Structural Effects of Multiple Pathogenic Mutations Suggest a Model for the Initiation of Misfolding of the Prion Protein

A molecular understanding of the prion diseases requires delineation of the origin of misfolding of the prion protein (PrP). An understanding of how different disease-linked mutations affect the structure and dynamics of native monomeric PrP can provide a clue about how misfolding commences. In this study, hydrogen-deuterium exchange mass spectrometry was used to show that several disease-linked mutant variants, which are thermodynamically destabilized, share a common structural perturbation in their native states: helix1 is destabilized to an extent that correlates well with the destabilization of the native protein. The mutant variants misfold and form oligomers faster than does the wild-type protein, at rates that increase exponentially with the extent to which helix1 is destabilized in the native protein. It appears, therefore, that the loss of helix1 structure marks the beginning of PrP misfolding and oligomerization.