Direct Observation Elongated Conformational States in α-Synuclein upon Liquid-Liquid Phase Separation

alpha-Synuclein (alpha-syn) is an intrinsically disordered protein (IDP) that undergoes liquid-liquid phase separation (LLPS), fibrillation, and forms insoluble intracellular Lewy bodies in neurons, which are the hallmark of Parkinson's Disease (PD). Neurotoxicity precedes the formation of aggregates and might be related to alpha-syn LLPS. The molecular mechanisms underlying the early stages of LLPS are still elusive. To obtain structural insights into alpha-syn upon LLPS, we take advantage of cross-linking/mass spectrometry (XL-MS) and introduce an innovative approach, termed COMPASS (COMPetitive PAiring StatisticS). In this work, we show that the conformational ensemble of alpha-syn shifts from a hairpin-like structure towards more elongated conformational states upon LLPS. We obtain insights into the critical initial stages of LLPS and establish a novel mass spectrometry-based approach that will aid to solve open questions in LLPS structural biology.

Automated summary

The conformational ensemble of alpha-synuclein shifts during liquid-liquid phase separation, and a novel mass spectrometry-based approach is established to solve open questions in LLPS structural biology.