Distinct regions of the colicin A translocation domain are involved in the interaction with TolA and TolB proteins upon import into Escherichia coli

Mol Microbiol. 1998 Jan;27(1):143-57. doi: 10.1046/j.1365-2958.1998.00667.x.


Group A colicins need proteins of the Escherichia coli envelope Tol complex (TolA, TolB, TolQ and TolR) to reach their cellular target. The N-terminal domain of colicins is involved in the import process. The N-terminal domains of colicins A and E1 have been shown to interact with TolA, and the N-terminal domain of colicin E3 has been shown to interact with TolB. We found that a pentapeptide conserved in the N-terminal domain of all group A colicins, the 'TolA box', was important for colicin A import but was not involved in the colicin A-TolA interaction. It was, however, involved in the colicin A-TolB interaction. The interactions of colicin A N-terminal domain deletion mutants with TolA and TolB were investigated. Random mutagenesis was performed on a construct allowing the colicin A N-terminal domain to be exported in the bacteria periplasm. This enabled us to select mutant protein domains unable to compete with the wild-type domain of the entire colicin A for import into the cells. Our results demonstrate that different regions of the colicin A N-terminal domain interact with TolA and TolB. The colicin A N-terminal domain was also shown to form a trimeric complex with TolA and TolB.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Bacterial Proteins / metabolism*
  • Blotting, Western
  • Colicins / metabolism*
  • Electrophoresis, Polyacrylamide Gel
  • Escherichia coli / genetics
  • Escherichia coli / metabolism*
  • Escherichia coli Proteins*
  • Membrane Proteins / metabolism
  • Mutagenesis
  • Periplasmic Proteins*
  • Phenotype
  • Plasmids / chemistry
  • Polymerase Chain Reaction


  • Bacterial Proteins
  • Colicins
  • Escherichia coli Proteins
  • Membrane Proteins
  • Periplasmic Proteins
  • tolA protein, E coli
  • tolB protein, E coli