Chaperonin GroEL accelerates protofibril formation and decorates fibrils of the Het-s prion protein

Proc Natl Acad Sci U S A. 2017 Aug 22;114(34):9104-9109. doi: 10.1073/pnas.1711645114. Epub 2017 Aug 7.


We have studied the interaction of the prototypical chaperonin GroEL with the prion domain of the Het-s protein using solution and solid-state NMR, electron and atomic force microscopies, and EPR. While GroEL accelerates Het-s protofibril formation by several orders of magnitude, the rate of appearance of fibrils is reduced. GroEL remains bound to Het-s throughout the aggregation process and densely decorates the fibrils at a regular spacing of ∼200 Å. GroEL binds to the Het-s fibrils via its apical domain located at the top of the large open ring. Thus, apo GroEL and bullet-shaped GroEL/GroES complexes in which only a single ring is capped by GroES interact with the Het-s fibrils; no evidence is seen for any interaction with football-shaped GroEL/GroES complexes in which both rings are capped by GroES. EPR spectroscopy shows that rotational motion of a nitroxide spin label, placed at the N-terminal end of the first β-strand of Het-s fibrils, is significantly reduced in both Het-s/GroEL aggregates and Het-s fibrils, but virtually completely eliminated in Het-s/GroEL fibrils, suggesting that in the latter, GroEL may come into close proximity to the nitroxide label. Solid-state NMR measurements indicate that GroEL binds to the mobile regions of the Het-s fibril comprising the N-terminal tail and a loop connecting β-strands 4 and 5, consistent with interactions involving GroEL binding consensus sequences located therein.

Keywords: EPR; NMR; amyloid–chaperone interactions; atomic force microscopy; electron microscopy.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, N.I.H., Intramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Acid Sequence
  • Amyloid / chemistry*
  • Amyloid / metabolism
  • Amyloid / ultrastructure
  • Chaperonin 10 / chemistry
  • Chaperonin 10 / genetics
  • Chaperonin 10 / metabolism
  • Chaperonin 60 / chemistry*
  • Chaperonin 60 / genetics
  • Chaperonin 60 / metabolism
  • Electron Spin Resonance Spectroscopy
  • Fungal Proteins / chemistry*
  • Fungal Proteins / genetics
  • Fungal Proteins / metabolism
  • Magnetic Resonance Spectroscopy
  • Microscopy, Atomic Force
  • Microscopy, Electron
  • Models, Molecular
  • Mutation
  • Prion Proteins / chemistry*
  • Prion Proteins / genetics
  • Prion Proteins / metabolism
  • Protein Binding
  • Protein Conformation


  • Amyloid
  • Chaperonin 10
  • Chaperonin 60
  • Fungal Proteins
  • HET-S protein, Podospora anserina
  • Prion Proteins