Disulfide-bond scanning reveals assembly state and β-strand tilt angle of the PFO β-barrel

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X-Ray Crystallography to Study the Oligomeric State Transition of the Thermotoga maritima M42 Aminopeptidase TmPep1050
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X-Ray Crystallography to Study the Oligomeric State Transition of the Thermotoga maritima M42 Aminopeptidase TmPep1050

Published on: May 13, 2020

Takehiro K Sato1, Rodney K Tweten, Arthur E Johnson

  • 1Department of Molecular and Cellular Medicine, Texas A&M Health Science Center, College Station, Texas, USA.

Nature Chemical Biology
|April 9, 2013
PubMed

Insights

Perfringolysin O (PFO) forms a pore in cell membranes. Its transition converts unfolded protein segments into a stable, aligned beta-barrel structure within the membrane.

Area of Science:

  • Biochemistry
  • Molecular Biology
  • Structural Biology

Background:

  • Perfringolysin O (PFO) is a bacterial toxin that forms pores in cell membranes.
  • PFO belongs to the cholesterol-dependent cytolysin family.
  • Pore formation involves oligomerization into a prepore complex and subsequent insertion into the lipid bilayer.

Purpose of the Study:

  • To elucidate the structural transitions of PFO during pore formation.
  • To understand the refolding and alignment of transmembrane beta-hairpins (TMHs).
  • To investigate the dynamics of the prepore complex (PPC) to pore transition.

Main Methods:

  • Interstrand disulfide-bond scanning was employed.
  • Low-temperature trapping of the PPC intermediate was utilized.
  • Structural analysis of the assembled PFO beta-barrel pore was performed.

Main Results:

  • Fully assembled PFO beta-barrel TMHs are strictly aligned and tilted at 20° to the membrane.
  • In the PPC intermediate, TMHs are unfolded with high mobility but lack stable alignment and hydrogen bonding.
  • The transition involves significant conformational changes and stabilization of TMHs within the membrane.

Conclusions:

  • The PFO pore formation is a dynamic process involving significant protein refolding.
  • The transition converts flexible, unfolded TMHs in the PPC to a stable, ordered beta-barrel structure in the membrane.
  • This structural conversion is crucial for the cytolytic activity of PFO.

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