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Query: UNIPROT:P06889 (Mol)
 630,302 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The sequence of N-linked oligosaccharides of differentially glycosylated murine I-Ak alpha-(alpha 2- and alpha 3-) and beta-chains was determined. I-Ak beta-chains predominantly bear a biantennary complex oligosaccharide with a core fucose, and with the peripheral sequence SA----Gal----GlcNAc----Man. The I-Ak alpha-chain has two N-linked glycosylation sites at Asn-82 and Asn-122. When Lubrol-insoluble alpha 3-chains are examined they are found to bear high-mannose oligosaccharides of either the Man9GlcNAc2 or Man8GlcNAc2 type at both sites. When Lubrol-soluble alpha 2-chains are examined, in about 85% of the molecules the Asn-82 site bears a biantennary complex oligosaccharide with core fucose, and with the peripheral sequence SA----Gal----GlcNAc----Man. Interestingly, the Asn-122 site bears a variety of structures. In about 50% of the molecules, the structure at Asn-122 is a biantennary complex oligosaccharide without core fucose and with the peripheral sequence SA----Gal----GlcNAc----Man. In addition, it can bear other complex structures which we did not define further. The apparently restricted addition of fucose to the oligosaccharide at the alpha-Asn-82 site, even when both alpha-sites bear biantennary complex structures with the same peripheral sequence, is a feature unique to this system. The unusual variety of structures present at the alpha-Asn-122 site may indicate differential processing in different cell types.
Mol Immunol 1985 Feb
PMID:Structural characterization of murine Ia antigen N-linked oligosaccharides and localization of specific structures to two unique alpha-chain glycosylation sites. 385 97

Brugia malayi microfilariae and gravid adult females were examined to determine whether chitin (poly beta(1----4)-linked N-acetylglucosamine) is a structural component of the microfilarial sheath. Two lectins which are specific for beta(1----4)-linked oligomers of N-acetylglucosamine bind to the sheaths of living microfilariae. Diflubenzuron, a potent inhibitor of chitin synthesis in insects and crustaceans, causes gravid female worms to shed progeny microfilariae with truncated sheaths. A chitin-like fraction (hot alkali-insoluble and chitinase-sensitive) can be isolated from gravid female (but not male) worms. This fraction can be metabolically labelled with radioactive glucosamine, but such labelling is inhibited by diflubenzuron. These data suggest that chitin synthesis is critical to microfilarial sheath morphogenesis in this parasitic nematode.
Mol Biochem Parasitol 1985 Oct
PMID:Chitin synthesis and sheath morphogenesis in Brugia malayi microfilariae. 393 52

Double labeling studies of the pattern of protein synthesis in goldfish and mouse brain identified a class of glycoproteins (the ependymins) whose turnover rate was enhanced after training. A variety of control experiments indicated that these macromolecules have an important role in the molecular and cell biology of learning. Antisera to the ependymins when injected into the brains of trained goldfish cause amnesia of a newly acquired behavior. Isolation and localization studies by immunocytochemical methods indicate that the ependymins are released into the brain extracellular fluid by a class of neurosecretory cells. In mammalian brain ependymin-containing cells are highly concentrated in the limibic system. The ependymins are constituted from two disulfide-linked acidic polypeptide chains (M.W.37K and 31K). They contain at least 5% covalently bound carbohydrate per chain with mannose, galactose, N-acetylglucosamine and N-acetylneuraminic acid as the predominant components. The highly soluble ependymins can rapidly polymerize to form an insoluble fibrous matrix if calcium is removed from solution by the addition of a Ca2+-chelating agent or dialysis. The self-aggregation property of the ependymins can be triggered by the depletion of Ca2+ from the extracellular space. Studies of the kinetics of the aggregation phenomenon by measurements of turbidity changes indicate that the process can be terminated but not reversed by restoring Ca2+ to its normal CSF level. Immunohistochemical studies of the brains of trained goldfish show the presence of punctate statining sites in the perimeter of certain cells located in specific brain regions. This suggests that ependymin aggregation might occur in vivo during learning. A molecular hypothesis relating the aggregation properties of the ependymins to neuroplasticity and learning is proposed.
Cell Mol Neurobiol 1985 Jun
PMID:The role of brain extracellular proteins in neuroplasticity and learning. 402 66

The development of erythrocytic stages of Plasmodium knowlesi separated from their host cells has been determined in terms of the capacity of the isolated organisms to carry out the synthesis and secretion of proteins. P. knowlesi trophozoites and schizonts were released from host cells by nitrogen decompression and cultivated in a medium consisting of 20 mM Na+; 120 mM K+; 1 mM Mg2+; no Ca2+; 100 mM Cl-; 20 mM HCO3-; 5 mM Hepes [pH 6.73], glucose, vitamins, amino acids and 10% fetal calf serum. The yield was about 97% intact parasites, judging by their ability to maintain a membrane potential, and these parasites had more than 80% the capacity of infected cells for nuclear replication and macromolecule biosynthesis. Pulse and pulse-chase labeling studies with [35S]methionine show that parasite-synthesized proteins with Mr 160 000, 140 000, 100 000 and 58 000 are exported from the parasite in soluble form. Proteins with Mr 140 000, 100 000, 58 000-60 000, 40 000 were recovered in a particulate fraction isolated from the parasite culture fluid. An Mr 62 000 protein synthesized in large amounts by isolated parasites during the last 2h of the developmental cycle, could not be detected in infected erythrocytes, and a minor early Mr 74 000 protein becomes prominent in free parasites but not infected cells toward the end of the developmental cycle. Parasite-synthesized proteins with Mr 230 000, 160 000, 140 000, 62 000, 58 000 and 45 000 were labeled by incubation with radioactive N-acetylglucosamine during short term incubation in vitro. About 80% of label incorporation occurred via N-glycosylation supported by dolichol derived from the blood, and about 20% via glycolytic intermediates.
Mol Biochem Parasitol 1985 Nov
PMID:Extracellular development of Plasmodium knowlesi erythrocytic stages in an artificial intracellular medium. 406 57

Salivary glycoproteins from 33 normal individuals were analyzed with a panel of mouse monoclonal antibodies to H-1, H-2, Lea, Leb, X, Y and precursor blood group determinants. Samples from 19/33 individuals co-expressed Leb and Y-determinants (secretors) and 6/33 co-expressed Lea and X-determinants (non-secretors). Erythrocytes of these individuals were typed Le (a-b+) and Le (a + b-), respectively. In seven other salivas, only one specificity, either Lea, Leb, X or Y, was expressed and in one sample none of these determinants could be detected. Only one saliva sample expressed H-1 specificity and none expressed H-2 or type 1 precursor determinants. The absence of H-1 and H-2 structures in secretors and the resulting expression of difucosylated Leb and Y-structures is probably a tissue-specific trait of salivary gland secretions. The strict co-expression of Leb with Y and Lea with X supports the conclusion that only one 2-O-fucosyl-galactose transferase, which can fucosylate both type 1 and type 2 chains, exists in salivary glands. The finding that a number of individuals expressed neither X- nor Y-specificities was unexpected in view of previous work showing that the 3-O-fucosyl N-acetylglucosamine transferase involved in forming this structure is a ubiquitous enzyme. The individualistic expression of blood group phenotypes in tissues should be considered when the altered expression of blood groups in malignancy and other diseases is studied.
Mol Immunol 1984 Nov
PMID:Analysis of the expression of H, Lewis, X, Y and precursor blood group determinants in saliva and red cells using a panel of mouse monoclonal antibodies. 608 46

Treatment of ovine pituitary follitropin with anhydrous hydrogen fluoride at 0 degrees C for 60 min resulted in the removal of approximately 80% of the sugars without affecting the polypeptide moiety. Fucose, sialic acid and N-acetylgalactosamine were eliminated completely while the loss of hexoses and N-acetylglucosamine amounted to 86% and 56% respectively. The treatment had no effect on the quaternary structure of the hormone. Consistent with the loss of carbohydrate, the elution volume of the hormone on Sephadex G100 was increased and the deglycosylated hormone lost its ability to interact with the lectin concanavalin-A immobilized on Sepharose. Deglycosylation rendered the hormone less acidic as reflected by altered electrophoretic mobility in polyacrylamide gels at pH 8.9 and 4.5. The UV absorption spectrum of the hormone was not affected by deglycosylation but tryptophan fluorescence was slightly decreased. The receptor-binding activity of the hormone as estimated by a specific radioreceptor assay using adult bovine testicular membranes and labeled 125I-FSH was increased by 250% following deglycosylation. In a conformation specific radioimmunoassay, the deglycosylated hormone showed 150% activity as compared to the native hormone. Thus, the full integrity of the carbohydrate moiety in ovine follitropin is not required for effective receptor binding and immunological activity.
Mol Cell Endocrinol 1982 Oct
PMID:Studies on pituitary follitropin. X. Biochemical, receptor binding and immunological properties of deglycosylated ovine hormone. 618 43

Native low mol. wt (LMr) kininogen from human plasma and a kinin-free kininogen from Cohn's plasma fraction IV (HC-antigen) were isolated and studied with regard to their immunological reactivity and carbohydrate heterogeneity. Antisera were prepared against the conformational and sequence-dependent determinants of the heavy chain which is the common denominator of plasma kininogens. The molecules were characterized by single radial immunodiffusion and SDS gel electrophoresis. The effect of exoglycosidase treatment was investigated by a radioimmunoassay. It was found that the antigenic combining sites were not influenced by the partial removal of carbohydrates. These results suggest that the determinant structures of LMr kininogen reside in the peptide backbone of the protein. Carbohydrate heterogeneity was shown by different binding to concanavalin A and wheat germ lectin. With concanavalin A 52% of the immunoreactive HC-antigen was reactive compared to 76% of the native LMr kininogen. The weak reactivity (11%) of the HC-antigen towards the wheat germ lectin indicates that the N-acetylglucosamine residues are apparently blocked or missing. Immunoreactive kininogen was in all cases measured by single radial immunodiffusion or an RIA. The molecular nature of the heterogeneity is discussed in relation to the known isoelectric variations of kininogen.
Mol Immunol 1983 Dec
PMID:Studies on the antigenicity and carbohydrates of human low molecular weight kininogen. 619 38

The specificity of a mouse anti-testicular cell monoclonal antibody, J1, was investigated. Previous studies suggested that N-acetyl-D-glucosamine (GlcNAc) was a constituent of the determinant recognized by J1. When the antibody was tested against a variety of purified glycolipids containing this saccharide in terminal, penultimate or internal positions, J1 reacted only with species expressing terminal GlcNAc. The influence of oligosaccharide chain length, branch substitution, and haptenic valence on J1 binding was examined using glycolipids prepared by a weak acid hydrolysis and exoglycosidase digestion of bovine I-active ganglioside. Degree of binding was inversely proportional to chain length and was proportional to hapten valence. Failure of J1 to bind partially deglycosylated transferrin implied binding preference for GlcNAc beta 1----3Gal over GlcNAc beta 1----2Man. Immunofluorescence analysis of J1 binding to human neutrophils failed to detect lactotriosylceramide on their surface, although this glycolipid has previously been isolated from these cells, suggesting that this structure exists in a cryptic or intracellular form. Binding results were consistent with J1 having low affinity for GlcNAc or GlcNAc beta 1----3Gal on a variety of lacto-series glycolipids.
Mol Immunol 1984 Oct
PMID:Fine specificity of a monoclonal anti-testicular cell antibody for glycolipids with terminal N-acetyl-D-glucosamine structure. 620 60

Microsomes forom Trypanosoma brucei contain glycosyltransferases able to incorporate N-[14C]acetylglucosamine into two different types of acceptors. A first transferase catalyzes the transfer of N-[14C]acetylglucosamine 1-phosphate from uridine diphosphate N-[14C]acetylglucosamine into dolichol monophosphate. The enzymatic activity requires Mn2+, is time and temperature dependent, has an optimum pH of 7.4 and is completely inhibited by the antibiotic tunicamycin. Exogenous dolichol monophosphate enhances the glycosyltransferase activity. The kinetics of incorporation are characterized by a Km of 2.6 microM for uridine diphosphate N-acetylglucosaminyltransferase are comparable to those reported for the first enzyme of the dolichol cycle described in several eukaryotes. N-Acetyl-glucosaminylpyrophosphoryl-dolichol is essentially the only product of the reaction. A second type of activity which is responsible for the direct transfer of N[14C]acetylglucosamine from uridine diphosphate N[14C]acetylglucosamine into several endogenous polypeptide acceptors, is also associated with T. brucei microsomes. The reaction, which might be due to more than one enzyme, is dependent on Mn2+, but differs from the other transferase in all other characteristics. Time course and optimal temperature are different, and the optimum pH is 6.5. The reaction is independent of the external addition of dolichol monophosphate and tunicamy cin has no inhibitory effect on the enzymatic activity. AKm of 1.6 microM was calculated fr uridine diphosphate N-acetylglucosamine.
Mol Biochem Parasitol 1982 Mar
PMID:Identification and characterisation of two N-acetylglucosaminyltransferases associated with Trypanosoma Brucei microsomes. 621 16

The interaction of 125I-labeled gonadotropin releasing hormone (GnRH) agonist, [D-Ser-(t-Bu)6,des-Gly10-ethylamide]-GnRH, and antagonist [D-pGlu1,D-Phe2,D-Trp3,6]-GnRH with rat pituitary membranes was studied. Their binding was affected differently by pretreatment of membranes with neuraminidase and by wheat-germ agglutinin. Pretreatment of the membranes with neuraminidase abolished the specific binding of both antagonist and agonist, in a dose-response manner, with the former being less affected. Wheat-germ agglutinin affected antagonist binding slightly (22% inhibition at 40 microgram/ml) but inhibited agonist binding more markedly (50% at 40 microgram/ml). This inhibitory effect was specific since it was readily reversed by N-acetylglucosamine. Other lectins, such as concanavalin A and soybean agglutinin affected the binding of both agonist and antagonist to only a small degree. These results suggest that the GnRH-receptor of rat pituitary is a glycoprotein which contains sialic acid residue and that GnRH agonists and antagonists bind differently to the same receptor.
Mol Cell Endocrinol 1982 Apr
PMID:GnRH-receptors of rat pituitary is a glycoprotein: differential effect of neuraminidase and lectins on agonists and antagonists binding. 628 72


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