Structural analysis of prion proteins by means of drift cell and traveling wave ion mobility mass spectrometry

Abstract

The prion protein (PrP) is implicitly involved in the pathogenesis of transmissible spongiform encephalopathies (TSEs). The conversion of normal cellular PrP (PrP(C)), a protein that is predominantly alpha-helical, to a beta-sheet-rich isoform (PrP(Sc)), which has a propensity to aggregate, is the key molecular event in prion diseases. During its short life span, PrP can experience two different pH environments; a mildly acidic environment, whilst cycling within the cell, and a neutral pH when it is glycosyl phosphatidylinositol (GPI)-anchored to the cell membrane. Ion mobility (IM) combined with mass spectrometry has been employed to differentiate between two conformational isoforms of recombinant Syrian hamster prion protein (SHaPrP). The recombinant proteins studied were alpha-helical SHaPrP(90-231) and beta-sheet-rich SHaPrP(90-231) at pH 5.5 and pH 7.0. The recombinant proteins have the same nominal mass-to-charge ratio (m/z) but differ in their secondary and tertiary structures. A comparison of traveling-wave (T-Wave) ion mobility and drift cell ion mobility (DCIM) mass spectrometry estimated and absolute cross-sections showed an excellent agreement between the two techniques. The use of T-Wave ion mobility as a shape-selective separation technique enabled differentiation between the estimated cross-sections and arrival time distributions (ATDs) of alpha-helical SHaPrP(90-231) and beta-sheet-rich SHaPrP(90-231) at pH 5.5. No differences in cross-section or ATD profiles were observed between the protein isoforms at pH 7.0. The findings have potential implications for a new ante-mortem screening assay, in bodily fluids, for prion misfolding diseases such as TSEs.

Native-Like and Denatured Cytochrome c Ions Yield Cation-to-Anion Proton Transfer Reaction Products with Similar Collision Cross-Sections

“…The Ω of those ions can depend weakly on charge state [10–13] and polarity [12], but the range of Ω values for each analyte usually exceeds the precision of those measurements. Electrospray ionization of proteins from acidic, denaturing solutions [14–16], as well as prion [17] and intrinsically disordered [18] proteins from neutral, aqueous solutions, yields ions with a broad range of charges states and whose Ω depend strongly on their charge state. An improved understanding of the phenomena underlying these observations is important for maximizing the structural information that can be drawn from IM experiments.…”

Structural Characterisation of Non-Deamidated Acidic Variants of Erwinia chrysanthemi L-asparaginase Using Small-Angle X-ray Scattering and Ion-Mobility Mass Spectrometry

“…More significantly, however, the peak width of the CCS distribution for D was much broader than that of F (Fig. 9, panel c), indicating that D was sampling a wider range of conformations compared to F. Differences in the IM-MS full-width half-maximum of these peaks is indicative of increased conformational heterogeneity, as observed for other proteins (42,43). These results strongly indicate that D has more conformational heterogeneity compared to F, an observation that fits well with the SAXS data and is probably the more relevant measure from the IM-MS experiments.…”

Conformations and Assembly of Amyloid Oligomers by Electrospray Ionisation - Ion Mobility Spectrometry - Mass Spectrometry

“…These two conformations have the same nominal m/z but alternate secondary and tertiary structures. and ATD were able to distinguish between the two conformations at pH 5.5 whereas no distinction could be obtained at pH 7.0 [79] (Fig. 4).…”