Picornaviral proteins are expressed as a single polyprotein which is cleaved by the viral 3C cysteine protease.

1: Structure of human rhinovirus 3C protease reveals a trypsin- like polypeptide fold, RNA-binding site, and means for cleaving precursor polyprotein. Matthews DA, Smith WW, Ferre RA, Condon B, Budahazi G, Sisson W, Villafranca JE, Janson CA, McElroy HE, Gribskov CL, et al; Cell 1994;77:761-771. PMID:7515772

2: Picornaviral 3C cysteine proteinases have a fold similar to chymotrypsin-like serine proteinases. Allaire M, Chernaia MM, Malcolm BA, James MN; Nature 1994;369:72-76. PMID:8164744