Normal prion protein has an activity like that of superoxide dismutase

We show here that mouse prion protein (PrPC) either as recombinant protein or immunoprecipitated from brain tissue has superoxide dismutase (SOD) activity. SOD activity was also associated with recombinant chicken PrPC confirming the evolutionary conserved phenotype suggested by sequence similarity. Acquisition of copper by PrPC during protein folding endowed SOD activity on the protein but the addition of copper following refolding did not. PrPC dependent SOD activity was abolished by deletion of the octapeptide-repeat region involved in copper binding. These results describe an enzymic function for PrPC consistent with its cellular distribution and suggest it has a direct role in cellular resistance to oxidative stress.