Purification and properties of the cellular and scrapie hamster prion proteins

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Abstract
During scrapie infection an abnormal isoform of the prion protein (PrP), designated PrPsc, accumulates and is found to copurify with infectivity; to date, no nucleic acid has been found which is scrapie-sepecific. Both uninfected and scrapie-infected cells synthesize a Prp isoform, denoted PrPc, which exhibits physical properties that differntiate it from PrPsc was purified by immunoaffinity chromatography using a PrP- sepecific monoclonal antibody cross-linked to protein-A-Avidgel. PrPsc was purified by detergent extraction, poly(ethylene glycol) precipation and repeated differentila centrifugation of PrPsc polymers. Both PrP isoforms were found to have the same N-terminal amino acid sequence which begins at a predicted signal peptide cleavage site. The first 8 residues of PrPc found to be KKXPKPGG and the first 29 residues of PrPc were found to be KKXPKPGGWNTGGSXYPGQGSPGGNRYPP. Arg residue 3 and 15 in PrPsc and 3 PrPc appear to be modified since no contain an intramolecular disulfide bond, liking Cys 179 and 214, which creates a loop of 36 amino acid containing the two N- linked glycosylation sites. Developement of purification of how PrPsc is synthesized either form PrPc or a precursor.