Characterization and molecular cloning of the lectin from Helianthus tuberosus

A lectin called Helianthus tuberosus agglutinin or Heltuba has been isolated from tubers of the Jerusalem artichoke, a typical representative of the Asteraceae family. Heltuba is a tetrameric protein composed of four identical subunits of 15.5 kDa and exhibits a preferential specificity towards oligomannosides. Cloning of the corresponding cDNAs revealed that the mature lectin polypeptide comprises the entire open reading frame of the cDNA suggesting that the primary translation product is not processed and that the lectin is a cytosolic protein. Searches in the databases revealed sequence similarity with lectins from the taxonomically unrelated Convolvulaceae and Moraceae species. Therefore, the discovery of Heltuba is of great importance in view of the occurrence and molecular evolution of the jacalin-related lectins.