Isolation and purification of scrapie-associated fibrils and prion protein from scrapie-infected hamster brain

Abstract

We report the purification of prion protein (PrP) 27–30 and scrapie-associated fibrils (SAF) from hamsters infected with the 263K strain of scrapie. SDS-PAGE of fractions purified from scrapie-infected brains revealed several bands at approximately 28·5 kDa, 23·9 kDa and 14·3 kDa and, in one set of preparations, a protein of M r 26 kDa was found in both scrapie-infected and sham-inoculated animals. The specificity of PrPs was confirmed by Western blotting. Ultrastructural analysis of fractions from scrapie-infected brains revealed numerous fibrils measuring approximately 20 nm in diameter and 100 to 200 nm in length. The substructure of these fibrils consisted of protofilaments which were usually straight and rarely helically arranged. We conclude that the electron microscopical appearance of SAF depends much on the purification scheme. The PrP27-30 as well as proteins of lower M r are easily detectable in scrapie-infected brains. The detection of protein of a M r 26 kDa in both scrapie-infected and sham-inoculated animals suggests that this form of PrP may exist in equilibrium with PrP33-35 c ∗ ∗ PrP 33-35 c = cellular isoform; Prp 33-35 sc = scrapie isoform. .