Purification and characterization of a mitogenic lectin and a lectin-binding protein from Vicia sativa

From the seeds of Vicia sativa, a novel mitogenic lectin was isolated. Purification was carried out by affinity chromatography on Sephadex G-100. The tetrameric lectin is a glycoprotein with a molecular weight of Mr 40 000; it consists of two large beta-subunits (Mr 14 000) and two small alpha-subunits (Mr 6000). The N-terminal sequence of both subunits and their amino acid compositions were determined. The lectin agglutinates human erythrocytes, preferring group B, and erythrocytes from rabbits and horses; no agglutination takes place with sheep erythrocytes. Agglutination is inhibited by mono-, di- and tri-saccharides with the configuration of glucose at the free 4-hydroxyl group. The lectin stimulates mitosis in lymphocytes of mice. From the seeds of the same plant, a protein was isolated which binds to the lectin described above. The lectin binder consists of subunits with a molecular weight of 53 500.