Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0027960 (mole)
 21,279 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Acetylcholine receptors in skeletal muscle and fish electric organs are intrinsic membrane proteins whose function is to bind acetylcholine released from the nerve ending and trigger the opening of a cation-specific channel in the postsynaptic membrane, thereby facilitating transmission of the nerve signal to the muscle. Investigations from several laboratories indicate that acetylcholine receptors from fish electric organs are composed of four homologous glycoprotein subunits of apparent relative molecular masses (Mr) approximating 40, 50, 57 and 64 x 10(3) designated, respectively, alpha, beta, gamma and delta. These subunits are present in receptor monomers in the mole ratio alpha 2 beta gamma delta. Receptor purified from skeletal muscle appears to have a similar structure. The alpha subunits are unknown. It is known that the cation channel regulated by acetylcholine binding is located within the receptor monomer. Experimental autoimmune myasthenia gravis (EAMG) is induced by immunizing animals with purified receptor. The mechanisms by which neuromuscular transmission is impaired in this model are very similar to those in myasthenia gravis (MG). Although there are many immunogenic determinants on receptors, and EAMG can be induced in rats by any of the denatured subunits, there is a main immunogenic region at which most of the antibodies to native receptors are directed. The main immunogenic region is a conformationally dependent part of the external surface of alpha subunits other than the acetylcholine-binding site or the attached carbohydrate. Antisera from MG patients are also directed primarily at this region. No correlation was detected between the specificities of antibodies to receptor in patients' sera and the severity of their weakness.
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PMID:Structure of the acetylcholine receptor and specificities of antibodies to it in myasthenia gravis. 692 7

The IgG2a monoclonal antibody (MoAb) 376.96S, secreted by a hybridoma derived from a mouse immunized with cultured human melanoma cells COLO 38, reacts with a single 94,000-dalton glycoprotein that is peripherally associated with the plasma cell membrane of cultured melanoma cells. Indirect immunofluorescence analysis with cryostat thin sections of human tissues showed that this antigen is absent from a large variety of normal tissues but is readily detectable on melanomas, nevi, and several different carcinomas. The MoAb 376.96S binds with cultured melanoma and carcinoma cell lines to a similar extent and can mediate both complement-dependent and cell-dependent lysis of these cells. The 94,000-dalton glycoprotein detected by MoAb 376.96S is distinct in its tissue distribution, antigenicity, and molecular profile from several structures previously identified with monoclonal antibodies that have similar molecular weights.
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PMID:A 94,000-dalton glycoprotein expressed by human melanoma and carcinoma cells. 695 Oct 87

[3H]-Glycerol-labelled lipoteichoic acid (LTA) was extracted from Streptococcus sanguis cells using aqueous phenol. Chemical analysis of the LTA yielded phosphate:glycerol:glucose:fatty acids in the mole ratio 1.0:0.97:0.76:0.03. The LTA inhibited the interaction between Strep. sanguis cells and a high mol. wt blood-group-reactive glycoprotein (BGR-glycoprotein) isolated from human saliva and reduced Strep. sanguis-mediated haemagglutination activity. Purified LTA from Strep. mutans strains OMZ61 and HS6, which have been shown not to interact with the BGR-glycoprotein, also inhibited the BGR-glycoprotein mediated aggregation of Strep. sanguis, as did an antiserum prepared against Lactobacillus casei LTA. It is proposed that the binding of the salivary glycoprotein to Strep. sanguis cells in achieved through LTA associated with bacterial surface fibrils.
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PMID:Blood-group-reactive glycoprotein from human saliva interacts with lipoteichoic acid on the surface of Streptococcus sanguis cells. 695 42

The proteinaceous coat associated with the cytoplasmic side of milk lipid globule membranes (MLGM) was prepared from bovine and caprine milk by removal of membrane material with non-ionic detergent. These coat preparations, which were enriched in two major proteins, a glycoprotein of polypeptide M, 67 000 (butyrophilin) and a non-glycosylated protein of polypeptide Mr 155 000 (xanthine oxidase), contained small amounts of fatty acids which could not be removed by exhaustive extractions with organic solvents. Both butyrophilin and xanthine oxidase of bovine MLGM were excised and eluted from SDS-polyacrylamide gels and were shown to contain 1 to 2 moles of bound fatty acids per mole of protein. Palmitic, stearic and oleic acids were the predominant protein-bound fatty acids, but no specificity for binding of individual fatty acids was observed. The fatty acids were not rendered soluble in organic solvents when the protein preparations were incubated with phospholipases A or C or with trypsin. Treatment with 0.25 M NaOH at 100 degrees C for 1 h or with 1 M hydroxylamine at 4 degrees C for 16 h, however, released virtually all of the fatty acids associated with these proteins. Similar results were obtained with two major proteins, bands 3 and 4.1, or rat erythrocyte plasma membrane. By contrast, skeletal muscle actin and serum albumin had no bound fatty acids that could be released by alkali treatment. These results show that fatty acids are bound to a number of membrane-associated proteins, both glycosylated and unglycosylated, via linkages that resist purification of the proteins on SDS-polyacrylamide gel electrophoresis and are suggestive of covalent attachment of fatty acids to these proteins. The possible involvement of this acylation in processes characterized by local changes of membrane shape and plasticity is discussed.
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PMID:Tight attachment of fatty acids to proteins associated with milk lipid globule membrane. 706 4

The negative charges on the various trophoblast was investigated, in order to cast light on the biological roles, by electron microscopy using cationized ferritin as an ultrastructural marker, in comparison with surface glycoprotein. The following results were obtained: 1. The surface glycoprotein distributed on the trophoblastic plasma membrane forming regularly situated aggregates, 15 to 20 millimicron in diameter separated by 50 to 100 millimicron from neighboring ones. 2. The negative charge on the cell surface was distributed in two different configurations: A strongly negative part and weakly negative one. 3. The placental villi were revealed to carry an extremely high level of negative surface charge. 4. One maternal lymphocyte in a first trimester pregnancy was calculated to carry a 5.9 x 10(-11) Coulomb negative surface charge. 5. In a simplified model, the electronic repulsive force between the lymphocyte and placental villus was calculated as 5.7 x 10(-4) Newton, showing that the electronegative charge on human trophoblast was strong enough to repel the negatively charged lymphocyte against the lymphocyte gradient. 6. For villi from spontaneous abortion with mild degeneration, the surface glycoprotein was observed to make prominent aggregates on the trophoblastic surface in concomitance with the reduced negative surface charge. 7. With the observation by electron microscopy, The complete mole differed essentially from the partial mole in that former resembled normal villi while the later spontaneous abortion.
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PMID:[Negative surface charge of human trophoblast and its biological role (author's transl)]. 706 54

1. A method was developed whereby [1-14C]glucosamine was used in a perfused rat liver system to prepare over 2 mg of alpha 1-acid glycoprotein with highly radioactive sialic acid and glucosamine residues. 2. The liver secreted radioactive alpha 1-acid glycoprotein over a 4-6 h period, and this glycoprotein was purified from the perfusate by chromatography on DEAE-cellulose at pH 3.6. 3. The sialic acid on the isolated glycoprotein had a specific radioactivity of 3.1 Ci/mol, whereas the glucosamine-specific radioactivity was 4.3 Ci/mole. The latter amino-sugar residues on the isolated protein were only 13-fold less radioactive than the initially added [1-14C]glucosamine. Orosomucoid with a specific radioactivity of 31.3 microCi/mg of protein was obtainable by using [6-3H]glucosamine. 4. The amino acid composition of the purified orosomucoid was comparable with that found by others for the same glycoprotein isolated from rat serum. A partial characterization of the carbohydrate structure was done by sequential digestion with neuraminidase, beta-D-galactosidase and beta-D-hexosaminidase. 5. Many other radioactive glycoproteins were found to be secreted into the perfusate by the liver. Thus this experimental system should prove useful for obtaining other serum glycoprotein with highly radioactive sugar moieties.
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PMID:Use of radioactive glucosamine in the perfused rat liver to prepare alpha 1-acid glycoprotein (orosomucoid) with 3H- or 14C-labelled sialic acid and N-acetylglucosamine residues. 710 33

The problem of determining small but significant amounts of carbohydrates, in purified proteins, has been studied using the membrane protein, cytochrome b5. A newly developed method that involves direct gas chromatography-mass spectrometry of sugars obtained by hydrolysis of proteins purified by sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS PAGE) allows the identification and determination of small amounts of carbohydrates (e.g., 20 micrograms of glycoprotein containing a minimum of 0.1% monosaccharide), even in the presence of relatively high amounts of impurities. Application of this method to cytochrome b5 fragments obtained by tryptic digestion from rat liver microsomes and purified by combined gel filtration and ion exchange chromatography, followed by SDS PAGE, has consistently yielded values below 0.07 mol of the individual sugars and aminosugars per mole cytochrome b5. It is concluded that cytochrome b5, at least its trypsin-released major amino-terminal fragment, is not constitutively glycosylated.
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PMID:Absence of sugars in electrophoretically purified cytochrome b5 demonstrated by combined gas chromatography-mass spectrometry. 725 67

CD59 is an 18-kDa glycoprotein widely expressed on human cells. An important structural feature of CD59 is its attachment to the cell surface via a glycosyl-phosphatidylinositol (GPI) anchor. CD59, like many GPI-anchored proteins, has been found in urine, serum, and other body fluids. The structures of the GPI anchor and the asparagine-linked sugar chain of a soluble form of CD59 in urine, U-CD59, were determined. Purified U-CD59 released 1 mol of inositol per mole of protein by nitrous acid deamination, which cleaved between glucosamine and inositol present commonly in the GPI anchor. This indicates that a GPI anchor, which ended with inositol, is linked at the carboxy terminus of U-CD59. The peptide containing an asparagine-linked sugar chain and the peptide containing a glycan portion of the GPI anchor were isolated after trypsin digestion of U-CD59. The asparagine-linked sugar chains and the glycan portion of the GPI anchor were isolated from these peptides following hydrazinolysis or deamination and dephosphorylation, respectively. Their structures were analyzed by sequential exoglycosidase digestion and methylation analyses. The structures of the asparagine-linked sugar chains of U-CD59 were biantennary complex type, only 4.2% of which are monosialylated. The backbone structure of the GPI anchor was similar to that of Try-panosoma brucei variant surface glycoprotein, but showed significant variations in its side-chain moieties. This is the first detailed structural analysis of the human GPI anchor and the first detailed analysis of the carboxyl-terminal structure of the soluble-form GPI-anchored protein. The results indicate that the backbone structure of the GPI anchor is conserved from parasites to human and that at least a part of the soluble-form GPI-anchored protein has the structure produced by the action of glycan-phosphatidylinositol-specific phospholipase D.
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PMID:Structural study on the glycosyl-phosphatidylinositol anchor and the asparagine-linked sugar chain of a soluble form of CD59 in human urine. 751 86

RS7-3G11 is a murine monoclonal antibody (MAb) raised against human non-small-cell lung carcinoma, and is under clinical evaluation. The epithelial/carcinoma antigen EGP-1, defined by RS7-3G11, was isolated and purified to homogeneity from a cervical carcinoma cell line, ME180. EGP-1 is a glycoprotein with an average molecular mass of 47.8 kDa. Metabolic labeling of the antigen with 32P-orthophosphate and subsequent immunoprecipitation with RS7-3G11 showed that it is a phosphoprotein. Phosphoamino acid analysis of the in vivo phosphorylated EGP-1 revealed that the phosphorylation is on serine. In vitro analysis with purified antigen demonstrated that protein kinase C, and not protein kinase A, is involved in phosphorylating the antigen in vitro. In vitro analysis indicated a stoichiometry of phosphorylation of 0.54 mole of phosphate per mole of EGP-1. Phosphoamino acid analysis and phosphopeptide mapping of the antigen phosphorylated in vitro by protein kinase C showed that phosphorylation occurred on a serine residue, specifically on serine 303, located in the cytoplasmic domain of EGP-1. Treatment of ME180 cells with phorbol ester increased the phosphorylation of EGP-1. The biological function of EGP-1 remains to be elucidated. In this report we elucidate an involvement of protein kinase C in phosphorylating EGP-1, which may signify a role for this antigen in signal transduction across the cell membrane.
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PMID:The epithelial/carcinoma antigen EGP-1, recognized by monoclonal antibody RS7-3G11, is phosphorylated on serine 303. 763 74

The melanosome is a secretory organelle unique to the melanocyte and its neoplastic counterpart, malignant melanoma. The synthesis and assembly of these intracytoplasmic organelles is not yet fully understood. We have developed a murine monoclonal antibody (MoAb) against melanosomes isolated from human melanocytes (newborn foreskin) cultured in the presence of 12-O tetradecanoyl phorbol-13-acetate (TPA). This MoAb, designated HMSA-5 (Human Melanosome-Specific Antigen-5) (IgG1), recognised a cytoplasmic antigen in both normal human melanocytes and neoplastic cells, such as common and dysplastic melanocytic nevi, and malignant melanoma. None of the carcinoma or sarcoma specimens tested showed positive reactivity with MoAb HMSA-5. Under immunoelectron microscopy, immuno-gold deposition was seen on microvesicles associated with melanosomes, and a portion of the ER-Golgi complexes. Radioimmunoprecipitation analysis showed that the HMSA-5 reactive antigen was a glycoprotein of M(r) 69 to 73 kDa. A pulse-chase time course study showed that the amount of antigen detected by MoAb HMSA-5 decreased over a 24 h period without significant expression on the cell surface, or corresponding appearance of the antigen in the culture supernatant. This glycoprotein appears to play a role in the early stages of melanosomal development, and the HMSA-5 reactive epitope may be lost during subsequent maturation processes. Importantly, HMSA-5 can be identified in all forms of human melanocytes, hence it can be considered a new common melanocytic marker even on routine paraffin sections.
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PMID:A murine monoclonal antibody, MoAb HMSA-5, against a melanosomal component highly expressed in early stages, and common to normal and neoplastic melanocytes. 767 81


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