Characterization of the putative fusogenic domain in vesicular stomatitis virus glycoprotein G

Area of Science:

• Virology
• Molecular Biology
• Cell Biology

Background:

• The envelope glycoprotein G of vesicular stomatitis virus (VSV) mediates membrane fusion at acidic pH.
• A highly conserved segment (amino acids 123-137) of the G protein is implicated in fusogenic activity.

Purpose of the Study:

• To elucidate the role of the conserved amino acid segment (123-137) in low-pH-induced membrane fusion.
• To identify specific residues critical for the fusogenic function of VSV glycoprotein G.

Main Methods:

• Site-directed mutagenesis was employed to alter specific amino acids within the 123-137 region of the G protein.
• Mutant glycoproteins were expressed in COS cells and assayed for acid-pH-induced cell-cell fusion.
• Protein transport to the cell surface was assessed to differentiate fusion defects from transport deficiencies.

Main Results:

• Substitution of Pro-123 with Leu did not affect fusogenic activity.
• Mutations at Phe-125 and Asp-137 altered the pH optimum and reduced fusion efficiency.
• Mutations of Gly-124 to Ala and Pro-127 to Gly/Leu significantly inhibited cell-cell fusion (approx. 90%) without impairing cell surface transport.
• Deletions within the segment often resulted in transport-defective mutants.

Conclusions:

• The conserved residues Gly-124 and Pro-127 are critical for VSV G protein-mediated membrane fusion.
• These residues are likely located within the fusion peptide, directly participating in the fusion process.
• The identified conserved domain represents a putative fusion domain of the VSV G protein.