Cloning, sequence analysis and expression in E-coli of the cDNA of the thrombin-like enzyme (pallabin) from the venom of Agkistrodon halys pallas

The cDNA of the thrombin-like enzyme (pallabin) from the venom of Agkistrod on halys pallas was cloned and sequenced. The length of the cDNA is 923bp w hich includes 120bp of noncoding region and 780bp of coding region. Pallabi n was synthesized as a prozymogen with 260 amino acids, which includes a si gnal peptide of 18 amino acids, a proposed propeptide of 6 amino acids and a matured peptide of 236 amino acids. Pallabin exhibits a strong amino acid similarity to the serine proteases isolated from other snake venoms. It co ntains 12 cysteins which form 6 disulfide bridges. Like other serine protea ses, it also has three conserved catalytically active sites: His(41), Asp(8 6) and Ser(182). To our knowledge, this study is the first report concernin g the cDNA of a thrombin-like enzyme from Agkistrodon halys pallas. The cDN A was cloned into the expression plasmid pT7ZZa and expressed in E.coli. Th e recombinant pallabin immunologically reacted with its specific antibody.