Cofactor Molecules Induce Structural Transformation during Infectious Prion Formation

The spread of misfolded proteins may occur in many neurodegenerative diseases. Mammalian prions are currently the only misfolded proteins in which high specific biological infectivity can be produced in vitro. Using a system that generates infectious prions de novo from purified recombinant PrP and conversion cofactors palmitoyl-oleoyl-phosphatidylglycerol (POPG) and RNA, we examined by deuterium exchange mass spectrometry (DXMS) the stepwise protein conformational changes that occur during prion formation. We found that initial incubation with POPG causes major structural changes in PrP involving all three α helices and one β strand, with subsequent addition of RNA rendering the N terminus highly exposed. Final conversion into the infectious PrPSc form was accompanied by globally decreased solvent exposure, with persistence of the major cofactor-induced conformational features. Thus, we report that cofactor molecules appear to induce major structural rearrangements during prion formation, initiating a dynamic sequence of conformational changes resulting in biologically active prions. [Display omitted] •Nonprotein cofactors induce a major structural rearrangement in prion protein•Specific cofactor-induced changes in PrP persist through infectious PrPSc formation•Infectious PrPSc formation also involves global closure in PrP conformation•PrP rearrangement suggests key cofactor role in specifying prion structure Prions are the only misfolded proteins in which high specific biological infectivity has been produced in vitro. Miller et al. examine the stepwise conformational changes in prion formation by DXMS, finding cofactor-dependent structural rearrangement in PrP prior to global closure during final PrPSc generation.