title: Conformational dynamics of α-synuclein: insights from mass spectrometry.
abstract: The aggregation and deposition of α-synuclein in Lewy bodies is associated with the progression of Parkinson's disease. Here, Mass Spectrometry (MS) is used in combination with Ion Mobility (IM), chemical crosslinking and Electron Capture Dissociation (ECD) to probe transient structural elements of α-synuclein and its oligomers. Each of these reveals different aspects of the conformational heterogeneity of this 14 kDa protein. IM-MS analysis indicates that this protein is highly disordered, presenting in positive ionisation mode with a charge state range of 5 ≤z≤ 21 for the monomer, along with a collision cross section range of ∼1600 Å(2). Chemical crosslinking applied in conjunction with IM-MS captures solution phase conformational families enabling comparison with those exhibited in the gas phase. Crosslinking IM-MS identifies 3 distinct conformational families, Compact (∼1200 Å(2)), Extended (∼1500 Å(2)) and Unfolded (∼2350 Å(2)) which correlate with those observed in solution. ECD-Fourier Transform-Ion Cyclotron Resonance Mass Spectrometry (ECD-FT-ICR MS) highlights the effect of pH on α-synuclein structure, identifying the conformational flexibility of the N and C termini as well as providing evidence for structure in the core and at times the C terminus. A hypothesis is proposed for the variability displayed in the structural rearrangement of α-synuclein following changes in solution pH. Following a 120 h aggregation time course, we observe an increase in the ratio of dimer to monomer, but no gross conformational changes in either, beyond the significant variations that are observed day-to-day from this conformationally dynamic protein.
authors.affiliation: Manchester Institute of Biotechnology, University of Manchester, Manchester, M1 7DN, UK. Perdita.barran@manchester.ac.uk.
authors.forename: Ashley S
authors.initials: AS
authors.lastname: Phillips
authors.forename: Alexandre F
authors.initials: AF
authors.lastname: Gomes
authors.forename: Jason M D
authors.initials: JM
authors.lastname: Kalapothakis
authors.forename: Jay E
authors.initials: JE
authors.lastname: Gillam
authors.forename: Jonas
authors.initials: J
authors.lastname: Gasparavicius
authors.forename: Fabio C
authors.initials: FC
authors.lastname: Gozzo
authors.forename: Tilo
authors.initials: T
authors.lastname: Kunath
authors.forename: Cait
authors.initials: C
authors.lastname: MacPhee
authors.forename: Perdita E
authors.initials: PE
authors.lastname: Barran
mesh_terms: D000595:Amino Acid Sequence; D006801:Humans; D006863:Hydrogen-Ion Concentration; D013058:Mass Spectrometry; D008969:Molecular Sequence Data; D066329:Protein Aggregates; D011487:Protein Conformation; D051844:alpha-Synuclein / Q000737:chemistry* / Q000648:ultrastructure
chemical_list: D066329:Protein Aggregates; D051844:alpha-Synuclein