Biophysical analysis of DOPAC-induced alterations in -Synuclein and E46K membrane binding dynamics

α-Synuclein (Syn) is an intrinsically disordered protein involved in synaptic plasticity, adopting an α-helical conformation upon membrane binding. The E46K mutation, linked to early-onset Parkinson’s disease (PD), promotes a more compact protein state and increases membrane affinity. Here, we investigated the effects of DOPAC, a catechol derivative, on Syn and E46K interactions with lipid membranes using small unilamellar vesicles (SUVs) and an array of biophysical techniques, including far-UV circular dichroism (CD), surface plasmon resonance (SPR), and hydrogen-deuterium exchange mass spectrometry (HDXMS). Both proteins exhibit similar membrane affinity, but E46K undergoes faster lipid-induced folding and slower interaction kinetics. When pre-incubated with DOPAC, Syn shows increased deuterium exchange in the 55–70 region, whereas E46K remains unaffected. However, under membranebound conditions, DOPAC enhances solvent exposure in E46K, leading to its partial displacement, while no direct interaction with Syn is observed. These findings suggest that DOPAC modulates Synmembrane interactions while preferentially affecting the membrane-bound E46K species, enhancing their structural dynamics. By influencing Syn aggregation and membrane interactions, DOPAC may play a role in neurodegenerative processes, offering insights into potential therapeutic strategies for PD.