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.
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