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PubMed1988

Early cortical plate specific glycoprotein in a marsupial species belongs to the same family as fetuin and alpha 2HS glycoprotein.

Two related glycoproteins, fetuin in species of the order Artiodactyla (cattle, sheep, pig) and alpha 2HS glycoprotein in the human [(1987) Cell Tissue Res. 248, 33-41] have a very specific distribution in the developing brain. We have isolated and determined the first 15 N-terminal residues of a similarly distributed glycoprotein in the developing brain of the tammar wallaby (Macropus eugenii). The degree of homology is the same between wallaby glycoprotein and alpha 2HS glycoprotein as between fetuin and alpha 2HS glycoprotein (46%). Antibodies made to synthetic peptides of fetuin were used to identify the wallaby glycoprotein. A polyclonal antibody to the purified glycoprotein was used for immunocytochemical identification of brain cells positive for this protein.

Amino Acid Sequence↗
PubMed1991

Identification of the rat bone 60K acidic glycoprotein as alpha 2HS-glycoprotein.

Previous reports have described an Mr 60,000-64,000 glycoprotein present in guanidium chloride (GdmCl)/EDTA extracts of bovine and rat bone. We have purified this protein from the long bones of rats and have raised polyclonal antibodies to the purified protein. The 60K glycoprotein has amino acid and carbohydrate compositions that are similar to those reported for the 60-64K protein(s). Several lines of evidence indicate that the 60K bone glycoprotein is the rat homologue of human alpha 2HS-glycoprotein. First, immunochemical data demonstrated that the 60K bone glycoprotein was present in serum as well as in EDTA/GdmCl extracts of bone. Second, immunolocalization and metabolic labelling experiments showed that the 60K protein is synthesized in liver and not in bone cells, although it is sequestered in vascularized regions of bone matrix. Finally, the NH2-terminal sequence for the rat 60K bone glycoprotein was highly similar to that of the human alpha 2HS-glycoprotein A chain. A surprising finding was that small amounts of contaminating 60K/alpha 2HS-glycoprotein were found in several protein fractions purified by ion-exchange chromatography of bone EDTA/GdmCl extracts. Because this protein was found to be highly immunogenic, the presence of anti-60K antibodies in anti-sera prepared against purified bone proteins should be considered as a potential problem.

Amino Acid Sequence↗
PubMed1973

Studies on bone matrix glycoproteins. Incorporation of (1-14C)glucosamine and plasma (14C)glycoprotein into rabbit cortical bone.

The radioactively labelled constituents present in bone matrix were compared 12 days after injection of either [(14)C]glucosamine or plasma [(14)C]glycoprotein. Both precursors are utilized in the synthesis of organic matrix by bone tissue. Cortical bone from animals injected with [(14)C]glucosamine contains radioactivity derived from glucosamine and plasma glycoproteins and all glycoprotein fractions are labelled. Plasma [(14)C]glycoprotein labels the less acidic glycoproteins to a greater extent than the more acidic components. An antibody has been raised against the less-acidic-glycoprotein fraction of bone. The latter contains a glycoprotein of alpha-mobility that appears to be concentrated specifically in bone tissue and which is present also in plasma. This alpha-glycoprotein accounts for a large proportion of the components labelled and retained in bone matrix after [(14)C]glucosamine injection.

Albumins↗
PubMed1977

Some factors affecting the production, by cultured baby-hamster kidney cells, of BHK glycoprotein I which cross-reacts immunologically with Tamm-Horsfall glycoprotein.

Cultured baby-hamster kidney cells (BHK-21/C13), which are adapted to grow in suspension (strain 2P), roduce a glycoprotein, termed BHK glycoprotein I, which cross-reacts immunologically with hamster urinary (Tamm-Horsfall glycoprotein. BHK glycoprotein I was isolated in an electrophoretically (sodium dodecyl sulphate/polyacrylamide gel) homogeneous form by application of affinity chromatography to the medium in which cells had been cultured. Insolubilized anti-(Tamm-Horsfall glycoprotein immunoglobulin G) was used as the adsorbent. The amount of BHK glycoprotein I associated with the cultured cells was found by both radioimmunoassay and immunofluorescence to be related to the amount of Ca2+ in the medium and to the particular stage of the cell cycle. 5'-Nucleotidase was also shed by the cells into the culture medium in amounts related to the stage of the cell cycle. The turnover of hamster Tamm-Horsfall glycoprotein in vivo appeared to be considerably more rapid than can be accounted for by cell turnover. Hamster Tamm-Horsfall glycoprotein was shown to be ineffective in inhibiting agglutination of chicken erythrocytes caused by influenza virus.

Calcium↗
PubMed1979

Synthesis of membrane glycoproteins in rat small-intestinal villus cells. Redistribution of L-[1,5,6-3H]fucose-labelled membrane glycoproteins among Golgi, lateral basal and microvillus membranes in vivo.

The biogenesis of plasmalemma glycoproteins of rat small-intestinal villus cells was studied by following the incorporation of l-[1,5,6-(3)H]fucose, given intraperitoneally with and without chase, into Golgi, lateral basal and microvillus membranes. Each membrane fraction showed distinct kinetics of incorporation of labelled fucose and was differently affected by the chase, which produced a much greater decrease in incorporation of label into Golgi and microvillus than into lateral basal membranes. The kinetic data suggest a redistribution of newly synthesized glycoproteins from the site of fucosylation, the Golgi complex, directly into both lateral basal and microvillus membranes. The observed biphasic pattern of label incorporation into the microvillus membrane fraction may be evidence for a second indirect route of incorporation. The selective effect of the chase suggests the presence of two different pools of radioactive fucose in the Golgi complex that differ in (1) their accessibility to dilution with non-radioactive fucose, and (2) their utilization for the biosynthesis of membrane glycoproteins subsequently destined for either the microvillus or the lateral basal parts of the plasmalemma. The radioactively labelled glycoproteins of the different membrane fractions were separated by sodium dodecyl sulphate/polyacrylamide-slab-gel electrophoresis and identified by fluorography. The patterns of labelled glycoproteins in Golgi and lateral basal membranes were identical at all times. At least 14 bands could be identified shortly after radioactive-fucose injection. Most seemed to disappear at later times, although one of them, which was never observed in microvillus membranes, increased in relative intensity. All but two of the labelled glycoproteins present in the microvillus membrane corresponded to those observed in Golgi and lateral basal membranes shortly after fucose injection. The patterns of labelled glycoproteins in all membrane fractions were little affected by the chase. These data support a flow concept for the insertion of most surface-membrane glycoproteins of the intestinal villus cells.

Animals↗
PubMed1992

Identification of two porcine brush border glycoproteins that bind the K88ac adhesin of Escherichia coli and correlation of these glycoproteins with the adhesive phenotype.

In this study, we identified two brush border glycoproteins (210 and 240 kDa) that bind both K88ac+ Escherichia coli and purified K88ac adhesin. The specificity of these binding glycoproteins for the K88ac adhesin was demonstrated in studies in which the binding of 35S-labeled K88ac+ E. coli and biotinylated K88ac adhesin to these glycoproteins was blocked in the presence of a 100-fold molar excess of unlabeled K88ac adhesin but not in the presence of the K99 adhesin. Pretreatment of adhesive brush borders with sodium metaperiodate destroyed both binding activities, indicating that the interaction between the K88ac adhesin and the binding glycoproteins requires the glycoprotein carbohydrate moiety. It was demonstrated previously that K88ac+ E. coli binds to adhesive brush borders but not to nonadhesive brush borders (R. Sellwood, R. A. Gibbons, G. W. Jones, and J. M. Rutter, J. Med. Microbiol. 8:405-411, 1975). In the present study, brush borders isolated from 10 different pigs were tested first for brush border adhesiveness and then for the presence of the binding glycoproteins. In all cases, the binding glycoproteins were detected only in the adhesive brush border preparations. These two binding glycoproteins may be the receptors used by K88ac+ ETEC to adhere to intestinal brush border cells. Their presence on adhesive brush borders and absence on nonadhesive brush borders may be the basis for resistance and susceptibility of pigs to K88ac+ ETEC infections.

Adhesins, Escherichia coli↗
PubMed1989

Evidence for attachment of fatty acid to varicella-zoster virus glycoproteins and effect of cerulenin on the maturation of varicella-zoster virus glycoproteins.

Varicella-zoster virus (VZV) contains four major glycoproteins designated gpI, gpII, gpIII, and gpIV. In the present study the presence and role of fatty acids in these glycoproteins were examined. The incorporation of fatty acid into the glycoproteins that span the membranes of VZV was studied. For this, virus-infected human embryo fibroblast cells were labeled with [3H]-palmitic acid, an extract of the cells was treated with monoclonal antibodies to VZV glycoproteins, and the precipitate was analyzed by SDS-PAGE. The electrophoretic pattern showed that gpI was heavily labeled and that gpII and gpIV were lightly labeled. Cerulenin, an antibiotic that inhibits de novo fatty acid biosynthesis, was used to examine the effects of fatty acids on replication of VZV and posttranslation processing of glycoproteins. Treatment of the cells with cerulenin significantly inhibited viral growth, but did not affect protein synthesis in the cells. Examination of processing of viral glycoproteins in these cerulenin-treated cells revealed the accumulation of precursor proteins and a decrease in the amount of mature glycoproteins. These data suggest that fatty acid acylation of VZV glycoproteins is necessary for formation of complete infectious virions.

Antibodies, Monoclonal↗
PubMed1988

Purification of the 170- to 180-kilodalton membrane glycoprotein associated with multidrug resistance. 170- to 180-kilodalton membrane glycoprotein is an ATPase.

170-180-kDa membrane glycoprotein (P-glycoprotein) associated with multidrug resistance is involved in drug transport mechanisms across the plasma membrane of resistant cells. From sequence analysis of cDNAs of the P-glycoprotein gene, it is postulated that the active drug-efflux pump function may be attributable to the protein. However, purification of the P-glycoprotein while preserving its enzymatic activity has not been reported. In this study, we have purified the P-glycoprotein from the human myelogenous leukemia K562 cell line resistant to adriamycin (K562/ADM) by means of one-step immunoaffinity chromatography using a monoclonal antibody against P-glycoprotein. The procedure was simple and efficiently yielded an electrophoretically homogeneous P-glycoprotein sample. By solubilization with 3-[(3-cholamidopropyl)dimethylammonio]-1-propanesulfonate, the purified P-glycoprotein was found to have ATPase activity. This ATP hydrolysis may be coupled with the active efflux of anticancer drugs across the plasma membrane of multidrug-resistant cells.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed1993

Alpha 1-acid glycoprotein expression in human leukocytes: possible correlation between alpha 1-acid glycoprotein and inflammatory cytokines in rheumatoid arthritis.

alpha 1-Acid glycoprotein is an acute-phase reactant that becomes markedly elevated in serum during inflammation and has an immunosuppressive effect on lymphocyte functions. Patients with collagen diseases had significant increases of alpha 1-acid glycoprotein in their serum and on the surface of peripheral leukocytes compared with controls. The levels from patients with rheumatoid arthritis were higher than those from patients with systemic lupus erythematosus, mixed connective tissue disease, and Behçet's disease. In patients with rheumatoid arthritis, the value of serum alpha 1-acid glycoprotein correlated with disease activity. Among leukocyte subpopulations, monocytes showed more alpha 1-acid glycoprotein on their surface than polymorphonuclear leukocytes and lymphocytes. The cell surface expression of alpha 1-acid glycoprotein on cultured monocytes surface peaked after 48 h. Interleukin-1 beta and tumor necrosis factor-alpha stimulated the production of alpha 1-acid glycoprotein RNA message in peripheral blood mononuclear cells over 18-24 h during cell culture. The results show that serum alpha 1-acid glycoprotein reflects systemic disease activity in rheumatoid arthritis. Furthermore, monocytes may serve as a source of production of alpha 1-acid glycoprotein.

Adult↗
PubMed1992

Identification of equine herpesvirus 4 glycoprotein G: a type-specific, secreted glycoprotein.

Equine herpesvirus 4 (EHV4) glycoproteins of M(r) 63K and 250K were identified in the supernatant of infected cell cultures. The 63K glycoprotein was type-specific; that is, it reacted with monospecific sera from horses that had been immunized or infected with EHV4, but not with monospecific sera from horses immunized or infected with EHV1, a closely related alphaherpesvirus. It was postulated that the secreted protein may be the homologue of similarly secreted glycoproteins of herpes simplex virus 2 glycoprotein G (HSV2 gG) and pseudorabies virus (PRV) gX, which is the homologue of HSV2 gG. The US region of the EHV4 genome, toward the internal repeat structure, was sequenced. Four open reading frames (ORFs) were identified of which ORF4 showed 52% similarity to the gene-encoding PRV gX in a 650-nucleotide region. ORF4 coded for a primary translational product of 405 amino acids which has a predicted size of 44K. The amino acid sequence of ORF4 showed 28% identity with PRV gX and 16% identity with HSV2 gG, although significantly greater identity was observed in the N-terminal region including the conservation of 4 cysteine residues. Accordingly, we designate ORF4 as EHV4 gG. The predicted amino acid sequence of the EHV4 gG showed characteristics of an envelope glycoprotein. Expression of the entire EHV4 gG gene in the bacterial expression vector pGEX-3X produced a type-specific fusion protein of M(r) 70K of which the gG portion composes 43K. Antibody that was affinity purified from selected portions of Western blots containing the 70K gG fusion protein reacted with the 63K secreted glycoprotein. Conversely, antibody affinity purified to the 63K secreted product reacted with the 70K gG fusion protein. These results showed that the EHV4 63K secreted glycoprotein was EHV4 gG, the third alphaherpesvirus gG homologue known to be, at least in part, secreted. The type-specificity of this glycoprotein provides, for the first time, the opportunity to differentiate between antibodies present in polyclonal sera from EHV4, EHV1, and dual-infected horses and this has important implications for understanding the epidemiology of these viruses.

Amino Acid Sequence↗
PubMed1979

Changes in serum alpha 1 antitrypsin, alpha1 acid glycoprotein and beta 2 glycoprotein I in patients with malignant hepatocellular carcinoma.

Serum alpha 1 antitrypsin, alpha 1 acid glycoprotein and beta 2 glycoprotein I concentrations were determined in 36 patients with malignant hepatocellularcarcinoma, 30 with cirrhosis and 35 with hepatitis by quantitative immunoelectrophoresis. Serum alpha 1 antitrypsin and alpha 1 acid glycoprotein levels were significantly higher in patients with hepatocellularcarcinoma than in those with cirrhosis (p less than 0.001) or hepatitis (p less than 0.001). Elevated levels of alpha 1 antitrypsin were found in 88.9% of patients with hepatoma compared to 23.3% of patients with cirrhosis and 28.6% of patients with hepatitis. Raised levels of alpha 1 acid glycoprotein were also found in 80.6% of patients with hepatoma compared to 20% of patients with cirrhosis and in only 5.7% of patients with hepatitis. beta 2 glycoprotein I levels were similar in the three conditions and therefore not useful for differential diagnosis. In monitoring the progress of tumor growth alpha 1 antitrypsin and alpha 1 acid glycoprotein levels were found to increase during the growth phase. Measurements of these two glycoproteins are suggested for differential diagnosis of these liver diseases, as tumor markers for the detection of hepatocarcinoma, and for the monitoring of the progress during treatment.

Carcinoma, Hepatocellular↗
PubMed1995

A 7-kDa pollen coating-borne peptide from Brassica napus interacts with S-locus glycoprotein and S-locus-related glycoprotein.

Two S(self-incompatibility)-family glycoproteins have been identified in stigmas of self-compatible (SC) Brassica napus L. by their ability to interact, in vitro, with a peptide fraction from the pollen coating containing a PCP7-like peptide, PCP7 (pollen coat peptide 7[kDa]) being a pollen coat peptide from self-incompatible (SI) Brassica oleracea L. which has been shown to interact with S-locus glycoproteins (SLGs). Electrophoretic purification and N-terminal amino-acid sequencing of these stigmatic glycoproteins confirmed one to be an SLG and the other to be a class 1 S-locus-related glycoprotein (SLR1). This is the first reported isolation of SLG and SLR1 proteins from SC B. napus and the first time that a PCP7-like peptide has been shown to interact with an S-class glycoprotein other than SLG. On the basis of these findings we suggest that an ability to interact with PCP7 or a PCP7-like peptide is a property of SLGs, SLR1s and possibly other S-glycoproteins and may thus provide a novel route to the identification of these glycoproteins in stigmatic extracts. The levels of the SLG in stigmas of SC B. napus were relatively much lower than the levels of the SLR1--the opposite to the situation in SI B. oleracea. This finding is discussed in terms of translational control of SLGs and SLR1, and the possible implications for self-incompatibility in B. oleracea and self-compatibility in B. napus.

Amino Acid Sequence↗
PubMed1977

Synaptosomal plasma membrane glycoproteins. II. Isolation of fucosyl-glycoproteins by affinity chromatography on the Ulex europeus lectin specific for L-fucose.

After solubilization in sodium dodecyl sulphate, almost 90% of synaptosomal plasma membrane glycoproteins were separated from the bulk of synaptosomal plasma membrane proteins by sequential affinity chromatography on two immobilized lectins: concanavalin A and the Ulex europeus lectin specific for L-fucose. Four fractions were obtained and their sugar composition and electrophoretic patterns were determined. Fucosyl-glycoproteins contain more than 26% of protein and 85% of the protein-bound sugar of synaptosomal plasma membrane; hence they constitute a major class of glycoproteins in these membranes. The presence of some glucose in glycoproteins fractions obtained after affinity chromatography on the two lectins suggests that this sugar could be a structural component of some brain glycoproteins. Polyacrylamide gel electrophoresis revealed at least 28 major bands in fucosylglycoprotein fractions, and 11 in other fractions. Several of these major bands appear to contain more than one glycoprotein each. This heterogeneity appears to be mostly the result of the heterogeneity of the neuronal population in the central nervous system. Microheterogeneity of glycoprotein sugar chains and possible contamination of synaptosomal plasma membranes play, in our opinion, only a minor role.

Animals↗
PubMed1983

Role of glycoproteins in neuronal differentiation. Inhibition of neurite outgrowth and the major cell surface glycoprotein of murine neuroblastoma cells by a purified tunicamycin homologue.

Mouse neuroblastoma cells in culture can be induced to differentiate morphologically by serum deprivation or by dibutyryl cyclic AMP (db-cAMP), e.g. they appear flattened, adhere more firmly to the culture substratum and extend long neuritic processes, and thus represent a widely used model system for neuronal cells. This differentiation is accompanied by modulation of cell surface components, such as the induction of a high molecular weight (HMW) glycoprotein (200 kD). We have studied the role of glycoproteins in the process of neuronal differentiation, using a purified homologue of the antibiotic tunicamycin (Al-tunicamycin) and neuroblastoma N115 cells grown in culture. Al-tunicamycin markedly inhibited (up to 60-75%) the incorporation of radioactively labelled sugars into cellular proteins of differentiating neuroblastoma cells. Concomitantly, the cells altered their morphology, they became rounded and less adhesive and retracted their neurites. Changes in the appearance, glycosylation and electrophoretic mobility of several cellular and secreted glycoproteins were observed, when cells were incubated in the presence of Al-tunicamycin. The most striking effect of Al-tunicamycin on the composition of cellular glycoproteins was the marked reduction in appearance of the 200 kD glycoprotein. The findings suggest that glycoproteins and in particular the neuron-specific 200 kD glycoprotein, are related to morphological differentiation processes, mainly to cellular adhesion and neurite outgrowth.

Animals↗
PubMed1986

Neutralization epitope of varicella zoster virus on native viral glycoprotein gp118 (VZV glycoprotein gpIII).

Varicella-zoster virus (VZV) specifies the formation of several glycoproteins, including a 118,000-Da mature structural product (gp118). The biologic and biochemical properties of gp118 were studied after production of murine monoclonal antibodies to both a lowpassage laboratory strain (VZV-32) and an attenuated vaccine strain (VZV-Oka). Structural analyses performed with the three glycosidases endo-beta-N-acetylglucosaminidase H (endoglycosidase H), endo-beta-N-acetylglucosaminidase F (endoglycosidase F), and endo-alpha-N-acetylgalactosaminidase demonstrated that gp118 was predominantly an N-linked complex type glycoprotein built upon a polypeptide backbone of approximately 79,000 Da. Sialic acid residues were present on the mature glycoprotein, but these terminal sugars were absent from the partially glycosylated intermediate forms recovered from monensin-treated infected cultures. Unlike another VZV-specified glycoprotein gp98, no new oligosaccharide moieties were observed on gp118 after addition of tunicamycin to VZV-infected cultures. By plaque reduction assays with a panel of monoclonal antibodies, we defined an epitope on this glycoprotein which elicited a complement-independent neutralizing antibody response of high magnitude. The epitope was highly conserved, since it was present on a laboratory VZV strain, wild type isolates, as well as the attenuated vaccine strain (VZV-Oka). Competitive blocking experiments with the same anti-gp118 monoclonal antibodies indicated that four neutralizing antibodies were directed against similar or identical epitopes whereas one nonneutralizing antibody reacted with a different antigenic site. Thus, this study demonstrates the presence of an immunodominant neutralization epitope on native viral glycoprotein gp118. Under a new consensus nomenclature, this glycoprotein will be designated VZV gpIII.

Antibodies, Monoclonal↗
PubMed1992

Recognition of the oligosaccharide and protein moieties of glycoproteins by the UDP-Glc:glycoprotein glucosyltransferase.

It was found, in cell-free assays, that the Man8GlcNAc2 and Man7GlcNAc2 isomers having the mannose unit to which the glucose is added were glucosylated by the rat liver glucosyltransferase at 50 and 15%, respectively, of the rate of Man9GlcNAc2 glucosylation. This indicates that processing by endoplasmic reticulum mannosidases decreases the extent of glycoprotein glucosylation. All five different glycoproteins tested (bovine and porcine thyroglobulins, phytohemagglutinin, soybean agglutinin, and bovine pancreas ribonuclease B) were found to be poorly glucosylated or not glucosylated unless they were subjected to treatments that modified their native conformations. The effect of denaturation was not to expose the oligosaccharides but to make protein determinants, required for enzymatic activity, accessible to the glucosyltransferase because (a) cleavage of denatured glycoproteins by unspecific (Pronase) or specific (trypsin) proteases abolished their glucose acceptor capacities almost completely except when the tryptic peptides were held together by disulfide bonds and (b) high mannose oligosaccharides in native glycoproteins, although poorly glucosylated or not glucosylated, were accessible to macromolecular probes as concanavalin A-Sepharose, endo-beta-N-acetylglucosaminidase H, and jack bean alpha-mannosidase. In addition, denatured, endo-beta-N-acetylglucosaminidase H deglycosylated glycoproteins were found to be potent inhibitors of the glucosylation of denatured glycoproteins. It is suggested that in vivo only unfolded, partially folded, and malfolded glycoproteins are glucosylated and that glucosylation stops upon adoption of the correct conformation, a process that hides the protein determinants (possibly hydrophobic amino acids) from the glucosyltransferase.

Animals↗
PubMed2001

Glycoengineering of therapeutic glycoproteins: in vitro galactosylation and sialylation of glycoproteins with terminal N-acetylglucosamine and galactose residues.

Therapeutic glycoproteins produced in different host cells by recombinant DNA technology often contain terminal GlcNAc and Gal residues. Such glycoproteins clear rapidly from the serum as a consequence of binding to the mannose receptor and/or the asialoglycoprotein receptor in the liver. To increase the serum half-life of these glycoproteins, we carried out in vitro glycosylation experiments using TNFR-IgG, an immunoadhesin molecule, as a model therapeutic glycoprotein. TNFR-IgG is a disulfide-linked dimer of a polypeptide composed of the extracellular portion of the human type 1 (p55) tumor necrosis factor receptor (TNFR) fused to the hinge and Fc regions of the human IgG(1) heavy chain. This bivalent antibody-like molecule contains four N-glycosylation sites per polypeptide, three in the receptor portion and one in the Fc. The heterogeneous N-linked oligosaccharides of TNFR-IgG contain sialic acid (Sia), Gal, and GlcNAc as terminal sugar residues. To increase the level of terminal sialylation, we regalactosylated and/or resialylated TNFR-IgG using beta-1,4-galactosyltransferase (beta1,4GT) and/or alpha-2,3-sialyltransferase (alpha2,3ST). Treatment of TNFR-IgG with beta1,4GT and UDP-Gal, in the presence of MnCl(2), followed by MALDI-TOF-MS analysis of PNGase F-released N-glycans showed that the number of oligosaccharides with terminal GlcNAc residues was significantly decreased with a concomitant increase in the number of terminal Gal residues. Similar treatment of TNFR-IgG with alpha2,3ST and CMP-sialic acid (CMP-Sia), in the presence of MnCl(2), produced a molecule with an approximately 11% increase in the level of terminal sialylation but still contained oligosaccharides with terminal GlcNAc residues. When TNFR-IgG was treated with a combination of beta1,4GT and alpha2,3ST (either in a single step or in a stepwise fashion), the level of terminal sialylation was increased by approximately 20-23%. These results suggest that in vitro galactosylation and sialylation of therapeutic glycoproteins with terminal GlcNAc and Gal residues can be achieved in a single step, and the results are similar to those for the stepwise reaction. This type of in vitro glycosylation is applicable to other glycoproteins containing terminal GlcNAc and Gal residues and could prove to be useful in increasing the serum half-life of therapeutic glycoproteins.

Acetylglucosamine↗
PubMed1997

Carbohydrate moiety of Plasmodium falciparum glycoproteins: the nature of the carbohydrate-peptide linkage in the MSP-2 glycoprotein.

Metabolic labelling of Plasmodium falciparum parasites with [3H]GlcN, [3H]Man, [3H]Gal and [3H]ethanolamine, and subsequent purification by SDS-PAGE of the labelled material provided effective labelling of the MSP-1, 195 kDa, and MSP-2, 42-53 kDa, glycoproteins. Reductive beta-elimination of the MSP-2 released from the gel consisted of glycopeptides containing labelled sugars. Processing of the eliminated components and identification of the sugar residues demonstrated the presence of N-acetylglucosaminitol and N-acetylgalactosaminitol amongst other labelled sugars. Reductive beta-elimination with sodium hydroxide-sodium borotritide-borohydride showed the presence of glucosaminitol and alanine in the hydrolysis products. The MSP-2 was retained on solid phase wheat-germ agglutinin and was released from the lectin by treatment with GlcNAc. Upon treatment with O-glycanase the MSP-2 glycoprotein released labelled amino sugar, and derived oligosaccharides on treatment with exoglycosidases released labelled components corresponding to the metabolically incorporated sugars. Labelled Gal was incorporated into the MSP-2 glycoprotein using [3H]UDP-Gal and galactosyltransferase. The galactosylated glycoprotein released labelled Gal upon treatment with beta-galactosidase. The results of the present study suggest that the carbohydrate chains of the MSP-2 glycoprotein are attached to the protein backbone via GlcNAc- and GalNAc-serine/threonine in O-glycosyl linkage and the glycoprotein has terminal GlcNAc and Gal residues. The carbohydrate moieties of MSP-2, glycoprotein consist mainly of short chains linked to the protein core.

Animals↗