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Cysteine residues in a yeast viral A/B toxin crucially control host cell killing via pH-triggered disulfide

Yutaka Suzuki1, Sara L Schwartz1, Nina C Mueller1

  • 1Molecular and Cell Biology, Department of Biosciences, and Center of Human and Molecular Biology (ZHMB), Saarland University, D-66123 Saarbruecken, Germany.

Molecular Biology of the Cell
|February 24, 2017
PubMed

Insights

The K28 toxin

Area of Science:

  • Molecular biology
  • Cell biology
  • Biochemistry

Background:

  • K28 is a viral toxin targeting yeast and fungi.
  • It enters cells via endocytosis and ER transport.
  • Cytosolic translocation mechanism remains unclear.

Purpose of the Study:

  • Investigate the mechanism of K28 toxin translocation across the ER membrane.
  • Identify factors controlling toxin conformation and host cell killing.

Main Methods:

  • Analysis of K28 toxin structure and function under varying pH conditions.
  • Investigated the role of protein disulfide isomerase (PDI).

Main Results:

  • pH-triggered thiol rearrangements in K28 control its conformation and activity.
  • Low pH stabilizes the active heterodimer; neutral pH induces inactive oligomers.
  • PDI prevents K28 oligomerization in the ER lumen.
  • pH changes trigger release of cytotoxic alpha monomers, suggesting intrinsic reduction.

Conclusions:

  • pH-dependent thiol rearrangements are critical for K28 toxin activity.
  • This provides a novel mechanism for toxin translocation and host cell intoxication.

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