Structural changes of membrane-anchored native PrPC

Misfolding and subsequent aggregation of endogeneous proteins constitute essential steps in many human disorders, including Alzheimer and prion diseases. In most prion protein-folding studies, the posttranslational modifications, the lipid anchor in particular, were lacking. Here, we studied a fully posttranslationally modified cellular prion protein, carrying two N-glycosylations and the natural GPI anchor. We used time-resolved FTIR to study the prion protein secondary structure changes when binding to a raft-like lipid membrane via its GPI anchor. We observed that membrane anchoring above a threshold concentration induced refolding of the prion protein to intermolecular beta-sheets. Such transition is not observed in solution and is membrane specific. Excessive membrane anchoring, analyzed with molecular sensitivity, is thought to be a crucial event in the development of prion diseases.