Elucidation of structure and biological properties of the prion protein scrapie (PrP Sc) is fundamental to an understanding of the mechanism of conformational transition of cellular (PrP C) into disease-specific isoforms and the pathogenesis of prion diseases. Unfortunately, the insolubility and heterogeneity of PrP Sc have limited these studies. The observation that a construct of 106 amino acids (termed PrP106 or miniprion), derived from mouse PrP and containing two deletions (Δ23-88, Δ41-176), becomes protease-resistant when expressed in scrapie-infected neuroblastoma cells and sustains prion replication when expressed in PrP 0/0 mice prompted us to generate a corresponding synthetic peptide (sPrP106) to be used for biochemical and cell culture studies. sPrP106 was obtained successfully with a straight forward procedure, which combines classical stepwise solid phase synthesis with a purification strategy based on transient labeling with a lipophilic chromatographic probe. sPrP106 readily adopted a β-sheet structure, aggregated into branched filamentous structures without ultrastructural and tinctorial properties of amyloid, exhibited a proteinase K-resistant domain spanning residues 134-217, was highly toxic to primary neuronal cultures, and induced a remarkable increase in membrane microviscosity. These features are central properties of PrP Sc and make sPrP106 sPrPI06 an excellent tool for investigating the molecular basis of the conformational conversion of PrP C into PrP Sc and prion disease pathogenesis.
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