Molecular Cloning of Two Different Mannose‐Binding Lectins from Tulip Bulbs

Abstract

Two lectins were isolated from the bulbs of Tulipa cv. Apeldoom and their corresponding cDNA clones analyzed. The first, called TxLMII (second mannose-binding Tulipa 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 Tulipa 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 Nacetylgalactosamine-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.

Isolation and partial characterization of a small chitin‐binding lectin from mistletoe (Viscum album)

“…Detailed studies of the different lectins present in a number of monocot species such as garlic (Allium sativum), ramsons (Allium ursinum) and tulip (Tulipa sp. ), have demonstrated that they are all closely related at the molecular level [19][20][21].…”

Isolation, characterization, molecular cloning and molecular modelling of two lectins of different specificities from bluebell (Scilla campanulata) bulbs

“…A combination of mannose and GalNAc also failed to prevent the agglutination of rabbit erythrocytes by SCAfet. Therefore the apparent complex specificity of SCAfet cannot be ascribed to the simultaneous occurrence of both mannose-and GalNAc-binding domains as was demonstrated for a related fetuin-binding lectin from tulip bulbs [11]. Assays with some animal glycoproteins revealed that the agglutination activity of SCAfet can be inhibited by thyroglobulin, asialofetuin, fetuin and ovomucoid, the concentrations required for 50 % inhibition being 60, 16, 250 and 125 µg\ml respectively.…”

“…In a later experiment cDNA clones encoding the S. campanulata lectins were used as probes. Hybridization was performed overnight as reported previously [11]. Colonies that produced positive signals were selected and rescreened at low density under the same conditions.…”

“…Recombinant lectin clones were screened with the use of synthetic oligonucleotides derived from the N-terminal amino acid sequences of the S. campanulata lectin polypeptides (QPDDNH, 3h-TGA\G TTA\G TCA\G TCN GGC\T TG-5h ; DNHPQI, 3h-ATC\T TGN GGA\G TGA\G TTA\G TC-5h) or the random-primer-labelled cDNA clones encoding the tulip lectins [11] as probes. In a later experiment cDNA clones encoding the S. campanulata lectins were used as probes.…”

“…12 kDa. The degree of similarity between the individual domains varies but can result in two domains that recognize structurally different sugars as is exemplified by the tulip lectin TxLC-I, the protomers of which consist of an N-terminal mannose-binding domain tandemly arrayed to an independently acting GalNAcbinding C-terminal domain [11]. For these reasons the monocot mannose-binding lectins represent a unique system for the study of the molecular evolution of a large family of carbohydratebinding proteins in terms of both sequence and structure similarities.…”