title: Poliovirus-encoded proteinase 3C: a possible evolutionary link between cellular serine and cysteine proteinase families.
abstract: Here we demonstrate significant similarities between the amino acid sequences of trypsin (a serine protease) and the N-terminal piece of a specific fragment of the poliovirus polyprotein encompassing the sequence of the viral proteinase 3C, and also between cathepsin H (a cysteine protease) and the C-terminal piece of the same fragment. A coherent alignment of the sequences of the 3 proteases was obtained, in which the principal catalytically active residues occupy identical positions. A hypothesis is proposed that the viral enzyme may provide an evolutionary link between serine and cysteine protease families.
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D005075:Biological Evolution; D056655:Cathepsin H; D002403:Cathepsins / Q000235:genetics; D002417:Cattle; D003546:Cysteine Endopeptidases; D012321:DNA-Directed RNA Polymerases / Q000235:genetics; D010450:Endopeptidases / Q000235:genetics*; D017955:Poliovirus / Q000201:enzymology / Q000235:genetics*; D012367:RNA, Viral / Q000032:analysis; D051381:Rats; D012697:Serine Endopeptidases; D014357:Trypsin / Q000235:genetics
chemical_list: D012367:RNA, Viral; D012321:DNA-Directed RNA Polymerases; D002403:Cathepsins; D010450:Endopeptidases; D012697:Serine Endopeptidases; D014357:Trypsin; D003546:Cysteine Endopeptidases; D056655:Cathepsin H; C534128:Ctsh protein, rat