  During the lifecycle of a virus, viral proteins and other components
self-assemble to form a symmetric protein shell called a capsid. This assembly
process is subject to multiple competing constraints, including the need to
form a thermostable shell while avoiding kinetic traps. It has been proposed
that viral assembly satisfies these constraints through allosteric regulation,
including the interconversion of capsid proteins among conformations with
different propensities for assembly. In this article we use computational and
theoretical modeling to explore how such allostery affects the assembly of
icosahedral shells. We simulate assembly under a wide range of protein
concentrations, protein binding affinities, and two different mechanisms of
allosteric control. We find that, above a threshold strength of allosteric
control, assembly becomes robust over a broad range of subunit binding
affinities and concentrations, allowing the formation of highly thermostable
capsids. Our results suggest that allostery can significantly shift the range
of protein binding affinities that lead to successful assembly, and thus should
be accounted for in models that are used to estimate interaction parameters
from experimental data.
