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Query: UNIPROT:P17931 (galectin-3)
 2,860 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The effect of chemical modification on a galactose-specific lectin isolated from a fatty acid auxotroph of Saccharomyces cerevisiae was investigated in order to identify the type of amino acids involved in its agglutinating activity. Modification of 50 free amino groups with succinic anhydride or citraconic anhydride led to an almost complete loss of activity. This could not be protected by the inhibitory sugar methyl alpha-D-galactopyranoside. Treatment with N-bromosuccinimide and N-acetylimidazole, for the modification of tryptophan and tyrosine residues, did not affect lectin activity. Modification of carboxy groups with glycine ethyl ester greatly affected lectin activity, although sugars afford partial protection. Modification of four thiol groups with N-ethylmaleimide was accompanied by a loss of 85% of the agglutinating activity, and two thiol groups were found to be present at the sugar-binding site of the lectin. Modification of 18 arginine residues with cyclohexane-1,2-dione and 26 histidine residues with ethoxyformic anhydride led to a loss of lectin activity. However, in these cases, modification was not protected by the abovementioned inhibitory sugar, suggesting the absence of these groups at the sugar-binding site. In all the cases, immunodiffusion studies with modified lectin showed no gross structural changes which could disrupt antigenic sites of the lectin.
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PMID:Chemical modification studies on a lectin from Saccharomyces cerevisiae (baker's yeast). 312 65

Ricin B-chain (RTB) is a galactose-specific lectin that folds into two globular domains, each of which binds a single galactoside. The two binding sites are structurally similar and both contain a conserved tripeptide kink and an aromatic residue that comprises a sugar-binding platform. Whereas the critical RTB residues implicated in lectin activity are conserved in domain 1 of Ricinus communis agglutinin (RCA) B-chain, the sugar platform aromatic residue Tyr-248 present in domain 2 of RTB is replaced by His in RCA B-chain. In this study, key residues in the vicinity of the binding sites of the Ricinus lectin B-chains were altered by site-directed mutagenesis. The recombinant B-chains were produced in Xenopus oocytes in soluble, stable, and core-glycosylated forms. Both sites of RCA B-chain must be simultaneously modified in order to abolish lectin activity, indicating the presence of two independent, functional binding sites/molecule. Activity associated with the domain 2 site of RCA B-chain is abrogated by the conversion of Trp-258 to Ser. Moreover, the domain 2 site appears responsible for a weak binding interaction recombinant RCA B-chain with GalNAc, not observed with native tetrameric RCA. Finally, the introduction of His at position 248 of RTB severely disrupts but does not abolish GalNAc binding.
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PMID:Mutational analysis of the Ricinus lectin B-chains. Galactose-binding ability of the 2 gamma subdomain of Ricinus communis agglutinin B-chain. 765 99

The expression of galectin-3 (formerly known as IgE-binding protein or Mac-2) in rat bone marrow (BM) was investigated by FACS, immunocytochemical and immunoblot analysis. The functional significance of rat recombinant galectin-3 on mouse recombinant granulocyte-macrophage colony-stimulating factor (GM-CSF)-driven proliferation of macrophage progenitors and gene transcription was further examined. Immunocytochemical analysis of in situ BM sections demonstrated galectin-3 in myelopoietic cells and surrounding stroma, whereas erythropoietic and lymphopoietic environments essentially lacked galectin-3 expression. FACS analysis demonstrated that incubation of freshly isolated BMC with lactose, a competing ligand for galectin-3 binding to glycoconjugates, decreased binding of antigalectin antibodies to cells primarily expressing the myeloid antigen recognized by mAb His-54. Similarly, lectin-mediated binding of exogenous galectin-3 to myeloid lineage cells was also demonstrated. Immunoblot analysis of BM eluates demonstrated galectin-3 both in the extracellular matrix and in a lactose elutable form, bound to the surface of BMC. [3H]Thymidine incorporation studies on BMC cultured in the presence of galectin-3 demonstrated suppression of GM-CSF-induced proliferation by galectin-3. In addition, differential display analysis of immediate early gene expression in BMC cultured in the presence of galectin-3 revealed a 76.2% inhibition of GM-CSF-induced gene transcription by galectin-3 assessed by the number of PCR-fragments generated. Our data suggest a role for galectin-3 in the organization of myelopoietic compartments in rat BM and regulation of the action of growth factors on myelopoietic precursor cells.
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PMID:Galectin-3 inhibits granulocyte-macrophage colony-stimulating factor (GM-CSF)-driven rat bone marrow cell proliferation and GM-CSF-induced gene transcription. 924 34

For proteins in solution the validity of certain crystallographic parameters can be ascertained by a combination of molecular-dynamics (MD) simulations and NMR spectroscopy. Using the laser photo-CIDNP (chemically induced dynamic nuclear polarization) technique as a measure for surface accessibility of histidine, tyrosine and tryptophan, the spectra of bovine galectin-1 and Erythrina corallodendron lectin (EcorL) are readily reconcilable with the crystallographic data for these two proteins. The results emphasise the role of Trp68/Trp69 for carbohydrate binding in bovine galectin-1/chicken galectins and of Trp194 in murine galectin-3. This feature derived from the crystal structure of bovine galectin-1 is maintained in solution for the prototype human homologue, two avian galectins and the chimera-type murine galectin-3, as the spectra corroborate the CIDNP-inferable spatial parameters of the four calculated models for binding-site architecture. In EcorL, Tyr106/Tyr108 are constituents of the extended combining pocket, which can be shielded in solution by ligand presence. Discrepancies between results from modelling and CIDNP measurements concern primarily the lack of reactivity of histidine residues for human and avian prototype galectins and of Tyr82/Tyr229 of the plant lectin. Site-directed mutagenesis of EcorL is assumed to provide information on the role of a certain residue for functional aspects. When single-site mutants of EcorL ([Ala106]EcorL, [Ala108]EcorL, [Ala229]EcorL) were subjected to molecular-dynamics (MD) simulations, the apparent surface accessibilities even of spatially separated amino acid side chains could non-uniformly be affected. This conclusion is supported by the assessment of the spectra for the mutant proteins. On the basis of these CIDNP-results modelling of the binding-site architecture of the lectin indicates the occurrence of notable alterations in the orientation of Tyr106/Tyr108 phenyl rings. The implied potential effect of single-site mutations on conformational features of a protein will deserve attention for the interpretation of studies comparing wild-type and mutant proteins.
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PMID:Involvement of laser photo-CIDNP (chemically induced dynamic nuclear polarization)-reactive amino acid side chains in ligand binding by galactoside-specific lectins in solution. 936 50

Chemical modification studies have been carried out on the galactose-specific lectin (SGSL) purified from snake gourd (Trichosanthes anguina) seeds. Modification of the imidazole side chains of histidine residues with ethoxyformic anhydride resulted in a complete loss of activity of the lectin. A total of 9.5 (+/- 0.7) histidine residues were modified per dimer of M(r) 55,000 when the reaction was carried out for 2 hours. A partial protection was observed when the modification was done in the presence of 0.1 M galactose, indicating that histidine residues are directly involved in the sugar-binding activity of the lectin. Complete recovery of the lectin activity was observed when the modification was reversed by treatment with hydroxylamine. In immunodiffusion experiments, the histidine-modified lectin reacted with rabbit antiserum raised against the native SGSL forming a precipitin line, indicating that the loss of activity upon modification was not due to changes in the overall conformation of the lectin. Modification of the side chains of lysine, cysteine and tyrosine residues did not result in any change in the activity of SGSL.
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PMID:Identification of histidine residues in the sugar binding site of snake gourd (Trichosanthes anguina) seed lectin. 950 53

We have used the yeast two-hybrid system to search for cytoplasmic proteins that might assist in the intracellular trafficking of the soluble beta-galactoside-binding protein, galectin-3. We utilised as bait murine full-length galectin-3 to screen a murine 3T3 cDNA library. Several interacting clones were found to encode a partial open reading frame and a full-length clone was obtained by rapid amplification of cDNA ends methodology. In various assays in vitro the novel protein was shown to bind galectin-3 in a carbohydrate-independent manner. The novel protein contains an unusually high content of cysteine and histidine residues and shows significant sequence homologies with several metal ion-binding motifs present in known proteins. Confocal immunofluorescence microscopy of permeabilised 3T3 cells shows a prominent perinuclear, as well as cytoplasmic, localisation of the novel protein.
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PMID:Interaction of a novel cysteine and histidine-rich cytoplasmic protein with galectin-3 in a carbohydrate-independent manner. 1074 73

Earlier work described the cloning of a gene from murine 3T3 cells encoding a cytoplasmic protein Chrp containing a cysteine- and histidine-rich motif characteristic of Zn-finger proteins. The interaction of Chrp with murine galectin-3 first became evident in a yeast two-hybrid screen, but it was also observed in co-precipitation experiments from 3T3 cell lysates. Here, the formation of equimolar complexes by murine Chrp and hamster galectin-3 is shown. Moreover, we found that Chrp binds to the carbohydrate-recognition domain (CRD) of hamster galectin-3 and not to the N-terminal domain carrying the proline- and glycine-rich repeats characteristic of galectin-3 and absent in other galectins. However, galectin-1 does not bind to Chrp, although its CRD is homologous to the galectin-3 CRD. Finally, we report that galectin-3, in a complex with Chrp, binds to laminin in surface plasmon resonance experiments with similar kinetics and affinity as it does in the free state. The formation of higher-order complexes containing these proteins and additional binding partners may be relevant to cytoplasmic functions involving galectin-3.
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PMID:Specificity of interactions of galectin-3 with Chrp, a cysteine- and histidine-rich cytoplasmic protein. 1276 88

A galactose-specific lectin has earlier been isolated from the seeds of Dolichos lablab in our laboratory by conventional protein purification methods. We now established conditions to bind the lectin on Sepharose-galactose gel in the presence of 1.5 M ammonium sulfate in Tris-buffered saline, pH 7.4. It can be specifically eluted with 0.3 M galactose. The purified lectin is a glycoprotein, binds to Con A, agglutinates erythrocytes, and has an apparent native molecular weight of 120 +/- 5 kDa. In SDS-PAGE under reducing conditions, it dissociates into two subunits of molecular mass (Mr) 31 and 29 kDa. Among a number of sugars tested for inhibitory activity of the lectin, galactose was found to be a potent inhibitor. Rabbit polyclonal antibody to the purified lectin specifically reacted with the lectin subunits in Western blot analysis and additionally, an antibody raised to the isolated 31 kDa subunit show reactivity with both the subunits. Amino terminal sequences of both the subunits are identical. The purified lectin is stable up to 40 degrees C with a pH optimum of 7.4. The lectin has a high content of acidic amino acids and lacks sulfur-containing amino acids. Chemical modification of the lectin with group-specific reagents indicates the possible role of histidine, lysine, and tyrosine residues in lectin activity.
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PMID:Affinity purification, physicochemical and immunological characterization of a galactose-specific lectin from the seeds of Dolichos lablab (Indian lablab beans). 1612 71

The tumor-associated antigen 90K (TAA90K)/Mac-2-binding protein implicated in cancer progression and metastasis is modified by beta1-6 branched N-linked oligosaccharides in colon cancer cells, glycans shown to contribute to cancer metastasis. To elucidate the role of TAA90K in colon cancer, we examined its expression and function in human colon tumors and colon carcinoma cell lines. Immunohistochemical analyses of colon tumors revealed elevated expression of TAA90K in all samples analyzed compared to normal colon. To examine the function of TAA90K in colon cancer, we carried out protein and cell binding assays using TAA90K-His purified from HT-29 cells colon carcinoma cells infected with recombinant vaccinia virus expressing TAA90K containing a C-terminal poly-histidine tag. TAA90K-His bound to fibronectin, collagen IV, laminins-1, -5, and -10 and galectin-3 (Mac-2) but poorly to collagen I and galectin-1. As expected, binding of TAA90K to galectin-3 was dependent on carbohydrate since it was inhibitable by lactose and asiolofetuin, and a TAA90K-His glycoform purified from HT-29 cells treated with the glycosylation inhibitor 1-deoxymannojirimycin bound poorly to galectin-3. Unlike TAA90K isolated from other cell types, TAA90K-His isolated from colon cancer cells failed to mediate adhesion of colon cancer and normal cell lines, possibly due to cell-type specific glycosylation of TAA90K-His and/or its putative cellular receptor. However, at low concentrations, TAA90K-His enhanced galectin-3-mediated HT-29 cell adhesion while at high concentrations, it inhibited cell adhesion. Thus, a possible mechanism by which TAA90K may contribute to colon cancer progression is by modulating tumor cell adhesion to extracellular proteins, including galectin-3.
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PMID:Tumor-associated antigen 90K/Mac-2-binding protein: possible role in colon cancer. 1651 58

alpha2-seminoglycoprotein (alpha2-SGP), purified from human seminal plasma, is a carrier of glycoprotein for the ABO blood grouping. The alpha2-SGP exists in the secretions of the seminal vesicle and various glands. However, the function of alpha2-SGP is, as yet, unknown. In this study, we determined that two internal amino acid sequences of 8 and 12 residues of alpha2-SGP were Ala-Val-Asp-Thr-Trp-Ser-Trp-Gly and Thr-Leu-Gln-Ala-Leu-Glu-Phe-His-Thr-Val-Pro-Phe. These sequences were completely coincident with the domain 3 of human Mac-2 binding protein (M2BP), which was identified as a tumor-associated antigen. In addition, we also confirmed an alpha2-SGP binding activity to galectin-3 that was one of a ligand for M2BP, and the immunological cross-reactivity between alpha2-SGP and M2BP. These findings strongly suggested that alpha2-SGP was identical with M2BP.
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PMID:Homology between ABH-carrier alpha2-seminoglycoprotein and Mac-2 binding protein. 1690 10


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