Dataset Information

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.

SUBMITTER: Ferreon AC

PROVIDER: S-EPMC2667048 | biostudies-literature | 2009 Apr

REPOSITORIES: biostudies-literature

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

Ferreon Allan Chris M AC Gambin Yann Y Lemke Edward A EA Deniz Ashok A AA

Proceedings of the National Academy of Sciences of the United States of America 20090317 14

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 native ...[more]

PMID: 19293380

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Project description:Human alpha-Synuclein (alphaSyn) is a natively unfolded protein whose aggregation into amyloid fibrils is involved in the pathology of Parkinson disease. A full comprehension of the structure and dynamics of early intermediates leading to the aggregated states is an unsolved problem of essential importance to researchers attempting to decipher the molecular mechanisms of alphaSyn aggregation and formation of fibrils. Traditional bulk techniques used so far to solve this problem point to a direct correlation between alphaSyn's unique conformational properties and its propensity to aggregate, but these techniques can only provide ensemble-averaged information for monomers and oligomers alike. They therefore cannot characterize the full complexity of the conformational equilibria that trigger the aggregation process. We applied atomic force microscopy-based single-molecule mechanical unfolding methodology to study the conformational equilibrium of human wild-type and mutant alphaSyn. The conformational heterogeneity of monomeric alphaSyn was characterized at the single-molecule level. Three main classes of conformations, including disordered and "beta-like" structures, were directly observed and quantified without any interference from oligomeric soluble forms. The relative abundance of the "beta-like" structures significantly increased in different conditions promoting the aggregation of alphaSyn: the presence of Cu2+, the pathogenic A30P mutation, and high ionic strength. This methodology can explore the full conformational space of a protein at the single-molecule level, detecting even poorly populated conformers and measuring their distribution in a variety of biologically important conditions. To the best of our knowledge, we present for the first time evidence of a conformational equilibrium that controls the population of a specific class of monomeric alphaSyn conformers, positively correlated with conditions known to promote the formation of aggregates. A new tool is thus made available to test directly the influence of mutations and pharmacological strategies on the conformational equilibrium of monomeric alphaSyn.

Dataset Information

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

Publications

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

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