Interplay of alpha-synuclein binding and conformational switching probed by single-molecule fluorescence.

Abstract

We studied the coupled binding and folding of alpha-synuclein, an intrinsically disordered protein linked with Parkinson's disease. Using single-molecule fluorescence resonance energy transfer and correlation methods, we directly probed protein membrane association, structural distributions, and dynamics. Results revealed an intricate energy landscape on which binding of alpha-synuclein to amphiphilic small molecules or membrane-like partners modulates conformational transitions between a natively unfolded state and multiple alpha-helical structures. Alpha-synuclein conformation is not continuously tunable, but instead partitions into 2 main classes of folding landscape structural minima. The switch between a broken and an extended helical structure can be triggered by changing the concentration of binding partners or by varying the curvature of the binding surfaces presented by micelles or bilayers composed of the lipid-mimetic SDS. Single-molecule experiments with lipid vesicles of various composition showed that a low fraction of negatively charged lipids, similar to that found in biological membranes, was sufficient to drive alpha-synuclein binding and folding, resulting here in the induction of an extended helical structure. Overall, our results imply that the 2 folded structures are preencoded by the alpha-synuclein amino acid sequence, and are tunable by small-molecule supramolecular states and differing membrane properties, suggesting novel control elements for biological and amyloid regulation of alpha-synuclein.

• Authors: Allan Chris M Ferreon, Yann Gambin, Edward A Lemke, Ashok A Deniz
• Journal: Proceedings of the National Academy of Sciences of the United States of America (Proc Natl Acad Sci U S A) Vol. 106 Issue 14 Pg. 5645-50 (Apr 07 2009) ISSN: 1091-6490 [Electronic] United States
• PMID: 19293380 (Publication Type: Journal Article, Research Support, N.I.H., Extramural, Research Support, Non-U.S. Gov't)

Chemical References

• Lipid Bilayers
• Micelles
• alpha-Synuclein
• Sodium Dodecyl Sulfate

Topics

• Fluorescence Resonance Energy Transfer
• Lipid Bilayers
• Micelles
• Protein Binding
• Protein Conformation
• Protein Folding
• Sodium Dodecyl Sulfate
• alpha-Synuclein (chemistry)