C-Terminal Cu^II Coordination to α-Synuclein Enhances Aggregation

Area of Science:

• Biochemistry
• Neuroscience
• Structural Biology

Background:

• Alpha-synuclein (αS) is a key protein implicated in Parkinson's disease (PD) pathogenesis.
• Copper (CuII) ions modulate αS structure, aggregation, and cellular localization.
• N-terminal acetylation of αS (NAcαS) affects its properties, including copper binding.

Purpose of the Study:

• To characterize the CuII coordination modes of N-terminally acetylated αS (NAcαS) using EPR spectroscopy.
• To investigate the impact of distinct CuII binding sites on NAcαS structure and aggregation, particularly in disease-relevant variants.

Main Methods:

• Electron Paramagnetic Resonance (EPR) spectroscopy for detailed characterization of CuII coordination.
• EPR hyperfine structure analyses and Peisach-Blumberg correlation.
• Generation and analysis of N-terminally acetylated H50Q variant (NAcH50Q) with and without CuII.

Main Results:

• Established an N3O1 CuII binding mode for NAcαS involving His50 and a secondary C-terminal site.
• The NAcH50Q variant shifts CuII binding to the C-terminus.
• Fibrillar NAcH50Q-CuII exhibits increased β-sheet character and hydrophobicity compared to NAcαS-CuII.

Conclusions:

• Distinct CuII binding sites differentially impact NAcαS structure, with C-terminal binding exacerbating H50Q mutation effects.
• N-terminal acetylation enhances CuII coordination properties.
• Understanding CuII's role in NAcαS and NAcH50Q misfolding may illuminate PD environmental factors.