Description:
<jats:p>Two lectins were isolated from the bulbs of <jats:italic>Tulipa</jats:italic> cv. Apeldoom and their corresponding cDNA clones analyzed. The first, called TxLMII (second mannose‐binding <jats:italic>Tulipa</jats:italic> hybrid lectin), is a novel mannose‐binding tulip lectin. Based on its molecular structure, carbohydrate‐binding specificity and amino acid sequence, TxLMII belongs to the superfamily of mannose‐binding monocot lectins which are also found in representatives of the plant families Amaryllidaceae, Alliaceae, Orchidaceae and Araceae. Molecular cloning of the second lectin, called TxLCI (first <jats:italic>Tulipa</jats:italic> hybrid lectin with complex specificity), allowed determination unambiguously of the molecular structure of this previously described protein. In addition, evidence is presented that each TxLCI subunit possesses a mannose‐binding site and an <jats:italic>N</jats:italic>‐acetylgalactosamine‐binding site, which act independently of each other. Both binding sites are located in a separate domain of the lectin polypeptide. Since the first domain of TxLCT shows sequence similarity to TxLMII, it is suggested that their genes evolved from a common ancestor.</jats:p>