Descriptionα-Synuclein (αsyn), the main component of Lewy Body (LB), is the pathogenesis of Parkinson’s disease (PD) as well as other synucleinopathies. αSyn is intrinsically disordered and its aggregation process is affected by sequence replacement and environment factors. In this dissertation, nuclear magnetic resonance (NMR) was employed to characterize the conformations of αsyn and its variants and Thioflavin T (ThT) fluorescence was utilized to identify aggregation kinetics. The correlation between aggregation kinetics and conformation revealed specific aggregation-prone conformations, thereby providing new insights into the molecular mechanism of αsyn aggregation and possible therapeutic targets for PD.
Investigation of key residues or regions determining the difference of aggregation between human and mouse αsyn reveals that the N terminal substitution A53T plays a key role in controlling the growth rates. The helical propensity of residues 6‒31 and 50‒ 56 also have a good correlation with the aggregation growth rate. The low population of this aggregation-prone conformation in the equilibrium state leads to the proposal of possible selective molecular recognition mechanism for aggregation. The aggregation-prone mutant induces a population shift, which facilitates mutual conformational selection of the favored conformational states and leads to induced-fit structural rearrangement to the formation of stable fibril structures. Further studies on trifluoroethanol (TFE)-induced αsyn aggregation reveal a transient helical intermediate containing the same aggregation-prone region (residues 6‒31) as human-mouse chimera proteins. Finally, the more physiological, acetylated forms of αsyn and A53T familial mutations are investigated. The study is the first identification of conformation and aggregation changes induced by acetylation on αsyn and its familial mutation. The results on the acetylated αsyn and A53T compared with the non-acetylated form confirm that the helical propensity in the particular region (residues 6‒31) is important for fast αsyn aggregation.