Major capsid protein VP1 Protein, Murine polyomavirus (sf9, His)

The major capsid protein VP1 forms a 40 nm diameter icosahedral capsid with T=7 symmetry, comprising 72 pentamers linked by disulfide bonds and associated with VP2 or VP3 proteins. VP1 interacts with terminal alpha(2,3)-linked sialic acids on the cell surface, facilitating virion attachment to target cells and inducing caveolin-mediated endocytosis. During internalization, the virion traffics to the endoplasmic reticulum, where VP1 undergoes isomerization of interpentamer disulfide bonds, triggering initial uncoating. Subsequently, the endoplasmic reticulum-associated degradation machinery likely aids translocation to the cytosol before nuclear entry. Nuclear entry involves selective exposure and importin recognition of the VP2/VP3 nuclear localization signal. In the late phase of infection, newly synthesized VP1 encapsulates replicated genomic DNA in the nucleus and contributes to rearranging nucleosomes around viral DNA. VP1 forms homomultimers through disulfide linkage, constituting the virus capsid composed of 72 icosahedral units, each comprising five disulfide-linked copies of VP1. VP1 also interacts with minor capsid proteins VP2 and VP3.