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Monitoring the Assembly of a Secreted Bacterial Virulence Factor Using Site-specific Crosslinking
11:33

Monitoring the Assembly of a Secreted Bacterial Virulence Factor Using Site-specific Crosslinking

Published on: December 17, 2013

Oligomerization of type III secretion proteins PopB and PopD precedes pore formation in Pseudomonas

Guy Schoehn1, Anne Marie Di Guilmi, David Lemaire

  • 1Laboratoire de Virologie Moléculaire Structurale, Grenoble, France.

The EMBO Journal
|October 1, 2003
PubMed

Insights

Pseudomonas aeruginosa uses a type III secretion system to inject toxins. Researchers characterized PopB and PopD proteins, revealing oligomeric forms are key to translocon pore formation in host membranes.

Area of Science:

  • Microbiology
  • Molecular Biology
  • Structural Biology

Background:

  • * Pseudomonas aeruginosa causes opportunistic infections and chronic respiratory diseases.
  • * Type III secretion systems (T3SS) deliver effector proteins into host cells via a translocon.
  • * PopB and PopD are key T3SS translocon components in P. aeruginosa.

Purpose of the Study:

  • * To functionally and structurally characterize PopB and PopD proteins.
  • * To elucidate their role in translocon formation.
  • * To understand the mechanism of membrane pore formation.

Main Methods:

  • * Protein complex formation analysis (heterodimers, heterooligomers).
  • * Membrane binding and disruption assays under varying pH.
  • * Electron microscopy for structural visualization of membrane-associated complexes.

Main Results:

  • * PopB and PopD form soluble complexes with chaperone PcrH as heterodimers or metastable heterooligomers.
  • * Only oligomeric forms bind and disrupt cholesterol-rich membranes.
  • * Membrane association leads to ring formation (80 Å wide) with central cavities (40 Å wide).
  • * pH influences PopB/PcrH and PopD membrane activity.

Conclusions:

  • * Metastable oligomer formation precedes membrane association and translocon ring generation.
  • * This mechanism is crucial for P. aeruginosa pathogenesis.
  • * Similar mechanisms may exist in other T3SS-utilizing pathogens.

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