title: Expression of a cloned gene segment of poliovirus in E. coli: evidence for autocatalytic production of the viral proteinase.
abstract: The poliovirus polyprotein is proteolytically processed predominantly by a virus-encoded proteinase (P3-7c) that cleaves glutamine-glycine amino acid pairs. The biosynthesis of the viral proteinase, itself a product of glutamine-glycine cleavages, was studied by constructing a bacterial expression plasmid that contained a cloned segment of the poliovirus genome slightly larger than the coding region for P3-7c. The induction of expression of this plasmid in E. coli produced several poliovirus-specific polypeptides. One polypeptide, an unstable protein called 3i, was the product of fortuitous in-phase initiation of translation within the coding region of P3-7c. Three other induced polypeptides were products of proteolytic cleavages, the smallest (polypeptide 3) having the properties (amino-terminal amino acids, carboxy-terminal amino acids, size, antigenicity) of P3-7c. Insertion of a DNA linker into the P3-7c coding region results in the loss of P3-7c-specific glutamine-glycine cleavage activity. We conclude that P3-7c was produced by autocatalytic cleavage.
mesh_terms: D000595:Amino Acid Sequence; D003001:Cloning, Molecular; D004279:DNA, Viral / Q000235:genetics; D010450:Endopeptidases / Q000235:genetics*; D004926:Escherichia coli / Q000235:genetics; D005786:Gene Expression Regulation; D005796:Genes; D006868:Hydrolysis; D017955:Poliovirus / Q000201:enzymology / Q000235:genetics*; D014176:Protein Biosynthesis; D011499:Protein Processing, Post-Translational; D014764:Viral Proteins / Q000235:genetics*
chemical_list: D004279:DNA, Viral; D014764:Viral Proteins; D010450:Endopeptidases