics
  • Lipopolysaccharides
  • Membrane Proteins / genetics*
  • Molecular Chaperones*
  • Mutation
  • Peptidylprolyl Isomerase*
  • Periplasmic Proteins*
  • Protein Disulfide-Isomerases
  • Protein Folding*
  • Recombinant Fusion Proteins
  • Regulon / genetics
  • Serine Endopeptidases / genetics
  • Sigma Factor / physiology
  • Suppression, Genetic
  • Transcription Factors / physiology


  • Bacterial Outer Membrane Proteins
  • Bacterial Proteins
  • Carrier Proteins
  • DNA-Binding Proteins
  • Detergents
  • Escherichia coli Proteins
  • Heat-Shock Proteins
  • Lipopolysaccharides
  • Membrane Proteins
  • Molecular Chaperones
  • Periplasmic Proteins
  • Recombinant Fusion Proteins
  • Sigma Factor
  • Transcription Factors
  • sporulation-specific sigma factors
  • Skp protein, E coli
  • ompH protein, bacteria
  • DegP protease
  • Serine Endopeptidases
  • Isomerases
  • ADP-L-glycero-D-mannoheptose-6-epimerase
  • Carbohydrate Epimerases
  • SurA protein, E coli
  • periplasmic peptidylprolyl cis-trans isomerase
  • Immunophilins
  • Peptidylprolyl Isomerase
  • FkpA protein, E coli
  • Protein Disulfide-Isomerases