Lectins of the <Emphasis Type="Italic">Nicotiana tabacum</Emphasis> pollen grain walls stimulating in vitro pollen germination

Proteins diffusing from tobacco pollen grains into external medium, being inactivated by low temperature (0°C), were shown to stimulate pollen germination in vitro. Fractionation of these proteins by affinity chromatography using α-D-methylmannopyranoside (MMP) immobilized on agarose resulted in the isolation of lectins stimulating germination. The mol wts of these lectins were estimated by SDS-PAGE as 58, 69, and 74 kD. A stimulatory effect of these lectins was determined by their specific interaction with carbohydrate determinants because a competitive sugar (0.3 M MMP) suppressed completely lectin effect on germination. Polyvalent lectins capable of erythrocyte agglutination were also found among diffused proteins. These lectins are glycoproteins with Glu/Man carbohydrate determinants. MMP did not affect their capability of agglutination. This finding permits a conclusion that pollen grain wall contains lectins differing in their carbohydrate specificity.     

豆科凝集素研究进展

豆科凝集素是植物凝集素中最丰富,也是研究最多的一类凝集素。在生理条件下豆科凝集素大多是以二聚体或四聚体的形式存在,这种低聚物的形式给予豆科凝集素较强的糖专一性和大分子结构的稳定性。豆科凝集素除作为植物储存物质的作用外,还具有识别糖蛋白、糖肽及生物膜中碳水化合物和作为植物与微生物的共生介质等生理功能。现对豆科凝集素的结构、功能及其在生物学、农业和医学方面的应用进行了综述。     

The comparison of lectins from albumin complexes of certain representatives of the speciesPhaseolus vulgaris

Using biospecific chromatography on D-Glc-Separon-fetuin, lectins were isolated from seed albumin complexes of four cultivars ofPhaseolus vulgaris (Veltruská Saxa, Vainica Saavegra, Krupnaya sakharnaya, Olympia) andPhaseolus vulgaris ssp.aborigineus (wild form, considered to be one of the ancestors of cultivated beans). In the lectins isolated the agglutinating activity against human erythrocytes of the A, B, and O groups was estimated, as well as against trypsin-treated and non-treated rabbit erythrocytes. Further analyses involved their mitogenic activity against lymphocytes of murine spleen, their isoelectric points by isoelectric focusing in polyacrylamide gels, and eventually their immunospecific similarity with the lectins of the standard cultivar ofPhaseolus vulgaris, Veltruská Saxa. The lectins of all taxa were mitogenic, but differed from one another in their agglutinating activity and in the number and isoelectric points of the zones, as revealed by both isoelectric focusing and immunoelectrophoresis. In the case of the cultivar Vainica Saavegra, which is a seggregating population, even the lectins of individual seed groups were different.     

Carbohydrate and glycoprotein specificity of two endogenous cerebellar lectins

Two endogenous cerebellar mannose binding lectins have been isolated in an active form by immunoaffinity chromatography employing their respective immobilized antibodies. One of them, termed cerebellar soluble lectin (CSL), was extracted in the absence of detergents, whereas the other, called Receptor 1 (R1), was soluble only in the presence of detergents. Tests of inhibition of agglutination of erythrocytes were performed with mono-, oligo and polysaccharides, as well as glycoconjugates of known structures. On the basis of agglutinating activities these 2 lectins are different from the previously reported lectins in brain, since they were not inhibited by galactosides and lactosides and were only marginally inhibited by glycosaminoglycans. CSL and R1 were better inhibited by mannose-rich glycopeptides as compared to the corresponding oligosaccharides. The different inhibition patterns obtained with glycans of known structures indicated that these lectins are very discriminative. Although CSL and R1 have similar specificities, they differed in their binding properties towards glycopeptides of ovalbumin. Both lectins showed considerable affinity for endogenous cerebellar glycopeptides, also rich in mannose. These glycopeptides belong to a few endogenous Con A-binding cerebellar glycoprotein subunits and are not present on other endogenous Con A-binding glycoproteins. In the forebrain, where CSL and R1 were also present, at least some of the glycoproteins interacting with the lectins were different from that observed in the cerebellum. Our data overall suggest that specific cell recognition in the nervous system could be invoked via the interactions between widely distributed lectins and cell-specific glycoproteins.     

Interaction of pea (Pisum sativum L.) lectins with rhizobial strains

Lectins from two varieties (PG-3 and LFP-48) of pea have been purified by affinity chromatography on Sephadex G-50. The specific activity increased by 23 and 25 folds, respectively. These lectins from both the varieties were found to be specific for mannose. The purified fluorescein isothiocyanate (FITC)-labelled lectins showed binding reaction with homologous as well as heterologous strains of Rhizobium spp. The results revealed that pea lectins are not highly specific to their respective rhizobia. Moreover, these lectins showed a greater stimulatory effect on homologous Rhizobium leguminosarum strains.     

Current knowledge about presumable functions of plant lectins

Current data on the diversity of plant lectins and their functional importance for plants, caused primarily by their capacity to link carbohydrate ligands specifically and convertibly, are reviewed. For instance, the role of plant lectins in the recognition of alien organisms and in the adaptation of plants to various stress-induced effects is discussed. In addition to centres of specific affinity to carbohydrates, plant lectins are characterized by the presence of sites responsible for hydrophobic interactions with non-carbohydrate molecules. These sites link to plant hormones, proteins, and other metabolites, thus participating in the regulation of metabolic processes controlling growth, development, and differentiation in plants. The structure and biological properties of ribosome-inactivating proteins having and not having lectin activity are discussed, as well as their role in plant protection from pests and pathogens. Current data on the assumed functions of the independent groups of plant lectins with specific endogenic role are given. These include chitin-specific lectins synthesized in phloem, which are capable of forming protein-protein and RNA-protein complexes and translocating via vessels, which thus play their specific intra- or intercellular interactions, processes of growth, development, and protection of plants. Other groups of plant lectins, induced by jasmonate, such as Nictaba (Nicotiana tabaccum agglutinin), and cereal lectins related to jacalin, which are localised in the cytoplasm and nucleus, probably play regulatory role in the formation of stress response in plants. The structure and currently discussed functions of wheat germ agglutinin, a typical representative of cereal lectins, are analysed in detail.     

The fucosyl specific lectins of Ulex europaeus and Sarothamnus scoparius. Biochemical characteristics and binding properties to human B-lymphocytes.

From the seeds of the gorse, Ulex europaeus and of the broom, Sarothamnus scoparius L-fucosyl-specific lectins were isolated by affinity chromatography on L-fucosyl-epoxy-Sepharose. The lectins showed similarities in their molecular weights, amino acid composition, carbohydrate content and in the finger-prints of their tryptic peptides. The fluorescein-labeled lectins of both seeds attached especially to the plasma membranes of human B-lymphocytes.     

A patent review of the antimicrobial applications of lectins: Perspectives on therapy of infectious diseases

Patents of lectins with antiviral, antibacterial and antifungal applications were searched and reviewed. Lectins are proteins that reversibly bind to specific carbohydrates and have the potential for therapy of infectious diseases as biopharmaceuticals, biomedical tools or in drug design. Given the rising concerns over drug resistance and epidemics, our patent review aims to add information, open horizons and indicate our view of the future perspectives about the antimicrobial applications of lectins. Patents with publications until December 2020 were retrieved from Espacenet using defined search terms and Boolean operators. The documents were used to identify the geographical and temporal distribution of the patents, characterize their lectins, and classify and summarize their antiviral, antibiotic and antifungal applications. Lectins are promising antiviral agents against viruses with epidemics and drug resistance concerns. Mannose-binding lectins were the most suggested antiviral agents since glycans with mannose residues are commonly involved in viral entry mechanisms. They were also immobilized onto surfaces to trap viral particles and inhibit their spread and replication. Many patents described the extraction, isolation, amino acid and nucleotide sequences, and expression vectors of lectins with antibiotic and/or antifungal activities in terms of MIC and IC₅₀ for in vitro assays. The inventions also included lectins as biological tools in nanosensors for antibiotics susceptibility tests, drug-delivery systems for the treatment of resistant bacteria, diagnostics of viral diseases and as a vaccine adjuvant. Although research and development of new medicines is highly expensive, antimicrobial lectins may be worth investments given the emergence of epidemics and drug resistance. For this purpose, less invasive routes should be developed as alternatives to the parenteral administration of biologics. While anti-glycan neutralizing antibodies are difficult to develop due to the low immunogenicity of carbohydrates, lectins can be produced more easily and have a broad-spectrum activity. Protein engineering technologies may make the antimicrobial applications of lectins more successful.     

Dependence on cations for the binding activity of lectins as determined by affinity electrophoresis

The metal ion content of eighteen different lectins was determined. The lectins were demetallized and the binding activity of native and demetallized forms were investigated using non-denaturing polyacrylamide affinity gel electrophoresis. The binding activities of all lectins were dependent on their metal ion content; when the cations were removed the lectins lost their carbohydrate binding activity. There was a marked difference in the strength with which lectins bind divalent cations.     

Lectins detect changes of the glycosylation status of plasma membrane constituents during late apoptosis.

BACKGROUND: Mechanisms governing the normal resolution processes of inflammation are poorly understood, yet their elucidation may lead to a greater understanding of the pathogenesis of chronic inflammation. The removal of apoptotic cell material and their potentially histotoxic contents is a prerequisite of resolution. Engulfment by macrophages is an important disposal route, and changes in the apoptotic cells that are associated with their recognition by macrophages are the subject of this report. METHODS: Apoptosis and necrosis in primary cells and cell lines were induced by various stimuli. The binding profile of 23 different lectins for vital, apoptotic, and necrotic cells were analyzed by flow cytometry. RESULTS: We observed that lectins were able to attach to the cell surfaces of vital and dying cells. Some lectins exhibited membrane destructive properties and, consecutively, changed the morphology of the cells as detected by flow cytometry. Other lectins did not show differences in their binding to viable and apoptotic cells. Those lectins were, therefore, not used for analyses of surface changes. The lectins Griffonia simplificolia II (GSL II), Narcissus pseudonarcissus (NPn), and Ulex europaeus I (UEA I) showed no cytotoxic activity and bound preferentially to dying cells. Primary and secondary necrotic cells displayed an equal staining intensity, which was substantially higher than for apoptotic cells. The binding of GSL II, NPn, and UEA to dying cells increased in a time-dependent manner and was delayed to AxV positivity and the decrease in the mitochondrial membrane potential of apoptotic cells. The kinetic of the lectin staining correlated with the increase in subG1-DNA. GSL II, NPn, and UEA are specific for N-acetylglucosamine, mannose, and fucose, respectively. CONCLUSION: According to their binding specificity, we conclude that N-acetylglucosamine-, mannose-, and fucose-containing epitopes are increasingly exposed on cells undergoing apoptosis.     

Interaction of pea (Pisum sativum L.) lectins with rhizobial strains

Lectins from two varieties (PG-3 and LFP-48) of pea have been purified by affinity chromatography on Sephadex G-50. The specific activity increased by 23 and 25 folds, respectively. These lectins from both the varieties were found to be specific for mannose. The purified fluorescein isothiocyanate (FITC) – labelled lectins showed binding reaction with homologous as well as heterologous strains of Rhizobium spp. The results revealed that pea lectins are not highly specific to their respective rhizobia. Moreover, these lectins showed a greater stimulatory effect on homologous Rhizobium leguminosarum strains.     

Legume lectins interact with muramic acid and N-acetylmuramic acid

The inhibitory potency of both muramic acid (MurAc) and N-acetylmuramic acid (MurNAc) on various legume lectins, including Glc/Man- and Gal/GalNAc-specific lectins, was investigated by a haemagglutination inhibition technique. Data indicated that many lectins, especially those specific for Glc/Man, specifically interact with MurAc and MurNAc often to a greater extent than with other monosaccharides and their derivatives, such as N-acetylglucosamine (GlcNAc) and sialic acid. Glc/Man-specific lectins were also shown to interact with the muramyl-dipeptide MurNAc-D-Ala-D-isoGln. These interactions could explain why various lectins readily agglutinate some bacterial strains of which cell walls contain peptidoglycans with high amounts of MurNAc.     

Purification of 3 monomeric monocot mannose-binding lectins and their evaluation for antipoxviral activity: potential applications in multiple viral diseases caused by enveloped viruses.

Three monomeric monocot lectins from Zephyranthes carinata, Zephyranthes candida, and Gloriosa superba with carbohydrate specificity towards mannose derivatives and (or) oligomannose have been isolated and purified from their storage tissues. The lectins were purified by anion-exchange chromatography on DEAE-Sephacyl and by gel filtration chromatography on Biogel P-200 followed by high-performance liquid chromatography. The purified lectins, Z. carinata, Z. candida, and G. superba had molecular masses of 12, 11.5, and 12.5 kDa, respectively, as determined by gel filtration and SDS-PAGE, indicating that they are monomers. In a hapten inhibition assay, methyl-alpha-D-mannopyranoside inhibited agglutination of both Z. candida and Z. carinata; the latter was also inhibited by Man(alpha1-2)Man and Man(alpha1-3)Man. Gloriosa superba showed inhibition only with Man(alpha1-4)Man of all of the sugars and glycoproteins tested. All purified lectins agglutinated red blood cells from rabbit, whereas G. superba was also reactive towards erythrocytes from guinea pig. All of the lectins were nonglycosylated and did not require metal ions for their activity. They were labile above 60 degrees C and were affected by denaturing agents such as urea, thiourea, and guanidine-HCl. The lectins were virtually nonmitogenic, like other members of Amaryllidaceae and Liliaceae. Of the 3 lectins, G. superba was found to be highly toxic to the BSC-1 cell line (African green monkey kidney epithelial cells), while both of the Zephyranthes species showed significant in vitro inhibition of poxvirus replication in BSC-1 cells without any toxic effects to the cells. In addition, Z. candida also exhibited significant anticancer activity against SNB-78, a CNS human cancer cell line.     

Effect of lectins on the transport of food ingredients in Caco-2 cell cultures

We investigated the effect of several lectins, such as soy bean lectin (SBA), concanavalin A (Con A), and wheat germ agglutinin (WGA), on the transport of some food ingredients (isoflavones, quercetin glycosides, carnosine/anserine) across Caco-2 cell monolayers. After incubation of food ingredients (0.03 approximately 2 mmol/L) in the presence or absence of lectins (1 approximately 180 microg/ml) on the apical side, aliquots were taken from the apical and basolateral solution, and were subjected to HPLC analysis. We also examined the effect of lectins on the permeability of the tight junction by measuring the transepithelial electrical resistance (TER) value of the Caco-2 cell monolayer. Isoflavones, which was not transported to the basolateral solution without lectins, could be transported in the presence of lectins, whereas their aglycones were detected at the same levels with or without the lectin treatment. The transport of quercetin glycosides also increased in the presence of lectins, however, that of peptides was not affected by the lectins. Con A and WGA, but SBA, decreased the TER value, indicating that Con A and WGA increased the transport via paracellular pathway, whereas SBA did via a different pathway.     

Current trends of lectins from microfungi

Lectins are widespread in nature and have been isolated from plants, animals, microorganisms, and viruses. Although several lectins have been reported from microfungi, many more genera still remain unexplored and their physiological role is also uncertain. Microfungal lectins show wide disparity regarding their specificity to erythrocytes. Only a few lectins display specificity to particular human blood types. In addition, they also show agglutination to various animal erythrocytes. Many lectins from microfungi exhibit stringent specificity to animal glycoproteins, while a few have much more simplified sugar binding properties. The role of few microfungal lectins in host-parasite interactions, as storage proteins, and in growth and morphogenesis has been proposed. The current review focuses on an overview of lectins from microfungi, their specificity towards erythrocytes and carbohydrates, physicochemical characteristics, and their possible role and applications.     

Cell-wall lectins during winter wheat cold hardening

The polypeptide composition and functional activity of cell-wall lectins from roots of winter wheat (Triticum aestivum L., cv. Mironovskaya 808) seedlings during cold hardening were studied. Several phases of lectin activity changes were observed, which indicates their involvement in the development of general adaptation syndrome of the cell. After 0.5-h low-temperature treatment, marked alterations occurred in the profile of protein elution: lectins with mol wts of 78 and 42.5 kD disappeared and new ones with mol wts of 72, 69, 37, and 34.5 kD appeared. It was established that 17.5-and 69-kD lectins and most lectins eluted with glucose were arabinogalactan proteins (AGP), which permitted a supposition that these lectins were involved in the interaction between the cell wall and cytoskeleton. After 7-day-long hardening, total protein content reduced and lectins with mol wts of 69 and 37 kD disappeared, which corresponded to reduced lectin activity by the end of hardening. A transient appearance of 37-and 69-kD lectins, which are AGP, might indicate their involvement in the triggering the development of plant-cell defense responses.     

Current trends of lectins from microfungi

Lectins are widespread in nature and have been isolated from plants, animals, microorganisms, and viruses. Although several lectins have been reported from microfungi, many more genera still remain unexplored and their physiological role is also uncertain. Microfungal lectins show wide disparity regarding their specificity to erythrocytes. Only a few lectins display specificity to particular human blood types. In addition, they also show agglutination to various animal erythrocytes. Many lectins from microfungi exhibit stringent specificity to animal glycoproteins, while a few have much more simplified sugar binding properties. The role of few microfungal lectins in host-parasite interactions, as storage proteins, and in growth and morphogenesis has been proposed. The current review focuses on an overview of lectins from microfungi, their specificity towards erythrocytes and carbohydrates, physicochemical characteristics, and their possible role and applications.     

Lectins and the problem of phitopatogene recognition by a host plant

Under consideration are some questions concerning participation of lectins in the plant pathogenesis, including their role in the recognition of microbes and elicitors, and as a protective agent limiting pathogenic growth and displacements. "Classical" lectins also probably play an important role in these processes along with lectin-like receptor kinases. The principal features of those "classical" lectins are their relativly high concentration in the plant tissues, monosaccharide specificity, and limited number of the isolecin forms. Therefore, in supposing their participation in the biological recognition, it is needed to clarify how does a limited number of lectins with a limited number of carbohydrate groups can provide recognition of a potentially huge number of pathogens. This task can be fulfilled by recognition of carbohydrate residues peculiar to a particular microbe group by the "classical" lectins. These recognition processes are similar to acivity of the animal inherited immune system responsible for a rapid primary protection even in animals with well developed antibody system. A mechanism widening the carbohydrate specificity of the carbohydrate-binding center includes interaction with hydrophobic substituents in a carbohydrate residue, as well as lectin modular organization allowing for regulation of lectin binding with oligo- and polysaccharides. The free lectins effect on the microbe growth in both plants and animals. Such an action may be inhibiting in pathogenesis, while in the case of symbiotic relations, the lectin can bear signal that readdresses metabolism of a future symbiont. So, lectins seem to serve as natural deciphering device for information contained in the carbohydrate polymers, and reading of this information is the main lectin function in the cell.     

Proteolytic activity of lectins from the nitrogen-fixing bacterium Bacillus polymyxa

Two lectins (LI and LII) stripped from the surface of Bacillus polymyxa 1460 cells were found to possess proteolytic activity, which was associated with their hemagglutinating activity. The inhibition of the hemagglutinating activity of lectins by specific carbohydrate haptens changed their enzyme activities. The inhibition of hemagglutinating activity by glucuronic acid or fructose 1,6-diphosphate decreased the proteolytic activities of both lectins, whereas the blocking of this activity with D-glucosamine or D-galactosamine increased the proteolytic activity of LII. The molecules of the B. polymyxa lectins are suggested to contain two active centers responsible for hemagglutinating and proteolytic activities.     

Immunological cross-reactivity between beta-galactoside-binding lectins of vertebrates. Possible relationship of antigenicity to oligomeric structure

Structural relationships among five beta-galactoside-binding lectins isolated from human, mouse and chick were studied using immunochemical methods. The lectins examined were human placenta lectin with a 14-kDa subunit (human 14K lectin), two types of mouse lectin (mouse 15K and mouse 16K lectin), and two types of chick lectin (chick 14K and chick 16K lectin). Five polyclonal antibodies raised against these lectins were used. Antibody to human 14K lectin cross-reacted with mouse 15K and chick 14K lectins. Antibodies to both mouse 15K and chick 14K lectins cross-reacted with human 14K and chick 16K lectins. Antibody to chick 16K lectin cross-reacted with mouse 15K lectin. An immunological relationship was not found between human 14K and chick 16K lectins, or between mouse 15K and chick 14K lectins. Mouse 16K lectin did not show any immunological relationship with any of the other lectins. A monoclonal antibody raised against chick 14K lectin cross-reacted with chick 16K lectin. These results cannot be explained simply in terms of phylogenic distance but suggest that vertebrate beta-galactoside-binding lectins can be classified into two structural groups on the basis of their antigenicities. One group, which is characterized as a monomer type, includes human 14K and chick 14K lectins. The other group, which is characterized as a dimer type, includes mouse 15K and chick 16K lectins.