Prions, proteinase K and infectivity.

It has been described that the breakdown of β-sheets in PrP (Sc) by denaturation results in loss of infectivity and PK-sensitivity, suggesting a relationship between the structure and PK-resistance. It is also known that an important fraction of total PrP (Sc) is PK-sensitive and can be isolated by the method we already described. Consequently, we decided to employ the PK-sensitive fraction of PrP (Sc) as a potential and useful tool for structural studies. Thus, two essential questions were addressed in our recent article. First, the difference in the infectivity between the sensitive and resistant fractions and second, whether sensitive and resistant PrP (Sc) shared the same conformation or were only different size multimers with the same basic conformation. Here we discuss our latest data in light of recent infectivity studies and their possible implications on the conformation of the prion.