Structural Studies of Prion Fibrils and Other Protein Fibrils

National Institute Of Diabetes And Digestive And Kidney Diseases

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Abstract

Progress in FY2022 was in the following areas: (1) MOLECULAR STRUCTURE OF SUP35NM FIBRILS: Sup35p is the yeast protein whose intra-cellular aggregation into amyloid-like fibrils produces the transmissible PSI+ prion phenotype. Together with Reed Wickner of NIDDK, we have shown previously that Sup35NM fibrils (containing the N-terminal and middle domains of Sup35p) contain in-register parallel beta-sheets. Other aspects of Sup35NM fibril structure are unclear and controversial. We are now working towards determining the full molecular structure of Sup35NM fibrils, using cryo-EM methods. In FY2021, cryoEM images of Sup35NM were obtained, but proved to be intractable due to a high level of structural heterogeneity. We are now working on methods for generating homogeneous Sup35NM fibrils, based on repeated seeded growth under controlled conditions. Initial negative-stain TEM images are promising, and cryoEM images will be obtained in the next month. We expect to have results from these studies in the coming year.