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Structure and function of colicin S4, a colicin with a duplicated receptor-binding domain

Thomas Arnold1, Kornelius Zeth, Dirk Linke

  • 1Department I, Protein Evolution, Max Planck Institute for Developmental Biology, Spemannstrasse 35, 72076 Tübingen, Germany.

The Journal of Biological Chemistry
|December 6, 2008
PubMed

Insights

Colicin S4 uses specific outer membrane proteins (OmpW, OmpF) and the Tol system to enter E. coli. Its crystal structure reveals a unique duplicated receptor-binding domain essential for OmpW interaction.

Area of Science:

  • Bacteriology
  • Structural Biology
  • Molecular Biology

Background:

  • Colicins are bacteriocins produced by Escherichia coli, acting as toxic proteins to inhibit competing strains.
  • These proteins utilize host cell machinery for entry, including transport, diffusion, and efflux systems.
  • The general structure of colicins involves translocation, receptor-binding, and activity domains.

Purpose of the Study:

  • To elucidate the entry pathway and structural characteristics of colicin S4.
  • To determine the specific host cell receptors and systems involved in colicin S4 translocation.
  • To identify the structural basis for colicin S4's interaction with its primary receptor, OmpW.

Main Methods:

  • Tracking the functional pathway of colicin S4 within the host cell.
  • Solving the crystal structure of colicin S4 at 2.5 A resolution.
  • Site-directed mutagenesis of potential receptor-binding residues in colicin S4.

Main Results:

  • Colicin S4 specifically interacts with OmpW, OmpF, and the Tol system for cellular entry.
  • The crystal structure of colicin S4 displays a compact arrangement of four domains, featuring a duplicated receptor-binding domain.
  • Mutational analysis identified key residues in the receptor-binding domains responsible for OmpW binding.

Conclusions:

  • Colicin S4 employs a multi-step entry mechanism involving outer membrane proteins and the Tol system.
  • The unique duplicated receptor-binding domain is crucial for colicin S4's specific recognition of OmpW.
  • Understanding colicin S4's structure-function relationship provides insights into bacteriocin-host interactions.

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