Structure of membrane-bound alpha-synuclein from site-directed spin labeling and computational refinement

Area of Science:

• Biochemistry
• Structural Biology
• Neuroscience

Background:

• Alpha-synuclein is linked to Parkinson disease pathogenesis.
• Its physiological functions and membrane-bound structure are not well understood.
• Interactions with synaptic vesicles suggest a role in neurotransmission.

Purpose of the Study:

• To determine the structure of alpha-synuclein in a physiologically relevant lipid bilayer environment.
• To investigate how membrane binding influences alpha-synuclein conformation.

Main Methods:

• Site-directed spin labeling coupled with Electron Paramagnetic Resonance (EPR) spectroscopy.
• Continuous-wave EPR for secondary structure and membrane immersion.
• Pulsed EPR for long-range distance measurements.
• Molecular dynamics simulations restrained by EPR data.

Main Results:

• Alpha-synuclein forms an extended, curved alpha-helix (>90 amino acids) parallel to the lipid bilayer.
• This helical structure exhibits a superhelical twist, interacting with lipid headgroups and acyl chains.
• The determined structure contrasts sharply with the antiparallel helical conformation induced by SDS detergent.

Conclusions:

• The study reveals the alpha-synuclein structure in a native-like membrane environment.
• Findings highlight the critical importance of using lipid bilayers for studying membrane protein structures.
• The distinct membrane-bound conformation may be crucial for alpha-synuclein's physiological roles and disease mechanisms.