The Impact of the E46K Mutation on the Properties of α-Synuclein in Its Monomeric and Oligomeric States†

The third and most recently identified Parkinson's disease-linked variant of the neuronal protein α-synuclein to be identified (E46K) results in widespread brain pathology and early onset Parkinson symptoms (Zarranz et al. (2004) Ann. Neurol. 55, 164−173). Herein, we present biochemical and biophysical characterization of E46K α-synuclein in various states of aggregation. Circular dichroism and nuclear magnetic resonance spectroscopy illustrate that the E46K mutation results in subtle changes in the conformation of the monomeric protein both free in solution and in the presence of SDS micelles. However, it does not alter the overall helical propensity of the protein in the presence of phospholipids. E46K α-synuclein formed insoluble fibrils in vitro more rapidly than the wild type protein, and electron microscopy revealed that E46K α-synuclein fibrils possess a typical amyloid ultrastructure. E46K α-synuclein protofibrils, soluble aggregates that form during the transition from the monomeric form to the f...