Purification and characterization of N-acetyl-D-galactosamine-binding lectin from Falcata japonica

An N-acetyl-D-galactosamine-binding lectin from Falcata japonica seeds was purified by affinity column chromatography of N-acetyl-D-galactosamine coupled to epoxy-activated Sepharose 6B. A 1000-fold purification of lectin was obtained from the crude extracts. The purified lectin agglutinated blood group A red cells, but neither blood group B nor O red cells. Polyacrylamide gel electrophoresis of the lectin showed one diffuse band. Molecular weights of 125,000 and 117,000 were estimated by gel filtration and ultracentrifugal analysis, respectively. SDS-polyacrylamide gel electrophoresis of the lectin also showed a single band which has a molecular weight of 34,000. Therefore, the lectin molecule was estimated to be a tetramer composed of four identical non-covalently bound subunits. F. japonica lectin was a glycoprotein containing 5% total carbohydrate, and the amino acid composition was characterized by a high content of aspartic acid, serine and glycine, a low content of methionine and the absence of cysteine.