Other Plant Lectins

Gabor, F., Klausegger, U., Wirth, M., The interaction between wheat germ agglutinin and other plant lectins with prostate cancer cells Du-145. Int J Pharm 221, 35—47 (2001). 

Many of the macromolecular properties of the lectin from peanut (Arachis hypogaea) have been found to conform to general properties observed for numerous other plant lectins. At pH 8, the lectin exists as a compactly folded tetramer (mol. wt. 9.8 x 10 ) but at low pH it exists as a globular dimer. In dissociating solvents, four equal sized polypeptides are observable. 

Some of the best investigated anti-nutrients are the enzyme inhibitors present in legumes and other plants. The Bowman-Birk and the Kunitz inhibitors of trypsin and other proteases are among the best characterized. In contrast to the non-specific and widespread influences of tannins and lectins (Carmona, 1996), the Bowman-Birk, Kunitz and other such inhibitors target specific enzymes. Corresponding with this, proteases and other digestive enzymes vary in sensitivity to the different inhibitors. 

Crude chloroform-methanol-water (30 60 8, v/v) extracts of immunostainedTLC bands were analyzed without further purification by nanoelectrospray low-energy mass spectrometry. The authors showed that this effective PLC/MS-joined procedure offers a wide range of applications for any carbohydrate-binding agents such as bacterial toxins, plant lectins, and others. Phenyl-boronic acid (PBA) immobilized on stationary support phases can be put to similar applications. This technology, named boronate affinity chromatography (BAC), consists of a chemical reaction of 1,2- and 1,3-diols with the bonded-phase PBA to form a stable... 

In this Section will be discussed plant lectins that specifically bind to a-D-galactopyranosyl residues. Lectins of a special class that are specific for j8-D-glycosidic linkages487 also exist in the seeds and other tissues of plants. Various aspects of lectins have been reviewed by Goldstein and Hayes.488... 

A number of mannose-specific agglutinines (lectins) from Galanthus nivalis, Hippeastrum hybrid, Narcissus pseudonarcissus, Listera ovata, Cymbidium hybrid, Epipactis helleborine, and the N-acetylglucosamine-specific lectin from Urtica dioica have been found to inhibit HIV-1 and HIV-2 infection at similar concentrations as dextran sulfate (IC50 0.2 to 0.6 fig/ml), or even lower (IC50 0.04 to 0.08 pg/ml. Akin to sulfated polysaccharides, the plant lectins also exhibit activity against various enveloped viruses other than HIV, i.e., HSV-1, HSV-2, CMV, RSV, and influenza virus. Plant lectins would primarily interfere with the virus-cell fusion process. Their precise mode of action remains to be resolved. 

Some plant galactomannans are also known to interact with milk proteins,310 plant lectins,311 and protein antibodies.312 It is not yet known whether these polysaccharides can exist in the form of complexes with seed proteins. Such complex-formation often results in increased stability of proteins towards heat inactivation, proteolytic degradation, and other unfavorable conditions. 

Ricin was found by Stillmark in 1889 as the first plant lectin derived from the seeds of the castor plant, Ricinus communis L., a member of the Euphorbiaceae or spurge family. Other members of this family include the popular houseplants poinsettia E. pulcherrima), and the croton species. The term castor bean is used commonly to refer to both the plant and seed of R. communis. Ricinus communis commonly grows along streams and riverbeds in addition to subtropical locations high in nutrients. Ricinus communis is a coarse perennial, 10-13 m tall in the tropics, with a stem 7.5-15 cm... 

In the other method, I-labeled aniline was prepared by the chlora-mine-T method, diazotized, and allowed to react with the protein under basic conditions (Fig. 1). Presumably it couples to the phenol moiety of tyrosine residues. If this is the case, the product is analogous to that obtained by direct iodination by the chloramine-T or lactoperoxidase procedures. Papain and certain plant lectins in which cysteine residues are part of the active site were labeled without loss of activity. When variations of the chloramine-T or lactoperoxidase methods were used, 64-83% of the activity was lost. 

In an important discovery, Foriers and coworkers [71], and others [72,73], observed an intriguing relationship between concanavalin A, a homotetramer, and the pea, lentil, Vicia faba (all composed of two light a-chains and two heavy P-chains), as well as other leguminous plant lectins. Termed a circular permutation of amino acid sequences. 

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