Compact conformations of α-synuclein induced by alcohols and copper.
The intrinsically disordered protein α-synuclein aggregates into amyloid fibrils, a process known to be implicated in several neurodegenerative states. Partially folded forms of the protein are thought to trigger the aggregation process. Here, α-synuclein conformers are characterized by analysis of the charge-state distributions observed in electrospray-ionization mass spectrometry under negative-ion mode. It is found that, even at neutral pH, a small fraction of the molecular population is in a compact conformation. Several distinct partially folded forms are then identified under conditions that promote α-synuclein aggregation, such as solutions of simple and fluorinated alcohols. Specific intermediates accumulate at increasing concentrations of ethanol, hexafluoro-2-propanol, and trifluoroethanol. Finally, extensive folding induced by Cu(2+) binding is revealed by titrations in the presence of Cu(2+)-glycine. The data confirm the existence of a single, high-affinity binding site for Cu(2+). Because accumulation of this partially folded form correlates with enhancement of fibrillation kinetics, it is likely to represent an amyloidogenic intermediate in α-synuclein conformational transitions.
Department of Biotechnology and Biosciences, University of Milano-Bicocca, 20126 Milan, Italy.
Antonino
A
Natalello
Federico
F
Benetti
Silvia Maria
SM
Doglia
Giuseppe
G
Legname
Rita
R
Grandori
D019327:Copper Sulfate / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D000432:Methanol / Q000737:chemistry*; D020005:Propanols / Q000737:chemistry*; D017510:Protein Folding; D017434:Protein Structure, Tertiary; D021241:Spectrometry, Mass, Electrospray Ionization; D014270:Trifluoroethanol / Q000737:chemistry*; D051844:alpha-Synuclein / Q000737:chemistry*; D006845:Hydrocarbons, Fluorinated
D019327:Copper Sulfate; D000432:Methanol; D020005:Propanols; D014270:Trifluoroethanol; D051844:alpha-Synuclein; C001337:hexafluoroisopropanol; D006845:Hydrocarbons, Fluorinated