Characterization and molecular cloning of one novel C-type lectin from the venom of Taiwan habu (Trimeresurus mucrosquamatus)

One novel snake venom factor (termed trimecetin) was isolated and purified from the venom of Taiwan habu (Trimeresurus mucrosquamatus). The purified venom factor was shown to consist of two subunit chains linked by one disulfide bond. This two-chain factor showed high sequence homology at their N-terminal segments to some previously reported venom proteins such as alboaggregin-B isolated from Trimeresurus albolabris and agkicetin from Agkistrodon acutus. The cDNA clones corresponding to the two subunit chains, a basic chain (pI 8.97) of 133 amino acids and an acidic chain (pI 6.32) of 121 amino acids, were found to share a sequence similarity of 42.6 %. Similar to botrocetin, bitiscetin and flavocetin A characterized from other snake species, trimecetin from Taiwan habu was also shown to be a C-type lectin based on the phylogenetic and sequence comparisons of various two-chain factors from snake species of different families. The unique functional variation and evolution of trimecetin may offer some insights into the mechanism underlying the receptor recognition associated with activation or inhibition of platelet aggregation for this family of snake venom proteins.