C-terminal juxtamembrane region of full-length M2 protein forms a membrane surface associated amphipathic helix

Area of Science:

• Structural biology
• Virology
• Biophysics

Background:

• Influenza A M2 protein is crucial for viral budding and proton transport.
• Limited structural data exist for the full-length M2 protein, with existing models of truncated constructs showing disagreement.
• The C-terminal juxtamembrane region (residues 50-60) is vital for M2 protein function in viral budding.

Purpose of the Study:

• To determine the structure of the C-terminal juxtamembrane region (residues 50-60) in the full-length influenza A M2 protein.
• To compare the structural characteristics of this region in the full-length M2 protein with those in a truncated construct.

Main Methods:

• Site-directed spin-labeling electron paramagnetic resonance (EPR) spectroscopy was employed.
• Experiments were conducted in lipid bilayers to mimic the native membrane environment.
• Continuous wave EPR spectra and power saturation data were analyzed in the presence of oxygen.

Main Results:

• The C-terminal juxtamembrane region (residues 50-60) of the full-length M2 protein adopts a membrane surface-associated amphipathic helical structure.
• EPR spectral line shapes and oxygen accessibility data were similar between the full-length M2 protein and a truncated construct.
• These findings suggest the C-terminal region's structure is conserved across different M2 protein forms.

Conclusions:

• The C-terminal juxtamembrane region of the full-length influenza A M2 protein forms an amphipathic helix at the membrane surface.
• The structural integrity of this region is comparable between full-length and truncated M2 proteins.
• This structural information contributes to understanding the M2 protein's role in viral budding and proton transport.