Volume 5, Issue S1
December 1983, pages 1-163
pp 1-7 December 1983
Studies on the distribution of theDolichos biflorus lectin during the life cycle of the plant have shown that the seed lectin appears at about 27 days after flowering and is localized in the cotyledons. Although this lectin disappears during the absorption of the cotyledons, a related molecule that cross reacts with antibodies to the seed lectin, appears in the stems and leaves of the plant. Structural studies on this cross reactive material show that it appears to have one subunit in common with the active subunit of the seed lectin and another subunit that has a higher molecular weight than the seed lectin subunits. The subunits of the seed lectin and cross reactive material may all represent different degrees of completion or modification of a common gene product.
The cross reactive material has been found to have carbohydrate binding activity at low ionic strength and a significant amount of this “lectin-like” glycoprotein appears to be associated with the cell wall. Further studies on the distribution and properties of lectins during the life-cycle of the plant may be valuable in obtaining a better insight into the physiological role(s) of these molecules in the plants.
pp 9-17 December 1983
Metal ion activation of saccharide binding has been studied for concana-valin A near pH 7.0. Although two metal ions, a transition metal ion and a Ca2+ ion, can bind, both are not required. Ca2+ alone, Mn2+ alone, or Ca2+ with other transition metal ions can activate this lectin. Only one Ca2+ ion per subunit or only one Mn2+ per subunit is sufficient. Metal ion binding was studied by magnetic resonance techniques and direct binding assays. Saccharide binding activity was monitored by following the fluorescence of 4-methylumbelliferyl a-D-mannopyranoside. When Ca2+ binds to demetalized concanavalin A, the transition metal ion site is hindered. When Mn2+ alone binds to demetalized concanavalin A, saccharide binding activity is induced. A subsequent conformational change, not necessary for carbohydrate binding activity, covers the Mn2+.
pp 19-23 December 1983
The recognition of lysosomal enzymes by various carbohydrate specific cell surface receptors is reviewed. In particular the biosynthesis of mannose 6-phosphate residues in lysosomal enzymes and their role for targeting of lysosomal enzymes to lysosomes are discussed.
pp 25-30 December 1983
Human erythrocyte specific lectin was isolated from the seeds ofErythrina variegata Linn. var.orientalis Linn. Merrill. The lectin preferentially agglutinated erythrocytes in the sequence of O>B>A = AB. The lectin was purified 19-fold by affinity chromatography on acid treated sepharose 4B with an yield of 81%. The purified lectin was found homogeneous on polyacrylamide gel electrophoresis. The erythroagglutination reaction was inhibited by N-acetyl-D-galactosamine, D-galactose and lactose at very low concentration. The haemagglutination by the purified lectin was not inhibited by different hexose and pentose sugars even at high concentration. The purified lectin was a glycoprotein and agglutinated leucocytes at 3 μg protein concentration. The lectin induced transformation of peripheral blood lymphocytes in cultures.
pp 31-39 December 1983
The binding ofRicinus communis agglutinin andAbrus agglutinin to 4-methylumbelliferyl β-D-galactopyranoside was studied by equilibrium dialysis, fluo-rescence quenching and fluorescence polarization. The number of binding sites and the association constant value obtained by fluorescence polarization for bothRicinus communis agglutinin andAbrus agglutinin are in close agreement with those obtained by the other methods. This indicates the potential of ligand-fluorescence polarization measurements in the investigation of lectin-sugar interactions.
pp 41-51 December 1983
The effect of intact diphtheria toxin and of its fragment A on protein synthesis in mouse liver mitoplasts (digitonin-treated mitochondria) was studied. Fragment A inhibited protein synthesis in intact mitoplasts to the same extent as the uncoupler, carbonylcyanidep-trifluoromethoxyphenylhydrazone, but similar effects were not observed in lyzed mitoplasts. Intact diphtheria toxin was without effect in either case.
Fragment A strongly stimulated mitochondrial ATPase activity. At concentrations which efficiently inhibited mitochondrial protein synthesis and stimulated ATPase activity, fragment A had no effect on the intramitochondrial concentration of nicotin-amide adenine dinucleotides. Moreover, it did not catalyze ADP ribosylation of mitochondrial proteins. The results indicate that the effects observed did not involve the NAD+-glycohydrolase activity of fragment A.
[125I]-Labelled fragment A was bound to mitoplasts to about the same extent as the labelled intact diphtheria toxin.
The present results suggest that fragment A of diphtheria toxin is capable of inhibiting the energy coupling in mitoplasts, thereby inhibiting protein synthesis. The detailed mechanism of the uncoupling and its possible physiological significance remains to be elucidated
pp 53-59 December 1983
The exposed carbohydrate residues on the cell surface of both tumourigenic and nontumourigenic strains ofAgrobacterium have been investigated using lectins as probes. N-acetyl-D-galactosamine and β-D-galactose were found to be present as the exposed groups on the cell surfaces of heAgrobacterium strains. These carbohydrate residues are attached to lipids on the outer membrane of the bacteria as lipopolysaccha-rides. Fluorescently labelled lectins were used to observe bacterial agglutination in fluorescence microscope. The involvement of these exposed carbohydrate groups in host-pathogen interaction was demonstrated by actual inhibition of tumour initiation at wound sites on host plant.
pp 61-64 December 1983
Concanavalin A bound to Sepharose has been used for the purification of brain β-galactosidase, α-L-fucosidase, α-D-mannosidase, arylsulphatase and β-glucuronidase.0 Several factorsviz pH, temperature and concentration of α-methyl glucoside influenced the binding and elution of these enzymes. A lysosomal acid α-mannosidase and a cytosolic neutral mannosidase were separable by concanavalin A-Sepharose chromatography. Similarly lysosomal and microsomal β-glucuronidases were separable using gradient elution with α-methyl glucoside. The results indicate the usefulness of this lectin for the isolation of wide variety of enzymes under specified experimental conditions.
pp 65-71 December 1983
The physical-chemical and carbohydrate binding specificity ofGriffonia simplicifolia I (GS I) isolectins, one of the 4 lectins isolated fromGriffonia simplicifolia seeds, are described.
Association constants for the binding of methyl α- and β-D-galactopyranoside and methyl 2-acetamido-2-deoxy-α-D-galactopyranoside to the A4, A2 B2 and B4 isolectins are reported.
Precipitation reactions of theGriffonia simplicifolia isolectins with guaran and type B blood group substance are described.
The hypothesis that subunit B is a precursor of subunit A, a process involving proteolytic cleavage of the B subunit, was tested by conducting structural studies on the 2 subunits. The results indicated that the A and B subunits are probably products of 2 separate but closely related, possibly contiguous genes.
pp 73-81 December 1983
The process of fluorochromasia involves the hydrolysis by cells of fluorescein diacetate resulting in an intracellular accumulation of fluorescein. The polarization of the fluorescence of the fluorescein appears to depend on the intracellular fluorescein concentration, the distribution of fluorescein within the cell and the viscosity of the cell cytoplasm.
The parameters of fluorochromasia were studied with thymocytes from normal BALB/c mice and from mice bearing an intraperitoneal NK/LY/R lymphoma. During the course of tumour proliferation, the response toT-cell mitogens increased whereas the response to other lectins,e.g. wheat germ agglutinin, decreased or remained unaltered. These changes were consistent with the corresponding increase in immunocompetent cells within the thymus, observed by microelectrophoresis. Thus this sensitive technique provides a useful quantitative assessment of the lectin-lymphoid cell interaction.
pp 83-91 December 1983
Two lectins, a tetramer designated LBL4 and an octamer LBL8 designated have been purified from the lima beanPhaseolus lunatus. The tetramer appears to be nonmitogenic for human lymphocytes and is a weak mitogen for bovine cells. The octamer and a chemically cross-linked form of the tetramer are good mitogens. The lima bean lectin binds to only certain sub-populations of human lymphocytes. The primary class which does not bind appears to be a sub-population ofT-lymphocytes. Comparisons of cell binding with other lectins which bind to 2-acetamido-2-deoxy-D-galactose have been carried out. Quantitative analysis of the binding to human erythrocytes is co-operative but binding to lymphocytes is non-co-operative. These results show that there may not be a direct correlation between mitogenic stimulation and cooperative binding to membrane receptors.
pp 93-100 December 1983
Precisions are given on the fine specificity and on the usefulness of immobilized concanavalin A,Lens culinaris, Vicia faba andPisum sativum agglutinins for fractionation of glycopeptides with the N-glycosylamine linkage.
While insolubilized concanavalin A represents a very useful tool for the fractionation of both N-acetyllactosaminic and oligomannosidic type glycopeptides or related oligo-saccharides, immobilizedLens culinaris, as well asVicia faba orPisum sativum agglutinins allow the subfractionation of some N-acetyllactosaminic glycopeptide populations on the basis of the presence of an α-L-fucose residue substituting in C-6 position the N-acetylglucosamine residue involved in the N-glycosylamine bond.
pp 101-104 December 1983
Newly synthesized lysosomal enzymes were found to contain N-acetylglucosamine residues in phosphodiester linkage to the 6 position of the mannose residues on high-mannose type oligosaccharides. The formation of these structures was shown to be catalyzed by a specific N-acetylglucosaminylphosphotransferase enzyme, that utilises UDP-N-acetylglucosamine as a donor. The phosphorylation reaction can take place on any of four or five positions on the high-mannose oligosaccharide. Subsequently an α-N-acetylglucosaminylphosphodiesterase removes the outer blocking N-acetylglucosamine residues to generate the mature phosphomannsoyl recognition signal. This signal is responsible for the targetting of newly synthesized lysosomal enzymes to lysosomes. The human syndromes of I-cell disease (Mucolipidosis II) and pseudo-Hurler polydystrophy (Mucolipidosis III) were shown to be caused by deficiency of the first enzyme in the pathway, the UDP-N-acetylglucosamine: Glycoprotein N-acetylglucosaminylphosphotransferase.
pp 105-120 December 1983
The binding of fluorescently labelled carbohydrates to concanavalin A and wheat germ agglutinin was studied at equilibrium and by the stopped-flow and temperature jump relaxation methods. Ligand were mainly die 4-methylumbelliferyl glycosides of α (1 → 2)-linked manno-oligosaccharides and of β (1 → 4)-linked chito oligosaccharides as limited homologous series. They offer distinct advantages, parti cularly for kinetic studies.
Enthalpie and kinetic considerations suggest that concanavalin A specifically binds a single mannopyranosyl group in α (1 →2)-linked manno-oligosaccharides. This occurs preferentially at the non-reducing end. Glycosylation of a carbohydrate withe.g. an aryl group does not afect die binding kinetics and for all carbohydrates the association rate is comparable but relatively slow, which indicates that a common process is involved in the binding of all carbohydrates to concanavalin A. The affinity of a carbohydrate for concanavalin A is determined by the dissociation-rate parameter, resulting in a longer residence time for a better ligand.
Interaction of chito-oligosaccharides with wheat germ agglutinin is complex. With the larger members of the 4-methylumbelliferyl chito-oligosaccharides, binding studies were only possible at low fractional saturation to avoid formation of unsoluble complexes. The binding kinetics of wheat germ agglutinin are faster than with concanavalin A and are consistent with a wheat germ agglutinin binding region composed of two adjacent subsites. For binding of the monoside as well as the bioside, two consistent kinetic models apply. They have common that for each ligand there exist two complexes with comparable population.
pp 121-129 December 1983
The kinetics of haemolysis of rabbit erythrocytes byCroton tiglium lectin was studied as a function of concentration of the lectin and erythrocytes. The length of the prelytic period decreased with increasing lectin concentrations, indicating that the secondary events at the membrane which follow the binding of the lectin to cell surface carbohydrate receptors are accelerated at higher surface concentrations of the lectin. The rate or extent of haemolysis was not affected by the inclusion of ions like K+, Ca2+ and Mg2+ in the medium or by the substitution of ionic medium by a non-ionic medium. The inhibition of haemagglutination and haemolysis of rabbit red cells byCroton tiglium lectin by antilectin rabbit serum was observed. A possible mechanism of haemolysis by the lectin is discussed.
pp 131-135 December 1983
N-Acetyl-D-galactosamine in β-linkage being ubiquitous in cell surface glycoproteins, their interaction with lectins specific for this sugar moiety may be a significant event in cell adhesion phenomena. This article discusses the common β-N-acetyl galactosamine-specific lectins, with particular stress on the lectin from winged beans (Psophocarpus tetragonolobus).
pp 137-148 December 1983
The redistribution of surface receptors induced by the binding of concanavalin A to different types of lymphoid cells was studied by the techniques of cell electrophoresis and fluorescence microscopy. The cells studied included, splenic lymphocytes from normal healthy as well as terminally leukaemic mice, thymocytes from mice of varying ages from newborns to adults and antigen sensitised or educated lymphocytes. These cells were in different stages of growth and/or differentiation. The nature and especially the behaviour of surface receptors in response to treatment with concanavalin A under capping conditions differed markedly but appeared to be dependent on the differentiational status of the cells. On this basis, the adult thymocytes were found to consist of two sub-populations differing in their proliferative and differentiational status. The proportions of these varied during their ontogenic development. Lymphocytes specifically committed to an antigen bound concanavalin A but were found to be incapable of bringing about the redistribution of the surface receptor-ligand complexes.
pp 149-155 December 1983
Disintegration of influenza virions with 0.2% w/v sodium deoxycholate releases haemagglutinin and neuraminidase, which in the presence of detergent are both adsorbed to the lectin fromCrotalaria juncea, coupled to Sepharose 2B.
The binding is mediated through galactosyl residues on haemagglutinin and neural-minidase, which are completely displaced in 0.2 M lactose and co-elute in a narrow zone.
The immunogenicity of haemagglutinin and neuraminidase in mice is markedly increased after adsorption onto lipid, particles constituting “intralipid” (Kabi Vitrum, Stocholm, Sweden).
pp 157-163 December 1983
Multiple forms of ricin have been isolated from castor bean seeds. Two forms, ricin-1 and ricin-2, differ in their isoelectric pI values and toxicity towards IMR-32 cells. Inhibition of IMR-32 DNA polymerase α2 is more pronounced with ricin-1 (65%) than with ricin-2 (10%). Ricin B chain (pI = 5.2) isolated from ricin-1 binds to IMR-32 cell surfaces as well as inhibits DNA polymerase α2 activity when studiedin vitro. The presence of galβ-linked glycoconjugates near the active site of IMR-32 DNA polymerase α2 has been proposed. Replication modulators which bind to the glycose portion of the enzymes involved in the replication system may need a mandatory binding to cell surface glycoconjugates for their activity.
Volume 44 | Issue 5
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