格拉姆柱花草(Stylosanthes gracilis H.B.K.cv.Graham)凝集素的纯化与性质研究

为了探讨凝集素在豆科植物与根瘤菌的识别过程中的作用,用ＤＥＡＥ－３２离子交换层析和ＳｅｐｈａｄｅｘＧ－１５０凝胶过滤分离、纯化格拉姆柱花草种子凝集素（ＳＧＬ）,其分子量约为４５ｋＤ,由两个相同的亚基组成,等电点约ｐＨ５．８,它是一种糖蛋白,含糖量约为２．６％．ＳＧＬ的热稳定性强．ＳＧＬ的血凝活性能被甘露糖所抑制．ＳＧＬ对红细胞的凝集作用可能具有种属专一性;ＳＧＬ具有强的促有丝分裂作用;荧光标记实验显示：９株能与格拉姆柱花草植株结瘤的菌株有７株能与ＳＧＬ结合,６株不能与之结瘤的菌株,只有１株能与ＳＧＬ结合,这表明不同根瘤菌菌株对ＳＧＬ的结合能力,和它们在格拉姆柱花草上结瘤能力之间可能具有一定的生物学相关性．     

A1 and A2 erythrocytes can be distinguished by reagents that do not detect structural differences between the two cell types

The differential reactivity of four mouse monoclonal antibodies (AbCB, AbHT29-36, AbM2, and AbS12) and Dolichos biflorus lectin with A1 and A2 erythrocytes was analyzed. Only AbS12 and D. biflorus lectin were able to preferentially agglutinate A1 erythrocytes. AbS12 is known to react only with short chain, unbranched structures (such as Aa-2 and Ab-2 glycolipids) and not with longer chains or with type 3 and type 4 structures. D. biflorus was shown to have a similar specificity by lectin staining of glycolipids separated by thin-layer chromatography. Analysis of the binding of radiolabeled AbCB and AbS12 to A1 and A2 erythrocytes by Scatchard analysis showed that, whereas the former antibody recognizes high-affinity sites on both A1 and A2 cells, AbS12 reacts with high-affinity sites only on A1 cells. Because A1 and A2 erythrocytes have a similar complement of short chain type 2 glycolipids, although in different amounts, it is suggested that AbS12 and D. biflorus lectin differentiate between the two cell types on the basis of quantitative, nonstructural features. This is in contrast to AbTH1, which reacts with a repetitive A epitope (type 3 A chain) and distinguishes between A1 and A2 cells based on the preferential expression of type 3 A chains in A1 erythrocytes. Thus, two views of A1/A2, i.e., qualitative vs quantitative are correct, depending on the properties of the reagent being used to distinguish between the two cell types.     

Effect of pH on the binding of Vicia graminea lectin to erythrocytes. Dependence on the chemical character of red-cell receptors

Binding of the radioactive Vicia graminea lectin to human blood-group M and N erythrocytes and to horse erythrocytes was studied at pH 6-10. Binding of the lectin to untreated human erythrocytes and to those treated with Vibrio cholerae neuraminidase increased severalfold from pH 6 to pH 8 and was maintained at the maximal level up to pH 9/9.5. On the other hand, interaction of V. graminea lectin with native or desialylated horse erythrocytes was not significantly affected by pH and small differences in the binding were opposite to those found with human erythrocytes: the binding decreased when pH increased from 6 to 9.5. Binding of the lectin to all erythrocytes tested at pH 10 was lowered to about 80% of the maximal values. The differences in pH dependence of V. graminea lectin binding to human and horse erythrocytes most probably resulted from the presence of amino groups in human red-cell receptors and their absence from receptors of horse erythrocytes. The earlier data on the enhancing effect of amino group modification on the interaction of human red-cell glycopeptides with V. graminea lectin support the conclusion that an increase in the lectin binding to human erythrocytes at pH 6-8 is confined to the decreased protonization of the receptor amino groups. V. graminea lectin was irreversibly inactivated at pH 3 and was inactivated by EDTA at pH 7.4 and reactivated by Ca2+ or Mn2+. This suggested that the lectin is a metaloprotein, requiring bivalent cations for the full binding activity. Some quantitative differences between the binding properties of V. graminea lectin, prepared from different batches of seeds, are reported.     

Isolation and characterization of a lectin from tulip bulbs, Tulipa gesneriana

A lectin, which agglutinated specifically the yeast cells of the Saccharomyces genus, was isolated from tulip bulbs (Tulipa gesneriana) using affinity chromatography on mannan-Sepharose 4B. Its relative molecular mass was determined by gel filtration to be approximately 67,000. On polyacrylamide gel electrophoresis in sodium dodecyl sulfate, a relative molecular mass of 17,000 was obtained, suggesting that the lectin is a tetramer. Binding studies performed with iodinated lectin indicated that Saccharomyces cerevisiae cells contained approximately 5.7 X 10(6) binding sites per cell, whereas little binding was observed with yeasts other than the Saccharomyces genus, bacteria and animal erythrocytes. D-Mannose, D-mannose 6-phosphate, L-fucose and L-fucosylamine were potent inhibitors of the lectin binding to S. cerevisiae cells, while, D-glucose, D-galactose and D-mannosamine were inactive, indicating that hydroxyl group at C-2 of D-mannose was essential for the lectin binding. Furthermore, inhibition experiments, using various manno-oligosaccharides, suggested that the lectin recognized (1----6)-linked manno-oligosaccharide units larger than mannobiose.     

Surfactant protein A differentially regulates peripheral and inflammatory neutrophil chemotaxis

Surfactant protein A (SP-A), a pulmonary lectin, plays an important role in regulating innate immune cell function. Besides accelerating pathogen clearance by pulmonary phagocytes, SP-A also stimulates alveolar macrophage chemotaxis and directed actin polymerization. We hypothesized that SP-A would also stimulate neutrophil chemotaxis. With the use of a Boyden chamber assay, we found that SP-A (0.5-25 microg/ml) did not stimulate chemotaxis of rat peripheral neutrophils or inflammatory bronchoalveolar lavage (BAL) neutrophils isolated from LPS-treated lungs. However, SP-A affected neutrophil chemotaxis toward the bacterial peptide formyl-met-leu-phe (fMLP). Surprisingly, the effect was different for the two neutrophil populations: SP-A reduced peripheral neutrophil chemotaxis toward fMLP (49 +/- 5% fMLP alone) and enhanced inflammatory BAL neutrophil chemotaxis (277 +/- 48% fMLP alone). This differential effect was not seen for the homologous proteins mannose binding lectin and complement protein 1q but was recapitulated by type IV collagen. SP-A bound both neutrophil populations comparably and did not alter formyl peptide binding. These data support a role for SP-A in regulating neutrophil migration in pulmonary tissue.     

A lectin from the thigh muscle of Rana tigerina

Lectin activity has been detected in the thigh muscle extracts of Rana tigerina, which was found to agglutinate both trypsinized and untrypsinized rabbit erythrocytes. The lectin has been purified to homogeneity by MEPBS (0.01 M phosphate-buffered saline (pH 7.2) with 4 mM beta-mercaptoethanol) buffer extraction of the tissue and affinity chromatography on acid-treated Sepharose 6B. The molecular weight (Mr) of the purified lectin was determined by SDS-polyacrylamide gel electrophoresis and gel filtration on Sephadex G-75, which gave values of 15,500 +/- 1000 and 32,000 +/- 1000, respectively, suggesting that the lectin is a dimer. Amino acid composition data of the lectin has revealed that it contains a high proportion of glycine and alanine, and low amounts of sulphur-containing amino acids. Hapten-inhibition study of this lectin has shown that it is galactose-specific. Hemagglutination activity of the lectin can also be inhibited by beta-galactoside containing oligosaccharides.     

Isolation and characterization of a lectin from the cephalochordate Branchiostoma lanceolatum (Pallas).

1. A lectin was isolated from an extract of Branchiostoma lanceolatum by affinity chromatography using an asialo-A-peptone-cellulose column. 2 The lectin is a glycoprotein with a carbohydrate content of 2.7%. The mol. wt is 392,000 +/- 28,000. Two subunits of identical size (183,000 +/- 3000) are linked by non-covalent bonds. 3. The lectin agglutinates a variety of erythrocytes including human A, B, O red blood cells as well as human lymphocytes. 4. Hemagglutination activity is inhibited best by N,N',N"-triacetylchitotriose, followed by N,N'-diacetylchitobiose, which is half as inhibitory. 5. Lectin activity is constant between pH 5 and 10. Divalent cations are not required for binding reactions. Activity is totally destroyed by heating to 60 degrees C for 30 min. 6. The lectin is precipitated from the extract by 30-40% ammonium sulfate saturation.     

Vicia villosa B4 lectin is the second anti-Tn lectin shown to react better with blood group N than M antigen

Earlier studies showed thatMoluccella laevis lectin, which has anti-Tn specificity, reacts more strongly with native or desialylated blood group N glycophorin A than with the respective glycophorins of blood group M. We now present results indicating thatVicia villosa B4 anti-Tn lectin, which does not show detectable reaction with untreated glycophorins or erythrocytes, reacts better with desialylated blood group N antigen than with asialo M antigen. This was demonstrated by three assays: (1) agglutination of asialoerythrocytes; (2) binding of biotinylated lectin to asialoerythrocytes immobilized on ELISA plates; and (3) inhibition of lectin binding to asialo-agalactoglycophorin with asialoglycophorins M and N. These results supply further support for the conclusion that glycophorin of blood group N has more GalNAc residues unsubstituted with Gal (Tn receptors) than glycophorin of blood group M.Abbreviations GPA glycophorin A - GPA-M and GPA-N GPA from OM and ON erythrocytes, respectively - MLL Moluccella laevis lectin - PBS 0.02m phosphate buffer/0.15m NaCl, pH 7.4 - PNA peanut agglutinin - RBC erythrocytes - TBS 0.05m Tris buffer/0.15m NaCl, pH 7.4 - TBS-T TBS containing 0.02% Tween 20 - VVL Vicia villosa B4 lectin     

A sialic acid-binding lectin from ovine placenta: purification,specificity and interaction with actin

A sialic-acid-specific lectin from ovine placental cotyledons was purified by affinity chromatography on bovine submaxillary mucin-agarose followed by gel filtration, and it showed a molecular weight of 65 000 by sodium dodecylsulfate-polyacrylamide gel electrophoresis. This lectin has the capacity to interact with actin, since in binds to actin-F in a cosedimentation assay and it acts as a mediator in the binding of action to the affinity column. The lectin agglutinated rabbit and rat erythrocytes, but not human A, B or O erythrocytes. Haemagglutination inhibition assays of different saccharides, glycoproteins and glycolipids indicate that this lectin has affinity for sialic acid, which is enhanced by its O-acetylation. The N-terminal sequence of the protein shows 92% identity with rabbit and porcine uterine calreticulin.     

Isolating and characterising a lectin from Galactia lindenii seeds that recognises blood group H determinants

A lectin was isolated from Galactia lindenii seeds and characterised. The lectin, purified by affinity chromatography, readily agglutinated O(H) human erythrocytes and interacted weakly with rabbit and rat erythrocytes. Specificity towards blood group H-type determinants was established; among them H-type 2 (alpha-L-Fuc (1-2)-beta-D-Gal (1-4)-beta-D-GlcNAc-O-R) was recognised by the lectin. The binding to the glycoconjugate was partially inhibited by GalNAc and Me-beta-Gal. The protein is an M=104,256 tetramer which dissociates into identical M=26,064 subunits under non-reducing conditions. Its amino acid composition, pI, A(1%), and N-terminal sequence (23 residues) were determined. The N-terminal region showed a unique sequence found hitherto only in some lectins (designated type-II) from the Dioclea genus. This work presents the evidence concerning a distinct type of lectin found in the Diocleinae tribe able to recognise the H-type 2 human blood group determinant and clearly different from the Glc/Man-specific lectins. The protein is a potential tool in cellular and histochemical studies.     

Isolation of an N-acetyl-D-glucosamine specific lectin from the rhizomes of Arundo donax with antiproliferative activity

A lectin with antiproliferative activity towards human cancer cell lines and mitogenic towards human peripheral blood mononuclear cells was purified from the rhizomes of Arundo donax (Linn.) by affinity chromatography on N-acetyl-d-glucosamine linked to epoxy-activated sepharose-6B. The pure preparation apparently yielded a single band of approximately 15 kDa on SDS-PAGE, pH 8.3, under both reducing and non-reducing conditions. The molecular mass of native lectin was 32 kDa as determined by gel filtration chromatography. This showed the lectin to be a dimer, with subunits not held together by disulphide linkages. The A. donax lectin (ADL) agglutinated rabbit erythrocytes and the agglutination was inhibited by N-acetyl-d-glucosamine and its di- and trimer. The lectin was thermostable upto 55 degrees C and showed optimum activity in the range of pH 7.0-9.0 and comprised of 2.1% carbohydrate content.     

The B4 lectin from Vicia villosa seeds interacts with N-acetylgalactosamine residues alpha-linked to serine or threonine residues in cell surface glycoproteins

We have examined the carbohydrate binding specificity of the B4 lectin from Vicia villosa seeds. The B4 lectin agglutinates Tn-exposed erythrocytes specifically and binds to these erythrocytes (1.4 X 10(6) sites/cell) with an association constant of 4.2 X 10(7) M-1. The concentrations of saccharides and glycopeptides of defined structure which cause 50% inhibition of B4 lectin binding to Tn-exposed erythrocytes were determined. N-Acetylgalactosamine is the best monosaccharide inhibitor, causing 50% inhibition of binding at a concentration of 0.04 mM. Other monosaccharides inhibit lectin binding in the following order of decreasing potency: N-acetylgalactosamine greater than methyl-alpha-galactopyranoside greater than p-nitrophenyl-alpha- or beta-galactopyranoside greater than methyl-beta-galactopyranoside, galactose greater than galactosamine greater than mannose, N-acetylglucosamine. The disaccharide Gal beta 1,3GalNAc causes 50% inhibition of binding at a concentration of 2.8 mM, a concentration similar to that of the p-nitrophenyl-alpha- or beta-galactopyranosides. Glycopeptides containing O-glycosidically linked oligosaccharide units are significantly more potent inhibitors of lectin binding than the oligosaccharide units alone. The most potent glycopeptide inhibitor is a fetuin glycopeptide containing two alpha-linked N-acetylgalactosamine units. This glycopeptide causes 50% inhibition of lectin binding at a concentration of 0.00034 mM and probably closely resembles the B4 lectin binding site on Tn-exposed erythrocytes.     

从绿藻礁膜（Monostroma nitidum Wittr）分离半乳糖专一的凝集素

礁膜（Monostroma nitidum Wittr）经 25%～80%硫酸铵分级、DEAE-纤维素52离子交换层析和Sephadex G-200凝胶过滤层析,得到纯化礁膜凝集素（Monostroma nitidum lectin,MNL）,在SDS-PAGE上显示单一蛋白染色带. 用Sephadex G-200层析测得其分子质量为66.6 kD, 用SDS-PAGE测得其分子质量为66.2 kD．该凝集素可以凝集人A、B、AB、O型红细胞,且凝集活性相同. 在对人（A、B、AB、O）、兔、鲤、鲫、鼠、羊、鸡、狗的红细胞凝集作用中,兔凝集作用最强．该凝集素在pH 4.00～10.53范围内均有活性,但在pH 5.20～9.40范围内活性最大．经100 ℃热处理30 min后,该凝集素对兔红细胞血凝活性保留25%,活性最大的温度范围为25～55 ℃．MNL被EDTA抑制,最小抑制浓度为3.13 mmol/L,但对 Ca^２＋和Mg^２＋不敏感．该凝集素凝集兔红细胞的作用不被D -果糖、D-甘露糖、D-葡萄糖、蔗糖、麦芽糖、γ-球蛋白、牛甲状腺球蛋白所抑制,但被D- 半乳糖和乳糖抑制,最小抑制浓度分别为5 mmol/L和2.5 mmol/L．     

Mucin binding mitogenic lectin from freshwater Indian gastropod Belamyia bengalensis: purification and molecular characterization

A lectin was purified from the hemolymph of the freshwater Indian gastropod Belamyia bengalensis. The purification involved successive ion-exchange chromatography on Resource Q and gel filtration on Superose 12 column in FPLC system. Homogeneity of the protein was confirmed by polyacrylamide gel electrophoresis. Belamyia bengalensis lectin (BBL) was a monomeric protein with a molecular weight of 33 kDa as demonstrated by gel filtration and SDS-PAGE. It is a glycoprotein containing 6% total sugar and its activity is highly dependent on Ca(2+). BBL agglutinated human erythrocytes and is a blood group non-specific lectin. It agglutinated animal erythrocytes also. Hapten inhibition studies indicated that BBL shows binding specificity only for N-acetyl-D-glucosamine and N-acetyl-D-galactosamine at a high concentration among the mono- and oligosaccharides tested. Among the glycoproteins used for hemagglutination-inhibition assay, porcine submaxillary mucin was found to be the best inhibitor. Chemical modification studies indicated that Lys, Arg, and Trp are essential for the sugar-binding activity of BBL. Circular dichroism spectra revealed high content of alpha-helical structure in the lectin. BBL is a potent mitogen as it stimulated the T-lymphocyte proliferation, specifically the Th1 subset.     

Improved lectin-mediated immobilization of human red blood cells in superporous agarose beads

A new type of agarose bead, superporous agarose, was used as a gel support for immobilization of human red blood cells (RBCs) mediated by wheat germ lectin. The number of immobilized cells was similar to that obtained with commercial wheat germ lectin-agarose but the cell stability appeared to be superior. This allowed improved frontal affinity chromatographic analyses of cytochalasin B (CB)-binding to the glucose transporter GLUT1 which established a ratio of one CB-binding site per GLUT1 dimer for both plain RBCs or those treated with different poly amino acids. The measured dissociation constants, 70+/-14 nM for CB and 12+/-3 mM for glucose binding to GLUT1, are similar to those reported earlier.     

Studies on hemagglutinins (lectins) from plasma of murrel fish, family Channidae

Hemagglutinating activity can be identified in the plasma of different species of murrel fish. This activity may be divided into four types according to their agglutinability towards erythrocytes from different sources. Type I plasma agglutinates human blood group A erythrocytes, type II can agglutinate neuraminidase treated human A B O erythrocytes, type III shows no agglutinating activity towards human erythrocytes, while type IV agglutinates human erythrocytes non-specifically. All of them bind to DEAE-cellulose but elute out by different salt concentrations. Type IV plasma is found to be a combination of three separate hemagglutinins, which are separable by sequential binding to human A B O erythrocytes. Blood group A specific lectin activity is purified from this plasma using formalinised A group erythrocytes. The apparent homogeneity of this purified lectin is established by polyacrylamide gel electrophoresis, isoelectric focusing and immunodiffusion. This agglutinin is antigenically identical with that isolated from type I plasma by affinity chromatography on N-acetyl-D-galactosamine coupled to epoxy-activated cellulose column. Their molecular weights are also found to be identical (Mr 140,000) in polyacrylamide gel electrophoresis, having two identical subunits. Forssman glycolipid (0.03 mM) was found to be the most potent inhibitor of agglutination, although Gal beta 1-3 GalNAc (0.09 mM) is also a good inhibitor. Exhaustive dialysis of the purified lectin (hemagglutinin) against EDTA denatures it irreversibly by dissociating it to its subunit structure. Thus human A group agglutinating activity isolated from type I and type IV plasma are identical.     

Isolation and characterization of differentiated alveolar type II cells from fetal human lung

A method has been developed for isolating differentiated type II cells from human lung of 18-24-week gestation. The procedure involves an initial 4-day culture of lung explants in the presence of dexamethasone (10 nM) and triiodothyronine (2 nM). Type II cells (and fibroblasts) are isolated by trypsin digestion of the explants, two differential adherence steps and incubation overnight in primary culture. This method provides a high yield of type II cells ((50 +/- 15) X 10(6) cells/g wet weight of explant) with a purity of 85 +/- 5% in 16 experiments. The type II cells contain numerous perinuclear granules which stain darkly with toluidine blue and Papanicolaou stain; electron microscopy showed these inclusions to be lamellar bodies with tightly stacked, well defined lamellae. Type II cells, but not fibroblasts, were positive by immunofluorescence histology for surfactant apoprotein and binding of Maclura pomifera lectin which binds to the surface of type II but not type I cells in vivo. The rate of both [3H]acetate and [3H]choline incorporation into phosphatidylcholine (PC) was several-fold greater in type II cells than fibroblasts; the saturation of PC was 36.2 and 25.9%, respectively. Release of saturated PC was stimulated by terbutaline, the ionophore A23187, and tetradecanoyl phorbol acetate in type II cells but not fibroblasts. We conclude that differentiated type II cells can be isolated in relatively high yield and purity from hormone-treated explants of fetal human lung.     

Distribution of insulin receptors in human erythrocyte membranes. Insulin binding to sealed right-side-out and inside-out human erythrocyte vesicles

Analyses of insulin binding to human erythrocytes and to resealed right-side-out and inside-out erythrocyte membrane vesicles have revealed that high affinity insulin binding receptors are present on both sides of the erythrocyte membranes. Insulin binding to human erythrocytes was examined with the use of a binding assay designed to minimize the potential errors arising from the low binding capacity of this cell type and from non-specific binding in the assay. Scatchard analysis of equilibrium binding to the cells revealed a class of high affinity sites with a dissociation constant (Kd) of (1.5 +/- 0.5) X 10(-8) M and a maximum binding capacity of 50 +/- 5 sites per cell. Interestingly, both resealed right-side-out and inside-out membrane vesicles exhibited nearly identical specific sites for insulin binding. At the high affinity binding sites, for both right-side-out and inside-out vesicles, the dissociation constant (Kd) was (1.5 +/- 0.5) X 10(-8) M, and the maximum binding capacity was 17 +/- 3 sites per cell equivalent. These findings suggest that insulin receptors are present on both sides of the plasma membrane and are consistent with the participation of the erythrocyte insulin receptors in an endocytic/recycling pathway which mediates receptor-ligand internalization/externalization.     

Small angle neutron scattering as sensitive tool to detect ligand-dependent shape changes in a plant lectin with β-trefoil folding and their dependence on the nature of the solvent

The galactoside-specific Viscum album L. agglutinin (VAA) is a potent biohazard akin to ricin and a mitogen for immune and tumor cells. These activities depend on cell surface binding to glycans. It is an open question whether the process of ligand binding alters the lectin's shape. Small angle neutron scattering (SANS) experiments revealed that the carbohydrate ligand lactose induced a decrease of the radius of gyration of dimeric VAA from 54.5 +/- 1 to 49.5 +/- 1 A in water. Apparently, VAA in aqueous solution and at the concentrations tested at 3.6 mg/ml and above adopts a compacted structure as response to ligand binding. In contrast to the behavior in aqueous solution, lactose binding in DMSO resulted in an increase of the lectin's radius of gyration from 49 +/- 1 to 55.5 +/- 1 A. Because shape changes may be reflected in the thermostability of the protein, this parameter was examined by activity assays of protein exposed to 60 degrees C and 70 degrees C and by differential scanning calorimetry (DSC). In line with the lactose-induced conformational alterations revealed by the SANS experiments, lactose presence enhanced the thermostability of VAA in water. Thus, binding of the carbohydrate ligand in solution can entail changes in shape and thermostability in the case of the tested plant lectin.     

Membrane bilayer balance and erythrocyte shape: a quantitative assessment

When human erythrocytes are incubated with certain phospholipids, the cells become spiculate echinocytes, resembling red cells subjected to metabolic starvation or Ca2+ loading. The present study examines (1) the mode of binding of saturated phosphatidylcholines and egg lysophosphatidylcholine to erythrocytes and (2) the quantitative relationship between phospholipid incorporation and red cell shape. We find that the phospholipids studied become intercalated into erythrocyte membranes, not simply adsorbed to the cell surface. Spin-labeling and radiolabeling data show that the incorporation of (4 +/- 1) X 10(6) molecules of exogenous phosphatidylcholine per cell converts discocytes to stage 3 echinocytes with about 35 conical spicules. This amount of lipid incorporation is estimated to expand the red cell membrane outer monolayer by 1.7% +/- 0.6%. Calculations of the inner and outer monolayer surface areas of model discocytes and stage 3 echinocytes yield an estimated difference of 0.7% +/- 0.2%.