A lectin-resistant mouse lymphoma cell line is deficient in glucosidase II, a glycoprotein-processing enzyme.
10 Sep 1982-Journal of Biological Chemistry (American Society for Biochemistry and Molecular Biology)-Vol. 257, Iss: 17, pp 10357-10363
TL;DR: In vitro enzyme assays demonstrated that the PHAR2.7 cell line is deficient in glucosidase II, the enzyme which removes the two inner glucose residues from the oligosaccharides of newly glycosylated proteins.
About: This article is published in Journal of Biological Chemistry.The article was published on 1982-09-10 and is currently open access. It has received 107 citations till now. The article focuses on the topics: Oligosaccharide & Mannose.
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TL;DR: It is time for the diverse functional roles of glycans to be fully incorporated into the mainstream of biological sciences, as they are no different from other major macromolecular building blocks of life, simply more rapidly evolving and complex.
Abstract: Simple and complex carbohydrates (glycans) have long been known to play major metabolic, structural and physical roles in biological systems. Targeted microbial binding to host glycans has also been studied for decades. But such biological roles can only explain some of the remarkable complexity and organismal diversity of glycans in nature. Reviewing the subject about two decades ago, one could find very few clear-cut instances of glycan-recognition-specific biological roles of glycans that were of intrinsic value to the organism expressing them. In striking contrast there is now a profusion of examples, such that this updated review cannot be comprehensive. Instead, a historical overview is presented, broad principles outlined and a few examples cited, representing diverse types of roles, mediated by various glycan classes, in different evolutionary lineages. What remains unchanged is the fact that while all theories regarding biological roles of glycans are supported by compelling evidence, exceptions to each can be found. In retrospect, this is not surprising. Complex and diverse glycans appear to be ubiquitous to all cells in nature, and essential to all life forms. Thus, >3 billion years of evolution consistently generated organisms that use these molecules for many key biological roles, even while sometimes coopting them for minor functions. In this respect, glycans are no different from other major macromolecular building blocks of life (nucleic acids, proteins and lipids), simply more rapidly evolving and complex. It is time for the diverse functional roles of glycans to be fully incorporated into the mainstream of biological sciences.
1,588 citations
TL;DR: A number of inhibitors have been identified that interfere with glycoprotein biosynthesis, processing, or transport, such as tunicamycin, tridecaptin, and flavomycin this paper.
Abstract: A number of glycoproteins have oligosaccharides linked to protein in a GlcNAc----asparagine bond. These oligosaccharides may be either of the complex, the high-mannose or the hybrid structure. Each type of oligosaccharides is initially biosynthesized via lipid-linked oligosaccharides to form a Glc3Man9GlcNAc2-pyrophosphoryl-dolichol and transfer of this oligosaccharide to protein. The oligosaccharide portion is then processed, first of all by removal of all three glucose residues to give a Man9GlcNAc2-protein. This structure may be the immediate precursor to the high-mannose structure or it may be further processed by the removal of a number of mannose residues. Initially four alpha 1,2-linked mannoses are removed to give a Man5 - GlcNAc2 -protein which is then lengthened by the addition of a GlcNAc residue. This new structure, the GlcNAc- Man5 - GlcNAc2 -protein, is the substrate for mannosidase II which removes the alpha 1,3- and alpha 1,6-linked mannoses . Then the other sugars, GlcNAc, galactose, and sialic acid, are added sequentially to give the complex types of glycoproteins. A number of inhibitors have been identified that interfere with glycoprotein biosynthesis, processing, or transport. Some of these inhibitors have been valuable tools to study the reaction pathways while others have been extremely useful for examining the role of carbohydrate in glycoprotein function. For example, tunicamycin and its analogs prevent protein glycosylation by inhibiting the first step in the lipid-linked pathway, i.e., the formation of Glc NAc-pyrophosphoryl-dolichol. These antibiotics have been widely used in a number of functional studies. Another antibiotic that inhibits the lipid-linked saccharide pathway is amphomycin, which blocks the formation of dolichyl-phosphoryl-mannose. In vitro, this antibiotic gives rise to a Man5GlcNAc2 -pyrophosphoryl-dolichol from GDP-[14C]mannose, indicating that the first five mannose residues come directly from GDP-mannose rather than from dolichyl-phosphoryl-mannose. Other antibodies that have been shown to act at the lipid-level are diumycin , tsushimycin , tridecaptin, and flavomycin. In addition to these types of compounds, a number of sugar analogs such as 2-deoxyglucose, fluoroglucose , glucosamine, etc. have been utilized in some interesting experiments. Several compounds have been shown to inhibit glycoprotein processing. One of these, the alkaloid swainsonine , inhibits mannosidase II that removes alpha-1,3 and alpha-1,6 mannose residues from the GlcNAc- Man5GlcNAc2 -peptide. Thus, in cultured cells or in enveloped viruses, swainsonine causes the formation of a hybrid structure.(ABSTRACT TRUNCATED AT 400 WORDS)
1,067 citations
01 Jan 1987
TL;DR: A number of glycoproteins have oligosaccharides linked to protein in a GlcNAc----asparagine bond that are either of the complex, the high-mannose or the hybrid structure and a number of inhibitors have been identified that interfere with glycoprotein biosynthesis, processing, or transport.
900 citations
TL;DR: The lectin-monoglucosylated oligosaccharide interaction is one of the alternative ways by which cells retain improperly folded glycoproteins in the endoplasmic reticulum and increases folding efficiency, prevents premature glycoprotein oligomerization and degradation, and suppresses formation of non-native disulfide bonds.
Abstract: An unconventional mechanism for retaining improperly folded glycoproteins and facilitating acquisition of their native tertiary and quaternary structures operates in the endoplasmic reticulum. Recognition of folding glycoproteins by two resident lectins, membrane-bound calnexin and its soluble homolog, calreticulin, is mediated by protein-linked monoglucosylated oligosaccharides. These oligosaccharides contain glucose (Glc), mannose (Man), and N-acetylglucosamine (GlcNAc) in the general form Glc1Man7-9GlcNAc2. They are formed by glucosidase I- and II-catalyzed partial deglucosylation of the oligosaccharide transferred from dolichol diphosphate derivatives to Asn residues in nascent polypeptide chains (Glc3Man9GlcNAc2). Further deglucosylation of the oligosaccharides by glucosidase II liberates glycoproteins from their calnexin/calreticulin anchors. Monoglucosylated glycans are then recreated by the UDP-Glc:glycoprotein glucosyltransferase (GT), and thus recognized again by the lectins, only when linked to improperly folded protein moieties, as GT behaves as a sensor of glycoprotein conformations. The deglucosylation-reglucosylation cycle continues until proper folding is achieved. The lectin-monoglucosylated oligosaccharide interaction is one of the alternative ways by which cells retain improperly folded glycoproteins in the endoplasmic reticulum. Although it decreases the folding rate, it increases folding efficiency, prevents premature glycoprotein oligomerization and degradation, and suppresses formation of non-native disulfide bonds by hindering aggregation and thus allowing interaction of protein moieties of folding glycoproteins with classical chaperones and other proteins that assist in folding.
633 citations
626 citations
References
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TL;DR: Modifications are introduced, based on a test given by Feigl for reducing sugars, which eliminate the heating step, and in which the reagents are applied in organic solvents, thus removing the danger of migration of the sugar spots.
Abstract: THE ammoniacal silver nitrate spray1 used for the detection of sugars has several disadvantages; to those mentioned by Partridge2 should be added the necessity for very careful control of the heating step, particularly important in laboratories lacking special apparatus. We have introduced modifications, based on a test given by Feigl3 for reducing sugars, which eliminate the heating step, and in which the reagents are applied in organic solvents, thus removing the danger of migration of the sugar spots. The method has been in use for more than a year, and has proved easy to handle and extremely reliable.
3,526 citations
1,330 citations
TL;DR: Glycopeptide binding to lentil lectin-Sepharose was enhanced by the exposure of terminal N-acetylglucosamine residues on the glycopeptides, whereas binding to pea lectin -Sepharoses was enhancedBy the exposure to terminal mannose residues, and the differences in carbohydrate binding specificity were exploited to fractionate a mixture of [2-3H]mannose-labeled glycoproteins derived from mouse lymphoma cell gly
564 citations
TL;DR: This chapter elaborates the primary structure and metabolism of the N -linked glycans, and presents the hypothesis that the catabolism of N -acetyl-lactosainine glycans starts by the action of endo-2-acetamido- 2-deoxy-β- D -glucosidases in liberating oligosaccharides that are then degraded by exoglycosidases.
Abstract: Publisher Summary This chapter provides an overview of the primary structure of glycoprotein glycans. There exists a certain unity of structure among glycans. All are derived by the substitution of common, core oligosaccharides ( inv fractions) by variable oligosaccharide structures ( var fractions), which are the basis of their specificity. The var fractions present a limited number of the types of structure. In the case of N -glycosylproteins, in which the glycan-protein bond is asparaginyl-2-acetamido-2-deoxyglucose, the glycans are of three fundamental types: the oligomannosidic, the N -acetyllactosaminic, and the mixed, oligomannosidic- N -acetyl-lactosaminic. The determination of the structures of oligosaccharides from the urines of glycoproteinoses, diseases characterized by a deficit in lysosomal enzymes catabolizing the glycans of glycoprotein, allows reconstruction of the different stages of glycoprotein catabolism, and presentation of the hypothesis that the catabolism of N -acetyl-lactosainine glycans starts by the action of endo-2-acetamido-2-deoxy-β- D -glucosidases in liberating oligosaccharides that are then degraded by exoglycosidases. This chapter elaborates the primary structure and metabolism of the N -linked glycans. Development and improvement of procedures for the study of the primary structure of glycans is also discussed.
528 citations
TL;DR: Iodinated glycopeptides (50 to 200 x lo3 cpm/pmol) have been utilized to examine the structural determinants affecting interaction with the saccharide binding site of concanavalin A by Scatchard plot analyses of saturation curves.
447 citations