Conformational equilibria of intrinsically disordered proteins probed by single molecule methodologies

Many intrinsically-unstructured-proteins are involved, through their aggregation into amyloid fibrils, in neuro-degenerative pathologies like Parkinson’s, Alzheimer’s and prion diseases. The process of aggregation is still poorly understood because traditional bulk methods can only provide ensemble-averaged information for monomers and oligomers alike. These limitations can be circumvented by the novel AFM-based single-molecule approach we have recently developed to study the conformational equilibria of these proteins (1,2). This methodology proved very effective in characterizing the conformational diversity of wild type (WT) alpha-synuclein and we observed that in several unrelated conditions linked to the pathogenicity of Parkinson’s disease the conformational equilibrium of this protein shifts toward beta-sheet-containing structures. The direct relationship of these beta-structures to alpha-synuclein toxicity was confirmed by our single-molecule study of the conformational heterogeneity of its pathologic mutants A30P, A53T and E46K. (2)