Selective oxidation of methionine residues in prion proteins.

Prion proteins are central to the pathogenesis of several neurodegenerative diseases through the postulated conversion of the endogenous cellular isoform (PrPc) into a pathogenic isoform (PrPSc). Although the cellular function of normal prion protein remains unresolved a number of studies have shown that prion proteins may be involved in the cellular response to oxidative stress. Here, using purified recombinant sources of mouse and chicken PrP refolded in the presence of copper (II) we show that the methionine residues of the protein are uniquely susceptible to oxidation. We suggest that Met residues may form an essential part of the mechanism of the antioxidant activity exhibited by normal prion protein.