The major polypeptide of scrapie-associated fibrils (SAF) has the same size, charge distribution and N-terminal protein sequence as predicted for the normal brain protein (PrP).
Scrapie-associated fibrils (SAF) are unique structures characteristic of the group of unconventional slow infections which includes scrapie and Creutzfeldt-Jakob disease. A major component of hamster fibrils has been described as a protease-resistant glycoprotein with an apparent mol. wt of 27,000-30,000 (PrP27-30). However, we report here that if fibrils are prepared by procedures designed to minimise proteolysis the PrP proteins co-purifying with hamster SAF have mol. wts of 33,000-35,000 (PrP33-35) and 26,000-29,000 (PrP26-29). We find a Lys-Lys-Arg-Pro-Lys sequence at the amino terminus of these SAF proteins, that is absent from PrP27-30, and which has recently been predicted to be the N-terminal sequence of the native PrP protein of uninfected brain. The major SAF protein (PrP33-35) and its normal brain homologue are shown to have the same apparent mol. wt and ionic charge distribution by two-dimensional gel analysis, silver staining and immunoblotting. These results support our view that PrP33-35 and the normal brain PrP protein may have the same covalent structure, and that the PrP protein is recruited into these amyloid-like SAF or into association with a non-protein component of SAF by an irreversible event initiated directly or indirectly by scrapie infection.
D000595:Amino Acid Sequence; D000818:Animals; D001921:Brain / Q000382:microbiology*; D001923:Brain Chemistry; D002850:Chromatography, Gel / Q000379:methods; D006224:Cricetinae; D004591:Electrophoresis, Polyacrylamide Gel / Q000379:methods; D009419:Nerve Tissue Proteins / Q000302:isolation & purification*; D011328:Prions / Q000032:analysis*; D014764:Viral Proteins / Q000302:isolation & purification*
D009419:Nerve Tissue Proteins; D011328:Prions; D014764:Viral Proteins