A galactoside-specific Dalbergieae legume lectin from seeds of Vataireopsis araroba (Aguiar) Ducke.

Abstract

The Dalbergieae lectin group encompasses several lectins with significant differences in their carbohydrate specificities and biological properties. The current work reports on the purification and characterization of a GalNAc/Gal-specific lectin from Vataireopsis araroba (Aguiar) Ducke, designated as VaL. The lectin was purified from the seeds in a single step using guar gum affinity chromatography. The lectin migrated as a single band of about 35 kDa on SDS-PAGE and, in native conditions, occurs as a homodimer. The purified lectin is stable at temperatures up to 60 °C and in a pH range from 7 to 8 and requires divalent cations for its activity. Sugar-inhibition assays demonstrate the lectin specificity towards N-acetyl-D-galactosamine, D-galactose and related sugars. Furthermore, glycan array analyses show that VaL interacts preferentially with glycans containing terminal GalNAc/Galβ1-4GlcNAc. Biological activity assays were performed using three insect cell lines: CF1 midgut cells from the spruce budworm Choristoneura fumiferana, S2 embryo cells from the fruit fly Drosophila melanogaster, and GutAW midgut cells from the corn earworm Helicoverpa zea. In vitro assays indicated a biostatic effect for VaL on CF1 cells, but not on S2 and GutAW cells. The lectin presented a biostatic effect by reducing the cell growth and inducing cell agglutination, suggesting an interaction with glycans on the cell surface. VaL has been characterized as a galactoside-specific lectin of the Dalbergieae tribe, with sequence similarity to lectins from Vatairea and Arachis.