C-type galactoside-binding lectin from Bothrops jararaca venom: comparison of its structure and function with those of botrocetin.

A Ca(2+)-dependent type (C-type) galactoside-binding lectin was purified from venom of the snake Bothrops jararaca by thiodigalactoside-Sepharose affinity column chromatography. B. jararaca lectin is a disulfide-linked homodimer composed of 14-kDa subunits. The N-terminal 55-residue amino acid sequence was determined and appeared to belong to the animal C-type lectin family. This 55-residue sequence showed 37% identity with botrocetin, an exogenous von Willebrand factor modulator purified from the same venom, and 85% identity with a lectin from rattlesnake (Crotalus atrox) venom. B. jararaca lectin showed Ca(2+)-dependent hemagglutination activity but did not induce platelet aggregation in the presence or absence of Ca2+ and von Willebrand factor and did not inhibit platelet aggregation induced by botrocetin and von Willebrand factor. On the other hand, botrocetin, which also contains a C-type lectin motif in the N-terminal sequence, did not show hemagglutinating activity toward rabbit and human erythrocytes, nor binding activity toward immobilized glycoproteins. These results indicate that at least two structurally similar but functionally distinct proteins, both belonging to the C-type lectin family, are present in the venom of B. jararaca.