Characterization and molecular cloning of the lectin from Helianthus tuberosus

A lectin called Helianthus tuberosus agglutinin or Heltuba has been isolate d from tubers of the Jerusalem artichoke, a typical representative of the A steraceae family. Heltuba is a tetrameric protein composed of four identica l subunits of 15.5 kDa and exhibits a preferential specificity towards olig omannosides. Cloning of the corresponding cDNAs revealed that the mature le ctin polypeptide comprises the entire open reading frame of the cDNA sugges ting that the primary translation product is not processed and that the lec tin is a cytosolic protein. Searches in the databases revealed sequence sim ilarity with lectins from the taxonomically unrelated Convolvulaceae and Mo raceae species. Therefore, the discovery of Heltuba is of great importance in view of the occurrence and molecular evolution of the jacalin-related le ctins.