Capsid protein. Probably binds RNA and plays a role in packaging (By similarity). The virus has a tripartite genome (RNA1, RNA2 and RNA3) and an encapsidated subgenomic RNA (RNA4) from which the coat protein is expressed. Virions are icosahedral, not enveloped, with 32 capsomers per nucleocapsid. Belongs to the bromovirus capsid protein family.