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Strain-specific morphologies of yeast prion amyloid fibrils

Ruben Diaz-Avalos1, Chih-Yen King, Joseph Wall

  • 1Institute of Molecular Biophysics, Florida State University, Tallahassee, FL 32306-4380, USA. diaz@sb.fsu.edu

Proceedings of the National Academy of Sciences of the United States of America
|July 12, 2005
PubMed

Insights

Structural differences in yeast prion [PSI] amyloid fibrils were found using mass per length measurements. These findings support the protein-only prion theory but require further molecular explanation.

Area of Science:

  • Biochemistry
  • Structural Biology
  • Yeast Genetics

Background:

  • The yeast prion [PSI] is propagated by amyloid fibrils formed from the Sup35 protein.
  • Different strains of [PSI] exist, denoted as [VH], [VK], and [VL].
  • The protein-only prion theory predicts specific structures for these prion strains.

Purpose of the Study:

  • To investigate the structural differences between [VH], [VK], and [VL] yeast prion [PSI] amyloid fibrils.
  • To assess whether observed structural variations align with the protein-only prion theory.
  • To explore the molecular basis of strain-specific fibril morphology.

Main Methods:

  • Mass per length (mpl) measurements were performed on single amyloid fibrils.
  • Fibrils were assembled from purified recombinant Sup35 prion protein.
  • Seeded growth was used with nuclei extracted from yeast bearing the three [PSI] strains.

Main Results:

  • Amyloid fibrils exhibited unanticipated mass per length differences.
  • [VH] strain fibrils showed a bimodal mpl distribution (1.0 and 1.2 prions/repeat).
  • [VK] strain fibrils had a mean mpl of 1.15 prions/repeat, with wavy morphology.
  • [VL] strain fibrils had a mean mpl of 1.05 prions/repeat and included double fibrils.
  • Infectious and noninfectious fibrils displayed heterogeneous morphologies.

Conclusions:

  • Observed strain-specific morphological differences in amyloid fibrils directly confirm structural predictions of the protein-only prion theory.
  • The observed structural variations do not yet have a clear molecular explanation.
  • Further research is needed to elucidate the molecular mechanisms underlying prion strain diversity.

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