Assembles with VP1 and VP2 to form an icosahedral capsid. VP1 is about 5 time more abundant than VP1-FSD in the virion. Assembles with VP1 and VP1-FSD to form an icosahedral capsid. Replicates genomic and antigenomic RNA. a ribonucleoside 5'-triphosphate + RNA(n) = diphosphate + RNA(n+1) ATP + H2O = ADP + H(+) + phosphate N-acetylated. Proteolytic cleavages of the polyprotein yield mature proteins. Produced by -1 ribosomal frameshifting.