title: Purification and properties of the cellular and scrapie hamster prion proteins.
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-specific. Both uninfected and scrapie-infected cells synthesize a PrP isoform, denoted PrPC, which exhibits physical properties that differentiate it from PrPSc. PrPC was purified by immunoaffinity chromatography using a PrP-specific monoclonal antibody cross-linked to protein-A--Avidgel. PrPSc was purified by detergent extraction, poly(ethylene glycol) precipitation and repeated differential 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 were found to be KKXPKPGG and the first 29 residues of PrPSc were found to be KKXPKPGGWNTGGSXYPGQGSPGGNRYPP. Arg residues 3 and 15 in PrPSc and 3 in PrPC appear to be modified since no detectable signals (denoted X) were found at these positions during gas-phase sequencing. Both PrP isoforms were found to contain an intramolecular disulfide bond, linking Cys 179 and 214, which creates a loop of 36 amino acids containing the two N-linked glycosylation sites. Development of a purification protocol for PrPC should facilitate comparisons of the two PrP isoforms and lead to an understanding of how PrPSc is synthesized either from PrPC or a precursor.
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001923:Brain Chemistry; D006224:Cricetinae; D003429:Cross Reactions; D004220:Disulfides / Q000032:analysis; D004591:Electrophoresis, Polyacrylamide Gel; D007158:Immunologic Techniques; D008647:Mesocricetus; D011328:Prions / Q000032:analysis*; D011499:Protein Processing, Post-Translational; D012608:Scrapie / Q000378:metabolism*; D014158:Transcription, Genetic; D014764:Viral Proteins / Q000235:genetics / Q000302:isolation & purification*
chemical_list: D004220:Disulfides; D011328:Prions; D014764:Viral Proteins