A Cut above the Rest: Characterization of the Assembly of a Large Viral Icosahedral Capsid.

The head of virus SPN3US is composed of ~50 different proteins and is unusual because within its packaged genome there is a mass (>40 MDa) of ejection or E proteins that enter the cell. The assembly mechanisms of this complex structure are poorly understood. Previous studies showed that eight proteins in the mature SPN3US head had been cleaved by the prohead protease.