Mapping the functional domain of the prion protein.

Prion diseases such as Creutzfeldt-Jakob disease are possibly caused by the conversion of a normal cellular glycoprotein, the prion protein (PrPc) into an abnormal isoform (PrPSc). The process that causes this conversion is unknown, but to understand it requires a detailed insight into the normal activity of PrPc. It has become accepted from results of numerous studies that PrPc is a Cu-binding protein and that its normal function requires Cu. Further work has suggested that PrPc is an antioxidant with an activity like that of a superoxide dismutase. We have shown in this investigation that this activity is optimal for the whole protein and that deletion of parts of the protein reduce or abolish this activity. The protein therefore contains an active domain requiring certain regions such as the Cu-binding octameric repeat region and the hydrophobic core. These regions show high evolutionary conservation fitting with the idea that they are important to the active domain of the protein.