RNA and CuCl2 induced conformational changes of the recombinant ovine prion protein.

Prion diseases are a group of neurodegenerative illnesses caused by conformational conversion of benign, alpha-helix rich cellular prion protein (PrP(C)) into the highly stable, beta-sheet rich scrapie prion protein (PrP(Sc)) isoform. To date, the role of RNA on the conformational conversion of ovine prion protein in vitro remains unknown. To examine the effect of the interaction between RNA and PrP(C), conformations of recombinant ovine prion protein PrP23-256 (OvPrP23-256) binding various concentrations of RNA were analyzed by circular dichroism (CD) spectrum. The results indicated that the conformational conversion of OvPrP23-256 was triggered by RNA with a decrease in alpha-helix content and increase in beta-sheet. Moreover, the conformation of OvPrP23-256 interacting with both RNA and CuCl2 was also examined by CD spectrum, which showed that alpha-helix content decreased while beta-sheet increased dramatically. Proteinase K digestion assay disclosed that the recombinant ovine PrP(C) acquired PK resistance after RNA and/or Cu2+ treatment. It confirmed that the RNA/Cu2+ treatment in vitro altered the biochemical properties of ovine PrP(C). The implication of this finding, with respect to PrP(Sc), is that a dysfunctional state of a normal physiological process possibly facilitates diseases. The information gained from this study may provide useful approaches to study the pathogenesis of prion diseases.