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Energetics of colicin import revealed by genetic cross-complementation between the Tol and Ton systems

Roland Lloubès1, Emilie Goemaere, Xiang Zhang

  • 1UMR7255 CNRS-Aix-Marseille Université, 31 chemin Aiguier, 13402 Marseille, France. roland.lloubes@imm.cnrs.fr

Biochemical Society Transactions
|November 27, 2012
PubMed

Insights

Colicins utilize outer membrane receptors and import systems for cell entry. This study investigates the functional roles of Tol and ExbB-ExbD-TonB systems in colicin import and sensitivity.

Area of Science:

  • Microbiology
  • Molecular Biology
  • Biochemistry

Background:

  • Colicins are bacteriocins that target bacterial cells by binding to outer membrane receptors.
  • Colicins employ either the Tol or the ExbB-ExbD-TonB import system for translocation across the cell envelope.
  • The Tol system comprises TolA, TolB, TolQ, and TolR, while the ExbB-ExbD-TonB system is involved in group B colicin import.

Purpose of the Study:

  • To investigate the functional phenotypes of tolQ and exbB mutants in colicin import.
  • To analyze cross-complementation data of amino acid substitutions within ExbB or TolQ transmembrane helices (TMHs).
  • To explore the relationship between colicin sensitivity and the functionality of the Tol system.

Main Methods:

  • Analysis of functional phenotypes in tolQ and exbB mutants.
  • Cross-complementation studies involving amino acid substitutions in ExbB and TolQ TMHs.
  • Assessment of colicin sensitivity in various mutant strains.

Main Results:

  • Demonstrated functional interchangeability between TolQ and ExbB, and TolR and ExbD, but not TolA and TonB.
  • Observed energy requirement for group B colicin uptake and for the dissociation of colicin E9-immunity protein complex.
  • Identified a specific phenotype of group A colicin sensitivity linked to a non-functional Tol system.

Conclusions:

  • The study elucidates the specific roles and interchangeability of components within the colicin import systems.
  • Findings provide insights into the energy requirements for colicin translocation and complex dissociation.
  • A distinct correlation between Tol system functionality and group A colicin sensitivity was established.

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