Structural polyprotein: precursor of all the viral capsid proteins. Forms, together with protein VP2 and protein VP3, an icosahedral capsid protecting the viral RNA genome. The icosahedral capsid has a pseudo-T=3 symmetry with a diameter of approximately 300 Angstroms, and is composed of 60 copies of each capsid proteins. Forms, together with protein VP1 and protein VP3, an icosahedral capsid protecting the viral RNA genome. The icosahedral capsid has a pseudo-T=3 symmetry with a diameter of approximately 300 Angstroms, and is composed of 60 copies of each capsid proteins. Forms, together with protein VP1 and protein VP2, an icosahedral capsid protecting the viral RNA genome. The icosahedral capsid has a pseudo-T=3 symmetry with a diameter of approximately 300 Angstroms, and is composed of 60 copies of each capsid proteins. Specific enzymatic cleavages in vivo yield mature proteins. Belongs to the picornaviruses polyprotein family. Translation initiates on an Ala codon through an unusual Internal Ribosome Entry Site (IRES). Extended N-terminus.