Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

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Query: EC:3.4.21.4 (trypsin)
42,187 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The concanavalin A (Con A)-induced agglutinability of normal, preneoplastic, and neoplastic mouse mammary epithelial cells was examined. Cells freshly dissociated from normal mammary glands, hyperplastic alveolar nodules, or primary mammary adenocarcinomas by collagenase digestion in the presence of bovine serum albumin were strongly agglutinated by low concentrations of Con A. After short-term culture in vitro, however, cells from all three types of tissue were only weakly agglutinated by Con A, as measured by both suspension and hemadsorption assays. By comparison, cells of three established mammary tumor culture lines agglutinated strongly in the presence of the lectin. Treatment of the normal, preneoplastic, and neoplastic mammary cells in primary cultures with either trypsin or collagenase had little or no effect on their agglutinability, whereas hyaluronidase significantly increased their reactivity. Studies with fluorescein-tagged Con A indicated that all three cell types were capable of binding the lectin. The results were consistent with previous evidence suggesting that neoplastic transformation of mouse mammary epithelial cells is not manifested in vitro by several of the alterations in growth patterns, intercellular interactions, and surface properties that usually accompany transformation of fibroblastic cells.
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PMID:Concanavalin A-induced agglutinability of normal, preneoplastic, and neoplastic mouse mammary cells. 28 51

A new non-strain-specific ascites subline of the TA3 mammary adenocarcinoma TA3-MM, which arose in vivo from the strain-specific TA3-St subline during an acute respiratory illness of the syngeneic mouse strain A/HeHa hosts, possessed at its surface a glycoprotein not found on the parent TA3-St cell. This glycoprotein, termed TA3-MM epiglycanin, was characterized by a high molecular weight (500,000), by potent inhibition of hemagglutination by the Vicia gramines lectin, and by carbohydrate and amino acid compositions nearly identical to those of the glycoprotein epiglycanin present at the surface of the allotransplantable TA3-Ha ascites cell. By electron microscopic examination, TA3-MM epiglycanin appeared as long extended rods with widths (2.5 nm) and lengths (450--500 nm) similar to those of TA3-Ha epiglycanin. Incubation of each of two sublines of the TA3-MM ascites cell, TA3-MM/1 and TA3-MM/2, with a modified trypsin followed by column chromatography produced approximately 1.0- and 0.2-fold as much epiglycanin-like material, respectively, as was obtained from the TA3--a ascites cell. Continuous growth of the TA3-MM cell in suspension culture resulted in an almost complete disappearance of epiglycanin in a manner demonstrated earlier for the TA3-Ha cell grown under similar conditions. Allotransplantability in the TA3-MM cell may be due, at least in part, to masking a histocompatibility antigens by epiglycanin-like molecules.
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PMID:Isolation and partial characterization of an epiglycanin-like glycoprotein from a new non-strain-specific subline of TA3 murine mammary adenocarcinoma. 28 25

The glycoprotein I complex, consisting of two polypeptides of Mr 210,000 and 150,000, was isolated from human platelet membranes by wheat germ lectin affinity chromatography. Glycocalicin, a soluble loosely bound membrane glycoprotein of Mr 150,000 related to the glycoprotein I system, was also purified. The isolated polypeptides were radioiodinated in sodium dodecyl sulfate/polyacrylamide gels and digested with trypsin, and the labeled peptide digest was analyzed by two-dimensional high-voltage electrophoresis and thin-layer chromatography. The two polypeptides of Mr 210,000 and 150,000 in the glycoprotein I complex had essentially identical radioactive peptide maps. Glycocalicin had a completely different tryptic peptide map. These studies shed light on the molecular relationships of some of the components of the platelet membrane glycoprotein I system. The possibility is raised that the receptorlike function of the intrinsic platelet membrane glycoproteins may be related to the polymeric subunit associations of the constituent polypeptides.
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PMID:Structural analysis of human platelet membrane glycoprotein I complex. 28 80

We have partially purified a lymphokine, costimulator, which is necessary to induce mitogenesis in mouse thymocytes in vitro. Costimulator is released from mouse leukocytes exposed to Con A for 12 to 18 hr. It has been purified more than 100 X by gel exclusion chromatography and isoelectric focusing. Thymocytes from CBA/J mice respond to the mitogenic lectin Con A only if the costimulator concentration is above a certain level. Culturing such cells with Con A at a density below 1 X 10(6) cells/ml produces costimulator concentrations too low for mitogenesis. This system has been developed into a quantitative assay for costimulator, to monitor purification, recovery, and biologic activity in various methods of molecular characterization. The activity is trypsin sensitive, and has a buoyant density characteristic of protein or glycoprotein. However, for a protein, it is relatively heat stable. Its m.w., established by carrying out sedimentation, gel filtration, and buoyant density measurements, is 30,500, and its frictional coefficient is 1.45. Costimulator purified by isoelectric focusing is active at 10(-10) M or lower in tissue culture.
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PMID:Partial purification and molecular characterization of a lymphokine (costimulator) required for the mitogenic response of mouse thymocytes in vitro. 30 26

Limited digestion of the intact subunit of concanavalin A (Mr = 26,000) with trypsin followed by affinity chromatography on Sephadex G-100 has yielded a highly purified product designated here as Tn-Con A. Chemical studies have shown that Tn-Con A is composed of several components: a large fragment (Tn I, Mr = 19,000) spanning residues 1 to 172, and lower molecular weight polypeptides that are noncovalently associated with Tn I to form the active molecule. The molecular weight of Tn-Con A at pH 7 was 90,000, suggesting that, like native concanavalin A, it was a tetramer at physiological pH. Equilibrium dialysis experiments showed that Tn-Con A bound 1 molecule of alpha-methyl-D-glucoside/22,000 g atoms of protein and therefore that four saccharides are bound by the tetrameric molecule. Tn-Con A and native concanavalin A competed for the same receptors on the lymphocyte surface. Moreover, Tn-Con A was mitogenic for both mouse and human lymphocytes with dose-response curves similar to those of the native lectin. All of these results indicate that tryptic hydrolysis of concanavalin A produces a fragmented molecule retaining the saccharide-binding, subunit association, and mitogenic capacity of the native protein.
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PMID:Binding and functional properties of concanavalin A and its derivatives. II. A proteolytic product with saccharide-binding activity. 34 87

Specific cell membrane receptors for interferon have been postulated based on a variety of different observations, such as the following: trypsin treatment of monkey-mouse hybrid cells preferentially destroys sensitivity to primate interferon (9); syngeneic mice immunized with human-mouse hybrid cells develop surface-directed antibodies, which only block antiviral action of human interferon (24); interferon covalently bound to Sepharose beads retains its antiviral activity despite the fact that diameters of the beads are several times those of the cells (1,10,19); cells challenged with polyl:C to produce interferon do not develop resistance to viral infection in the presence of interferon antiserum (30). Interferon has a strong and specific affinity for the carbohydrate side chain of cell membrane gangliosides. Preincubation of Sepharose-bound interferon with gangliosides inhibits antiviral activity in the following order of potency: GM2 greater than or equal to GTl greater than GMl greater than or equal to GDla (3). Derivatives of GM2 lacking either terminal N-acetyl-galactosamine or terminal N-acetyl-neuraminic acid are not (or very little) inhibitory; in addition, binding to gangliosides is reversed by N-acetyl-neuraminyl-lactose, the trisaccharide common to all gangliosides. These data clearly demonstrate interferon's specificity for the carbohydrate moiety of the ganglioside molecule (6). Phaeseolus vulgaris lectin, which blocks antiviral action of interferon (4), also prevents binding of interferon to ganglioside-Sepharose affinity columns (2). Many substances of known affinity for gangliosides likewise inhibit action of interferon. These include cholera (15) and tetanus toxins (2), thyrotropin (5,23) and human chorionic gonadotropin (5). Although a more general effect on the state of the membrane or on cellular metabolism by these substances cannot be ruled out, competition for interferon binding sites appears to be the most plausible explanation. Increased sensitivity of certain transformed cells to interferon upon uptake of exogenous gangliosides not only supports the concept that these glycolipids are involved in binding of interferon to the membrane, but furthermore points to the importance of interferon-ganglioside interaction for triggering of the antiviral response (29).
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PMID:Membrane receptors for interferon. 35 55

Solubilized surface proteins from normal human lymphocytes were obtained by mild trypsin digestion. The binding of membrane components to labelled Ricinus sanguineus agglutinin (molecular weight = 120,000 daltons) was studied by a gel filtration method. The bound and unbound lectin amounts were determined from the gel filtration patterns. The binding parameters were calculated from Scatchard plots. They were compared to the parameters obtained at the same temperature for the lectin-intact lymphocyte system. The respective values for the affinity constant, were 3.5 x 10(6) M-1 and 6 x 10(6) M-1. The calculation of the number of sites per cell in each system specifies the yield of the trypsin digestion.
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PMID:Interaction between the Ricinus sanguineus agglutinin and receptor sites isolated from normal human lymphocytes. 43 56

Erythrocytes of different species (chicken, sheep, man, mouse, rat, guinea pig) except rabbit erythrocytes strongly adhere to the marginal zone of mouse spleen follicles in frozen sections. This adherence reaction (AR) is not restricted to red blood cells but is also observed with human lymphocytes. Pretreatment of the tissue sections with trypsin, mercaptoethanol, periodate, chloroform/methanol, acetone, and heating the sections abolishes AR whereas neuraminidase (VCN) treatment of the sections has an amplifying effect. AR is inhibited by preincubation of the neuraminidase- or untreated sections with neuraminic acid (NA). Treatment of the erythrocytes with VCN completely abolishes AR whereas treatment with other enzymes (hyaluronidase, collagenase) is ineffective in this respect. Determination of NA in the erythrocyte membrane before and after VCN treatment reveals a positive correlation between the amount of NA and AR. Rabbit red blood cells have the lowest NA content in their membranes and, in addition, there is little effect of VCN treatment in further reducing it. It is possible that a lectin-like substance is responsible for AR. The biologic significance of AR is hypothetical, but since AR occurs in an area of the spleen playing a role in antigen trapping it is conceivable that this trapping may be mediated by interaction of NA and NA receptor(s).
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PMID:Erythrocyte adherence to the marginal zone of mouse spleen follicle mediated by receptor(s) for neuraminic acid. 46 83

In order to elucidate receptors of proteolytic enzyme-treated red cells which react with Phaseolus coccineus L. lectin, the receptors prepared by affinity chromatography were serologically investigated. P. coccineus lectin had high agglutinin activity for bromelin-, papain- and pronase-treated red cells but that for the cells treated with ficin and trypsin was relatively low. Analyses of chemical composition revealed that sialic acid of the receptors from normal red cells was considerably much as compared with that from the treated cells. On the contrary, the enzyme treatment did not affect particularly carbohydrate composition of the receptors. Disc electrophoresis showed that the patterns of receptors from red cells treated with bromelin or papain were different from those from the other cells. On two-dimensional immunoelectrophoresis, the receptor of trypsin-treated cells gave five precipitation lines against anti-stroma and that of papain-treated cells three lines, but any other receptors showed no line. These findings indicate that there are plural receptors for P. coccineus lectin in red cells treated with each of proteolytic enzymes and that the receptors from respective red cells have electrophoretically and serologically different property.
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PMID:On the receptors of human red cells reacting with Phaseolus coccineus L. lectin. 49 65

Addition of 2 to 10 micrograms of wheat germ agglutinin (WGA), a lectin from Triticum vulgaris specific for N-acetyl-D-glucosamine, per ml to suspensions of mouse fibroblasts (L cells) blocked the attachment of 14C-labeled Chlamydia psittaci 6BC to the L-cell surface. WGA and strain 6BC competed for similar sites on L cells, but once bound, one was not replaced by the other. N-Acetyl-D-glucosamine, but not other monosaccharides of related structure, antagonized the blocking action of WGA. Lectins with specificities other than that of WGA prevented chlamydial attachment only at much higher concentrations or not at all. Exposure of L cells to trypsin and to high multiplicities of strain 6BC decreased the amount of subsequently added 3H-labeled WGA that was bound by these cells. WGA also blocked the attachment of strain 6BC to other established cell lines of murine, simian, and human origin. A lymphogranuloma venereum strain (440L) of C. trachomatis was just as sensitive to the blocking action of WGA as was strain 6BC. It appears that the attachment of both C. psittaci and C. trachomatis to host cells of diverse origin involves an N-acetyl-D-glucosamine-containing entity that binds WGA with high affinity.
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PMID:Wheat germ agglutinin blockage of chlamydial attachment sites: antagonism by N-acetyl-D-glucosamine. 50 Jan 95


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