This study focuses on the structural and functional characterizations of novel venom phospholipases A 2 (PLA 2s) from Trimeresurus gracilis, an endemic Taiwanese pitviper. The PLA 2 cDNAs were cloned from venom glands and sequenced. The majority of the clones encoded a Glu6-containing PLA 2 (designated as Tgc-E6) whose deduced amino acid sequence resembled those of other Crotalinae acidic PLA 2s. Tgc-E6 was also purified and constituted about 6% (w/w) of the total venom proteins. For human platelet rich plasma, Tgc-E6 inhibited the ADP- and collagen-induced aggregation with an IC 50 of 272nM and 518nM, respectively. Like Ovophis okinavensis venom, T. gracilis venom did not contain any Lys49-PLA 2s, although a cDNA encoding Lys49-PLA 2 has been cloned from each of the species. Their predicted protein sequences are 94% identical, and their pI values 8.3 are lower than those of other Lys49-PLA 2s, mainly due to the acidic substitutions within positions 78-111, which are apparently more similar to those in Tgc-E6 than to those in other Lys49-PLA 2s. This unique structural feature of the venom PLA 2s thus render evidence for close phylogenetic relationship between both species. The structural variations in the venom acidic PLA 2s of the two species possibly have resulted from adaptation to different prey ecology.
- CDNA cloning and sequencing
- Pitviper systematic
- Platelet aggregation inhibitor
- Trimeresurus gracilis venom phospholipase
ASJC Scopus subject areas