The Purification, Properties, and Localization of an Abundant Legume Seed Lectin Cross-Reactive Material from Spartium junceum

The seeds of Spartium junceum contained a large quantity of lectin-like protein that did not appear to be either a hemagglutinin or active lectin. The cross-reactive material (CRM), like most legume seed lectins, was a tetrameric glycoprotein of about 130,000 M_r. The singlesized subunits of about 33,000 M_r were not covalently associated. The amino acid composition was typical of legume lectins and was rich in hydroxy-amino acids and poor in sulfur-containing amino acids. The Spartium CRM contained about 3.5% covalently associated carbohydrate, most likely of the high-mannose type, since the CRM was precipitated by concanavalin A. The CRM was localized by electron-microscopic immunocytochemistry and found to be exclusively in protein-filled vacuoles (protein bodies). Because this protein was so similar immunologically, structurally, and in its physiology, to classic legume seed lectins, it is most likely a lectin homolog. Similar seed lectin CRMs appear to be both common and widespread in the Leguminosae.