Purification, characterization and molecular cloning of chymotrypsin inhibitor peptides from the venom of Burmese Daboia russelii siamensis.

One novel Kunitz BPTI-like peptide designated as BBPTI-1, with chymotrypsin inhibitory activity was identified from the venom of Burmese Daboia russelii siamensis. It was purified by three steps of chromatography including gel filtration, cation exchange and reversed phase. A partial N-terminal sequence of BBPTI-1, HDRPKFCYLPADPGECLAHMRSF was obtained by automated Edman degradation and a Ki value of 4.77nM determined. Cloning of BBPTI-1 including the open reading frame and 3' untranslated region was achieved from cDNA libraries derived from lyophilized venom using a 3' RACE strategy. In addition a cDNA sequence, designated as BBPTI-5, was also obtained. Alignment of cDNA sequences showed that BBPTI-5 exhibited an identical sequence to BBPTI-1 cDNA except for an eight nucleotide deletion in the open reading frame. Gene variations that represented deletions in the BBPTI-5 cDNA resulted in a novel protease inhibitor analog. Amino acid sequence alignment revealed that deduced peptides derived from cloning of their respective precursor cDNAs from libraries showed high similarity and homology with other Kunitz BPTI proteinase inhibitors. BBPTI-1 and BBPTI-5 consist of 60 and 66 amino acid residues respectively, including six conserved cysteine residues. As these peptides have been reported to have influence on the processes of coagulation, fibrinolysis and inflammation, their potential application in biomedical contexts warrants further investigation.