Recent EPR-measurements on the mouse prion protein (mPrP) have indicated that the structured C-terminal domain is capable of binding Cu(II) with high affinity. The structure of Cu(II) binding sites in PrPc are unravelled by exploiting mixed quantum-classical Car-Parrinello simulations and by computing EPR hyperfine consts. for the paramagnetic Cu(II) center. The putative binding sites, once validated by comparing with the exptl. EPR parameters, provide detailed information concerning the Cu(II) localization and coordination. The influence of Cu(II) binding sites on the structural stability of the cellular form (PrPc) and its conversion to the scrapie form (PrPsc) is investigated. [on SciFinder (R)]