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Related Experiment Video

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Protein Misfolding Cyclic Amplification of Prions
10:12

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Published on: November 7, 2012

Conformational variations in an infectious protein determine prion strain differences.

Motomasa Tanaka1, Peter Chien, Nariman Naber

  • 1Howard Hughes Medical Institute, Department of Cellular and Molecular Pharmacology, University of California-San Francisco, San Francisco, California 94143, USA.

Nature
|March 19, 2004
PubMed
Summary

Prion strains arise from distinct protein conformations. This study shows that different Sup-NM amyloid structures directly cause specific prion strains in yeast, supporting the protein-only prion hypothesis.

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Area of Science:

  • Biochemistry
  • Molecular Biology
  • Yeast Genetics

Background:

  • Prion biology exhibits strain diversity, where identical proteins form distinct transmissible states.
  • The 'protein-only' hypothesis suggests these strains arise from different protein misfolding conformations.
  • Distinguishing cause from effect in prion strain conformation has been challenging due to difficulties in generating pure infectious material.

Purpose of the Study:

  • To investigate if distinct prion protein conformations directly cause prion strain variation.
  • To develop a method for generating infectious prion material from purified protein.
  • To test the 'protein-only' hypothesis by linking specific protein conformations to distinct prion strains.

Main Methods:

  • Developed a high-efficiency yeast infection protocol using recombinant Sup35 fragment (Sup-NM) amyloids.
  • Utilized thermal stability and electron paramagnetic resonance (EPR) spectroscopy to characterize amyloid conformations.
  • Inoculated yeast with distinct Sup-NM amyloid conformations to observe resulting prion phenotypes.

Main Results:

  • Sup-NM amyloids formed at different temperatures exhibited distinct and stable conformations.
  • Infection of yeast with these conformationally different amyloids resulted in the emergence of different [PSI+] prion strains.
  • Demonstrated that Sup-NM adopts an infectious conformation prior to cellular entry.

Conclusions:

  • Prion strain variation is directly determined by the specific conformation of the infectious prion protein.
  • This study provides direct evidence that protein conformation dictates prion strain diversity, supporting the 'protein-only' hypothesis.
  • The findings establish a direct link between the structural state of the prion protein and its resulting biological strain.