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Periplasmic chaperone FkpA is essential for imported colicin M toxicity

Julia Hullmann1, Silke I Patzer, Christin Römer

  • 1Microbiology/Membrane Physiology, University of Tübingen, Auf der Morgenstelle 28, D-72076 Tübingen, Germany.

Molecular Microbiology
|June 17, 2008
PubMed

Insights

The FkpA chaperone is essential for colicin M activity in Escherichia coli. This study reveals FkpA

Area of Science:

  • Microbiology
  • Molecular Biology
  • Protein Folding

Background:

  • Chaperones are crucial for proper protein folding.
  • Colicin M is a toxin that enters Escherichia coli cells.
  • The role of periplasmic chaperones in colicin activity was unclear.

Purpose of the Study:

  • To investigate the requirement of the FkpA chaperone for colicin M activity.
  • To elucidate the specific domains and functions of FkpA involved in colicin M intoxication.
  • To establish colicin M as a tool for identifying FkpA mutants.

Main Methods:

  • Utilized fkpA mutant strains of Escherichia coli to assess colicin M sensitivity.
  • Generated and characterized spontaneous and random FkpA mutants.
  • Performed in vitro assays with purified FkpA and colicin M, including proteinase K cleavage and renaturation experiments.
  • Investigated the effect of PPIase inhibitors on FkpA activity.

Main Results:

  • FkpA is essential for colicin M-mediated killing of Escherichia coli.
  • Mutations in FkpA's peptidyl-prolyl cis-trans isomerase (PPIase) domain and N-domain confer tolerance to colicin M.
  • FkpA directly interacts with colicin M, promoting its refolding and activity in the periplasm.
  • Only colicin M, among tested colicins, requires FkpA for activity.

Conclusions:

  • Colicin M unfolds during outer membrane import and requires FkpA for refolding in the periplasm.
  • The PPIase activity of FkpA is critical for colicin M's toxic function.
  • FkpA is a specific chaperone for colicin M, and colicin M can be used to isolate FkpA mutants.

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