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Query: UNIPROT:P06889 (Mol)
 630,302 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The binding between macrophage-like cells J774G8 and Leishmania braziliensis (NR) promastigotes was studied 'in vitro' by a radioisotopic assay under various conditions in the absence of serum. Different sugars, N-acetyl-D-glucosamine, D-glucose, D-mannose, D-galactose, and chitin, diminished the binding of the parasite, whereas other sugars, D-arabinose, D-fucose and D-xylose, did not affect the binding. The presence of a lectin-like ligand specific for N-acetyl-D-glucosamine has been detected on the cell surface of the Leishmania braziliensis (NR) by fluorescence microscopy. These data suggest that the binding of the parasite to the host's cell is a ligand-receptor interaction which involves the participation of a lectin-like component on the parasite cell surface.
Mol Biol Rep 1986
PMID:The localization of a lectin-like component on the Leishmania cell surface. 376 26

A solid phase variant of radioimmunoassay has been elaborated for screening toxin-producing strains of E. coli and V. cholerae grown on agar plates. The method is based on the ability of cholera-like toxins to be absorbed on nitrocellulose filters and their further identification with the use of homologous sera and [125I]-A protein from staphylococci. Sensitivity of the method reaches 20 pg. The proposed technique permits identification of intracellular enterotoxin and is aimed at a massive screening of E. coli strains, NAG-vibrios and V. cholerae strains for toxin production.
Mol Gen Mikrobiol Virusol 1985 Mar
PMID:[Determination of toxigenicity of Escherichia coli and Vibrio cholerae strains by radioimmunologic method]. 391 23

The specificity of a mouse anti-testicular cell monoclonal antibody, J1, was investigated. Previous studies suggested that N-acetyl-D-glucosamine (GlcNAc) was a constituent of the determinant recognized by J1. When the antibody was tested against a variety of purified glycolipids containing this saccharide in terminal, penultimate or internal positions, J1 reacted only with species expressing terminal GlcNAc. The influence of oligosaccharide chain length, branch substitution, and haptenic valence on J1 binding was examined using glycolipids prepared by a weak acid hydrolysis and exoglycosidase digestion of bovine I-active ganglioside. Degree of binding was inversely proportional to chain length and was proportional to hapten valence. Failure of J1 to bind partially deglycosylated transferrin implied binding preference for GlcNAc beta 1----3Gal over GlcNAc beta 1----2Man. Immunofluorescence analysis of J1 binding to human neutrophils failed to detect lactotriosylceramide on their surface, although this glycolipid has previously been isolated from these cells, suggesting that this structure exists in a cryptic or intracellular form. Binding results were consistent with J1 having low affinity for GlcNAc or GlcNAc beta 1----3Gal on a variety of lacto-series glycolipids.
Mol Immunol 1984 Oct
PMID:Fine specificity of a monoclonal anti-testicular cell antibody for glycolipids with terminal N-acetyl-D-glucosamine structure. 620 60

Lectins specific for D-mannose (concanavalin A), N-acetyl-D-glucosamine (wheat-germ agglutinin) or D-galactose (Ricinus communis agglutinin I) inhibited insulin binding and activated glucose transport in rat adipocytes [Cherqui, Caron, Capeau & Picard (1982) Mol. Cell. Endocrinol. 28, 627-643]. In the present investigation, the intracellular activities of insulin and lectins on lipogenesis and protein synthesis were studied under conditions where neither agent had an effect on membrane transport processes. (1) When glucose transport was rate-limiting (0.5 mM-glucose), insulin (0.8 ng/ml) and lectins (20 micrograms/ml) increased lipogenesis by 2.4-3-fold. (2) When passive diffusion of glucose was amplified (10 mM-glucose), insulin (0.8 ng/ml) and lectins (20 micrograms/ml) increased lipogenesis by 1.6-1.8-fold even in the presence of 50 microM-cytochalasin B, which completely blocked glucose transport. (3) Insulin (6 ng/ml), concanavalin A and wheat-germ agglutinin (40 micrograms/ml) stimulated the incorporation of L-[U-14C]leucine into fat-cell protein 1.5-fold but did not modify alpha-aminoisobutyric acid uptake or 14C-labelled protein degradation. (4) Peanut and soya-bean agglutinins (specific for O-glycosidically-linked oligosaccharides), known not to alter insulin binding, were ineffective. (5) Lectin effects were dose-dependent and were markedly inhibited by specific monosaccharides (50 mM). (6) Insulin and lectin maximal effects were not additive and were completely abolished by neuraminidase treatment of fat-cells (0.05 unit/ml). These data indicate involvement of surface sialylated glycoproteins of the complex N-linked type in the insulin stimulation of glucose and amino acid intracellular metabolic processes. They suggest, together with our previous results, that the transmission of the insulin signal for both membrane and intracellular effects occurs via glycosylated effector entities of, or closely linked to, the insulin-receptor complex.
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PMID:Evidence for surface glycoprotein involvement in the intracellular bioactivity of insulin in rat adipocytes. 635 47

The two unique sugar binding sites in wheat germ agglutinin, located in the subunit/subunit interface of the dimer molecule and termed primary and secondary binding sites, are compared in the light of the newly obtained chemical amino acid sequence and a high-resolution electron density map (1.8 A). Homology was found in the three amino acid residues directly involved in sugar binding: Tyr73II, Ser62II, Glu115I in the primary site, and Tyr159I, Ser148I, Asp29II in the secondary site (subscripts refer to promoters I and II). Thirteen corresponding side-chain atoms of these three homologous residues in the two sites could be superimposed with a root-mean-square difference of 1.39 A. The three sugar binding residues are located in subsite 1 of each extended binding location and contribute to binding of the terminal, non-reducing N-acetyl-D-glucosamine and N-acetyl-D-neuraminic acid residues only, and they provide three hydrogen bonds for complex stabilization. Two hydrogen bonds are made with the carbonyl and amido portions of the N-acetyl group and the third with the C-3 OH group of the sugar ring. It is suggested that small differences in the sugar binding affinities at these two unique sites exist, due to the different numbers of van der Waals' interactions made at these sites, which contribute to stabilizing, for instance, the wheat germ agglutinin/N,N'-diacetyl-chitobiose complex. The single tryptophan residue is located at a distance of approximately 13 A from the primary site and is thought to have no affect on sugar binding. In addition, the disposition of the four saccharide binding sites of the dimer with respect to three local, pseudo 2-fold symmetry axes, relating domains of opposite protomers, is discussed.
J Mol Biol 1984 Sep 05
PMID:Structural comparison of the two distinct sugar binding sites in wheat germ agglutinin isolectin II. 654 65

The carbohydrate moieties in the four isotypes of a variant surface glycoprotein from Trypanosoma congolense were analyzed. All variant surface glycoprotein isotypes were found to contain up to 15% by weight of D-galactose, D-mannose, and N-acetyl-D-glucosamine in molar ratios approaching 1:3.2:3.9 (isotypes I-III) or 1:2.4:2.4 (isotype IV); in addition, the presence of sialic acid could be demonstrated. After metabolic labelling with D-[6-3H]glucosamine, the four isoglycoproteins were successively digested with pronase and with endo-beta-N-acetylglucosaminidase H. Up to two thirds of the oligosaccharides were thus liberated and were separated by gel filtration, and by high performance liquid chromatography. Using methylation, gas chromatography, mass spectrometry and digestion with alpha-mannosidase, they were shown to be mainly typical oligomannosidic oligosaccharides of size classes Man5GlcNAc to Man9GlcNAc. The residual glycans were liberated by hydrazinolysis, and were fractionated by serotonin affinity chromatography. After separation by gel filtration, the neutral oligosaccharides from isotype I were subjected to methylation analysis and successive exoglycosidase digestions. They were found to be biantennary oligosaccharides of the N-acetyllactosaminic type: (GalGlcNAc)2Man3GlcNAc1-2. Only about 30% of the sialylated glycans were susceptible to neuraminidases. The T. congolense variant surface glycoprotein studied here contains mainly high mannose and biantennary 'complex' oligosaccharides as found in many other eukaryotic glycoproteins, except that they seem to carry unusually substituted/linked sialic acid residues.
Mol Biochem Parasitol 1984 Apr
PMID:Structural studies on the major oligosaccharides in a variant surface glycoprotein of Trypanosoma congolense. 674 84

The mechanism of invasion of human red blood cells by Plasmodium falciparum merozoites has been studied by several indirect methods. Red blood cells of the S+s+U+ and S-s-U- blood group phenotypes were trypsin treated and their susceptibility to invasion measured. Trypsin-treated S+s+U+ cells lack the portion of glycophorin A which bears the MN blood group determinants but possess glycophorin B, whereas trypsin-treated S-s-U- cells lack both the glycophorin A MN determinants and the glycophorin B molecule. Since the treated S-s-U- cells showed an even greater loss in susceptibility to invasion that the treated S+s+U+ cells, we conclude that glycophorin B does have a role In merozoite recognition, although it appears less important than glycophorin A. Attempts to decrease invasion by pretreatment with glycosidases were unsuccessful, except for the previously reported effect of neuraminidase. N-acetyl-D-glucosamine decreases the appearance of ring-stage parasites after in vitro reinvasion of P. falciparum. However, the persistence of intact and lysed schizont-infected cells when N-acetyl-D-glucosamine was present, several hours after disappearance of these cells from control cultures, leads us to conclude that this sugar has a deleterious effect on terminal stages of parasite maturation. It is therefore not possible to conclude that N-acetyl-D-glucosamine inhibits merozoite attachment and reinvasion specifically by competition for the receptor.
Mol Biochem Parasitol 1982 Nov
PMID:Studies on the role of red blood cell glycoproteins as receptors for invasion by Plasmodium falciparum merozoites. 675 49

The insulin receptor apparent affinity was markedly decreased in fat cells treated with lectins specific either for D-galactose (Ricinus communis agglutinin I, RCAI), D-mannose (concanavalin A, Con A, Lens culinaris agglutinin, LCA) or N-acetyl-D-glucosamine (wheat germ agglutinin, WGA), as indicated by a rightward shift of the binding competition curves and almost lineared Scatchard plots. Limulus polyphemus agglutinin (LPA), specific for sialic acid, was ineffective. All lectins enhanced 2-deoxy-D-glucose uptake with relative bioactivities (maximal lectin effect/maximal insulin effect) of 68-86%. Insulin and lectin stimulatory effects were antagonized by specific carbohydrates used as competitors and inhibited by cytochalasin B (70 microM). Maximal effects of insulin and lectins were not additive and were completely abolished in neuraminidase-treated fat cells. Lectins did not affect insulin degradation. These data show that sialylated glycosidic moieties containing D-galactose, D-mannose and N-acetyl-D-glucosamine units are involved in both processes of insulin 'high affinity' binding and activation of glucose transport but are not implicated in hormone degradation. They suggest that N-linked carbohydrate chains of the complex type may be essential for functional insulin receptor and post-receptor systems.
Mol Cell Endocrinol
PMID:Carbohydrate determinants involved in both the binding and action of insulin in rat adipocytes. 675 1

Simultaneous or sequential treatment of rat adipocytes with neuraminidase plus beta-galactosidase decreased insulin binding by 43%. No modification was observed with either enzyme individually. alpha-Mannosidase enhanced insulin binding (38%), whereas beta-N-acetylglucosaminidase and alpha-L-fucosidase were ineffective. Lectins that interact with galactose (Ricinus communis I, RCAI), mannose, Lens culinaris agglutinin (LCA), Concanavalin A (Con A) or N-acetylglucosamine (wheat-germ agglutinin, WGA) decreased insulin binding by 43, 57, 59 and 85% respectively. Lectin inhibition was dose-dependent, saturable and prevented by specific monosaccharides. RCAI, LCA, Con A and WGA decreased the insulin dissociation process by 45, 90, 78 and 84% respectively. Lectins specific for sialic acid, terminal galactose, N-acetylgalactosamine or fucose (Limulus polyphemus, peanut, soybean and Ulex I agglutinins) did not modify either insulin binding or dissociation. These results indicate involvement of penultimate D-galactose, internal N-acetyl-D-glucosamine and D-mannose residues in both processes. They suggest that, in rat adipocytes, a glycosidic moiety participates in the insulin-receptor interaction through N-linked oligosaccharides of the 'complex type'.
Mol Cell Endocrinol 1981 Sep
PMID:Further characterization of the insulin receptor glycosidic moiety in rat adipocytes. 679 21

The lectin of Euonymus europaeus at concentrations of 5-21 micrograms/ml causes activation of the classical complement (C) pathway (C1, C4, C2) when added to normal human serum at 37 degrees C. At higher concentrations, C3 is also consumed. The effect is dependent on a 'natural antibody' in serum of the IgM class which reacts with an epitope of the lectin. With physicochemical methods, the carbohydrate of the lectin was shown to be involved in the activation of C, but not involved in the agglutination of group B erythrocytes. Removal of N-acetyl-D-glucosamine from the lectin with an exoglycosidase greatly reduced the activation of C in serum, but it did not affect erythroagglutination. Using competitive binding studies with various sugars, it was confirmed that N-acetyl-D-glucosamine is the dominant specificity of a determinant for activation of the classical C pathway in serum.
Mol Immunol 1982 Dec
PMID:Effect of sequential glycolysis of the lectin of Euonymus europaeus on activation of the classical complement pathway in normal human serum. 716 23


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