UNIPROT:Q07644 - FACTA Search

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Query: UNIPROT:Q07644 (polypeptide)
72,197 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The 44G4 antigen is expressed in high amounts on human endothelial cells and at low levels on leukemic cells of pre-B and myelomonocytic origin. Its level of expression on the pre-B leukemic HOON cell line used for derivation of the corresponding mAb is intermediate but sufficient to permit the purification of the Ag. The molecule isolated by immunoaffinity from HOON is a glycoprotein since it bound to Ricinus communis agglutinin, wheat germ agglutinin, and peanut agglutinin lectins. The Ag was purified 2400-fold from a soluble taurocholate extract of HOON cells by affinity to wheat germ agglutinin-agarose and 44G4-IgG-Sepharose. The purified glycoprotein is likely a homodimer as it migrated on SDS-PAGE with an apparent m.w. of 170,000, nonreduced, and 95,000, reduced. Removal of N-linked oligosaccharides by endoglycosidase F led to a decrease in m.w. of 25,000; if neuraminidase and O-glycanase were also present, the total decrease in m.w. was 33,000 suggesting a polypeptide chain of 62,000 and 8,000 in O-linked substitutions. The glycoprotein digested with N-glycanase, neuraminidase, or O-glycanase could still be immunoprecipitated with the 44G4 mAb indicating that the antigenic epitope resides in the polypeptide. By Western blot analysis, the dissociated but nonreduced protein was reactive with 44G4, whereas the reduced and alkylated protein was not. Therefore, the epitope is dependent on the presence of intact disulfide bond(s). Sequential immunoprecipitation with OKT9 and 44G4 antibodies indicated that these epitopes are present on two distinct molecules and that 44G4 is distinct from the transferrin receptor despite a similar subunit structure.
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PMID:Biochemical characterization of the 44G4 antigen from the HOON pre-B leukemic cell line. 326 45

The p150,95 cell surface protein is a member of a family of heterodimeric leukocyte adhesion proteins that have homologous alpha subunits, each noncovalently associated with a common beta subunit. In this report we have metabolically labeled the U937 cell line at various timepoints during its phorbol myristic acetate-induced maturation to examine the kinetics of synthesis of these proteins during monocytic differentiation, and their maturation and glycosylation. The p150,95 alpha subunit was immunoprecipitated with p150,95-specific monoclonal antibody (MAb), or an antiserum to the denatured, purified alpha X subunit. The glycosylation and polypeptide chain length of the p150,95, Mac-1, and lymphocyte function associated antigen (LFA-1) alpha and beta subunits were compared by immunoprecipitation with subunit specific MAb and antisera, and by digestion with Endo H and N-glycanase. The p150,95 alpha subunit is synthesized as a precursor of 146,000 Mr, has five to six N-linked oligosaccharides, and has a polypeptide chain backbone of 132,000 Mr. Over 50% of the carbohydrate on the mature alpha subunit of 150,000 Mr was sensitive to Endo H digestion. The p150,95 alpha and beta precursors can associate before maturation into the mature form. Conversion to the mature form was accompanied by loss of reactivity with the antiserum to the denatured alpha X subunit, suggesting a change in conformation. Mac-1 and LFA-1 alpha subunits have precursors of 160,000 Mr and 165,000 Mr, respectively, and contain N-linked carbohydrates. The polypeptide chain length for the Mac-1 alpha subunit is 137,000 Mr, and for LFA-1 is 149,000 Mr. Only 14% of the oligosaccharide on the mature LFA-1 alpha subunit was sensitive to Endo H, suggesting that unlike p150,95, most is converted to the complex type. The differences noted in the Mr of the three homologous alpha subunits are therefore due to differences in both polypeptide chain length and carbohydrate processing during biosynthesis.
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PMID:Biosynthesis and glycosylation of p150,95 and related leukocyte adhesion proteins. 329 34

Thyroglobulin from colloid as well as from membrane fractions became radiolabeled upon incubation of calf thyroid slices with [35S]sulfate. The identity of the sulfate-labeled molecule was established by immunoprecipitation, polyacrylamide gel electrophoresis, Bio-Gel A-5m filtration, and DEAE-cellulose chromatography. Size analysis by gel filtration of [35S]glycopeptides and hydrazine-released oligosaccharides indicated that the sulfate was primarily located in the complex (unit B) carbohydrate units of thyroglobulin. Moreover, although [35S]sulfate-labeled oligosaccharides were cleaved by N-glycanase to the same extent as those labeled with [3H]mannose, they were not released by endo-beta-N-acetylglucosaminidase under conditions that led to the complete removal of polymannose carbohydrate (unit A). The failure of 35S-labeled glycopeptides and oligosaccharides to bind to immobilized Concanavalin-A indicated that the sulfate residues in calf thyroglobulin are located in carbohydrate units with three or more branches. No evidence for the occurrence of tyrosine sulfate was found upon examination of Pronase digests of radiolabeled thyroglobulin, and chemical analyses excluded the presence of this amino acid down to a level of 0.5 residues/polypeptide subunit. Studies with density gradient-separated membrane fractions as well as with puromycin indicated that sulfate addition is a late event in thyroglobulin biosynthesis which occurs in the Golgi compartment. Furthermore, it was observed that the nondimerized thyroglobulin subunit was much less sulfate labeled than the mature molecule. The location of the sulfated carbohydrate in a terminal portion of the calf thyroglobulin peptide chain was suggested by the observation that the subunit [mol wt (Mr) = 330,000] can undergo a transformation, presumably mediated by an endogenous protease, to a sulfate-free component (Mr = approximately 270,000) with the appearance of a 35S-labeled 60,000 Mr fragment; the release of a single sulfate-labeled peptide (Mr = 60,000) by mild trypsin treatment was consistent with a sequestration of sulfate groups in the thyroglobulin molecule.
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PMID:Biosynthesis of sulfated asparagine-linked complex carbohydrate units of calf thyroglobulin. 338 87

Antiserum was raised in rabbits against a bile canalicular glycoprotein of Mr = 110,000 purified to homogeneity from of rat liver. The antisera specifically immunoprecipitated a Mr = 110,000 polypeptide from hepatocytes metabolically labeled with [35S]methionine. When hepatocytes in primary culture were incubated with tunicamycin before labeling with [35S]methionine in the presence of tunicamycin, the major polypeptide immunoprecipitated by the specific antiserum from Triton X-100 extracts of cells had a molecular weight of 59,000. Enzymatic removal of N-linked carbohydrates from the Mr = 110,000 glycoprotein by N-glycanase digestion also yielded a polypeptide with minimum Mr = 59,000. In pulse-chase experiments using [35S]methionine, the Mr = 110,000 protein detected by the specific antisera first appears as Mr = 85,000 and 75,000 intermediate species which are endoglycosidase H sensitive. The Mr = 85,000 intermediate form is lost first with time followed by the Mr = 75,000 form giving rise to the Mr = 110,000 form that is endoglycosidase H resistant. Neuraminidase digestion of the Mr = 110,000 form generated an Mr 85,000 form but with a different carbohydrate structure than the intermediate Mr 85,000 form detected in the pulse-chase experiments. The time required to accomplish the processing of the Mr = 85,000 and 75,000 forms is relatively slow. Finally, the terminal sugars are added and the mature Mr = 110,000 glycoprotein is rapidly transported to the cell surface. A minimum time of 90 min is required for the Mr = 110,000 bile canalicular glycoprotein to be synthesized, processed, and reach the cell surface which is long relative to the time required (10 min) for another domain-specific protein, the receptor for asialoglycoproteins, to reach the sinusoidal surface. The Mr = 110,000 bile canalicular glycoprotein turns over in the bile canalicular domain with a half-life of 43 h while the asialoglycoprotein receptor turns over in the sinusoidal domain with a half-life of 23 h.
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PMID:Biosynthesis and turnover of a Mr = 110,000 glycoprotein localized to the hepatocyte bile canaliculus. 366

Various alpha and beta 3 subunit-specific antibodies were used to characterize some of the heterogeneous ligand-binding properties of gamma-aminobutyric acidA receptors. Polyclonal antibodies that were raised against the cytoplasmic amino acid sequence (380-392) of the rat beta 3 subunit recognized a single polypeptide of molecular mass of 58 kDa in Western blots with Ro7-1986 affinity-purified GABAA receptors from the rat brain, and a doublet of molecular mass of 54 kDa and 56 kDa in receptors from the bovine cortex, hippocampus, and cerebellum. Deglycosylation of purified receptors from the bovine cortex with N-glycanase resulted in a single band immunostained at molecular mass of 52 kDa. These anti-beta 3 subunit antibodies immunoprecipitated approximately 50% of [3H]flunitrazepam binding sites from soluble extracts of bovine cortex, whereas beta cyto antibodies, which probably recognize all beta subunit isoforms, precipitated almost 100% of benzodiazepine binding sites. These results indicate heterogeneity of GABAA receptor subunit composition with respect to the nature of beta subunits. The GABA analogue 4,5,6,7-tetrahydroisoxazolo[5,4-c]pyridin-3-ol (THIP), like GABA, shows heterogeneous binding affinities in brain homogenates. The higher affinity sites were previously suggested as corresponding to a 58-kDa polypeptide in rat that is photoaffinity-labeled with [3H]muscimol, a band that comigrates with the one stained by anti-beta 3 antibodies. However, THIP affinity was not significantly different between receptors containing beta 3 subunits and those lacking beta 3, as demonstrated by similar affinities in receptors that ere immunoprecipitated by anti-beta 3 antibodies and those that were not. Also, THIP displaced [3H]muscimol binding with similar multiple affinities across brain regions where different beta subunit variants are expressed with varying abundances. These observations suggest that the property of high affinity THIP binding cannot be explained solely by beta 3 subunits. The coupling efficiency between GABA and benzodiazepine binding sites appears to be determined by the nature of alpha subunits rather than of beta subunits. GABA enhanced [3H]flunitrazepam binding with different efficacies and potencies in receptors immunoprecipitated by anti-alpha 1, -alpha 2, and -alpha 3 subunit antibodies. In contrast, beta 3 subunit-enriched and disenriched receptors did not differ in this property. [3H]Flunitrazepam binding in GABAA receptors containing alpha 2 and alpha 3 subunits was enhanced to a significantly greater extent than were those with alpha 1. In addition, receptors containing alpha 1 and alpha 3 subunits had higher potencies of enhancement than did those with alpha 2 subunits.(ABSTRACT TRUNCATED AT 400 WORDS)
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PMID:Pharmacological subtypes of the gamma-aminobutyric acidA receptors defined by a gamma-aminobutyric acid analogue 4,5,6,7-tetrahydroisoxazolo[5,4-c] pyridin-3-ol and allosteric coupling: characterization using subunit-specific antibodies. 747 92

We report a carbohydrate-dependent supramolecular architecture in the extracellular giant hemoglobin (Hb) from the marine worm Perinereis aibuhitensis; we call this architectural mechanism carbohydrate gluing. This study is an extension of our accidental discovery of deterioration in the form of the Hb caused by a high concentration of glucose. The giant Hbs of annelids are natural supramolecules consisting of about 200 polypeptide chains that associate to form a double-layered hexagonal structure. This Hb has 0.5% (wt) carbohydrates, including mannose, xylose, fucose, galactose, glucose, N-acetylglucosamine (GlcNAc), and N-acetylgalactosamine (GalNAc). Using carbohydrate-staining assays, in conjunction with two-dimensional polyacrylamide gel electrophoresis, we found that two types of linker chains (L1 and L2; the nomenclature of the Hb subunits followed that for another marine worm, Tylorrhynchus heterochaetus) contained carbohydrates with both GlcNAc and GalNAc. Furthermore, two types of globins (a and A) have only GlcNAc-containing carbohydrates, whereas the other types of globins (b and B) had no carbohydrates. Monosaccharides including mannose, fucose, glucose, galactose, GlcNAc, and GalNAc reversibly dissociated the intact form of the Hb, but the removal of carbohydrate with N-glycanase resulted in irreversible dissociation. These results show that carbohydrate acts noncovalently to glue together the components to yield the complete quaternary supramolecular structure of the giant Hb. We suggest that this carbohydrate gluing may be mediated through lectin-like carbohydrate-binding by the associated structural chains ("linkers").
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PMID:Carbohydrate gluing, an architectural mechanism in the supramolecular structure of an annelid giant hemoglobin. 763 98

The dopamine transporter (DAT) in rat striatum was examined during postnatal development and aging after photolabeling with [125I]DEEP. The DAT-[125I]DEEP protein complex from adult rats (2 months) appeared as a broad diffuse band in SDS-PAGE gels with average apparent molecular mass of about 80,000 Da as previously found. However, the molecular mass was lower at birth (day 0) and at postnatal ages 4 and 14 days. In aged rats (104 weeks), the molecular mass was slightly higher than that found in young adults (60 days). In binding experiments with [3H]BTCP, there were age-related differences in Kd and Bmax with decreases in both Kd and Bmax found in aged rats. Treatment of photolabeled membranes with neuraminidase caused a reduction in DAT molecular mass, but age-related differences were maintained. Treatment with N-glycanase greatly reduced or eliminated the age-related differences. Several DAT peptide-specific polyclonal antibodies immunoprecipitated DAT-[125I]DEEP protein complex at different developmental ages. Taken together, these results suggest differential glycosylation of rat DAT occurs during postnatal development and aging; the increase is due to increases in the N-linked sugars rather than changes in either sialic acid content or the polypeptide.
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PMID:Developmentally regulated glycosylation of dopamine transporter. 769 70

gp57/42 is a membrane glycoprotein localized in the trans-Golgi, flagellar pocket region of the cell surface, endosomes and lysosomes of bloodstream forms of Trypanosoma brucei rhodesiense. Pulse-chase immunoprecipitation experiments revealed that gp57/42 acquires a unique N-linked oligosaccharide recognized by the CB1 monoclonal antibody 20-30 minutes after protein synthesis, probably in the trans-Golgi. We refer to gp57/42 molecules that carry the CB1 epitope as CB1-gp. Pulse labeled CB1-gp contained only one core protein, p57, when chase times were 30 minutes or less. As time of chase increased from 30 to 60 minutes, a new polypeptide, p42, appeared in N-glycanase-treated CB1 immunoprecipitates. Since p57 and p42 share 10 of 13 methionyl peptides, we conclude that p42 is a fragment of p57. Cleavage of p57 to p42 was not inhibited when cells were chased in two thiol protease inhibitors or in 3,4-diisocoumarin, but was inhibited by leupeptin. Cell surface biotinylation was used to determine if newly synthesized CB1-gp was transported from the Golgi to the surface. When cells were pulse labeled and chased for 30 minutes, as much as 40% of the radiolabeled CB1-gp could be biotinylated on the cell surface. The amount of CB1-gp that could be biotinylated decreased when chases were extended from 30 to 60 minutes, suggesting that pulse labeled CB1-gp left the surface. In contrast, pulse labeled variant surface glycoprotein molecules continued to accumulate on the surface where they could be biotinylated between 30 and 60 minutes of chase. Biotinylated CB1-gp derived from cells chased for 30 minutes contained p57 but no p42. However, when labeled cells were biotinylated after a 30 minute chase and then incubated another 30 minutes at 37 degrees C, the biotinylated CB1-gp contained both p57 and p42. The p57 in biotinylated CB1-gp was not cleaved to p42 if the additional incubation was done at 4 or 12 degrees C. This suggests that transport to a compartment where processing occurs and/or the processing enzymes are inhibited by low temperature. When surface biotinylation was done after a 60 minute chase, p42 was detected in biotinylated CB1-gp, suggesting that CB1-gp molecules had passed through the processing compartment and then appeared on the cell surface. Thus, a major portion of the newly synthesized CB1-gp is routed from the Golgi to endocytic compartments via the cell surface. In trypanosomes this process involves a unique surface domain, the flagellar pocket.(ABSTRACT TRUNCATED AT 400 WORDS)
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PMID:Transport of a lysosomal membrane glycoprotein from the Golgi to endosomes and lysosomes via the cell surface in African trypanosomes. 769 16

Among a panel of mouse mAbs generated to a human T cell clone, one mAb, V7.1, inhibited T cell activation in the mixed lymphocyte reaction and was studied further. V7.1 reacted strongly with Ag-specific T cell clones, in addition to freshly isolated monocytes and granulocytes. However, the mAb reacted weakly with freshly isolated PBLs (T cells, B cells, and NK cells), T cells stimulated with phytohemagglutinin, or Con A, and did not stain the vast majority of transformed cell lines of hemopoietic origin. Stimulation of T cells with anti-CD3, or the combination of anti-CD3 and PMA, or anti-CD3, PMA and ionomycin, markedly increased V7.1 surface staining. The mAb precipitated a single polypeptide chain of approximately 135 kDa from alloactivated T cells or monocytes, which was reduced to approximately 110 kDa after treatment with N-glycanase. The proliferative response of T cells to allogeneic monocytes or B lymphoblastoid cells was inhibited by V7.1, and inhibition was maximal when the mAb was present at the initiation of culture. V7.1 also exhibited dose-dependent inhibition of the T cell response to immobilized anti-CD3 Ab in the absence of APCs, indicating that the inhibitory effect of this Ab occurs at the T cell level. Expression of CD25 (IL-2R) on anti-CD3-activated T cells and secretion of IL-2 induced with anti-CD3 and PMA were inhibited by V7.1, whereas the Ab had no effect on T cell proliferation induced by PHA or Con A or on T cell-mediated cytotoxicity. These results indicate that V7.1 recognizes a novel leukocyte surface glycoprotein, designated V7, that is up-regulated on Ag but not lectin-activated T cells, and appears to play a role in TCR/CD3-dependent T cell activation. In an accompanying study, the gene encoding the V7 Ag is described and the molecule is shown to be a novel member of the Ig superfamily.
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PMID:V7, a novel leukocyte surface protein that participates in T cell activation. I. Tissue distribution and functional studies. 772 99

Acid ceramidase (N-acylsphingosine deacylase, EC 3.5.1.23) is the lysosomal enzyme catalyzing the hydrolysis of ceramide to sphingosine and free fatty acid. Its inherited deficiency causes ceramide accumulation in Farber's disease. The enzyme was purified to apparent homogeneity from human urine by sequential chromatography on octyl-Sepharose, concanavalin A-Sepharose, blue-Sepharose, and DEAE-cellulose. The final preparation, which was enriched approximately 4450-fold over the starting material, resulted in a polypeptide of approximately 50 kDa and could be reduced into two subunits of approximately 13 (alpha) and approximately 40 (beta) kDa. Treatment of the purified enzyme with endoglycosidase H or peptido-N-glycanase F reduced the molecular mass of the beta subunit to approximately 30-35 and approximately 27 kDa, respectively. In contrast, the molecular mass of the alpha subunit was unchanged. The purified enzyme had an apparent Km of 149 microM and a Vmax of 136 nmol/mg/h using N-lauroylsphingosine as substrate. Polyclonal antibodies were raised against the purified urinary enzyme and used to investigate the biosynthesis of acid ceramidase. Immunoprecipitation studies on metabolically labeled skin fibroblasts indicated that both subunits arose from a single precursor of approximately 55 kDa. A minor portion of newly synthesized acid ceramidase was secreted into the medium as a monomeric 47-kDa protein, indicating that generation of the mature heterodimeric enzyme occurred in endosomal and/or lysosomal compartments.
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PMID:Purification, characterization, and biosynthesis of human acid ceramidase. 774 40

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