RNA replication protein replicates the viral genomic RNA. The central part of this protein possibly functions as an ATP-binding helicase and/or methyltransferase (Probable). Capsid protein CP1 and CP2 assemble to form an icosahedral capsid, about 30 nm in diameter, and consisting of capsid proteins CP1 and CP2 in a 1:3 ratio. The capsid encapsulates the single-stranded RNA genome. While CP1 is produced as a C-terminal fusion of the replication protein, CP2 may be expressed from a 3'-co-terminal subgenomic RNA. a ribonucleoside 5'-triphosphate + RNA(n) = diphosphate + RNA(n+1) ATP + H2O = ADP + H(+) + phosphate