Sequential conformational rearrangements in flavivirus membrane fusion

Area of Science:

• Virology
• Structural Biology
• Biophysics

Background:

• West Nile Virus (WNV) entry into host cells relies on its envelope protein (E) mediating membrane fusion.
• This fusion process is triggered by low pH and involves significant conformational changes in the E protein.

Purpose of the Study:

• To elucidate the mechanism of WNV-mediated membrane fusion at a single-particle level.
• To identify rate-limiting steps and potential intermediates during the fusion process.
• To correlate structural features of the E protein with its fusion kinetics.

Main Methods:

• Utilized WNV virus-like particles (VLPs) to study hemifusion in a single-particle format.
• Introduced specific mutations into the E protein to assess their impact on fusion.
• Performed kinetic simulations to model the trimerization process.

Main Results:

• Individual E subunit trimerization and fusion loop engagement are rate-limiting for WNV fusion.
• Hemifusion necessitates the involvement of at least two adjacent E protein trimers.
• Monomer availability for trimerization at the virus-target membrane interface acts as a bottleneck.

Conclusions:

• A model for WNV membrane fusion is proposed, highlighting trimerization as a critical bottleneck.
• The findings provide insights into the structural requirements for viral fusion.
• The derived model has implications for understanding membrane fusion in broader biological contexts.