Characterization of monomeric intermediates during VSV glycoprotein structural transition

Area of Science:

• Virology
• Structural Biology
• Biophysics

Background:

• Enveloped virus entry relies on viral glycoprotein conformational changes to mediate membrane fusion.
• Existing crystal structures offer static pre- and post-fusion states, but the dynamic transition pathway is unclear.

Purpose of the Study:

• To characterize the low-pH-induced fusogenic structural transition of the vesicular stomatitis virus (VSV) glycoprotein G ectodomain (G(th)).
• To elucidate the conformational states and dynamics of VSV G during the fusion process in solution.

Main Methods:

• Analytical ultracentrifugation
• Circular dichroism
• Electron microscopy
• Small-angle X-ray scattering
• Negative staining electron microscopy

Main Results:

• At high pH, G(th) exists as a flexible monomer exploring diverse conformations.
• At low pH, the post-fusion trimer is observed, but the pre-fusion trimer is absent in solution.
• Monomeric G ectodomains are observed on viral surfaces at physiological and low pH.
• Decreasing pH leads to more elongated monomer conformations with significant domain movements but minimal secondary structure changes.

Conclusions:

• VSV G trimers likely dissociate into monomers at the viral surface during the low-pH-induced fusion transition.
• Monomeric VSV G ectodomains are proposed as crucial intermediates in the viral membrane fusion pathway.