Why large icosahedral viruses need scaffolding proteins

Area of Science:

• Biophysics
• Structural Biology
• Computational Biology

Background:

• Small viruses self-assemble, but large viruses like herpes simplex virus and infectious bursal disease virus (IBDV) require templates for capsid formation.
• The assembly mechanisms of large viral shells with icosahedral order (IO) remain largely unknown despite their prevalence.

Purpose of the Study:

• To investigate the role of templates in the error-free assembly of large viral capsids.
• To elucidate the mechanisms driving the formation of icosahedral order in viral shells.

Main Methods:

• Application of continuum elasticity theory to model viral shell growth.
• Development of a minimal model for simulating viral shell assembly around a template under nonequilibrium conditions.

Main Results:

• A nonspecific template dictates capsid radius and ensures error-free assembly into universally icosahedral shells.
• Continuum elasticity theory accurately predicts assembly outcomes, matching numerical simulations.
• Identified potential wells at disclination sites crucial for icosahedral vertex formation during growth.

Conclusions:

• Nonspecific templates are key to the precise assembly of large viral capsids.
• The study provides a theoretical framework explaining experimental observations and offers predictions for future research.
• Findings have implications for understanding spherical crystal formation beyond virology.