N-terminal truncation of prion protein affects both formation and conformation of abnormal protease-resistant prion protein generated in vitro

Transmissible spongiform encephalopathy diseases are characterized by conve rsion of the normal protease-sensitive host prion protein, PrP-sen, to an a bnormal protease-resistant form, PrP-res. In the current study, deletions w ere introduced into the flexible tail of PrP-sen (23-124) to determine if t his region was required for formation of PrP-res in a cell-free assay. PrP- res formation was significantly reduced by deletion of residues 34-94 relat ive to full-length hamster PrP. Deletion of another nineteen amino acids to residue 113 further reduced the amount of PrP-res formed. Furthermore, the presence of additional proteinase K cleavage sites indicated that deletion to residue 113 generated a protease-resistant product with an altered conf ormation. Conversion of PrP deletion mutants was also affected by post-tran slational modifications to PrP-sen. Conversion of unglycosylated PrP-sen ap peared to alter both the amount and the conformation of protease-resistant PrP-res produced from N-terminally truncated PrP-sen. The N-terminal region also affected the ability of hamster PrP to block mouse PrP-res formation in scrapie-infected mouse neuroblastoma cells. Thus, regions within the fle xible N-terminal tail of PrP influenced interactions required for both gene rating and disrupting PrP-res formation.