Burial of the Polymorphic Residue 129 in Amyloid Fibrils of Prion Stop Mutants

Misfolding of the natively alpha-helical prion protein into a beta-sheet rich isoform is related to various human diseases such as Creutzfeldt-Jakob disease and Gerstmann-Straussler-Scheinker syndrome. In humans, the disease phenotype is modified by a methionine/valine polymorphism at codon 129 of the prion protein gene. Using a combination of hydrogen/deuterium exchange coupled to NMR spectroscopy, hydroxyl radical probing detected by mass spectrometry, and site-directed mutagenesis, we demonstrate that stop mutants of the human prion protein have a conserved amyloid core. The 129 residue is deeply buried in the amyloid core structure, and its mutation strongly impacts aggregation. Taken together the data support a critical role of the polymorphic residue 129 of the human prion protein in aggregation and disease.