The N-terminal domain of colicin E3 interacts with TolB which is involved in the colicin translocation step

Mol Microbiol. 1997 Mar;23(5):909-20. doi: 10.1046/j.1365-2958.1997.2751640.x.


Colicins use two envelope multiprotein systems to reach their cellular target in susceptible cells of Escherichia coli: the Tol system for group A colicins and the TonB system for group B colicins. The N-terminal domain of colicins is involved in the translocation step. To determine whether it interacts in vivo with proteins of the translocation system, constructs were designed to produce and export to the cell periplasm the N-terminal domains of colicin E3 (group A) and colicin B (group B). Producing cells became specifically tolerant to entire extracellular colicins of the same group. The periplasmic N-terminal domains therefore compete with entire colicins for proteins of the translocation system and thus interact in situ with these proteins on the inner side of the outer membrane. In vivo cross-linking and co-immunoprecipitation experiments in cells producing the colicin E3 N-terminal domain demonstrated the existence of a 120 kDa complex containing the colicin domain and TolB. After in vitro cross-linking experiments with these two purified proteins, a 120 kDa complex was also obtained. This suggests that the complex obtained in vivo contains exclusively TolB and the colicin E3 domain. The N-terminal domain of a translocation-defective colicin E3 mutant was found to no longer interact with TolB. Hence, this interaction must play an important role in colicin E3 translocation.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Alkaline Phosphatase / metabolism
  • Antibodies, Bacterial / immunology
  • Bacterial Outer Membrane Proteins / metabolism
  • Bacterial Outer Membrane Proteins / physiology
  • Bacterial Proteins / genetics*
  • Bacterial Proteins / immunology
  • Bacterial Proteins / isolation & purification
  • Bacterial Proteins / metabolism
  • Blotting, Western
  • Cell Membrane / drug effects
  • Cell Membrane / metabolism
  • Colicins / genetics*
  • Colicins / immunology
  • Colicins / metabolism
  • Cytoplasm / metabolism
  • Deoxycholic Acid / pharmacology
  • Electrophoresis, Polyacrylamide Gel
  • Escherichia coli / genetics*
  • Escherichia coli / metabolism*
  • Escherichia coli Proteins*
  • Formaldehyde / metabolism
  • Formaldehyde / pharmacology
  • Gene Expression Regulation, Bacterial
  • Lipoproteins / metabolism
  • Microscopy, Electron
  • Peptides / isolation & purification
  • Peptidoglycan / metabolism
  • Periplasmic Proteins*
  • Plasmids
  • Point Mutation
  • Precipitin Tests
  • Proteoglycans*
  • Recombination, Genetic
  • Ribonucleases / metabolism
  • Sodium Dodecyl Sulfate / pharmacology
  • Translocation, Genetic
  • beta-Lactamases / metabolism


  • Antibodies, Bacterial
  • Bacterial Outer Membrane Proteins
  • Bacterial Proteins
  • Colicins
  • Escherichia coli Proteins
  • ExcC protein, E coli
  • Lipoproteins
  • Peptides
  • Peptidoglycan
  • Periplasmic Proteins
  • Proteoglycans
  • tolB protein, E coli
  • Deoxycholic Acid
  • PplA protein, Legionella pneumophila
  • Formaldehyde
  • Sodium Dodecyl Sulfate
  • Ribonucleases
  • Alkaline Phosphatase
  • beta-Lactamases