Structural analysis of prion proteins by means of drift cell and traveling wave ion mobility mass spectrometry |
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Authors: | Gillian R. Hilton Konstantinos Thalassinos Megan Grabenauer Narinder Sanghera Susan E. Slade Thomas Wyttenbach Philip J. Robinson Teresa J. T. Pinheiro Michael T. Bowers James H. Scrivens |
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Affiliation: | 1.Department of Biological Sciences,University of Warwick,Coventry,UK;2.Department of Chemistry,University of California-Santa Barbara,Santa Barbara,USA |
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Abstract: | The prion protein (PrP) is implicitly involved in the pathogenesis of transmissible spongiform encephalopathies (TSEs). The conversion of normal cellular PrP (PrPC), a protein that is predominantly α-helical, to a β-sheet-rich isoform (PrPSc), 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 α-helical SHaPrP(90-231) and β-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 α-helical SHaPrP(90-231) and β-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. |
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