Biophysical Characterization of Alpha Synuclein and its Role in Parkinson's Disease
The protein alpha synuclein is the primary component in the amyloid fibrils that form the pathogenic neural plaques in Parkinson's disease. The structural conversion of alpha synuclein in vivo from a membrane-bound α-helix to an amyloidogenic β-conformation is an essential step in the toxic aggregation of the protein. Unfortunately, the cellular processes that initiate this structural transition are complex and remain unclear. Nuclear magnetic resonance spectroscopy was used to analyze the electrostatic contributions from specific residues in alpha synuclein and to clarify their roles in the stabilization of secondary structure under various solution conditions. In order to identify amino acids important for nucleation and folding, we employed 1D, 2D and 3D NMR experiments to obtain discrete knowledge about alpha synuclein-lipid interactions, to determine pKa values for ionizable sidechain moieties and to quantify hydrogen exchange rates for the protein. In addition, we were able to demonstrate that at physiological temperature and in live E. coli cells, alpha synuclein remains unfolded. Our results expand the current biophysical model of alpha synuclein and confirm that its propensity to adopt α- or β-secondary structure is highly contingent on solution conditions, Robyn Croke-University of Connecticut 2011 consistent with the premise that the class of "intrinsically-disordered" proteins, including alpha synuclein, only fold when initiated by certain cellular factors and remain unfolded unless in the presence of such factors. Our data may provide a basis for future studies aimed at the misfolding of alpha synuclein during the aggregation process, and also help to reveal its normal function in vivo as well.