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The role of electrostatics in colicin nuclease domain translocation into bacterial cells

Daniel Walker1, Khédidja Mosbahi, Mireille Vankemmelbeke

  • 1Department of Biology, University of York, York YO10 5YW, United Kingdom.

The Journal of Biological Chemistry
|August 28, 2007
PubMed

Insights

Nuclease colicins, toxic proteins, enter Escherichia coli cells via electrostatic interactions with the inner membrane. Their translocation depends on FtsH, an inner membrane protein, not the Sec or Tat systems.

Area of Science:

  • Microbiology
  • Molecular Biology
  • Biochemistry

Background:

  • Nuclease colicins are cytotoxic proteins that target bacteria.
  • The translocation mechanism of nuclease colicins into the cytoplasm of Escherichia coli remains unclear.
  • Previous studies suggested electrostatic interactions with membranes are involved.

Purpose of the Study:

  • To investigate the in vivo mechanism of nuclease colicin translocation into Escherichia coli.
  • To determine the role of electrostatic interactions in colicin import.
  • To identify the cellular machinery involved in nuclease colicin uptake.

Main Methods:

  • Utilized Escherichia coli HDL11 strain with inducible anionic phospholipid levels.
  • Assessed cell killing by DNase colicin E9 and pore-forming colicins under varying inducer concentrations.
  • Correlated colicin net positive charge with cell killing rates.
  • Investigated the involvement of Sec, Tat, and FtsH in colicin translocation.

Main Results:

  • Cell killing by DNase colicin E9 was dependent on inducer levels in HDL11, unlike pore-forming colicins.
  • A positive correlation was observed between colicin DNase net positive charge and cell killing rate.
  • Nuclease colicin uptake was independent of Sec and Tat systems.
  • Toxicity of nuclease colicins was dependent on the functional inner membrane AAA(+) ATPase and protease, FtsH.

Conclusions:

  • Nuclease colicin import into Escherichia coli is mediated by electrostatic interactions with the bacterial inner membrane.
  • The translocation process relies on FtsH, an inner membrane protein, for uptake into the cytoplasm.
  • This mechanism differs from other colicins and highlights a novel pathway for toxin entry.

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