Identification of Additional Coat-Scaffolding Interactions in a Bacteriophage P22 Mutant Defective in Maturation

Scaffolding proteins play a critical role in the assembly of certain viruses by directing the formation and maturation of a precursor capsid. Using electron cryomicroscopy difference mapping, we have identified an altered arrangement of a mutant scaffolding within the bacteriophage P22 procapsid. This mutant scaffolding allows us to directly visualize scaffolding density within the P22 procapsid. Based on these observations we propose a model for why the mutant prevents scaffolding release and capsid maturation.