Time-Resolved SAXS Reveals Distinct Millisecond Metal-Induced Conformational Dynamics of Monomeric α-Synuclein

Area of Science:

• Biochemistry
• Structural Biology
• Neuroscience

Background:

• Alpha-synuclein (αSyn) aggregation is central to Parkinson's disease pathology.
• The role of transition metal ions in initiating αSyn conformational changes and aggregation remains unclear.
• Understanding early structural dynamics is crucial for deciphering disease mechanisms.

Purpose of the Study:

• To investigate the immediate structural rearrangements of wild-type alpha-synuclein (WT-αSyn) upon interaction with specific transition metal ions.
• To elucidate metal-specific conformational dynamics on a sub-second timescale.
• To provide mechanistic insights into metal-induced protein misfolding relevant to synucleinopathies.

Main Methods:

• Time-resolved small-angle X-ray scattering (TR-SAXS) in a microfluidic setup.
• Analysis using Guinier analysis, GNOM, and Ensemble Optimization Method (EOM).
• Fractal dimension analysis and hierarchical clustering.

Main Results:

• Distinct, metal-specific conformational transitions of WT-αSyn observed on the sub-second timescale.
• Fe3+ induced rapid compaction; Cu2+ promoted extended, heterogeneous conformations.
• Mn2+ and Zn2+ led to gradual, domain-specific compaction; Cu2+ favored early aggregation intermediates.

Conclusions:

• Metal ion binding differentially and rapidly reshapes the WT-αSyn conformation ensemble.
• These initial structural changes provide mechanistic insights into metal-induced misfolding pathways.
• Findings are relevant to understanding Parkinson's disease and other synucleinopathies.