We show here that mouse prion protein (PrPC) either as recombinant protein
or immunoprecipitated from brain tissue has superoxide dismutase (SOD) acti
vity. SOD activity was also associated with recombinant chicken PrPC confir
ming 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 funct
ion for PrPC consistent with its cellular distribution and suggest it has a
direct role in cellular resistance to oxidative stress.