Required for genome encapsidation. Forms ribonucleoprotein complexes along with TGB1 helicase and viral RNA. The N- and the C-terminus of this capsid protein may be exposed on the surface of the virus particle. The central core sequence may be important in maintaining correct tertiary structure of the capsid protein and/or play a role in interacting with the viral RNA. Belongs to the potexviruses coat protein family.