Group IB phospholipase A2 from Pseudonaja textilis

Pseudonaja textilis, an Australian Elapid, is known to produce a highly toxic venom. Both protein profiling and N-terminal sequence analysis showed the presence of four new phospholipases A2 in this venom. Besides being non-lethal, the phospholipase A2 proteins were found to be moderately active enzymes and they showed procoagulant property. cDNA cloning and characterization indicated the presence of two isoforms of PLA2 proteins in a single snake, each containing the “pancreatic loop,” characteristic of group IB phospholipase A2. The genomic cloning also confirmed the presence of two genes each containing four exons that are interrupted by three introns. Phylogenetic analysis showed that the venom group IB PLA2 gene is primitive and could have evolved from the same ancestor as the mammalian and venom group IA PLA2 genes. In the present study, we report that the Pt-PLA2 gene could be responsible for the production of PL1, 2, and 3 possibly via RNA editing process.