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PubMed1988

Carbohydrates of human immunodeficiency virus. Structures of oligosaccharides linked to the envelope glycoprotein 120.

Human T-cells (H9), persistently infected with the HTLV-III strain of human immunodeficiency virus, were metabolically labeled with D-[2-3H]mannose or D-[6-3H]glucosamine. The viral envelope glycoprotein, gp120, was isolated either from cell lysates or from cell-free culture supernatant. After proteolytic digestion, the radiolabeled oligosaccharides were sequentially liberated from glycopeptides by treatment with endo-beta-N-acetylhexosaminidase H and peptide:N-glycosidase F. Oligosaccharides released were separated from residual (glyco)peptides and fractionated according to size, charge, and fucose content. The individual oligosaccharide species obtained were characterized by digestion with exoglycosidases and by chromatographic comparison with standard oligosaccharides. Our results demonstrate that the intracellular gp120 carries predominantly oligomannosidic glycans comprising nine or eight mannose residues. The secreted glycoprotein is equally substituted by oligomannosidic species, containing seven to nine mannose residues, and by fucosylated, partially sialylated bi- and triantennary complex-type oligosaccharides.

Carbohydrate Conformation↗
PubMed1988

Evaluation of the role of rat liver Golgi endo-alpha-D-mannosidase in processing N-linked oligosaccharides.

Golgi membranes from rat liver have been shown to contain an endo-alpha-D-mannosidase which can convert Glc1Man9GlcNAc to Man8GlcNAc with the release of Glc alpha 1----3Man (Lubas, W. A., and Spiro, R. G. (1987) J. Biol. Chem. 262, 3775-3781). We now report that this enzyme has the capacity to cleave the alpha 1----2 linkage between the glucose-substituted mannose residue and the remainder of the polymannose branch in a wide range of oligosaccharides (Glc3Man9GlcNAc to Glc1Man4GlcNAc) as well as glycopeptides and oligosaccharide-lipids. Whereas the tri- and diglucosylated species (Glc3Man9GlcNAc and Glc2Man9GlcNAc), which yielded Glc3Man and Glc2Man, respectively, were processed more slowly than Glc1Man9GlcNAc, the monoglucosylated components with truncated mannose chains (Glc1Man8GlcNAc to Glc1Man4GlcNAc) were trimmed at an increased rate which was inversely related to the number of mannose residues present. The endomannosidase was not inhibited by a number of agents which are known to interfere with N-linked oligosaccharide processing by exoglycosidases, including 1-deoxynojirimycin, castanospermine, bromoconduritol, 1-deoxymannojirimycin, swainsonine, and EDTA. However, Tris and other buffers containing primary hydroxyl groups substantially decreased its activity. After Triton solubilization, the endomannosidase was observed to be bound to immobilized wheat germ agglutinin, indicating the presence of a type of carbohydrate unit consistent with Golgi localization of the enzyme. The Man8GlcNAc isomer produced by endomannosidase action was found to be processed by Golgi enzymes through a different sequence of intermediates than the rough endoplasmic reticulum-generated Man8GlcNAc variant, in which the terminal mannose of the middle branch is absent. Whereas the latter oligosaccharide is converted to Man5GlcNAc via Man7GlcNAc and Man6GlcNAc at an even rate, the processing of the endomannosidase-derived Man8GlcNAc stalls at the Man6GlcNAc stage due to the apparent resistance to Golgi mannosidase I of the alpha 1,2-linked mannose of the middle branch. The results of our study suggest that the Golgi endomannosidase takes part in a processing route for N-linked oligosaccharides which have retained glucose beyond the rough endoplasmic reticulum; the distinctive nature of this pathway may influence the ultimate structure of the resulting carbohydrate units.

Animals↗
PubMed1988

Sulfated N-linked oligosaccharides in mammalian cells. III. Characterization of a pancreatic carcinoma cell surface glycoprotein with N- and O-sulfate esters on asparagine-linked glycans.

In the preceding two papers, we described two new classes of sulfated N-linked oligosaccharides isolated from total cellular 35SO4-labeled macromolecules of different mammalian cell lines. The first class carries various combinations of sialic acids and 6-O-sulfate esters on typical complex-type chains, while the second carries heparin and heparan-like sequences. In this study, we have characterized a sulfophosphoglycoprotein of 140 kDa from FG-Met-2 pancreatic cancer cells whose oligosaccharides share some properties of both these classes. The molecule was localized to the cell surface by electron microscopy using a monoclonal antibody (S3-53) and by cell surface 125I-labeling. Metabolic labeling of the cells with radioactive glucosamine, methionine, inorganic sulfate, or phosphate all demonstrated a single 140-kDa molecule. Pulse-chase analysis and tunicamycin treatment indicated the glycosylation of a putative primary translation product of 110 kDa via an intermediate (120 kDa) to the mature form (140 kDa). Digestion with peptide:N-glycosidase F (PNGaseF) indicated a minimum of four N-linked glycosylation sites. PNGaseF released more than 90% of the [6-3H]GlcNH2 label and 40-70% of 35SO4 label from the immunoprecipitated 140-kDa molecule. The isolated oligosaccharides were characterized as described in the preceding two papers. The majority of [6-3H]GlcNH2-labeled molecules were susceptible to neuraminidase. More than 50% of the 35SO4 label was associated with only 5-10% of the 3H-labeled chains. Some of the sulfated chains were partly sialylated molecules with four to five negative charges. Treatment with nitrous acid released about 25% of the 35SO4 label as free sulfate, together with 6% of the [6-3H]GlcNH2 label, indicating the presence of N-sulfated glucosamine residues. Some of these oligosaccharides were degraded by heparinase and heparitinase. Therefore, while they are not as highly charged as typical heparin or heparan chains, they must share structural features that permit recognition by the enzymes. Thus, this 140-kDa glycoprotein contains at least four asparagine-linked chains substituted with a heterogeneous mixture of sulfated sequences. The heterogeneity of these molecules is as extensive as that described for whole-cell sulfated N-linked oligosaccharides in the preceding two papers.

Asparagine↗
PubMed1978

Alkali-stable oligosaccharides isolated by hydrazinolysis of M and N blood group glycoproteins.

Three alkali-stable oligosaccharides free of amino acids were purified from hydrazinolysis products of M or N blood group glycoprotein. These three oligosaccharides differed in the content of sialic acid and contained similar amounts of other carbohydrate components. The asparagine-linked oligosaccharides, obtained by strong alkaline degradation of M glycoprotein, showed similar electrophoretic mobilities and chemical composition to the oligosaccharides obtained by hydrazinolysis. It indicates that hydrazinolysis does not give a substantial degradation of carbohydrates of alkali-stable oligosaccharides of human red cell glycoprotein.

Chemical Phenomena↗
PubMed1987

Structures of the sialylated oligosaccharide chains in swine tracheal mucin glycoproteins.

The structures of the major sialylated oligosaccharide chains in swine tracheal mucin glycoprotein were established. The oligosaccharide chains were released by treatment with alkaline borohydride and isolated by gel filtration on Bio-Gel P6 columns and chromatography on DEAE-cellulose. The neutral oligosaccharide chains in this glycoprotein have been characterized in previous studies (Rana, S.S., Chandrasekaran, E.V., Kennedy, J., and Mendicino, J. (1984) J. Biol. Chem. 259, 12899-12907; Chandrasekaran, E.V., Rana, S.S., Davila, M., and Mendicino, J. (1984) J. Biol. Chem. 259, 12908-12914). The present study reports the isolation of four monosialylated chains ranging in length from 6 to 14 sugar units, two disialylated chains containing 6 and 12 sugar units, and one trisialylated chain containing 9 sugar units. The structure of the sialylated oligosaccharides was determined by permethylation analysis and sequential hydrolysis with specific exoglycosidases. The following structures (where GalNAcol is N-acetylgalactosaminitol) were assigned to these oligosaccharides.

Animals↗
PubMed1985

Characterization of a specific alpha-mannosidase involved in oligosaccharide processing in Saccharomyces cerevisiae.

Fractionation of a crude extract from Saccharomyces cerevisiae X-2180 on Sepharose 6B in the presence of 0.5% Triton X-100 resolves two enzyme fractions containing alpha-mannosidase activity. Fraction I which is excluded from the gel contains alpha-mannosidase activity toward both p-nitrophenyl-alpha-D-mannopyranoside and Man9GlcNAc oligosaccharide as substrates, whereas Fraction II which is included in the gel contains only oligosaccharide alpha-mannosidase activity. The latter enzyme is very specific and removes a single mannose residue from Man9GlcNAc, whereas the alpha-mannosidase activity of Fraction I removes several mannose residues from Man9GlcNAc oligosaccharide. High resolution 1H NMR analysis of the Man8GlcNAc formed from Man9GlcNAc in the presence of the alpha-mannosidase of Fraction II showed only a single isomer with the following structure: (see formula; see text) This specific enzyme is most probably involved in processing of oligosaccharide during biosynthesis of mannoproteins. The mannose analog of 1-deoxynojirimycin (50-500 microM), dideoxy-1,5-imino-D-mannitol, inhibits the oligosaccharide alpha-mannosidase activities of Fractions I and II to about the same extent, but has no effect on the nonspecific alpha-mannosidase which acts on p-nitrophenyl-alpha-D-mannopyranoside.

Hydrogen-Ion Concentration↗
PubMed1985

The effect of swainsonine and castanospermine on the sulfation of the oligosaccharide chains of N-linked glycoproteins.

MDCK (Madin-Darby canine kidney) cells infected with the NWS strain of influenza virus incorporate 35SO4 into complex types of oligosaccharides of the N-linked glycoproteins. On the other hand, when these virus-infected MDCK cells are incubated in the presence of swainsonine, an inhibitor of the processing mannosidase II, approximately 40-80% of the total [35S]glycopeptides were of the hybrid types of structures. Thus, these sulfated, hybrid types of glycopeptides were completely susceptible to digestion by endoglucosaminidase H, whereas the sulfated glycopeptides from infected cells incubated without swainsonine were completely resistant to endo-beta-N-acetylglucosaminidase H. When virus-infected MDCK cells were incubated in the presence of castanospermine, an inhibitor of the processing glucosidase I, the N-linked glycopeptides contained mostly oligosaccharide chains of the Glc3Man7-9GlcNAc2 types of structures, and these oligosaccharides were devoid of sulfate. Structural analysis of these abnormally processed oligosaccharides produced in the presence of swainsonine or castanospermine indicated that they differed principally in the processing of one oligosaccharide branch as indicated by the structures shown below. They also differed in that only the swainsonine-induced structures were sulfated. These data indicate that removal of glucose units and perhaps other processing steps are necessary before sulfate residues can be added. (Formula: see text).

Alkaloids↗
PubMed1985

Fractionation of L-fucose-containing oligosaccharides on immobilized Aleuria aurantia lectin.

The carbohydrate-binding specificity of Aleuria aurantia lectin was investigated by analyzing the behavior of a variety of fucose-containing oligosaccharides on an A. aurantia lectin-Sepharose column. Studies with complex-type oligosaccharides obtained from various glycoproteins by hydrazinolysis and their partial degradation fragments indicated that the presence of the alpha-fucosyl residue linked at the C-6 position of the proximal N-acetylglucosamine moiety is indispensable for binding to the lectin column. Binding was not affected by the structures of the outer chain moieties nor by the presence of the bisecting N-acetylglucosamine residue. These results indicated that A. aurantia lectin-Sepharose is useful for the group separation of mixtures of complex-type asparagine-linked sugar chains. Studies of glycosylated Bence Jones proteins indicated that this procedure is also applicable to intact glycoproteins. The behavior of oligosaccharides isolated from human milk and the urine of patients with fucosidosis indicated that the oligosaccharides with Fuc alpha 1----2Gal beta 1----4GlcNAc and Gal beta 1----4(Fuc alpha 1----3)GlcNAc groups interact with the lectin, but less strongly than complex-type sugar chains with a fucosylated core. Lacto-N-fucopentaitol II, which has a Gal beta 1----3(Fuc alpha 1----4)GlcNAc group, interacts less strongly than the above two groups with the matrix. Oligosaccharides with Fuc alpha 1----2Gal beta 1----3GlcNAc and Gal beta 1----4GlcNAc beta 1----3Gal beta 1----4(Fuc alpha 1----3)GlcNAc groups showed almost no interaction with the matrix.

Acetylglucosamine↗
PubMed1979

The initial stages of processing of protein-bound oligosaccharides in vitro.

Following the rapid enzymatic transfer of an oligosaccharide (GlcNAc2Man9Glc3) from a lipid carrier to endogenous protein acceptors in membrane preparations from NIL fibroblasts, the transferred oligosaccharide chain undergoes processing. Protein-bound oligosaccharides, released from the polypeptide backbone by treatment with endo-beta-N-acetylglucosaminidase H, were analyzed by gel filtration and by susceptibility to alpha-mannosidase digestion. The initial stages of this processing in vitro consist of sequential excision of 3 glucose residues prior to the removal of mannose residues. The array of oligosaccharides generated in vitro by membrane preparations from NIL cells appears to be identical with processed oligosaccharides derived in vivo in intact NIL cells.

Animals↗
PubMed1980

Characterization of large oligosaccharide-lipids synthesized in vitro by microsomes from Saccharomyces cerevisiae.

Conditions are described for optimizing the synthesis of large oligosaccharide-lipids in microsomal preparations from Saccharomyces cerevisiae. On incubating microsomes, with GDP-[14C]Man, the major product obtained was Man9GlcNAc2-P-P-dolichol, but when both GDP-[14C]Man and UDP-[3H]Glc were present in the incubation mixture about half of the Man9GlcNAc2 was elongated to Glc3Man9GlcNAc2-P-P-dolichol. Unlike particulate fractions from mammalian systems, little glucosylation of the yeast microsomal oligosaccharide-lipid was obtained when the concentration of UDP-Glc was less than 10 microM, but the synthesis of this product could be maximized by raising the concentration of UDP-Glc to 50 microM. Analysis of the yeast Man9GlcNAc2 species confirmed that 8 of the 9 mannose residues could be released with alpha-mannosidase, while the remaining mannosyl residue was in the core trisaccharide, Manbeta 1 leads to 4GlcNAc beta 1 leads to 4GlcNAc. Treatment of Glc3Man9GlcNAc2 with alpha-mannosidase released 5 of 9 mannose residues and yielded Glc3Man4GlcNAc2. This product appeared to be identical with that obtained in parallel experiments with double labeled oligosaccharide-lipid synthesized in oviduct microsomes. Streptomyces plicatus endo-beta-N-acetylglucosaminidase H (Endo-H) treatment of yeast microsomal glycoproteins that were labeled with sugar nucleotides established that 15% of the label was associated with N-linked oligosaccharides. The remaining labeled sugars were released with alkali, indicating that they were linked to serine or threonine. Based on the size and distribution of [3H]glucose and [14C]mannose in the Endo-H-released oligosaccharides, it was concluded that Glc3Man9GlcNAc2 was the primary species transferred to proteins in the yeast system.

Glycolipids↗
PubMed1984

Free alpha-like material from bovine pituitaries. Removal of its O-linked oligosaccharide permits combination with lutropin-beta.

Further characterization of the free alpha subunit immunoreactive material, not combined with beta subunit in extracts of bovine pituitaries, shows that the only significant modifications, relative to alpha subunits themselves, are the oligosaccharide O-linked to threonine-43, and heterogeneity of the carboxyl terminus. Removal of the O-linked carbohydrate with a mixture of glycosidases from Streptococcus pneumoniae results in an alpha-like material capable of combining with lutropin beta subunit and, thus, the presence of the oligosaccharide is responsible for the inability of the free alpha-like material to combine with beta subunits. Amino acid compositions of tryptic peptides spanning the entire sequence indicate no change in amino acid sequence of the free alpha-like material as compared to lutropin alpha. Further, based on the similar behavior reverse phase high performance liquid chromatography of the tryptic peptides as compared to their lutropin alpha counterparts, it is concluded that no additional post-translational modifications are present. The N-linked oligosaccharides of the free alpha-like material most likely contain terminal O-sulfated N-acetylhexosamines (as do the asparagine-linked carbohydrates from the pituitary hormones) as indicated by the presence of 3 mol of sulfate/mol of free alpha-like material and the resistance of these oligosaccharides to enzymatic deglycosylation. The O-linked oligosaccharide does not contain sulfated residues.

Amino Acid Sequence↗
PubMed1982

Structural characterization of neutral oligosaccharides of human midcycle cervical mucin.

It was previously shown that alkaline borohydride treatment of human midcycle cervical mucin releases a heterogeneous population of reduced neutral, sialylated, and sulfated oligosaccharides (Yurewicz, E. C., and Moghissi, K. S. (1981) J. Biol. Chem. 256, 11895-11905). Three major neutral oligosaccharides were isolated with approximate compositions of Fuc:Gal:GlcNAc:N-acetylgalactosaminitol (GalNAcol) = 0:2:1:1 (A1), 1:2:1:1 (A2), and 2:2:1:1 (A3). They comprised roughly 21%, 13%, and 8% of human cervical mucin oligosaccharide chains, respectively. In the present report, each was analyzed by periodate oxidation, methylation, and sequential degradation with glycosidases. A1 was shown to contain more than one component, but structural analyses clearly demonstrated the presence of one predominant (75%) tetrasaccharide. The proposed structure, Gal beta 1-4GlcNAc beta 1-6(Gal beta 1-3)GalNAcol, has previously been found in human gastric, submaxillary, and ovarian cyst mucins in their carbohydrate-to-protein linkage regions. beta-Galactosidase from Aspergillus niger selectively cleaved the Gal beta 1-4GlcNAc linkage in the intact tetrasaccharide. Enzymatic hydrolysis of the Gal beta 1-3GalNAcol linkage required prior removal of the Gal beta 1-4GlcNAc beta 1-unit attached to 0-6 of GalNAcol. The data for A2 indicated a mixture of two oligosaccharides, Gal beta 1-4,3(Fuc alpha 1-3,4)GlcNAc beta 1-6(Gal beta 1-3)GalNacol and Fuc alpha 1-2Gal beta 1-4GlcNac beta 1-6(Gal beta 1-3)-GalNacol, in an approximate molar ratio of 3 to 4:1, respectively. Two structures are consistent with the data obtained for A3: Fuc alpha 1-2Gal beta 1-4,3(Fuc alpha 1-3,4)GlcNAc beta 1-6(Gal beta 1-3)GalNAcol and/or Gal beta 1-4,3(Fuc alpha 1-3,4)GlcNac beta 1-6(Fuc alpha 1-2Gal beta 1-3)GalNacol. The results indicate that A1 represents the "core" tetrasaccharide of the larger human cervical mucin oligosaccharides A2 and A3.

Carbohydrate Conformation↗
PubMed1982

Incorporation of amino acid analogs interferes with the processing of the asparagine-linked oligosaccharide of the MOPC-46B kappa light chain.

The incorporation of the leucine analog, beta-hydroxyleucine, or the isoleucine analog, 4-thiaisoleucine, into the MPOC-46B kappa chain interfered with the processing of the oligosaccharide moiety of newly synthesized light chains. Analog-containing chains were secreted with endo-beta-N-acetylglucosaminidase H-sensitive oligosaccharides instead of the normal complex, endo-beta-N-acetylglucosaminidase H-resistant oligosaccharide. The incorporation of the analogs did not significantly decrease the overall secretion of the MPOC-46B-related proteins. These data form the basis for the hypothesis that the presence of the analog in the protein alters the peptide configuration sufficiently to prevent the processing of precursor high mannose oligosaccharides to complex oligosaccharides.

Amino Acids, Sulfur↗
PubMed1983

Protein glycosylation in Trypanosoma cruzi. The mechanism of glycosylation and structure of protein-bound oligosaccharides.

As reported previously (Parodi, A.J., and Cazzulo, J.J. (1982) J. Biol. Chem. 257, 7641-7645), label was incorporated first to the glucose residues of protein-bound Glc1Man9GlcNAc2, Glc1Man8GlcNAc2, and Glc1Man7GlcNAc2 when Trypanosoma cruzi cells, the causative agent of Chagas disease, were incubated with [U-14C]glucose. It is now reported that the glucose residues are removed from the oligosaccharides after a chase period. The relative proportion of Man9GlcNAc2, Man8GlcNAc2, Man7GlcNAc2, and Man6GlcNAc2 appeared to be the same after 120 and 180 min of chase, thus indicating that these compounds were the fully processed protein-bound oligosaccharides. No complex type protein-bound oligosaccharides were detected. Evidence is presented indicating that Glc1Man7GlcNAc2 was formed mainly by glucosylation of Man7GlcNAc2 and not by demannosylation of Glc1Man9GlcNAc2. Man9GlcNAc2 was the first oligosaccharide to be labeled when cells were incubated with [2-3H]mannose. Based on these and previous results, the overall mechanism of protein N-glycosylation appeared to be: (formula; see text) The structure of the oligosaccharides appeared to be similar to some of those present in human glycoproteins. T. cruzi cells isolated from distant locations in South America were found to share a common mechanism of protein glycosylation.

Animals↗
PubMed1984

Control of asparagine-linked oligosaccharide chain processing: studies on bovine pancreatic ribonuclease B. An in vitro system for the processing of exogenous glycoproteins.

To gain an understanding of why the polymannose-type oligosaccharide chain of bovine pancreatic ribonuclease B is not processed to a complex-type chain in vivo, the processing of this glycoprotein was studied in two cell-free systems. Addition of native 125I-ribonuclease B to rat liver Golgi membranes in the presence of UDP-GlcNAc resulted in the conversion of the high mannose chain to a complex type as evidenced by the acquisition of resistance to digestion with endoglucosaminidase H. Processing was linearly dependent on time and on the amount of Golgi membranes. Omission of UDP-GlcNAc from the reaction mixtures completely abolished processing of the glycoprotein. Product identification studies confirmed that the formation of ribonuclease that was resistant to digestion with endoglucosaminidase H was accompanied by the appearance of a complex-type oligosaccharide that contained one or more terminal beta-GlcNAc residues. In vitro processing of 125I-ribonuclease B that had been denatured by reduction and alkylation revealed that the rate of complex chain formation was only slightly greater than that observed with the native enzyme. In contrast to the results obtained with the heterologous rat liver system, Golgi membranes from bovine pancreas failed to process native ribonuclease B to the complex form. However, bovine pancreas Golgi membranes did readily process the denatured form of the enzyme. The presence of a factor in bovine pancreas that binds only to native ribonuclease B and thereby prevents its oligosaccharide chain from being processed was considered to be unlikely on the basis of gel filtration studies and mixing experiments. These findings indicate that some aspect of the conformation of native ribonuclease B prevents one or more of the processing enzymes of bovine pancreas from acting on the oligosaccharide chain. In addition, the substrate specificity of this processing enzyme(s) differs markedly from its counterpart in rat liver. These two factors, conformation of the substrate and specificity of the processing enzymes, apparently combine to produce the high mannose oligosaccharide chain of ribonuclease B observed in vivo.

Animals↗
PubMed1984

Structures of the oligosaccharide chains in swine trachea mucin glycoproteins.

The structures of large O-glycosidically linked oligosaccharides derived from swine trachea mucin glycoprotein were established. Reduced oligosaccharides released by treatment with alkaline borohydride were separated by gel filtration on Bio-Gel P-6 and the neutral oligosaccharides were isolated by chromatography on DEAE-cellulose. Eight oligosaccharides (DIa to BII), ranging in length from 8 to 15 sugar units, were isolated. On the basis of carbohydrate composition and analytical data from sequential treatment with exoglycosidases and permethylation analysis, the following structures were assigned to these oligosaccharides: (Formula: see text).

Animals↗
PubMed1984

Identification of methylphosphomannosyl residues as components of the high mannose oligosaccharides of Dictyostelium discoideum glycoproteins.

Lysosomal enzymes isolated from the slime mold Dictyostelium discoideum bind to the mannose 6-phosphate receptor which is present in many mammalian cells. While binding to the receptor suggests that the slime mold enzymes possess the same mannose 6-phosphate recognition marker as their mammalian counterparts, initial structural studies of the phosphorylated oligosaccharides have indicated that the phosphate is attached to high mannose-type units via an unusual phosphodiester linkage (Freeze, H.H., Yeh, R., Miller, A.L., and Kornfeld, S. (1983) J. Biol. Chem. 258, 14874-14879). To identify the components of the phosphodiester group we have isolated the phosphorylated high-mannose oligosaccharides from D. discoideum AX3 cells labeled with [2-3H]mannose or [6-3H]glucosamine and from the differentiation medium of unlabeled cells. The major phosphorylated species contain one or two phosphodiester groups and an average of 6 or 7 mannose residues. The phosphodiesters are relatively stable to both acid and base hydrolysis, but upon strong acid hydrolysis (conditions that completely hydrolyze the oligosaccharide) mannose 6-phosphate residues are liberated. Through a combination of techniques, including fast atom bombardment and direct chemical ionization mass spectrometry, it is shown that the mannose 6-phosphate residues of the intact oligosaccharide are diesterified to methyl groups. This indicates that slime mold possesses a different biosynthetic pathway for the formation of phosphorylated high mannose-type oligosaccharides than is utilized by higher organisms.

Chromatography, High Pressure Liquid↗
PubMed1984

Comparison and partial characterization of guinea pig Ia alpha- and beta-chain oligosaccharides.

The structures of the N-linked oligosaccharides of mature guinea pig Ia molecules were partially characterized by serial lectin affinity analysis. Those Ia antigens that are thought to be allelic products (Ia.3,5 and Ia.4,5) were found to bear identical oligosaccharides, whereas differences in glycopeptide distribution were found for Ia antigens known to be products of separate I subregions (Ia.2 and Ia.4,5). The two predominant oligosaccharides present on alpha-chains from all three Ia molecules were of the high mannnose type and the triantennary or tetraantennary complex type. Two structurally distinct beta-chains were isolated from Ia.3,5 and Ia.4,5 molecules; beta 1 bore primarily triantennary or tetraantennary complex oligosaccharides, and beta 2 had predominantly biantennary complex-type carbohydrate chains. The composition and distribution of the oligosaccharide moieties of guinea pig Ia molecules indicate that there are structural features shared among guinea pig, murine, and human Ia antigens.

Animals↗