| Abstract: | The poliovirus polyprotein is cleaved at three different amino acid pairs. Viral polypeptide 3C is responsible for processing at the most common pair (glutamineglycine). We have found that a cDNA fragment encoding parts of the capsid protein region (P1) and the nonstructural protein region (P2), and including the P1-P2 processing site (tyrosine-glycine), can be expressed in E. coli. The translation product was correctly processed. Disruption of the coding sequence of 2A, a nonstructural polypeptide mapping carboxy-terminal to the tyrosine-glycine cleavage site, by linker mutagenesis or deletion, prevented processing. Deletion of the adjacent polypeptide 2B had no such effect. Antibodies against 2A specifically inhibited processing at the 3C'-3D' processing site (tyrosine-glycine) in vitro. We conclude that poliovirus encodes the second proteinase 2A, which processes the polyprotein at tyrosine-glycine cleavage sites. |
