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At least 199 records · Page 11Linked to original sources
PubMed1993

Microsequence and mass spectral analysis of nonspecific cross-reacting antigen 160, a CD15-positive neutrophil membrane glycoprotein. Demonstration of identity with biliary glycoprotein.

Sequence information was obtained from low picomole amounts of nonspecific cross-reacting antigen (NCA) 160 (M(r) 160,000), a granulocyte membrane glycoprotein. Following affinity purification and SDS-polyacrylamide gel electrophoresis, the protein was electrotransferred to nitrocellulose, digested with trypsin, and the peptides were isolated using capillary reversed-phase liquid chromatography. Analysis of these peptides by Edman microsequencing and mass spectrometry established that NCA-160 was identical to biliary glycoprotein I, a protein that we previously cloned from a human colon library (1). NCA-160 from human granulocytes is a CD15-positive glycoprotein belonging to the carcinoembryonic antigen family and possesses putative transmembrane and cytoplasmic domains. Previous efforts to characterize this antigen at the protein level were hampered by a blocked NH2 terminus. In this study, we confirmed 20% of the deduced amino acid sequence starting with approximately 50 pmol of sample. Carbohydrate structural data is also presented on a single N-linked oligosaccharide moiety located in the A' domain. The capillary high performance liquid chromatography techniques used here, as well as mass spectrometry, were essential for high sensitivity analysis of the blotted, digested glycoprotein.

Amino Acid Sequence↗
PubMed1994

[Pregnancy-associated alpha2-glycoprotein and trophoblastic beta1-glycoprotein in the diagnosis of pyoinflammatory diseases after Cesarean section].

Blood serum pregnancy-associated alpha 2-glycoprotein and trophoblastic beta 1-glycoprotein were measured in puerperants with the normal postpartum period and with that complicated by pyo-inflammatory diseases after abdominal delivery. The levels of both proteins were found reduced in the patients with pyo-inflammatory diseases developing after cesarean section as early as on day 1 postpartum. that of alpha 2-glycoprotein by 1.2 times, that of trophoblastic beta 1-glycoprotein twofold.

Adolescent↗
PubMed1990

Secretory glycoproteins of the rat subcommissural organ are N-linked complex-type glycoproteins. Demonstration by combined use of lectins and specific glycosidases, and by the administration of Tunicamycin.

Two experimental protocols were used to investigate the secretory glycoproteins of the subcommissural organ (SCO). Protocol I: Lectins, specific exoglycosidases and immunocytochemistry were sequentially applied to the same section or to adjacent semithin sections of the rat SCO fixed in Bouin's fluid and embedded in methacrylate. Lectins used: concanavalin A (con A), wheat germ agglutinin, Limulus polyphemus agglutinin, Ricinus communis agglutinin and Arachis hypogeae agglutinin. Glycosidases used: neuroaminidase, beta-galactosidase, alpha-mannosidase, alpha-glucosidase and beta-N-acetyl-glucosaminidase. For immunocytochemistry an antiserum against bovine Reissner's fiber (AFRU) was used. Lectins and glycosidases were used in sequences that allowed the cleaved sugar residue to be identified as well as that appearing exposed as a terminal residue. This approach led to the following conclusions: (1) the terminal sugar chain of the secreted glycoproteins has the sequence sialic acid-galactose-glucosamine-; (2) the con A-binding material present in the rough endoplasmic reticulum corresponds to mannose; (3) the apical secretory granules and Reissner's fibers displayed a strong con A affinity after removing sialic acid, thus indicating the presence of internal mannosyl residues in the secreted material; (4) after removing most of the sugar moieties the secretory material continued to be strongly immunoreactive with AFRU. Protocol II: Rats were injected into the lateral ventricle with Tunica-mycin and killed 12, 24, 50 and 60 h after the injection. The SCO of rats from the last two groups showed a complete absence of con A binding sites. The results from the two experiments confirm that the secretory glycoproteins of the rat SCO are N-linked complex-type glycoproteins with the conformation previously suggested (Rodríguez et al. 1986).

Animals↗
PubMed1984

Urinary glycoproteins in acute leukemias: a 41 000 dalton glycoprotein follows the kinetic of cytoreduction.

Glycoproteins of leukemic cells and 24-hour urinary proteins were subjected to SDS polyacrylamide gel electrophoresis followed by affinity labelling I125 with Concanavalin A, indicating glycoproteins with mannose and/or glucose carbohydrate residues. Among the cellular glycoproteins a 41 000 dalton glycoprotein appeared under induction therapy in close correlation to the reduction of leukemic cells in ALL as well as in AML.

Cell Survival↗
PubMed1985

An acidic glycoprotein (100-K fucose-rich glycoprotein) from calf skin.

A new acidic glycoprotein was isolated from 4 M-guanidiunium chloride which had been extracted from neutral-salt-insoluble fractions of neonatal calf skin. During the process of purification, the glycoprotein co-migrated with proteodermatan sulphate and its sugar components mainly consisted of fucose, mannose and hexosamine. A broad band obtained by sodium dodecyl sulphate (SDS)-polyacrylamide gel electrophoresis suggested that the molecular weight was 100,000. High-voltage electrophoresis, revealed acidic fragments in its tryptic peptides, while its oligosaccharide chains were shown to have on acidic nature by electrophoresis on a cellulose acetate membrane. These results show that the glycoprotein differs from other glycoproteins (fibronectin, laminin, entactin, nidogen and the 31-K protein of chondrocyte membrane) which have been reported in connective tissues.

Animals↗
PubMed1982

Plasma proteins in human cortical bone: enrichment of alpha 2 HS-glycoprotein, alpha 1 acid-glycoprotein, and IgE.

Human cortical bones were extracted with EDTA, and the residue after EDTA extraction was digested with bacterial collagenase. Ten plasma proteins were identified and quantitated in the EDTA extracts. Three of them--IgE, IgD, and alpha 1acid-glycoprotein--had not previously been described in bone or dentine. Five plasma proteins identified in collagenase digests are albumin, IgG, IgA, IgE, and alpha 1acid-glycoprotein. IgE, alpha 1acid-glycoprotein, and alpha 2HS-glycoprotein were found to be concentrated in the bone more than other plasma proteins by factors between 11 and 525. The identification of plasma proteins was facilitated by the addition of polyethylene glycol in agarose gel. The presence of plasma proteins both in EDTA extracts and in collagenase digests suggests their structural role in bone.

Blood Proteins↗
PubMed1991

Pachytene spermatocyte protein(s) stimulate Sertoli cells grown in bicameral chambers: dose-dependent secretion of ceruloplasmin, sulfated glycoprotein-1, sulfated glycoprotein-2, and transferrin.

Interactions between pachytene spermatocytes and Sertoli cells were investigated using the bicameral culture chamber system. Pachytene spermatocytes were isolated from adult rats with a purity in excess of 90% by centrifugal elutriation. The pachytene spermatocytes were cultured in a defined media and pachytene spermatocyte protein prepared from the conditioned media by dialysis and lyophilization. This pachytene spermatocyte protein was reconstituted at various concentrations and incubated with confluent epithelial sheets of immature Sertoli cells cultured in bicameral chambers. Pachytene spermatocyte protein stimulated secretion of total [35S]methionine-labeled protein from Sertoli cells in a dose-dependent manner predominantly in an apical direction. This stimulatory effect of pachytene spermatocyte protein was domain specific from the apical surface of Sertoli cells, and seemed specific for secretion because total intracellular protein did not increase under the influence of pachytene spermatocyte protein. Pachytene spermatocyte protein and follicle-stimulating hormone additively stimulated Sertoli cell secretion. The physicochemical characteristics of the stimulatory pachytene spermatocyte protein are indicative of heat stability, whereas the stimulatory pachytene spermatocyte protein exhibit acid, dithiothreitol and trypsin sensitivity, and partial urea sensitivity. Furthermore, Sertoli cell secretion of ceruloplasmin, sulfated glycoprotein-1, sulfated glycoprotein-2, and transferrin in response to various concentrations of pachytene spermatocyte protein were determined by immunoprecipitate of these [35S]methionine-labeled proteins with polyclonal antibodies. Maximal stimulation of ceruloplasmin and sulfated glycoprotein-1 secretion from Sertoli cells was observed at a dose of 50 micrograms/ml pachytene spermatocyte protein, whereas maximal stimulation of sulfated glycoprotein-2 and transferrin secretion from Sertoli cells was observed at a dose of 100 micrograms/ml of pachytene spermatocyte protein. These results suggest that pachytene spermatocytes modulate Sertoli cell secretory function of at least four proteins in the regulation of spermatogenesis.

Animals↗
PubMed1989

P-glycoprotein gene (MDR1) cDNA from human adrenal: normal P-glycoprotein carries Gly185 with an altered pattern of multidrug resistance.

We isolated a full-length MDR1 cDNA from human adrenal where P-glycoprotein is expressed at high level. The deduced amino acid sequence shows two amino acid differences from the sequence of P-glycoprotein obtained from colchicine-selected multidrug resistant cultured cells. The amino acid substitution Gly----Val at codon 185 in P-glycoprotein from colchicine resistant cells occurred during selection of cells in colchicine. As previously reported, cells transfected with the MDR1 cDNA carrying Val185 acquire increased resistance to colchicine compared to other drugs. The other amino acid substitution Ser----Ala at codon 893 probably reflects genetic polymorphism. The MDR1 gene, the major member of the P-glycoprotein gene family expressed in human adrenal, is sufficient to confer multidrug-resistance on culture cells.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed1988

Modifications of concanavalin A patterns of alpha 1-acid glycoprotein and alpha 2-HS glycoprotein in alcoholic liver disease.

In order to test whether abnormalities in hepatocytes affect the glycoprotein carbohydrate moiety, crossed immunoaffinoelectrophoresis (CIAE) with Concanavalin A (Con A) was used to study serum alpha 1-acid glycoprotein (alpha 1-AGP) and alpha 2-HS glycoprotein (alpha 2-HS) obtained from alcoholic patients with biopsy-proven liver disease. Cirrhotic patients, placed in groups C1, C2 or C3, according to Pugh's classification, were compared to healthy donors (N) and to steatosic non-cirrhotic patients (S). Con A CIAE patterns revealed in group N three subpopulations for alpha 2-HS and four for alpha 1-AGP. Two main results emerged from this study: (1) in the alcoholic groups, the proportions of Con A-unreactive subpopulations of both glycoproteins increased. Moreover, group N could be separated from group S and group S from all the cirrhotic groups. (2) There was a good correlation between the relative amounts in Con A-unreactive subpopulations of alpha 1-AGP and alpha 2-HS. The increases observed in Con A-unreactive subpopulations are probably a general phenomenon related to alterations in glycosylation processing during liver cell damage.

Adult↗
PubMedDate not supplied

Carbohydrate-deficient glycoprotein syndrome: electrophoretic study of multiple serum glycoproteins.

The serum glycoproteins in three patients with the carbohydrate-deficient glycoprotein (CDG) syndrome were examined using isoelectric focusing in polyacrylamide gels, SDS-PAGE, and a two-dimensional electrophoretic technique. Increases in isoforms with higher isoelectric points (pI's) were observed in all asparagine-N-linked glycoproteins tested. Abnormal components of transferrin, antithrombin III and orosomucoid had smaller molecular weights, about 3000 and 6000 Da, than normal ones. Antithrombin III gave an increased cathodal band. Its pI and molecular weight were the same as those of a physiological variant of antithrombin III (beta fraction), which is known to lack the asparagine-N-linked oligosaccharide chain at asparagine-135. The evidence suggests that a deficiency of asparagine-N-linked oligosaccharide transfer occurs in multiple serum glycoproteins in patients with CDG syndrome. Thus, examination of serum by isoelectric focusing in polyacrylamide gels and SDS-PAGE should be very useful for differentiating the CDG syndrome type I from clinical and biochemical variants.

Antithrombin III↗
PubMed1988

KDN-glycoprotein: a novel deaminated neuraminic acid-rich glycoprotein isolated from vitelline envelope of rainbow trout eggs.

A new acidic glycoprotein containing deaminated neuraminic acid (KDN = 3-deoxy-D-glycero-D-galacto-nonulosonic acid; greater than 50%, w/w) was isolated from vitelline envelope of the unfertilized eggs of rainbow trout (Salmo gairdneri). This glycoprotein is designated as "KDN-glycoprotein" because it contains only KDN but no sialic acid as the acidic carbohydrate moieties. Other major carbohydrate components of KDN-glycoprotein were Gal and GalNAc. Thr and Ala accounted for 71% (mol/mol) of amino acid composition. A possible occurrence of KDN-KDN linkages, i.e. oligoKDN groups has been suggested in the carbohydrate chains presumably linked O-glycosidically to the core protein.

Amino Acids↗
PubMed1997

Microheterogeneity of serum glycoproteins and their liver precursors in patients with carbohydrate-deficient glycoprotein syndrome type I: apparent deficiencies in clusterin and serum amyloid P.

Serum and liver protein patterns were studied, respectively, in 5 patients (serum) and 1 patient (liver) with carbohydrate-deficient glycoprotein syndrome (CDGS) type I by high-resolution two-dimensional electrophoresis (2-DE) and sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). The pattern of serum glycoproteins in all 5 patients presented abnormal trains of isoforms with decreased mass (delta molecular weight 3000) and all showed a cathodal shift. Two-dimensional electrophoresis and SDS-PAGE mass analysis of transferrin, alpha1 -antitrypsin, haptoglobin beta-chain, and alpha1-acid glycoprotein after neuraminidase and N-glycosidase F treatments demonstrated that the additional trains of the isoforms found in CDGS type I contain homologous species of isoforms. Some of them still showed charge differences, and all still contained glycans except for transferrin, with some unusual nonglycosylated isoforms. In addition, deficiencies in clusterin and serum amyloid P, not described so far, have been found in all 5 patients. The two-dimensional pattern of immunodetected precursors of serum proteins in liver cells from 1 patient with CDGS showed abnormal low-mass precursors and the absence of the precursors normally found in controls. These results suggest that these abnormal precursors accumulate during the early oligosaccharide processing of the nascent protein-bound oligosaccharides and that glycoprotein precursors undergo an altered intracellular transport while the post-translational processing along the normal pathway is still apparently functioning in patients with CDGS.

Amyloid↗
PubMed2000

Recognition of local glycoprotein misfolding by the ER folding sensor UDP-glucose:glycoprotein glucosyltransferase.

The endoplasmic reticulum (ER) contains a stringent quality control system that ensures the correct folding of newly synthesized proteins to be exported via the secretory pathway. In this system UDP-Glc:glycoprotein glucosyltransferase (GT) serves as a glycoprotein specific folding sensor by specifically glucosylating N-linked glycans in misfolded glycoproteins thus retaining them in the calnexin/calreticulin chaperone cycle. To investigate how GT senses the folding status of glycoproteins, we generated RNase B heterodimers consisting of a folded and a misfolded domain. Only glycans linked to the misfolded domain were found to be glucosylated, indicating that the enzyme recognizes folding defects at the level of individual domains and only reglucosylates glycans directly attached to a misfolded domain. The result was confirmed with complexes of soybean agglutinin and misfolded thyroglobulin.

Alkylation↗
PubMed2003

Degraded myelin-associated glycoprotein (dMAG) formation from pure human brain myelin-associated glycoprotein (MAG) is not mediated by calpain or cathepsin L-like activities.

The myelin-associated glycoprotein (MAG) is a transmembrane cell adhesion molecule participating in myelin formation and maintenance. Calcium-activated/-dependent proteolysis of myelin-associated glycoprotein by calpain and cathepsin L-like activities has already been detected in purified myelin fractions, producing a soluble fragment, called degraded (d)MAG, characterized by the loss of the transmembrane and cytoplasmic domains. Here, we demonstrate and analyze dMAG formation from pure human brain myelin-associated glycoprotein. The activity never exhibited the high rate previously reported in human myelin fractions. Degradation is time-, temperature-, buffer- and structure-dependent, is inhibited at 4 degrees C and by denaturation of the sample, and is mediated by a trans-acting factor. There is no strict pH dependency of the proteolysis. Degradation was inhibited by excess aprotinin, but not by 1-10 micro g/mL aprotinin and was not eliminated by the use of an aprotinin-sepharose matrix during the purification. dMAG formation was not enhanced by calcium, nor inhibited by a wide variety of protease inhibitors, including specific calpain and cathepsin L inhibitors. Therefore, while cysteine proteases may be present in human myelin membrane fractions, they are not involved in dMAG formation from highly purified human brain myelin-associated glycoprotein preparations.

Aged↗
PubMed1976

Changes in cellular glycoproteins after transformation: identification of specific glycoproteins and antigens in sodium dodecyl sulfate gels.

The glycoproteins of whole cells have been analyzed by direct application of radio-iodinated lectins to sodium dodecyl sulfate gels, followed by autoradiography. By use of lectins with different carbohydrate specificities, different sets of glycoproteins have been visualized. The most prominent lectin-binding band in many gels is thelarge, external, transformation-sensitive (LETS) protein. Major glycoprotein differences are revealed when normal and virus-transformed cells are compared. Certain differences, however, are also seen when the glycoproteins are compared from two separately derived simian virus 40 transformants of 3T3 cells, suggesting a degree of clonal variation between these lines that may not relate to transformation. A complementary technique is used to detect specific antigens in sodium dodecyl sulfate gels by direct application of iodinated antibodies. An antiserum specific for the LETS protein is used to identify this antigen in the gels of both normal and transformed cells.

Antigens, Neoplasm↗
PubMed1987

Cloning of the alpha chain of human platelet glycoprotein Ib: a transmembrane protein with homology to leucine-rich alpha 2-glycoprotein.

Glycoprotein Ib is a surface membrane glycoprotein of platelets that functions as a receptor for von Willebrand factor. It is a heterodimer composed of an alpha and a beta chain linked by a disulfide bond(s). A phage lambda gt11 cDNA expression library prepared from mRNA from a human erythroleukemia cell line, HEL, was screened using an affinity-purified antibody to the glycocalicin portion of the alpha chain of glycoprotein Ib. Eleven positive clones were isolated and plaque-purified. The largest cDNA insert was 2420 nucleotides in length and coded for a leader sequence of 16 amino acids, a mature protein of 610 amino acids, and a stop codon. It also contained 42 nucleotides of 5' noncoding sequence and 497 nucleotides of 3' noncoding sequence, including a poly(A) tail. The amino acid sequence of the alpha chain of GPIb predicted from the cDNA agreed completely with the sequence of 156 amino acids that was determined by Edman degradation of peptides isolated from human platelet glycocalicin after digestion with trypsin or Staphylococcus aureus V8 protease. The extracytoplasmic domain of the alpha subunit of GPIb contains several noteworthy structural features, including a region of seven tandem repeats of 24 amino acids that are homologous with those present in leucine-rich alpha 2-glycoprotein. The extracytoplasmic domain also contains two hydrophilic regions, one rich in charged amino acids and a second rich in serine and threonine residues. The region rich in serine and threonine includes five repeats of nine amino acids as well as the majority of the O-linked carbohydrate sites present in the molecule. The extracytoplasmic domain is followed by a potential transmembrane segment of approximately 29 amino acids and a potential intracellular domain of approximately 100 amino acids located at the carboxyl end of the molecule.

Amino Acid Sequence↗
PubMed1994

Mice expressing both B7-1 and viral glycoprotein on pancreatic beta cells along with glycoprotein-specific transgenic T cells develop diabetes due to a breakdown of T-lymphocyte unresponsiveness.

T lymphocytes have been implicated in the onset of many autoimmune diseases; however, the mechanisms underlying T-cell activation toward self antigens are poorly understood. To study whether T-lymphocyte costimulation can overcome the immunologic unresponsiveness observed in an in vivo model, we have created transgenic mice expressing the costimulatory mouse molecule B7-1, a ligand for the CD28 receptor, on pancreatic beta cells. We now report that triple-transgenic mice expressing both B7-1 and a viral glycoprotein on their beta cells, along with T cells expressing the viral-glycoprotein-specific transgenic T-cell receptor, all develop insulitis (lymphocytic infiltration of the pancreatic islets) and diabetes. In striking contrast, the T cells in double-transgenic mice expressing the same viral glycoprotein (but no B7) on their pancreatic beta cells and the transgenic T-cell receptor on their T cells, reported earlier, remain indifferent to the glycoprotein-expressing beta cells. In fact, all three transgenes are required to initiate immune-mediated destruction of the beta cells. Mice expressing any of the transgenes alone, or any two in combination, maintain normal islet architecture and never spontaneously develop insulitis or diabetes. Our results show that aberrant B7 expression on peripheral tissues may play an important role in the activation of self-reactive T cells and further suggest that abnormal expression of costimulatory receptors may be involved in various T-cell-mediated autoimmune diseases.

Animals↗
PubMed2004

Hepatitis C virus glycoprotein E2 contains a membrane-proximal heptad repeat sequence that is essential for E1E2 glycoprotein heterodimerization and viral entry.

The E1 and E2 glycoproteins of hepatitis C virus form a noncovalently associated heterodimer that mediates viral entry. Glycoprotein E2 comprises a receptor-binding domain (residues 384-661) that is connected to the transmembrane domain (residues 716-746) via a highly conserved sequence containing a hydrophobic heptad repeat (residues 675-699). Alanine- and proline-scanning mutagenesis of the E2 heptad repeat revealed that Leu675, Ser678, Leu689, and Leu692 are important for E1E2 heterodimerization. Furthermore, Pro and Ala substitution of all but one heptad repeat residue (Ser678) blocked the entry of E1E2-HIV-1 pseudotypes into Huh7 cells, irrespective of an effect on heterodimerization. Two conserved prolines (Pro676 and Pro683), occupying consecutive b positions of the heptad, were not required for E1E2 heterodimerization; however, Pro683 was critical for viral entry. Thus, disruption of the predicted alpha-helical structure by proline at position 683 is important for E2 function. The inability of mutants to mediate viral entry was not explained by a loss of receptor binding function, because all mutants were able to interact with a recombinant form of the CD81 large extracellular loop. Chimeras formed between the E1 and E2 ectodomains and the transmembrane domains of flavivirus prM and E glycoproteins, respectively, were able to heterodimerize, although with lower efficiency in comparison with wild type E1E2. The heptad repeat of E2 therefore requires the native transmembrane domain for full heterodimerization and viral entry function. Our data indicate that the membraneproximal heptad repeat of E2 is functionally homologous to the stem of flavivirus E glycoproteins. We propose that E2 has mechanistic features in common with class II fusion proteins.

Alanine↗