Poliovirus replication proteins: RNA sequence encoding P3-1b and the sites of proteolytic processing.

Abstract
A partial amino-terminal amino acid sequence of each of the major proteins encoded by the replicase region (P3) of the poliovirus genome was determined. A comparison of this sequence information with the amino acid sequence predicted from the RNA sequence that has been determined for the 3'' region of the poliovirus genome has allowed the precise location of the proteolytic cleavage sites at which the initial polyprotein is processed to create the poliovirus products P3-1b (NCVP1b), P3-2 (NCVP2), P3-4b (NCVP4b) and P3-7c (NCVP7c). For each of these products and for the small genome-linked protein VPg, proteolytic cleavage occurs between a glutamine and a glycine residue to create the amino terminus of each protein. A single proteinase may be responsible for all of these cleavages. The sequence data allow the precise positioning of the genome-linked protein VPg within the precursor P3-lb just proximal to the amino terminus of polypeptide P3-2.