PrPSc typing by N-terminal sequencing and mass spectrometry

The heterogeneity of the clinicopathological phenotype in human prion disea ses is associated with the presence of the different forms of the abnormal prion protein, PrPSc. We have previously shown that PrPSc in FFI and a subt ype of familial CJD linked to the D178N mutation can be distinguished by th eir difference in gel mobility following proteinase K (PK) treatment. To fu rther characterize the structural difference of PrPSc in familial prion dis eases, N-terminal sequencing and mass spectrometry were used to identify th e protease cleavage sites in PrPSc extracted from affected brains. We found that the main PK cleavage sites of PrPSc are located at residue 97 in FFI, and residue 82 in both CJD(178) and a GSS subtype linked to the P102L muta tion. The differential accessibility to protease in the native PrPSc sugges ts that PrPSc exist as distinct conformers in different disease states.