Insights into the architecture of the Ure2p yeast protein assemblies from helical twisted fibrils.

The protein Ure2 from baker's yeast is associated with a heritable and transmissible phenotypic change in the yeast Saccharomyces cerevisiae. Such prion properties are thought to arise from the fact that Ure2p is able to self-assemble into insoluble fibrils. Assemblies of Ure2p are composed of full-length proteins in which the structure of the globular, functional, C-terminal domain is retained. We have carried out structural studies on full-length, wild-type Ure2p fibrils with a regularly twisted morphology. Using electron microscopy and cryo-electron microscopy with image analysis we show high-resolution images of the twisted filaments revealing details within the fibrillar structure. We examine these details in light of recent proposed models and discuss how this new information contributes to an understanding of the architecture of Ure2p yeast prion fibrils.