Precursor from which the VPg molecule is probably released at the onset of the RNA synthesis. Essential for virus replication. The C-terminus part of VPg/P1-C25 displays RNA-binding properties. Specific enzymatic cleavages in vivo yield mature proteins. The protease probably cleaves itself and releases the VPg protein. The VPg protein is probably further cleaved in its C-terminus (By similarity). Produced by conventional translation. Belongs to the peptidase S39B family.