Relation between duration of incubation period of prion infections and prion protein conformation.

In this paper, we propose the hypothesis that the long incubation period of prion infections is dependent upon a low rate of pathological prion formation and accumulation. Reduced pathological prion formation might be caused by the high content of β-sheets in the molecule. β-Sheet folding appears to proceed more slowly than folding of α-helices; the former are a major component of the prion secondary structure. This hypothesis strongly agrees with the data about folding of the artificial protein l-polylysine. This protein exists in two subforms: a rapidly folding α-helix-enriched form and a β-sheet-rich form having a very slow speed of secondary and tertiary structure formation. According to our hypothesis, the limiting factor for prion infection propagation is the speed of β-sheet folding in molecules of pathological prion but not the speed of migration of this protein through the host organism.