Purification and cloning of a novel C-type lectin-like protein with platelet aggregation activity from Trimeresurus mucrosquamatus venom.

Abstract TMVA, a novel C-type lectin-like protein that induces platelet aggregation in a dose-dependent manner, was purified from the venom of Trimeresurus mucrosquamatus . It consists of two subunits, α (15,536 Da) and β (14,873 Da). The mature amino acid sequences of the α (135 amino acids) and β subunits (123 amino acids) were deduced from cloned cDNAs. Both of the sequences show great similarity to C-type lectin-like venom proteins, including a carbohydrate recognition domain. The cysteine residues of TMVA are conserved at positions corresponding to those of flavocetin-A and convulxin, including the additional Cys135 in the α subunit and Cys3 in the β subunit. SDS-PAGE, mass spectrometry analysis and amino acid sequence showed that native TMVA exists as two convertible multimers of (αβ) 2 and (αβ) 4 with molecular weights of 63,680 and 128,518 Da, respectively. The (αβ) 2 complex is stabilized by an interchain disulfide bridge between the two αβ-heterodimers, whereas the stabilization of the (αβ) 4 complex seems to involve non-covalent interactions between the (αβ) 2 complexes.