title: Partially Unfolded Forms of the Prion Protein Populated under Misfolding-promoting Conditions: CHARACTERIZATION BY HYDROGEN EXCHANGE MASS SPECTROMETRY AND NMR.
abstract: The susceptibility of the cellular prion protein (PrP(C)) to convert to an alternative misfolded conformation (PrP(Sc)), which is the key event in the pathogenesis of prion diseases, is indicative of a conformationally flexible native (N) state. In the present study, hydrogen-deuterium exchange (HDX) in conjunction with mass spectrometry and nuclear magnetic resonance spectroscopy were used for the structural and energetic characterization of the N state of the full-length mouse prion protein, moPrP(23-231), under conditions that favor misfolding. The kinetics of HDX of 34 backbone amide hydrogens in the N state were determined at pH 4. In contrast to the results of previous HDX studies on the human and Syrian hamster prion proteins at a higher pH, various segments of moPrP were found to undergo different extents of subglobal unfolding events at pH 4, a pH at which the protein is known to be primed to misfold to a β-rich conformation. No residual structure around the disulfide bond was observed for the unfolded state at pH 4. The N state of the prion protein was observed to be at equilibrium with at least two partially unfolded forms (PUFs). These PUFs, which are accessed by stochastic fluctuations of the N state, have altered surface area exposure relative to the N state. One of these PUFs resembles a conformation previously implicated to be an initial intermediate in the conversion of monomeric protein into misfolded oligomer at pH 4.
authors: From the National Centre for Biological Sciences, Tata Institute of Fundamental Research, Bengaluru 560065, India.
authors: Roumita
authors: R
authors: Moulick
authors: From the National Centre for Biological Sciences, Tata Institute of Fundamental Research, Bengaluru 560065, India.
authors: Ranabir
authors: R
authors: Das
authors: From the National Centre for Biological Sciences, Tata Institute of Fundamental Research, Bengaluru 560065, India jayant@ncbs.res.in.
authors: Jayant B
authors: JB
authors: Udgaonkar
mesh_terms: D000818:Animals; D013058:Mass Spectrometry / Q000379:methods*; D051379:Mice; D010449:Peptide Mapping; D011328:Prions / Q000737:chemistry*; D058767:Protein Unfolding; D014508:Urea / Q000737:chemistry
chemical_list: D011328:Prions; D014508:Urea
keywords: hydrogen-deuterium exchange; mass spectrometry (MS); nuclear magnetic resonance (NMR); partially unfolded forms; prion; protein dynamic