Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:P17931 (galectin-3)
 2,860 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Carbohydrate-binding protein 35 (CBP35), also known as the macrophage surface antigen Mac-2, is a lactosamine-specific lectin whose extracellular properties include the ability to agglutinate cells and to bind avidly to the basement membrane glycoprotein laminin. Although these and other properties would be facilitated by dimerization of this lectin, previous studies have argued against multimeric forms of this protein. We report here that macrophage CBP35, purified by laminin affinity chromatography, exists as several distinct species (Mr 35,000, 67,000, and 80,000) when analyzed under non-reducing conditions. This unexpected finding prompted us to study the biochemistry of multimerization using recombinant CBP35 (rCBP35). rCBP35 expressed in Escherichia coli forms disulfide-linked homodimers (Mr 67,000). The dimeric form of CBP35 binds to laminin with higher affinity than does monomer and by a lactosamine-dependent mechanism. Site-directed mutagenesis indicated that cysteine 186, the single cysteine residue in CBP35, is required for dimerization. These results raise the possibility that homo- and heterodimeric forms of CBP35 contribute to its postulated functions in cell-matrix interactions and growth regulation.
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PMID:Carbohydrate-binding protein 35 (Mac-2), a laminin-binding lectin, forms functional dimers using cysteine 186. 191 66

Entamoeba histolytica trophozoites adhere to human colonic mucins and epithelial cells by a cell surface galactose-specific lectin. This lectin, which is composed of two subunits linked by disulfide bonds, has been shown to be a protective antigen in an animal model of amebiasis. We have determined the sequence of the mature form of the 170-kDa heavy subunit from cDNA clones and PCR-amplified fragments. The heavy subunit sequence consisted of a putative extracellular domain containing 1209 amino acids with 16 potential sites for N-linked glycosylation, a 26-amino acid hydrophobic region, and a 41-amino acid cytoplasmic tail. The presence of N-linked oligosaccharides was confirmed by culturing amebae with tunicamycin, which resulted in a decrease in the heavy subunit molecular mass to 160 kDa and a loss of lectin activity. The extracellular domain was remarkable for an extensive cysteine-rich domain that shared identify with similar regions of several other cell surface proteins and appeared to confer protease resistance to the subunit.
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PMID:Sequence of a cysteine-rich galactose-specific lectin of Entamoeba histolytica. 201 48

IgE-binding protein (epsilon BP) is a protein which has affinity for IgE and was originally identified in rat basophilic leukemia (RBL) cells. Subsequently, it was found to be the rat homolog of CBP35, a murine beta-galactoside-specific lectin. This protein is also designated as L-34 and RL-29 and studied independently by several laboratories. More recently, CBP35 (epsilon BP) was found to be equivalent to Mac-2, a surface marker on activated macrophages. Using rat epsilon BP cDNA, we have succeeded in expressing recombinant epsilon BP in Escherichia coli. Milligram quantities of homogeneous epsilon BP could be obtained from bacterial lysate in a one-step affinity purification procedure utilizing lactosyl-Sepharose 4B and elution with a lactose gradient. The recombinant epsilon BP (r epsilon BP) binds mouse IgE and retains reactivity to anti-peptide antibodies specific for a sequence within rat epsilon BP. The purified r epsilon BP exhibits binding activity to various saccharides, with affinity for N-acetyllactosamine greater than thiodigalactoside greater than lactose much greater than D-galactose greater than L-arabinose, an order identical to that exhibited by native epsilon BP isolated from RBL cells. The recombinant lectin displayed hemagglutination activity when tested with rabbit erythrocytes. Although epsilon BP shares sequence homology to other lectins containing S-type (thiol-dependent) carbohydrate-recognition domains, r epsilon BP is resistant to air oxidation and does not require reducing agents for maintaining its activity. Furthermore, the single cysteine residue appears to be unexposed and can be alkylated only when the protein is denatured in 5.6 M guanidinium hydrochloride. The availability of a source for a large quantity of epsilon BP should facilitate the analysis of biological function(s) and structure-activity relationships of this lectin.
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PMID:Expression of biologically active recombinant rat IgE-binding protein in Escherichia coli. 224 84

We have purified and sequenced a secreted glycoprotein from both the human breast carcinoma cell line, SK-BR-3, and human breast milk. The native protein binds specifically to a human macrophage-associated lectin known as Mac-2. This Mac-2 binding protein (Mac-2-BP) has an apparent native molecular mass of several million daltons and contains subunits of 85-97 kDa that are very susceptible to proteolysis at a dibasic cleavage site. Western analysis suggests that Mac-2-BP is found in serum, semen, saliva, urine, and tears, in addition to breast milk. The gene encoding Mac-2-BP was cloned from a cDNA bank of a human monocytic cell line, using degenerate PCR primers based on the protein sequence. Recombinant Mac-2-BP was expressed in Cos cells and secreted as a high molecular weight complex. The cDNA clone encodes a mature protein of 567 amino acids, preceded by an 18-amino acid leader. The mature protein contains 16 cysteines and has seven potential N-linked glycosylation sites. The first 106 amino acids represent a domain that is highly similar to an ancient protein superfamily defined by the macrophage scavenger receptor cysteine-rich domain.
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PMID:Cloning and characterization of a human Mac-2-binding protein, a new member of the superfamily defined by the macrophage scavenger receptor cysteine-rich domain. 839 Sep 86

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

The multidomain Mac-2 binding protein (M2BP) is present in serum and in the extracellular matrix in the form of linear and ring-shaped oligomers, which interact with galectin-3, fibronectin, collagens, integrins and other large glycoproteins. Domain 1 of M2BP (M2BP-1) shows homology with the cysteine-rich SRCR domain of scavanger receptor. Domains 2 and 3 are related to the dimerization domains BTB/POZ and IVR of the Drosophila kelch protein. Recombinant M2BP, its N-terminal domain M2BP-1 and a fragment consisting of putative domains 2, 3 and 4 (M2BP-2,3,4) were investigated by scanning transmission electron microscopy, transmission electron microscopy, analytical ultracentrifugation and binding assays. The ring oligomers formed by the intact protein are comprised of approximately 14 nm long segments composed of two 92 kDa M2BP monomers. Although the rings vary in size, decamers predominate. The various linear oligomers also observed are probably ring precursors, dimers predominate. M2BP-1 exhibits a native fold, does not oligomerize and is inactive in cell attachment. M2BP-2,3,4 aggregates to heterogeneous, protein filled ring-like structures as shown by metal shadowed preparations. These aggregates retain the cell-adhesive potential indicating native folding. It is hypothesized that the rings provide an interaction pattern for multivalent interactions of M2BP with target molecules or complexes of ligands.
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PMID:Domain organization of Mac-2 binding protein and its oligomerization to linear and ring-like structures. 1045 90

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

Both the ability of malignant cells to form multicellular aggregates via homotypic or heterotypic aggregation and their adhesion to the endothelium are important if not critical during early stages of cancer metastasis. The tumor-associated carbohydrate Thomsen-Friedenreich antigen (T antigen) and beta-galactoside binding lectins (galectins) have been implicated in tumor cell adhesion and tissue invasion. In this study, we demonstrate the involvement of T antigen in both homotypic aggregation of MDA-MB-435 human breast carcinoma cells and their adhesion to the endothelium. The T antigen-specific peptide P-30 (HGRFILPWWYAFSPS) selected from a bacteriophage display library was able to inhibit spontaneous homotypic aggregation of MDA-MB-435 cells up to 74% in a dose-dependent manner. Because T antigen has beta-galactose as a terminal sugar, the expression profile of beta-galactoside-binding lectins (galectins) in MDA-MB-435 cells was studied. Our data indicated the abundant expression of [35S]methionine/cysteine-labeled galectin-1 and galectin-3 in this cell line, which suggested possible interactions between galectins and T antigen. As revealed by laser confocal microscopy, both galectin-1 and galectin-3 also participate in the adhesion of the MDA-MB-435 cells to the endothelium. We observed the clustering of galectin-3 on endothelial cells at the sites of the contact with tumor cells, consistent with its possible interaction with T antigen on cancer cells The galectin-1 signal, however, strongly accumulated at the sites of cell-cell contacts predominantly on tumor cells. The T antigen-specific P-30 significantly (50%) inhibited this adhesion, which indicated that T antigen participates in the adhesion of MDA-MB-435 breast cancer cells to the endothelium. The ability of synthetic P-30 to inhibit both the spontaneous homotypic aggregation of MDA-MB-435 cells and their adhesion to the endothelium (>70 and 50%, respectively) suggests its potential functional significance for antiadhesive therapy of cancer metastasis.
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PMID:Effects of Thomsen-Friedenreich antigen-specific peptide P-30 on beta-galactoside-mediated homotypic aggregation and adhesion to the endothelium of MDA-MB-435 human breast carcinoma cells. 1082 25

Human Mac-2-binding protein (Mac-2-BP) is a secreted glycoprotein that is widely expressed. It binds to the human macrophage-associated lectin Mac-2 and has been suggested to have a role in host defence. Mouse cyclophilin C-associated protein (mCyCAP) is also a secreted glycoprotein that binds with high affinity to cyclophilin C in the absence of the immunosuppressive drug cyclosporin A. The two proteins share a similar domain structure and considerable sequence identity, including a highly conserved scavenger receptor cysteine-rich domain, and both of them exert their function within the immune system. To elucidate whether these molecules are also functional homologues, we compared their ligand binding properties using cell lines which express Mac-2-BP or mCyCAP as well as transfected cell lines stably expressing mCyCAP or a mutant version lacking the scavenger domain. These experiments show that Mac-2-BP is unable to bind to either human or mouse cyclophilin C and thatmCyCAP cannot bind to Mac-2. The scavenger domain is not required for the interaction between mCyCAP and cyclophilin C. We conclude that these proteins may be part of a larger family of proteins of immunological importance in which closer functional homologues might exists.
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PMID:Distinct ligand binding properties of Mac-2-binding protein and mouse cyclophilin [correction of mousephilin] C-associated protein. 1159 84

In search of specific and highly selective sugar clusters for cell receptors, such as membrane lectins, various disaccharides were coupled to small peptide cores through an amide bond. In a first step, the reducing disaccharides, i.e. lactose and three different dimannoses, were converted into glycosyl-pyroglutamyl-beta-alanine derivatives. The free carboxylic group of these conjugates was then coupled to the alpha and epsilon amino groups of the core peptide (Lys( n )-Ala-Cys-NH2) with n =1 to 5, with complete substitution leading to homogeneous glycoclusters. The thiol group of the cysteine residue was used to tag the glycosylated oligolysines upon reaction with fluorescein iodoacetamide. The affinity of these glycoclusters towards two plant lectins was assessed by surface plasmon resonance. The selectivity of their cell uptake was investigated by flow cytometry using two types of cells: a human hepatoma cell line (HepG2 cells) expressing the plasma membrane galactose-specific lectin, and monocyte-derived dendritic cells expressing the plasma membrane mannose-specific lectin. The glycoclusters containing four or five disaccharides were shown to bind plant lectins and cell surface membrane lectins with a narrow selectivity and with a high affinity.
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PMID:Oligolysine-based saccharide clusters: synthesis and specificity. 1211 48


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