Characterization of a lectin from the seeds of Erythrina vespertilio

A lectin was isolated from the seeds of Erythrina vespertilio by affinity chromatography on lactose-Sepharose 6B. The lectin has an M, of 59 000 and consists of two non-covalently associated subunits (M, ∼ 30 000). The lectin is devoid of cysteine but has six methionine residues/mol and a neutral sugar content of 9.7% The carbohydrate composition was mannose, N-acetylglucosamine, fucose, xylose and galactose in amounts of 15.0, 4.0, 1.0, 5.0 and 25 mol/59 000 g, respectively. Alkaline gel electrophoresis and isoelectric focusing showed that the affinity purified lectin consists of a family ofisolectins. Valine was the only N-terminal amino acid found and the N-terminal sequence was homologous with that found for other legume lectins. The lectin was inhibited by galactosyl containing carbohydrates; p-nitrophenyl-β-galactoside was the best inhibitor and the lectin showed a slight preference for β-galactosides. Comparison of its properties with those of other Erythrina lectins shows that most of the lectins of this genus are closely related.