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 Agkistrodon halys pallas was cloned and sequenced. The length of the cDNA is 923bp which includes 120bp of noncoding region and 780bp of coding region. Pallabin was synthesized as a prozymogen with 260 amino acids, which includes a signal 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 contains 12 cysteins which form 6 disulfide bridges. Like other serine proteases, it also has three conserved catalytically active sites: His41, Asp86 and Ser182. To our knowledge, this study is the first report concerning the cDNA of a thrombin-like enzyme from Agkistrodon halys pallas. The cDNA was cloned into the expression plasmid pT7ZZa and expressed in E.coli. The recombinant pallabin immunologically reacted with its specific antibody.