The oligosaccharide units of a human type L immunoglobulin M (Macroglobulin).
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ABSTRACT:
SUBMITTER: Johnson I
PROVIDER: S-EPMC1177075 | biostudies-other | 1971 Aug
REPOSITORIES: biostudies-other
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Project description:Two populations of immunoglobulin G (IgG) molecules were isolated from pooled rabbit serum. The first was almost devoid of galactosamine and was obtained in a yield of 7% of the total IgG; the second contained on average a single residue of galactosamine per molecule and was obtained in a yield of 30% of the total IgG. The galactosamine, which is present solely in the C2-oligosaccharide, appeared to be present on one H-chain and not the other in the four-chain structure. Evidence was obtained by the isolation of a glycopeptide linked through a disulphide bridge to a second peptide of the same sequence; the oligosaccharide attached to the first peptide was absent from the complementary peptide. Further evidence was obtained by degradation and analysis of the 5S IgG fragment, which comprises an intact half-molecule coupled through a disulphide bridge to the Fc fragment derived from the opposing half molecule (Goodman, 1965); only the intact H-chain carried the C2-oligosaccharide.
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Project description:The carbohydrate structure of rabbit immunoglobulin G isolated from pooled sera was investigated. Amino sugar analysis of fragments of the molecule allowed three oligosaccharides to be located at separate sites on the H-chain. The corresponding glycopeptides were isolated. The average composition of the C1-oligosaccharide was 2 glucosamine, 1 mannose and 2 galactose residues. It appeared to be present in approx. 15% of the H-chains; the carbohydrate was coupled through the amide group of asparagine in a peptide containing asparagine, glycine and threonine within the Fd fragment of the molecule. The average composition of the C2-oligosaccharide was 1 galactosamine, 1 galactose and either 1 or 2 sialic acid residues. It was present on approx. 40% of the H-chains and was attached glycosidically to the OH group of threonine in a peptide Ser-Lys-Pro-Thr-Cys-Pro-Pro-Glu-Leu in the hinge region of the molecule. The average composition of the C3-oligosaccharide was 5 glucosamine, 2 galactose, 5 mannose, 1 fucose and 1 sialic acid residue. It appeared to be present in all the H-chains and was linked through the amide group of asparagine in a peptide Gln-Gln-Phe-Asn-Ser-Thr-Ile-Arg within the Fc fragment of the molecule.
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Project description:The carbohydrate content of an A myeloma globulin was investigated. The carbohydrate content was found to be unchanged when the protein was isolated from the patient over a period of 18 months. The various polymeric forms of the protein contained similar proportions of carbohydrate. The A myeloma globulin contained approx. 2 residues of 6-deoxy-l-galactose (l-fucose), 14-15 of d-mannose, 12-13 of d-galactose, 12-13 of 2-acetamido-2-deoxy-d-glucose (N-acetyl-d-glucosamine), 6 of 2-acetamido-2-deoxy-d-galactose (N-acetyl-d-galactosamine) and 5 of N-acetylneuraminic acid (sialic acid), and these were distributed between six oligosaccharide units all of which were present on the heavy polypeptide chains. The oligosaccharide units showed two kinds of heterogeneity, which have been termed central and peripheral. Central heterogeneity was shown by the presence of three completely different core units, which had the following compositions: (1) 3 residues of d-galactose and 3 of 2-acetamido-2-deoxy-d-galactose, joined to protein by an O-glycosidic linkage between acetamidohexose and serine; (2) 3 residues of d-mannose, 2 of d-galactose and 3 of 2-acetamido-2-deoxy-d-glucose, joined to protein by an N-glycosidic linkage between acetamidohexose and aspartic acid; (3) 4 residues of d-mannose and 3 of 2-acetamido-2-deoxy-d-glucose with a linkage similar to that in (2). The core oligosaccharide units showed peripheral heterogeneity in the attachment of 6-deoxy-l-galactose, 2-acetamido-2-deoxy-d-glucose and N-acetylneuraminic acid. Tentative structures are proposed for these various types of oligosaccharide unit. Glycopeptides were isolated in which the sialic acid content exceeded that of d-galactose. Explanations are given for the electrophoretic mobility and staining characteristics of the various glycopeptides.
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Project description:Pyruvylation onto the terminus of oligosaccharide, widely seen from prokaryote to eukaryote, confers negative charges on the cell surface and seems to be functionally similar to sialylation, which is found at the end of human-type complex oligosaccharide. However, detailed molecular mechanisms underlying pyruvylation have not been clarified well. Here, we first determined the crystal structure of fission yeast pyruvyltransferase Pvg1p at a resolution of 2.46?Å. Subsequently, by combining molecular modeling with mutational analysis of active site residues, we obtained a Pvg1p mutant (Pvg1p(H168C)) that efficiently transferred pyruvyl moiety onto a human-type complex glycopeptide. The resultant pyruvylated human-type complex glycopeptide recognized similar lectins on lectin arrays as the ?2,6-sialyl glycopeptides. This newly-generated pyruvylation of human-type complex oligosaccharides would provide a novel method for glyco-bioengineering.
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Project description:High-mannose-type glycans (HMTGs) decorating viral spike proteins are targets for virus neutralization. For carbohydrate-binding proteins, multivalency is important for high avidity binding and potent inhibition. To define the chemical determinants controlling multivalent interactions we designed glycopeptide HMTG mimetics with systematically varied mannose valency and spacing. Using the potent antiviral lectin griffithsin (GRFT) as a model, we identified by NMR spectroscopy, SPR, analytical ultracentrifugation, and microcalorimetry glycopeptides that fully recapitulate the specificity and kinetics of binding to Man9 GlcNAc2 Asn and a synthetic nonamannoside. We find that mannose spacing and valency dictate whether glycopeptides engage GRFT in a face-to-face or an intermolecular binding mode. Surprisingly, although face-to-face interactions are of higher affinity, intermolecular interactions are longer lived. These findings yield key insights into mechanisms involved in glycan-mediated viral inhibition.
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Project description:Breast milk delivers nutrition and protection to the developing infant. There has been considerable research on the high-molecular-weight milk components; however, low-molecular-weight metabolites have received less attention. To determine the effect of maternal phenotype and diet on the human milk metabolome, milk collected at day 90 postpartum from 52 healthy women was analyzed by using proton nuclear magnetic resonance spectroscopy. Sixty-five milk metabolites were quantified (mono-, di-, and oligosaccharides; amino acids and derivatives; energy metabolites; fatty acids and associated metabolites; vitamins, nucleotides, and derivatives; and others). The biological variation, represented as the percentage CV of each metabolite, varied widely (4-120%), with several metabolites having low variation (<20%), including lactose, urea, glutamate, myo-inositol, and creatinine. Principal components analysis identified 2 clear groups of participants who were differentiable on the basis of milk oligosaccharide concentration and who were classified as secretors or nonsecretors of fucosyltransferase 2 (FUT2) gene products according to the concentration of 2'-fucosyllactose, lactodifucotetraose, and lacto-N-fucopentaose I. Exploration of the interrelations between the milk sugars by using Spearman rank correlations revealed significant positive and negative associations, including positive correlations between fucose and products of the FUT2 gene and negative correlations between fucose and products of the fucosyltransferase 3 (FUT3) gene. The total concentration of milk oligosaccharides was conserved among participants (%CV = 18%), suggesting tight regulation of total oligosaccharide production; however, concentrations of specific oligosaccharides varied widely between participants (%CV = 30.4-84.3%). The variability in certain milk metabolites suggests possible roles in infant or infant gut microbial development. This trial was registered at clinicaltrials.gov as NCT01817127.
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