A Coiled-Coil Peptide Shaping Lipid Bilayers upon Fusion

Area of Science:

• Biophysics
• Membrane Biology
• Protein Engineering

Background:

• Membrane fusion is crucial for cellular processes, with SNARE proteins as key mediators.
• Designed peptides K and E serve as a minimal model system to study membrane fusion mechanisms.
• The precise role of these peptides in overcoming fusion's energetic barriers requires elucidation.

Purpose of the Study:

• To investigate the interactions of peptides K and E with neutral lipid membranes.
• To determine how these peptides influence membrane structure and dynamics during fusion.
• To elucidate the molecular mechanisms by which peptides K and E promote membrane fusion.

Main Methods:

• Fluorescence spectroscopy to study peptide-membrane binding.
• Nuclear Magnetic Resonance (NMR) spectroscopy (15N and 31P) to analyze peptide orientation and lipid headgroup alignment.
• Circular Dichroism (CD) spectroscopy.
• Molecular Dynamics (MD) simulations to model peptide-membrane interactions and lipid behavior.

Main Results:

• Peptide K (cationic) binds to neutral PC/PE/cholesterol membranes, while peptide E (anionic) remains water-solubilized.
• Peptide K adopts a helical orientation parallel to the membrane surface.
• Incorporation of peptide K alters local bilayer curvature, reorients lipid headgroups, and modifies local lipid composition, inducing fusion-relevant effects.

Conclusions:

• Peptide K plays a dual role in membrane fusion: facilitating membrane proximity through coiled-coil formation and destabilizing membranes to promote fusion.
• The findings provide insights into the biophysical principles governing peptide-mediated membrane fusion.
• This model system advances our understanding of fusion mechanisms relevant to biological systems and potential therapeutic applications.