The dynamics of viruslike capsid assembly and disassembly

TL;DR

This study investigates the reversible assembly and disassembly of viruslike capsids, demonstrating that classical nucleation theory can quantitatively explain the dynamics observed in time-resolved experiments.

Contribution

It is the first work to confirm that viruslike shell assembly and disassembly follow classical nucleation theory with quantitative agreement.

Findings

T = 1 to T = 3 conversion is 10 times slower than the reverse.

Reversible size conversion can be modeled by classical nucleation theory.

Experimental results align with theoretical predictions.

Abstract

Cowpea chlorotic mottle virus (CCMV) is a widely used model for virus replication studies. A major challenge lies in distinguishing between the roles of the interaction between coat proteins and that between the coat proteins and the viral RNA in assembly and disassembly processes. Here, we report on the spontaneous and reversible size conversion of the empty capsids of a CCMV capsid protein functionalized with a hydrophobic elastin-like polypeptide which occurs following a pH jump. We monitor the concentration of T = 3 and T = 1 capsids as a function of time and show that the time evolution of the conversion from one T number to another is not symmetric: the conversion from T = 1 to T = 3 is a factor of 10 slower than that of T = 3 to T = 1. We explain our experimental findings using a simple model based on classical nucleation theory applied to virus capsids, in which we account for the change in the free protein concentration, as the different types of shells assemble and disassemble by shedding or absorbing single protein subunits. As far as we are aware, this is the first study confirming that both the assembly and disassembly of viruslike shells can be explained through classical nucleation theory, reproducing quantitatively results from time-resolved experiments.