Multifunctions of α-Synuclein Explained by Its Dynamic Heterogeneous Conformations with a Hierarchy of Transition Times

α-Synuclein plays essential roles in synaptic vesicle homeostasis and neurotransmitter release through the interaction with membrane, while α-synuclein aggregates have been associated with several neurodegenerative diseases, especially Parkinson's disease. The different roles of α-synuclein could be attributed to the heterogenous conformations adopted by this intrinsically disordered protein. To demystify the physiological functions of α-synuclein and understand its pathogenic mechanism of Parkinson's disease, characterizing the monomeric structural ensemble and identifying the aggregation-prone and non-aggregation-prone structures are of particular importance. Here, we use inter-residue distance distributions derived from time-resolved FRET experiments as constraints to guide discrete molecular dynamics simulations of α-synuclein monomer. We explore the conformational space of α-synuclein and verify the generated conformational ensemble by additional experiments including far-UV circular dichroism spectrum and cross-linking mass spectrometry. We find that some conformational states of α-synuclein are surprisingly stable displaying dynamic transitions less than milliseconds. A comprehensive analysis of the conformational ensemble uncovers important structural features and potential conformations that are critical to stabilize the monomeric state or induce different oligomerization pathways.