Cloning, characterization, and structural analysis of a C-type lectin from Bothrops insularis (BiL) venom.

Lectins are carbohydrate-binding molecules that mediate a variety of biological processes. In this work, we identify and characterize a lectin from Bothrops insularis venom, with respect to its biochemical properties and theoretical structure. Initially, from a venom gland cDNA library, we cloned and sequenced a cDNA encoding a protein with high identity to snake venom lectins. A lectin molecule was purified to homogeneity from the venom by affinity column and gel filtration. This protein named BiL displayed hemagglutinating activity that was inhibited by galactose, lactose, and EDTA. Mass spectrometry analysis and sodium dodecyl sulfate-polyacrylamide gel electrophoresis showed that BiL is a disulfide-linked dimeric protein consisting of monomers with 16,206 m/z. The amino acid sequence, deduced from its cDNA sequence, was confirmed by Edman sequencing and by peptide mass fingerprint analysis. BiL shows similarity to other C-type lectin family members. Modeling studies provide insights into BiL dimeric structure and its structural determinants for carbohydrate and calcium binding.