Structural properties of gp41 fusion peptide at a model membrane interface

Area of Science:

• Biophysics
• Structural Biology
• Surface Chemistry

Background:

• The N-terminal region of HIV gp41 is crucial for viral entry and membrane fusion.
• Understanding protein behavior at membrane interfaces is key to developing antiviral strategies.
• Previous studies have proposed various secondary structures for this protein segment.

Purpose of the Study:

• To determine the structure and orientation of the HIV gp41 N-terminus at a phospholipid monolayer interface.
• To identify the most plausible secondary structure among reported models.
• To elucidate the insertion angle of the protein into the membrane.

Main Methods:

• Surface-specific sum frequency generation (SFG) spectroscopy to probe Amide I vibrational modes.
• Modeling of SFG spectra based on the Brownian oscillator model and cumulant expansion.
• Comparison of experimental data with theoretical responses for different secondary structures and orientations.

Main Results:

• Experimental SFG spectra provided information on the protein's secondary structure at the interface.
• A specific plausible secondary structure for the N-terminal 23 amino acids of gp41 was identified.
• The orientation angle of protein insertion into the phospholipid monolayer was determined.

Conclusions:

• The study successfully characterized the HIV gp41 N-terminus structure and orientation at a membrane interface.
• Findings contribute to understanding the initial steps of viral fusion and membrane interaction.
• The methodology provides a powerful tool for studying membrane-associated proteins.