Purification, gene cloning and expression of an acidic phospholipase A2 from Agkistrodon shedaoensis Zhao

A protein with the activity of phospholipase A(2) named asAPLA(2) was purified to homogeneity from the venom of Agkistrodon shedaoensis Zhao through DEAE-Sepharose CL-6B anion exchange column, Source S, and Mono Q FPLC. Its molecular weight was estimated to be 19 kD by SDS-PAGE, and its pI was about 3.5 by IEF analysis. It inhibited the platelet aggregation that was induced by 1 micromol/ L ADP, and the IC(50) was determined to be 6 micromol/L. Degenerating primer was designed and synthesized according to the N-terminal amino acid sequence of asAPLA(2). Its full-length cDNA was cloned by RT-PCR from the total RNA extracted from the snake venom gland. Its molecular weight and the pI are determined to be 13,649 and 4.39 respectively as calculated by DNAclub and DNAstar software according to the deduced amino acid sequence. Then the gene was cloned into the expression plasmid pET-40b(+) and expressed in E. coli BL21(DE3). Western blot analysis indicated that the expressed protein cross-reacted with the antibody against the native enzyme.