Acetylation Rather than H50Q Mutation Impacts the Kinetics of Cu(II) Binding to α-Synuclein

The interaction between alpha-synuclein (alpha Syn) and Cu2+ has been suggested to be closely linked to brain copper homeostasis. Disruption of copper levels could induce misfolding and aggregation of alpha Syn, and thus contribute to the progression of Parkinson's disease (PD). Understanding the molecular mechanism of alpha Syn-Cu2+ interaction is important and controversies in Cu2+ coordination geometry with alpha Syn still exists. Herein, we find that the pathological H50Q mutation has no impact on the kinetics of Cu2+ binding to the high-affinity site of wild type alpha Syn (WT-alpha Syn), indicating the non-involvement of His50 in high-affinity Cu2+ binding to WT-alpha Syn. In contrast, the physiological N-terminally acetylated alpha Syn (NAc-alpha Syn) displays several orders of magnitude weaker Cu2+ binding affinity than WT-alpha Syn. Cu2+ coordination mode to NAc-alpha Syn has also been proposed based on EPR spectrum. In addition, we find that Cu2+ coordinated WT-alpha Syn is reduction-active in the presence of GSH, but essentially inactive towards ascorbate. Our work provides new insights into alpha Syn-Cu2+ interaction, which may help understand the multifaceted normal functions of alpha Syn as well as pathological consequences of alpha Syn aggregation.

Automated summary

The interaction between alpha-Synuclein and Cu2+ plays a role in brain copper homeostasis, potentially affecting the progression of Parkinson's disease. While the H50Q mutation does not impact Cu2+ binding to WT-alpha Syn, NAc-alpha Syn shows significantly weaker Cu2+ binding affinity. Cu2+ coordination mode to NAc-alpha Syn has been proposed based on EPR spectrum.