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PubMed1991

Characterization of the carbohydrate binding specificity of the leukoagglutinating lectin from Maackia amurensis. Comparison with other sialic acid-specific lectins.

The sialic acid-specific leukoagglutinating lectin from the seeds of Maackia amurensis (MAL) has been studied by the techniques of quantitative precipitin formation, hapten inhibition of precipitation, hapten inhibition using an enzyme-linked immunosorbent assay, and lectin affinity chromatography. The ability of the immobilized lectin to fractionate oligosaccharides based on their content of sialic acid has also been investigated. Our results indicate that MAL reacts with greatest affinity with the trisaccharide sequence Neu5Ac/Gc alpha 2,3Gal beta 1,4GlcNAc/Glc. The lectin requires three intact sugar units for binding and does not interact when the beta 1,4-linkage is replaced by a beta 1,3-linkage nor when the "reducing sugar" of the trisaccharide is reduced. Results from enzyme-linked immunosorbent assays show that an N-acetyllactosamine repeating sequence is not required; however, the N-acetyllactosamine repeating sequence does appear to enhance the binding of MAL to a series of glycolipids. In addition, the sialic acid may be substituted with either N-acetyl or N-glycolyl groups without reduction in binding. The C-8 and C-9 hydroxyl groups of sialic acid do not play a role in binding as shown by the strong reaction of periodate-treated glycoproteins. Comparison of the specificity of the three sialic acid-binding lectins indicates that Limax flavus agglutinin binds to Neu5Ac in any linkage and in any position in a glycoconjugate, Sambucus nigra lectin requires a disaccharide of the structure Neu5Ac alpha 2,6Gal/GalNAc, and MAL has a binding site complimentary to the trisaccharide Neu5Ac alpha 2,3Gal beta 1,4GlcNAc/Glc, to which sialic acid contributes less to the total binding affinity than for either S. nigra lectin or L. flavus agglutinin.

Agglutination↗

PubMed1988

Kluyveromyces bulgaricus yeast lectins. Isolation of N-acetylglucosamine and galactose-specific lectins: their relation with flocculation.

Kluyveromyces bulgaricus is a yeast which, upon culture in a calcium-enriched glucose-peptone medium, flocculates. Its flocculation can be reversed by the addition of galactose. In this paper, it is shown that two lectins can be isolated either from the concentrated culture broth or from the supernatant of deflocculated cells suspended in galactose solution. The N-acetylglucosamine-specific lectin, at pH 7.4, agglutinates untreated sheep red blood cells, but agglutinates neither untreated rabbit red blood cells nor glutaraldehyde-fixed sheep or rabbit red blood cells. Conversely, at pH 4.5, this lectin agglutinates glutaraldehyde-fixed sheep red blood cells. The galactose-specific lectin, at pH 7.4, agglutinates both untreated and glutaraldehyde-fixed rabbit red blood cells but does not agglutinate untreated or glutaraldehyde-fixed sheep red blood cells. At pH 4.5, this lectin agglutinates both glutaraldehyde-fixed sheep and rabbit red blood cells and induces flocculation of deflocculated K. bulgaricus cells. In all cases, the agglutination and the flocculation induced by one of these two lectins were inhibited by free or conjugated N-acetyl-D-glucosamine or by free or conjugated D-galactose, respectively. No glycosylhydrolase activity could be detected in the purified lectins.

Acetylglucosamine↗

PubMed1980

Two lactose binding lectins from chicken tissues. Purified lectin from intestine is different from those in liver and muscle.

Endogenous lactose-binding proteins from adult chicken liver and intestine have been purified to homogeneity by affinity chromatography on asialofetuinderivatized Sepharose, followed by isoelectric focusing. Since these carbohydrate-binding proteins are assayed as hemagglutinins, they are referred to by the operational term lectins. Although the hemagglutination activity of these lectins is inhibited by similar concentrations of inhibitory saccharides, they are not the same. They differ in specific hemagglutination activity, subunit molecular weight, and isoelectric point. They have very different peptide maps and show no detectable immunological cross-reactivity. Based on gel filtration studies, the liver lectin behaves as a dimer with apparent Mr = 31,000 +/- 1100, whereas the intestinal lectin behaves as a monomer with apparent Mr = 14,000 +/- 1700. Although clearly different from the intestinal lectin, the lectin from adult liver appears identical with the lectin previously purified from embryonic skeletal muscle.

Animals↗

PubMed1997

Further studies on vertebrate S-type lectins: cross-reactivity between toad and human lectins.

Galectins (S-type or S-Lac lectins) are a well-defined family of beta-galactoside animal lectins characterized by a high sequence homology in the carbohydrate-binding domain. We have previously purified and characterized the S-type lectin from the ovary of the toad Bufo arenarum. In this study, we purified the S-type lectins from Bufo arenarum ovary and human spleen by an improved method which included ion exchange and affinity chromatography. Antibody cross-reactivities between both lectins and some other S-type lectins showed that they share epitopes. Glycosylation studies carried out with detection/differentiation kits suggested that both lectins are not glycosylated.

Animals↗

PubMed1996

Concanavalin A and mistletoe lectin I differentially activate cation entry and exocytosis in human neutrophils: lectins may activate multiple subtypes of cation channels.

The mannose-specific lectin, concanavalin A (ConA), activates Ca2+ entry in human neutrophils by an as yet poorly defined mechanism. The question of whether the sugar specificity of lectins influences signal transduction is unresolved too. Therefore, we studied the effects of ConA in comparison to those of the beta-galactoside-specific lectin, mistletoe lectin I (MLI), on cation entry and exocytosis in human neutrophils. ConA- and MLI-activated influx of Ca2+, Mn2+, Ba2+, Sr2+, and Na+. Lectin-induced cation influxes were inhibited by 1-(beta-[3-(4-methoxyphenyl)propoxy]-4-methoxy-phenethyl) -1H-imidazole hydrochloride (SK&F 96365) and Gd3+. There were differences in the effectiveness of lectins to activate cation entry and of SK&F 96365, Gd3+, and modulators of protein phosphorylation to block entry. MLI but not ConA inhibited thapsigargin-induced Ca2+ entry. Under whole-cell voltage-clamp conditions, MLI activated an inward current that was substantially reduced by removal of extracellular Na+. ConA and MLI synergistically activated Ca2+ entry and lysozyme release. SK&F 96365 and removal of extracellular Ca2+ and Na+ partially inhibited exocytosis. Our data show the following: (1) ConA and MLI activate monovalent and divalent cation entry in human neutrophils by a SK&F 96365- and Gd3+-sensitive pathway, presumably nonselective cation channels. (2) Ca2+ and Na+ entry are involved in the activation of exocytosis by lectins. (3) The differential and/or synergistic effects of ConA and MLI on cation entry and exocytosis may be attributable to mannose- and beta-galactoside-specific activation of signal transduction pathways, i.e., activation of multiple and differentially regulated subtypes of nonselective cation channels.

Barium↗

PubMed2005

Characterization of a galactose binding serum lectin from the Indian catfish, Clarias batrachus: possible involvement of fish lectins in differential recognition of pathogens.

A lectin with molecular mass around 200 kDa was isolated from the serum of the Indian catfish Clarias batrachus. The bioactivity of this serum lectin was Ca2+ and pH dependent. The lectin appeared to be specific for alpha-methyl galactose and sialoglycoproteins like porcine and bovine submaxillary mucin and could agglutinate human, rabbit, mice, rat and chicken erythrocytes. This fish lectin was able to specifically agglutinate different gram negative bacteria. When it was checked against different strains of the fish pathogen Aeromonas sp., it significantly altered the viability and pathogenicity of the bacteria. Binding of the lectin to Aeromonas sp., resulted in a dose dependent increase in the bactericidal activity of fish macrophages. However, when the lectin was checked against different gram positive bacteria it could not agglutinate or affect the viability of those strains and also failed to bring about any significant change in the bactericidal potential of fish macrophages. The lectin was able to induce the proliferation of head kidney lymphocytes of Clarias and helped in the release of 'IL-1' like cytokines from head kidney macrophages.

Animals↗

PubMed1988

The Lectins of Sophora japonica: II. Purification, Properties, and N-Terminal Amino Acid Sequences of Five Lectins from Bark.

Five N-acetyl-galactosamine-specific lectins were isolated from the bark of the legume tree Sophora japonica. These lectins are immunologically and structurally very similar, but not identical, to the Sophora seed and leaf lectins. The carbohydrate specificities and hemagglutinin activities of these lectins are indistinguishable at pH 8.5 but their activities differ markedly at pH values below 8. All five lectins are tetrameric glycoproteins made up of different combinations of subunits of about 30,000, 30,100, 33,000 M(r) containing 3% to 5% covalently attached sugar. These lectins are the overwhelmingly dominant proteins in bark, but they do not appear to be present in other tissues. Amino terminal sequence analysis indicates that at least two distinct lectin genes are expressed in bark.

Journal Article↗

PubMed1999

Structures of the complexes of peanut lectin with methyl-beta-galactose and N-acetyllactosamine and a comparative study of carbohydrate binding in Gal/GalNAc-specific legume lectins.

The crystal structures of complexes of peanut lectin with methyl-beta-galactose and N-acetyllactosamine have been determined at 2.8 and 2.7 A, respectively. These, and the complexes involving lactose and the T-antigenic disaccharide reported previously, permit a detailed characterization of peanut-lectin-carbohydrate association and the role of water molecules therein. The water molecules in the combining site are substantially conserved in the four complexes. The role of interacting sugar hydroxyl groups, when absent, are often mimicked by ordered water molecules not only at the primary combining site, but also at the site of the second sugar ring. The similarity of peanut-lectin-sugar interactions with those in other galactose/N-acetylgalactosamine-specific lectins also extend to a substantial degree to water bridges. The comparative study provides a structural explanation for the exclusive specificity of peanut lectin for galactose at the monosaccharide level, compared with that of the other lectins for galactose as well as N-acetylgalactosamine. The complexes also provide a qualitative structural rationale for differences in the strengths of binding of peanut lectin to different sugars.

Amino Sugars↗

PubMed1996

Interaction of lectins with their ligand carbohydrate of alpha-fetoprotein: analysis by mixed-lectin affinity electrophoresis.

Serum or ascites alpha-fetoprotein (AFP) from patients with hepatocellular carcinoma and from a cord blood were analyzed by affinity electrophoresis with two lectins mixed in agarose gel in a combination of concanavalin A (Con A) and Lens culinaris agglutinin A (LCA-A) or of erythroagglutinating phytohemagglutinin (E-PHA) and Allomyrina dichotoma lectin (allo A). Con A- and LCA-A-reactive AFP-C2-L3 was not further retarded by mixing with either of the other lectin. It showed a mobility identical with that of AFP-C2 or AFP-L3. E-PHA- and allo A-reactive AFP-P4-A3 showed similar results. It migrated with intermediate mobilities of AFP-P4 and AFP-A3 depending on the concentrations of the two lectins mixed in the gel. The results indicate that the two mixed lectins compete with each other for the topologically different lectin-binding sites on the oligosaccharide of AFP molecule.

Carbohydrate Metabolism↗

PubMed1984

Receptors for pea and lentil lectins on human lymphoid cells: demonstration of distinct lectin-defined cell subclasses.

Lectins are useful probes for studying cell surface glycoconjugates. Pea (PL) and lentil (LL) lectin each requires for binding a fucosyl- and two alpha-mannosyl residues in core regions of glycopeptides, but differences in outer chain carbohydrates may alter their relative binding affinities. We used binding studies with [125I]-PL and LL and flow cytometry with fluorescein-conjugated (FITC)-PL and -LL to study their interactions with peripheral lymphocytes. Binding of both lectins to lymphocytes was saturable, reversible, and inhibited by alpha-methyl mannose. Scatchard analyses were consistent with two classes of receptors for each lectin. Flow cytometric analyses demonstrated that cell to cell receptor densities varied. Sixty-five percent of lymphocytes bound PL (mean 2 X 10(6) receptors/cell) and 45% bound LL (mean 3 X 10(6) receptors/cell). Competition studies demonstrated mutual inhibition, but flow cytometry revealed persistent FITC-PL or -LL binding depsite 20-fold molar excess of the other lectin. Distributions of receptors for PL and LL on lymphocytes were as follows: 45% of lymphocytes bound both PL and LL; 20% of lymphocytes bound PL alone; 35% of lymphocytes bound neither PL nor LL. Despite similar binding requirements for PL and LL and overlap between their receptors on lymphocytes, there appear to be subsets of receptors specific for each lectin. These results may reflect abilities of PL and LL to discriminate subtle carbohydrate differences on lymphocyte surfaces.

Binding, Competitive↗

PubMed1993

Transient appearance and localization of a 26-kDa lectin, a novel member of the Periplaneta lectin family, in regenerating cockroach leg.

A lectin consisting of a 26-kDa subunit was purified from the hemolymph of adult American cockroaches (Periplaneta americana) and shown to be a member of the Periplaneta lectin family. Immunoblotting analysis revealed that this lectin appeared transiently in regenerating legs after nymphal legs were amputated. Thus, its mode of appearance was similar to that of regenectin, another member of the Periplaneta lectin family. However, its time of appearance and localization in the regenerates were different from those of regenectin: the 26-kDa lectin appeared in regenerates in the middle stage of regeneration and was localized in the vicinity of the outside of newly formed epidermal cells. These results suggest that this lectin participates in the organization or stabilization of the epidermis during leg regeneration.

Animals↗

PubMed2002

Inhibition by lectins of glutamate receptor desensitization is determined by the lectin's sugar specificity at kainate but not AMPA receptors.

The lectin Concanavalin A (ConA) has long been known to potentiate current responses of native and recombinant ionotropic glutamate receptors (iGluRs), apparently by inhibition of receptor desensitization. We compared the effects of a broad range of lectins with different carbohydrate specificities on recombinant AMPA (GluR1) and kainate receptors (GluR6) expressed in Xenopus oocytes. Interestingly, the extent of inhibition of desensitization appears to depend on the sugar preference of lectins at kainate (KA) receptors, but not at alpha-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid (AMPA) receptors. None of the lectins potentiated current responses at non-glycosylated GluRs produced in tunicamycin-treated oocytes, demonstrating the requirement of lectin interaction with carbohydrate moieties of the receptors. At AMPA receptors, potentiation of current responses afforded by ConA and the well-known inhibitor of desensitization, cyclothiazide (CTZ), are additive, suggesting that the lectin and CTZ act independently. Current amplitudes of GluR1(L479Y), a nondesensitizing mutant, however, could not be further increased by ConA.

Animals↗

PubMed1988

Membrane glycoproteins and plant and animal proteins with lectin or lectin-like properties.

The fat cell, chiefly from porcine greater omentum, was treated with hypertonic sodium chloride and membranes left over from exuded fat were extracted with Triton X-100 and the extract subjected to gel electrophoresis. Of the 20 or more bands which showed on the gel, at least five were periodate-Schiff positive. By the treatment of the glycoproteins with Con A, followed by DEAE-cellulose, one with an apparent molecular weight of 74 kDA was obtained pure. The other components are not yet purified. However, two glycoproteins of apparent molecular weights of 89 and 112 kDa were obtained from the fat cell membrane by affinity chromatography. These were apparently lectins, since they possessed hemagglutinating activity and specificity towards maltose and caused adhesion among cells (erythrocytes) and aggregation of fat cells. The properties of lectins from various sources have also been studied: rice germ lectin, Allium sativum lectin, a lectin from a species of silkworm and one from loquat leaves. A crystalline protein called pinellin was isolated from Pinella ternata. Since it has been shown to exhibit cell aggregation and mitogenic activity, it is also a lectin, showing species as well as cell type specificity. Preliminary studies have also been made of the binding of pinellin to its receptor on fat cells. The protein has also been shown to possess an anti-implantation effect in rabbits. Studies have been made of membrane proteins on ram spermatozoa and Con A receptors on squamous epithelial cancer cells.

Adipose Tissue↗

PubMed1995

The seed lectins of black locust (Robinia pseudoacacia) are encoded by two genes which differ from the bark lectin genes.

Two lectins were isolated from Robinia pseudoacacia (black locust) seeds using affinity chromatography on fetuin-agarose, and ion exchange chromatography on a Neobar CS column. The first lectin, R. pseudoacacia seed agglutinin I, referred to as RPsAI, is a homotetramer of four 34 kDa subunits whereas the second lectin, referred to as RPsAII, is composed of four 29 kDa polypeptides. cDNA clones encoding the polypeptides of RPsAI and RPsAII were isolated and their sequences were determined. Both polypeptides are translated from mRNAs of ca. 1.2 kb encoding a precursor carrying a signal peptide. Alignment of the deduced amino acid sequences of the different clones indicates that the 34 and 29 kDa seed lectin polypeptides show 95% sequence identity. In spite of this striking homology, the 29 kDa polypeptide has only one putative glycosylation site whereas the 34 kDa subunit has four of these sites. Carbohydrate analysis revealed that the 34 kDa possesses three carbohydrate chains whereas the 29 kDa polypeptide is only partially glycosylated at one site. A comparison of the deduced amino acid sequences of the two seed and three bark lectin polypeptides demonstrated unambiguously that they are encoded by different genes. This implies that five different genes are involved in the control of the expression of the lectins in black locust.

Amino Acid Sequence↗

PubMed1989

Binding and precipitating activities of Erythrina lectins with complex type carbohydrates and synthetic cluster glycosides. A comparative study of the lectins from E. corallodendron, E. cristagalli, E. flabelliformis, and E. indica.

Erythrina lectins possess similar structural and carbohydrate binding properties. Recently, tri- and tetra-antennary complex type carbohydrates with non-reducing terminal galactose residues have been shown to be precipitated as tri- and tetravalent ligands, respectively, with certain Erythrina lectins [Bhattacharyya L, Haraldsson M, Brewer CF (1988) Biochemistry 27:1034-41]. The present work describes a comparative study of the binding and precipitating activities of four Erythrina lectins, viz., E. corallodendron, E. cristagalli, E. flabelliformis, and E. indica, with multi-antennary complex type carbohydrates and synthetic cluster glycosides. The results show that though their binding affinities are very similar, the Erythrina lectins show large differences in their precipitating activities with the carbohydrates. The results also indicate significant dependence of the precipitating activities of the lectins on the core structure of the carbohydrates. These findings provide a new dimension to the structure-activity relationship of the lectins and their interactions with asparagine-linked carbohydrates.

Carbohydrate Conformation↗

PubMed1989

The amino acid sequence of Erythrina corallodendron lectin and its homology with other legume lectins.

The primary sequence of Erythrina corallodendron lectin was deduced from analysis of the peptides derived from the lectin by digestion with trypsin, chymotrypsin, Staphylococcus aureus V8 protease, elastase and lysylendopeptidase-C, and of fragments generated by cleavage of the lectin with dilute formic acid in 6 M guanidine hydrochloride. Purification of the individual peptides was achieved by gel filtration, followed by reverse phase HPLC. The glycosylation site (Asn17-Leu18-Thr19) was deduced from analysis of the glycopeptide isolated from a pronase digest of the lectin before and after deglycosylation of the glycopeptide with endoglycosidase F. Comparison of the sequence of 244 residues thus obtained with those of 9 other legume lectins revealed extensive homologies, including 39 invariant positions and 60 partial identities. These data provide further evidence for the conservation of the lectin gene in leguminous plants.

Amino Acid Sequence↗

PubMed1978

Studies on lectins. XLIII. Isolation and characterization of the lectin from restharrow roots (Ononis hircina Jacq.).

From 1 kg of dried Ononis hircina Jacq. roots 36 mg of a lectin were isolated by affinity chromatography on O-beta-lactosyl polyacrylamide gel. The lectin is homogeneous as judged by ultracentrifugal analysis (S20,W=6.2 S), polyacrylamide disc electrophoresis at pH 8.6 or 4.5, gel filtration on thin layers of Sephadex G-200 (Mr = 110 000) and dodecyl sulfate electrophoresis (Mr of subunits 31 000, both in presence and absence of mercaptoethanol) and disc dodecyl sulfate electrophoresis (pH 9.5). The lectin contains much aspartic and glutamic acids, serine and threonine and also 7.2% of neutral sugar. It is relatively specific for human type O erythrocytes that are agglutinated at a minimal lectin concentration 0.3 microgram/ml. The erythroagglutinating activity is not stimulated by Ca2+, Zn2+, Mg2+, Mn2+, Co2+ or Ni2+ salts; it is inhibited most effectively by N-acetyl-D-galactosamine and a number of D-galactose derivatives. Dissociation constants of several lectin . sugar complexes were estimated by affinity electrophoresis. The lectin is not mitogenic in rabbit lymph node lymphocytes.

ABO Blood-Group System↗

PubMed2004

Fluoroalcohol-induced stabilization of the alpha-helical intermediates of lentil lectin: implication for non-hierarchical lectin folding.

An intermediate state of lentil lectin was characterized at pH 1 having low content of secondary as well as tertiary structure. Far- and near-UV CD spectroscopy showed loss of structure when pH was lowered from 7 to 0.8 but the structure loss was less than that of the protein in presence of 6M GndHCl. Intrinsic tryptophan fluorescence studies, ANS binding, and acrylamide quenching experiments supported the existence of the intermediate at low pH. The unfolding process of lentil lectin at pH 1 was also studied by GndHCl denaturation monitored by intrinsic fluorescence spectroscopy. The non-cooperative unfolding at pH 1, in contrast to cooperative unfolding of the native protein further confirmed the presence of loose tertiary structure. The unfolded structure of the lectin at pH 1 was also shown by limited tryptic digestion studies. Further studies were performed on this intermediate state of lentil lectin obtained at low pH in presence of fluoroalcohols 2,2,2-trifluoroethanol (TFE) and 1,1,1,3,3,3-hexafluoroisopropanol (HFIP). Lentil lectin is mainly a beta-sheet protein, and both TFE and HFIP stabilized the acid unfolded structure by inducing alpha-helical contacts. Interestingly, it was observed that induction of the non-native structure resulted in regain of protein activity to some extent. At pH 1, loss in activity was found with both dextran and bromelain while the reported intermediate at the given pH was found to regain activity with bromelain in presence of HFIP and TFE. HFIP induced more structure as compared to TFE and hence a greater regain in activity of about 30% was observed with HFIP as compared to a 15% regain with TFE. Activity with dextran in presence of fluoroalcohols could not be determined as turbidity developed in the corresponding blank preparations. Our results presented here point out the possibility of the formation of a helical structure preceding the formation of the native beta-sheet structure and thus support the non-hierarchical model of protein folding for lentil lectin.

Circular Dichroism↗