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PubMed1994

Structural analysis of two crystal forms of lentil lectin at 1.8 A resolution.

The structures of two crystal forms of lentil lectin are determined and refined at high resolution. Orthorhombic lentil lectin is refined at 1.80 A resolution to an R-factor of 0.184 and monoclinic lentil lectin at 1.75 A resolution to an R-factor of 0.175. These two structures are compared to each other and to the other available legume lectin structures. The monosaccharide binding pocket of each lectin monomer contains a tightly bound phosphate ion. This phosphate makes hydrogen bonding contacts with Asp-81 beta, Gly-99 beta, and Asn-125 beta, three residues that are highly conserved in most of the known legume lectin sequences and essential for monosaccharide recognition in all legume lectin crystal structures described thus far. A detailed analysis of the composition and properties of the hydrophobic contact network and hydrophobic nuclei in lentil lectin is presented. Contact map calculations reveal that dense clusters of nonpolar as well as polar side chains play a major role in secondary structure packing. This is illustrated by a large cluster of 24 mainly hydrophobic amino acids that is responsible for the majority of packing interactions between the two beta-sheets. Another series of four smaller and less hydrophobic clusters is found to mediate the packing of a number of loop structures upon the front sheet. A very dense, but not very conserved cluster is found to stabilize the transition metal binding site. The highly conserved and invariant nonpolar residues are distributed asymmetrically over the protein.

Amino Acid Sequence↗
PubMed2000

Change in the activity of lectins in cell structure of winter wheat crown under the action of low-temperature hardening and fusicoccin.

Haemagglutinating activity was determined in cell walls and total cell organelles of crown cells of Winter wheat (Triticum aestivum L. ) plants. The effect of fusicoccin (FC) was investigated using fractions obtained from plants hardened for 7 days at 2 degrees C and from untreated plants. FC concentration (5x10(-7) m) increased the frost resistance of the plants. The temporal pattern of lectin activity during hardening could be described by a single-peak curve. In the cell wall fraction, the highest activity manifested itself after one-day hardening, and in the fraction of organelles it peaked after five-days hardening. The carbohydrate specificity of lectins also changed during hardening; cell wall lectins completely lost their capacity for interaction with uridine diphosphoglucose, glucose 6-phosphate, D-galactosamine, and N-acetylglucosamine and the lectins of organelles retained some affinity only for amino sugars. After hardening the test plants, the activity of the lectins increased substantially in the cell walls and plastids, decreased in the nuclei, and was practically flat in mitochondria and microsomes. Consequently, low temperature and FC with their antistress effect improved frost resistance and stimulated the activity of the lectins of some cell structures of the tillering node of winter wheat. A similar action of low temperature and FC in increasing the activity of lectins of plastids was found. Further information was obtained on the subcellular localization of lectins providing additional information on their possible participation in the development of frost resistance of winter wheat.

Amino Sugars↗
PubMed1992

Soybean lectin binding neurons in the visual cortex of the rat contain parvalbumin and are covered by glial nets.

We carried out qualitative and quantitative studies on the distribution of soybean agglutinin-labelled cells in the visual cortex of the rat. Lectin-positive nerve cells mostly showed the morphological characteristics of small and large multipolar basket cells. Only a few cells appeared to be bipolar with a vertical or horizontal orientation. By light microscopy, soybean agglutinin binding sites were seen as discontinuous, punctate perineuronal staining (or pericellular nets) on the surface of about 9% of cortical neurons. Lectin-positive cells were predominantly localized in layers IV and V (16.9 and 12.4% of all neurons), where the intensity of staining was also the strongest. Combining lectin- and immunohistochemistry on cryo semithin sections, lectin-positive cells were shown to contain parvalbumin. Nerve cells in the visual cortex containing the related calcium binding-proteins, calbindin or calretinin were never soybean agglutinin-positive. Some glial cells and their processes were also soybean agglutinin-positive. The structure of the soybean agglutinin-positive pericellular nets was similar to that of glial nets visualized with the Golgi-method. Electron microscopy revealed that lectin binding sites were localized on the membranes and cytoplasm of glial processes ensheathing the axon terminals that impinged upon neurons and their proximal dendrites. Synaptic clefts and axon terminals were never reactive, thus explaining the discontinuous punctate labelling of the neuronal surface. Lectin binding sites were also found on the trans-face of the Golgi-complex of some lectin positive neurons suggesting that N-acetylgalactosamine-containing glycoconjugates, which are selectively detected by the lectin, are synthesized, at least partly, within the labelled neurons. We therefore consider possible the existence of specific interactions between parvalbumin positive basket cells and the glial network surrounding them, by which the neuron may determine the conditions of its own microenvironment.

Animals↗
PubMed1996

Lectin binding reveals divergent carbohydrate expression in human and mouse Peyer's patches.

The nature of cell-associated carbohydrates in the human intestine that may mediate transepithelial transport of bacterial and dietary lectins and their processing by the lymphoid cells of Peyer's patches is not known. Because the cell surface carbohydrate receptors for lectins may vary in different species, the glycoconjugates of human and mouse follicle-associated epithelium and gut-associated lymphoid tissue were compared. A panel of 27, mainly recently isolated, lectins were used to identify glycoconjugate expression in M-cells, enterocytes, goblet cells, lymphocytes and macrophages in mouse and human intestine. Mouse M-cells were exclusively labelled by fucose-specific lectins but in human follicle-associated epithelium no distinct M-cell staining pattern was observed. In the human Peyer's patches, Bryonia dioica lectin bound selectively to paracortical T-lymphocytes and Chelidonium majus lectin to germinal centre B-cells. Certain mannose-specific lectins (Galanthus nivalis, Hippeastrum hybrid) stained the tingible body macrophages in the germinal centre of human Peyer's patches but labelled the macrophages in the paracortical T-cell region of the mouse. The results indicate distinct differences in glycosylation between mouse and human Peyer's patches and their associated lymphoid cells. When considering cell surface glycoconjugates as target molecules for the gut immune system, care has to be taken to choose the appropriate lectin for each species.

Animals↗
PubMed1997

A novel method for the purification of recombinant subunit I of the Dolichos biflorus seed lectin.

Lectins are carbohydrate-binding proteins that are ubiquitous in nature. Their ability to specifically bind carbohydrates has been used as a means of purification mainly through affinity chromatography techniques. Plant lectins are one of the most thoroughly studied class of lectins, however, details of their in situ function remains elusive. Recent advances in recombinant DNA techniques have been used in several laboratories to study the function of these lectins by heterologous overexpression. The larger subunit of the Dolichos biflorus seed lectin was described by Chao et al. in 1994 and purification through affinity chromatography techniques was described. Here we report on a new method for the purification of this recombinant protein with techniques that are not dependent on the ability of the lectin to bind sugars. This method may have uses in the purification of mutant proteins that may not bind carbohydrates. Characterization of the purified protein by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and matrix-assisted laser desorption ionization (MALDI) mass spectroscopy shows that the lectin is over 99% pure with a molecular weight of 27,090 +/- 16.17 Da, and hemagglutination assays confirm that the lectin retains its biological activity.

Chromatography, Affinity↗
PubMed1976

Studies on phytohemagglutinins. XXVIII. Chemical modifications of the lectin from seeds of the lentil (Lens esculenta Moench.)

The reaction of lentil lectin with maleic anhydride yields maleyl derivatives with a degree of modification depending on the amount of used maleic anhydride. Hemagglutinating activity of maleyl derivatives decreases with the increasing number of modified lysine residues, but even at a maleylation of 90% of free -NH2 groups, the maleyl derivative of the lectin still retains a hemagglutinating activity. Maleylation of the lentil lectin is not accompanied by dissociation; the chemically modified lectin also retains its bound Mn. Maleyl derivatives of the lectin retain the ability to interact specifically with polysaccharides (Sephadex, mannan). After removal of maleyl groups in acidic medium, the hemagglutinating activity does not differ from that of the native lectin. Acetylation of the lentil lectin with N-acetylimidazole results in formation of a modified protein containing 3-5 acetylated -OH groups of the tyrosyl residues out of the total of 15 groups and 7-17 acetylated -NH2 groups out of the total of 26 free -NH2 groups, depending upon the reaction conditions. The presence of D-mannose in the reaction mixture does not affect the extent of modification of tyrosyl groups, but it decreases the modification of -NH2 groups. Acetyl derivatives of the lentil lectin do not possess hemagglutinating activity, but they retain the ability to interact with polysaccharides and to bind to erythrocytes. Acetylation does not affect the content of protein bound Mn. After de-O-acetylation, the hemagglutinating activity of the modified protein increases to the value of the native protein.

Acetates↗
PubMed1978

An anti-A1 lectin in the seeds of Amphicarpaea bracteata.

An anti-A1 lectin has been isolated from the extract of Amphicarpaea bracteata seeds by affinity chromatography on Epoxy-activated Sepharose 6B coupled to N-acetyl-D-galactosamine. The yield of the purified lectin was 86 microgram/g of seeds. The purified lectin shows one main band on electrophoresis in sodium dodecyl sulfate-polyacrylamide. The amino acid and neutral sugar composition indicate that this lectin is an acidic glycoprotein with a neutral sugar content of approx. 2%. The composition of the lectin is different from that of the Dolichos biflorus lectin but the two lectins have some common characteristics. The most powerful inhibitors of the agglutination of A1 red blood cells by the A. bracteata lectin is N-acetyl-D-galactosamine. Much weaker inhibitors of the agglutination are alpha-lactose, D-fucose, and five other sugars.

ABO Blood-Group System↗
PubMed1995

Expression of cDNA for a bark lectin of Robinia in transgenic tobacco plants.

A cDNA encoding a bark lectin of Robinia pseudoacacia was introduced into tobacco plants. The expression of the lectin cDNA under control of the 35S promoter was confirmed by Western blot analysis and a hemagglutination assay of extracts of transgenic plants. Western blot analysis revealed that the subunit of the lectin from tobacco had a molecular mass of 29 kDa. The sequence of nine amino acids from the N-terminus of the lectin from transgenic tobacco plants was identical to that of the bark lectin from Robinia, indicating that the lectin had been processed correctly at its N-terminus in tobacco. The molecular mass of the purified native lectin produced by tobacco plants was estimated to be 112 kDa by gel filtration on a column of Superdex 200. It is suggested that the lectin subunits assembled to form tetramers in transgenic tobacco plants.

Amino Acid Sequence↗
PubMed1975

Affinity chromatography of galactose containing biopolymers using covalently coupled Ricinus communis lectin to Sepharose 4B.

A galactose-specific lectin isolated from Ricinus communis beans has been covalently coupled to Sepharose 4B activated with cyanogen bromide. The immobilized lectin retains its polysaccharide-binding property. The Sepharose-lectin can be used for the purification of polysaccharides containing terminal nonreducing galactose. Only a small fraction of 'native fetuin' and 'native ceruloplasmin' are retarded on Sepharose-lectin. On analysis it was observed that they had a lower content of sialic acids as compared to the native and unbound glycoproteins (sialated fractions). However, on desialation, fetuin and ceruloplasmin were completely adsorbed to Sepharose-lectin. The asialoglycoproteins interact strongly with Sepharose-lectin as compared to 'partially sialated glycoproteins'. This has been attributed to the exposure of galactose residues of these glycoproteins on enzymatic desialation. These experiments demonstrated that Sepharose-lectin interacts with glycoproteins through their terminal, non-reducing galactose. On the basis of these experiments it is suggested that Sepharose-lectin can be used as an analytical tool for separation of 'fully sialated glycoproteins' from the 'partially sialated glycoproteins'.

Ceruloplasmin↗
PubMed1995

Purification and characterization of a lectin from the seeds of Erythrina costaricensis.

This work compares three methods used for the purification of the lectin of Erythrina costaricensis and presents new data regarding its physicochemical properties and N-terminal sequence. The lectin was isolated from the seeds of Erythrina costaricensis using O-alpha-D galactosyl polyacrylamide, galactose-derivatized Sepharose and ConA-Sepharose as affinity chromatography supports. The lectin content is about 110 mg/100 g dry flour. The protein agglutinates human and rabbit erythrocytes; other animal erythrocytes were not agglutinated. The agglutination is inhibited by galactosyl moieties, p-nitrophenyl-beta-galactoside being the strongest inhibitor. The lectin is a dimeric protein (56 kDa) with identical subunits, each with a mol. wt of 27.2 kDa. The lectin is a glycoprotein with 3.6% neutral sugars. The amino acid content shows a high proportion of acidic and hydroxy residues; cysteine is absent and there are 6 methionines/mol protein. The N-terminal sequence is similar to those of Erythrina lectins; Ala is the N-terminal amino acid. In summary this paper reports the isolation of a lectin which shares many structural and functional properties with other Erythrina lectins. However, differences in some of its characteristics (pI, interactions with animal erythrocytes, mitogenic ability) indicate some distinctions in structure amongst this group of proteins.

Amino Acid Sequence↗
PubMed1975

Interaction of Lens culinaris lectin, concanavalin A, Ricinus communis agglutinin and wheat germ agglutinin with the cell surface of normal and transformed rat liver cells.

The observation of BOREK et al. (1973) on nonagglutinability of transformed rat liver cells by Lens culinaris lectin and our ultrastructural findings of a greater mobility of the Lens culinaris lectin receptors on transformed rat liver cells as compared to normal rat liver cells (ROTH 1975) initiated the present agglutination experiments on liver cells with lectins. For agglutination assay the microhemadsorption technique after FURMANSKI et al. (1973) was used with exception of several tests on EDTA-detached cells. The transformed rat liver cells exhibited, in contrast to the findings of BOREK et al. (1973), a positive microhemadsorption with Lens culinaris lectin as well as with Concanavalin A, Ricinus communis lectin and wheat germ agglutinin whereas the normal rat liver cells became positive only after a brief trypsin treatment. The significance of the difference in agglutinability of rat liver cells with Lens culinaris lectin and the other lectins used is discussed with regard to the cell-cell interaction mediated by lectins.

Agglutination Tests↗
PubMedDate not supplied

Sialic acid-binding lectin with antibacterial activity from the horse mussel: further characterization and immunolocalization.

A heterogeneous sialic acid-binding lectin with affinity for bacterial LPS was isolated and partially characterized from hemolymph of the horse mussel Modiolus modiolus.(1) Using two-dimensional electrophoresis with immobilized pH gradients, the lectin revealed three subunits with different molecular weight and isoelectric points (pI); Mr14 (pI approximately 5.1 and approximately 5.5), 17.5 (pI approximately 5.5) and 20 (pI approximately 4.9) kDa. The affinity purified lectin existed in its native state as aggregates, and by stepwise centrifugation it could be fractionated into molecular entities with distinct specificities towards human and/or horse erythrocytes (modiolin H and/or E activity, respectively). While the medium size entities (range < or = 30 and < 100 kDa) exhibited only modiolin E activity and the lowest size entities (range < or = 5 and < 10 kDa) demonstrated only modiolin H activity, the largest aggregates (> or = 100 kDa-)expressed both activities. Antibacterial activity of the lectin has been observed against various marine bacteria, whereas the whole hemolymph was less effective. The lectin exhibited strong antibacterial effect against all tested strains of Vibrio anguillarum, Vibrio salmonicida, Vibrio viscosus, Vibrio wodanis, and Vibrio ordalii, slight effect on Aeromonas salmonicida salmonicida and Shewanella putrefaciens, and no inhibitory effect with Alteromonas sp. Hemolymph of the horse mussel demonstrated no antibacterial effect against A. salmonicida salmonicida, Alteromonas sp., Sh. putrefaciens and some strains of V. anguillarum, but slight effects against some strains of V. anguillarum and both strains of V. ordalii, and more predominantly against V. wodanis, V. salmonicida and V. viscosus. These results indicate that the lectin plays a role in elimination of bacteria. Circulating hemocytes were demonstrated to be the source of the lectins since granules of the hemocytes were immunoreactive to anti-hemolymph lectin antibody and protein A/gold labelling.

Aeromonas↗
PubMed1997

Radiolabeling of lectin from Robinia pseudoacacia by reductive methylation.

Lectin from the bark of Robinia pseudoacacia was radiolabeled by reductive methylation. Reductive methylation of the lectin with [14C]formaldehyde and a reducing agent, sodium borohydride, resulted in incorporation of 14C into the lectin but with considerable inactivation of carbohydrate binding activity. Dialysis of the labeled lectin against the buffer containing Ca2+ and Mn2+ partially restored the activity. Higher incorporation of 14C into the lectin was observed when sodium cyanoborohydride was used as a reducing agent. In this case, more than eighty percent of the labeled lectin retained carbohydrate binding activity. Autoradiography showed that the radiolabeled lectin had a molecular mass of 29 kDa, corresponding to that of the intact lectin subunit.

Carbon Radioisotopes↗
PubMed2000

Activation of caspase cascades in Korean mistletoe (Viscum album var. coloratum) lectin-II-induced apoptosis of human myeloleukemic U937 cells.

Mistletoe lectins are of high biological activity and exert cytotoxic effects. We have previously shown that Korean mistletoe, Viscum album var. coloratum, lectin-II specifically induces apoptotic cell death in cancer cells, not normal lymphocytes. The destructive mechanism by mistletoe lectins on tumor cells was mediated by activation of c-JUN N-terminal kinase (JNK)/stress-activated protein kinase. Herein, we investigated the involvement of caspase cascade and its proteolytic cleavage effects on biosubstrates of human myeloleukemic U937 cells by D-galactoside and N-acetyl-galactosamine-specific Korean mistletoe lectin-II. Mistletoe lectin-II induced ladder pattern DNA fragmentation and activation of caspase-3, -8, and -9 of U937 cells, but not caspase-1 protease, in a time- and dose-dependent manner. Consistent with catalytic activation of protease, both poly(ADP-ribose) polymerase (PARP) and protein kinase C-delta (PKC-delta) are also cleaved in mistletoe lectin-II-treated U937 cells. An inhibitor of caspase-3-like protease, DEVD-CHO peptide, significantly inhibited mistletoe lectin-II-induced apoptosis, PARP cleavage, and fragmentation of DNA. These results provide the evidence that Korean mistletoe lectin-II induces apoptotic death of U937 cells via activation of caspase cascades.

Adjuvants, Immunologic↗
PubMed1997

Isolation of a novel plant lectin with an unusual specificity from Calystegia sepium.

A novel plant lectin has been isolated from the rhizomes of Calystegia sepium (hedge bindweed) and partially characterized. The lectin is a dimeric protein composed of two identical non-covalently linked subunits of 16 kDa. Hapten inhibition studies indicate that the novel lectin is best inhibited by maltose and mannose and hence exhibits a sugar binding specificity that differs in some respects from that of all previously isolated plant lectins. Mitogenicity tests have shown that the Calystegia lectin is a powerful T-cell mitogen. Affinity purification of human, plant and fungal glycoproteins on immobilized C. sepium lectin demonstrates that this novel lectin can be used for the isolation of glycoconjugates from various sources. Moreover, it can be expected that by virtue of its distinct specificity, the new lectin will become an important tool in glycobiology.

Agglutination↗
PubMed2001

Lectin binding and endocytosis at the apical surface of human airway epithelia.

The specificity of lectin binding to distinct saccharides makes them valuable reagents for investigation and identification of cells within complex tissues and potentially for delivery of agents into cells. Therefore we examined lectin binding to airway epithelia. We used an in vitro model of primary cultures of well-differentiated human airway epithelia and applied the lectins to the apical surface of living epithelia. This approach limited binding specifically to the extracellular surface of the apical membrane. Of 32 lectins studied, we found 15 that bound to the apical membrane. The pattern varied from diffuse binding to the surface of nearly all the cells, to binding to a small subset of the cells. Our data combined with earlier studies identify lectins that may be used to detect specific populations of epithelial cells. Because lectins may be used to deliver a variety of agents, including gene transfer vectors, to airway cells, we examined endocytosis of lectins. We found that several lectins bound to the apical surface were actively taken up into the cells. These data may be of value for studies of airway epithelial structure and may facilitate the targeting of the epithelial apical surface.

Antineoplastic Agents↗
PubMed1979

Changes in the sensitivity of chick fibroblasts to Ricinus lectin (RCA I) toxicity in relation to the stage of embryo development.

The toxic effect of Ricinus lectin RCA I, as estimated by the inhibition of [3H]leucine incorporation, was investigated on chick-embryo fibroblasts at different stages of development. There appeared to be a differential susceptibility of chick-embryo fibroblasts to lectin RCA I. Fibroblasts from 16-day embryos were the most sensitive to its toxic effect in terms of both concentration and time, and cells from 8-day embryos were the least sensitive. This differential sensitivity to the toxic effect of lectin RCA I was closely related to the binding of the lectin: fibroblasts from 16-day embryos had more binding sites (1.5 x 10(7)/cell) with a high affinity than did 12-day (0.45 x 10(7)/cell) or 8-day embryos (0.2 x 10(7)/cell). Studies on the specificity and the removal of bound lectin RCA I by D-galactose indicated that the lectin binding was necessary but not sufficient in itself to cause the toxic effect and that the lectin needed to enter the cells in order to be toxic. The amount of lectin RCA I needed to induce a 50-60% toxicity enters fibroblasts of 16-day embryos more rapidly than those of 12- and 8-day embryos.

Animals↗
PubMed2006

Participation of a galactose-specific C-type lectin in Drosophila immunity.

A galactose-specific C-type lectin has been purified from a pupal extract of Drosophila melanogaster. This lectin gene, named DL1 (Drosophila lectin 1), is part of a gene cluster with the other two galactose-specific C-type lectin genes, named DL2 (Drosophila lectin 2) and DL3 (Drosophila lectin 3). These three genes are expressed differentially in fruit fly, but show similar haemagglutinating activities. The present study characterized the biochemical and biological properties of the DL1 protein. The recombinant DL1 protein bound to Escherichia coli and Erwinia chrysanthemi, but not to other Gram-negative or any other kinds of microbial strains that have been investigated. In addition, DL1 agglutinated E. coli and markedly intensified the association of a Drosophila haemocytes-derived cell line with E. coli. For in vivo genetic analysis of the lectin genes, we also established a null-mutant Drosophila. The induction of inducible antibacterial peptide genes was not impaired in the DL1 mutant, suggesting that the galactose-specific C-type lectin does not participate in the induction of antibacterial peptides, but possibly participates in the immune response via the haemocyte-mediated mechanism.

Amino Acid Sequence↗