Native Mass Spectrometry and Ultraviolet Photodissociation Reveal Conformation-selectivy of Zinc Ion to α-Synuclein

The conformation-specific binding mechanism between zinc ions (Zn2+) and α-synuclein (α-Syn) plays a pivotal role in elucidating the pathogenesis of Parkinson's disease. In this study, we employed native mass spectrometry (nMS) coupled with 193 nm ultraviolet photodissociation (UVPD) to unveil three distinct conformational states of α-Syn (low-charge, intermediate-charge, and high-charge conformations), which exhibited marked differences in Zn2+ binding. Experimental data demonstrated that the low-charge conformations exhibited the highest Zn2+ binding capacity, with over two binding sites and significantly greater binding affinity compared to the intermediate-charge conformations (binding one Zn2+) and the high-charge conformations (binding two Zn2+). Quantitative analysis of dissociation efficiency differences (ΔFY) revealed that Zn2+ binding induced conformation-dependent structural perturbations, with the most pronounced ΔFY variation observed in the low-charge conformations. Distribution patterns of Zn2+-bound protein fragments (holo fragments) generated by UVPD further confirmed significant divergence in fragmentation pathways among the three conformational states. By integrating primary spectral features, ΔFY variations, and holo fragment distributions, we propose distinct interaction mechanisms: the low-charge conformation predominantly stabilizes Zn2+-protein complexes through the electrostatic interaction of C terminal, the intermediate-charge conformation relies on coordination bonding, while the high-charge conformation exhibits a synergistic combination of both modes. This study elucidates the molecular mechanism of α-Syn-Zn2+ interactions from a multi-conformational dynamic equilibrium perspective, providing a theoretical foundation for the development of conformation-specific therapeutic strategies targeting Parkinson's disease.