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Li M, Zhu P, Huang Z, Huang Y, Lv X, Zheng Q, Zhu Z, Fan Z, Yang Y, Shi P. Aspirin damages the cell wall of Saccharomyces cerevisiae by inhibiting the expression and activity of dolichol-phosphate mannose synthase 1. FEBS Lett 2022; 596:369-380. [PMID: 35028934 DOI: 10.1002/1873-3468.14283] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2021] [Revised: 12/04/2021] [Accepted: 12/12/2021] [Indexed: 11/10/2022]
Abstract
Aspirin is a commonly used anti-inflammatory, analgesic and antithrombotic drug. It has attracted attention due to its potential antifungal therapeutic effect; however, the molecular mechanism is poorly understood. Here, the effects of aspirin on the cell wall of Saccharomyces cerevisiae were explored. We observed by scanning electron microscopy that aspirin could damage the cell wall ultrastructure. Meanwhile, a cellular surface hydrophobicity (CSH) assay showed that aspirin increased the hydrophobicity of the yeast cell surface. A drug sensitivity assay indicated that the overexpression of dolichol phosphate mannose synthase 1 (DPM1) reversed the cell wall damage and decreased the CSH induced by aspirin. Importantly, aspirin decreased the expression and enzyme activity of DPM1 in S. cerevisiae. Molecular docking results demonstrated that aspirin could directly bind to the Ser141 site of DPM1. Similarly, we found that aspirin damaged the cell wall and inhibited the expression of DPM1 in Candida albicans. These findings improve the current understanding of the action mode of aspirin and provide new strategies for antifungal drug design.
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Affiliation(s)
- Ming Li
- State Key Laboratory of Bioreactor Engineering, East China University of Science and Technology, China
| | - Pan Zhu
- State Key Laboratory of Bioreactor Engineering, East China University of Science and Technology, China
| | - Zhiwei Huang
- Key Lab of Science & Technology of Eco-textile, Ministry of Education, College of Chemistry, Chemical Engineering and Biotechnology, Donghua University, Shanghai, China
| | - Yunxia Huang
- School of Pharmacy, East China University of Science and Technology, Shanghai, China
| | - Xiaoguang Lv
- State Key Laboratory of Bioreactor Engineering, East China University of Science and Technology, China
| | - Qiaoqiao Zheng
- State Key Laboratory of Bioreactor Engineering, East China University of Science and Technology, China
| | - Ziting Zhu
- State Key Laboratory of Bioreactor Engineering, East China University of Science and Technology, China
| | - Zheyu Fan
- State Key Laboratory of Bioreactor Engineering, East China University of Science and Technology, China
| | - Youjun Yang
- School of Pharmacy, East China University of Science and Technology, Shanghai, China
| | - Ping Shi
- State Key Laboratory of Bioreactor Engineering, East China University of Science and Technology, China
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2
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Li ST, Lu TT, Xu XX, Ding Y, Li Z, Kitajima T, Dean N, Wang N, Gao XD. Reconstitution of the lipid-linked oligosaccharide pathway for assembly of high-mannose N-glycans. Nat Commun 2019; 10:1813. [PMID: 31000718 PMCID: PMC6472349 DOI: 10.1038/s41467-019-09752-3] [Citation(s) in RCA: 26] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2018] [Accepted: 03/29/2019] [Indexed: 11/11/2022] Open
Abstract
The asparagine (N)-linked Man9GlcNAc2 is required for glycoprotein folding and secretion. Understanding how its structure contributes to these functions has been stymied by our inability to produce this glycan as a homogenous structure of sufficient quantities for study. Here, we report the high yield chemoenzymatic synthesis of Man9GlcNAc2 and its biosynthetic intermediates by reconstituting the eukaryotic lipid-linked oligosaccharide (LLO) pathway. Endoplasmic reticulum mannosyltransferases (MTases) are expressed in E. coli and used for mannosylation of the dolichol mimic, phytanyl pyrophosphate GlcNAc2. These recombinant MTases recognize unique substrates and when combined, synthesize end products that precisely mimic those in vivo, demonstrating that ordered assembly of LLO is due to the strict enzyme substrate specificity. Indeed, non-physiological glycans are produced only when the luminal MTases are challenged with cytosolic substrates. Reconstitution of the LLO pathway to synthesize Man9GlcNAc2 in vitro provides an important tool for functional studies of the N-linked glycoprotein biosynthesis pathway. Attachment of the oligosaccharide Man9GlcNAc2 is required for glycoprotein folding and secretion but synthesizing this compound for structural and functional studies has remained challenging. Here, the authors achieve efficient Man9GlcNAc2 synthesis by reconstituting its biosynthetic pathway in vitro.
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Affiliation(s)
- Sheng-Tao Li
- Key Laboratory of Carbohydrate Chemistry and Biotechnology, Ministry of Education, School of Biotechnology, Jiangnan University, 214122, Wuxi, China
| | - Tian-Tian Lu
- Key Laboratory of Carbohydrate Chemistry and Biotechnology, Ministry of Education, School of Biotechnology, Jiangnan University, 214122, Wuxi, China
| | - Xin-Xin Xu
- Key Laboratory of Carbohydrate Chemistry and Biotechnology, Ministry of Education, School of Biotechnology, Jiangnan University, 214122, Wuxi, China
| | - Yi Ding
- Key Laboratory of Carbohydrate Chemistry and Biotechnology, Ministry of Education, School of Biotechnology, Jiangnan University, 214122, Wuxi, China
| | - Zijie Li
- Key Laboratory of Carbohydrate Chemistry and Biotechnology, Ministry of Education, School of Biotechnology, Jiangnan University, 214122, Wuxi, China
| | - Toshihiko Kitajima
- Key Laboratory of Carbohydrate Chemistry and Biotechnology, Ministry of Education, School of Biotechnology, Jiangnan University, 214122, Wuxi, China
| | - Neta Dean
- Department of Biochemistry and Cell Biology, Stony Brook University, Stony Brook, NY, 11794-5215, USA
| | - Ning Wang
- Key Laboratory of Carbohydrate Chemistry and Biotechnology, Ministry of Education, School of Biotechnology, Jiangnan University, 214122, Wuxi, China.
| | - Xiao-Dong Gao
- Key Laboratory of Carbohydrate Chemistry and Biotechnology, Ministry of Education, School of Biotechnology, Jiangnan University, 214122, Wuxi, China.
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Jadid N, Mialoundama AS, Heintz D, Ayoub D, Erhardt M, Mutterer J, Meyer D, Alioua A, Van Dorsselaer A, Rahier A, Camara B, Bouvier F. DOLICHOL PHOSPHATE MANNOSE SYNTHASE1 mediates the biogenesis of isoprenyl-linked glycans and influences development, stress response, and ammonium hypersensitivity in Arabidopsis. THE PLANT CELL 2011; 23:1985-2005. [PMID: 21558543 PMCID: PMC3123950 DOI: 10.1105/tpc.111.083634] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/25/2011] [Revised: 04/19/2011] [Accepted: 05/01/2011] [Indexed: 05/17/2023]
Abstract
The most abundant posttranslational modification in nature is the attachment of preassembled high-mannose-type glycans, which determines the fate and localization of the modified protein and modulates the biological functions of glycosylphosphatidylinositol-anchored and N-glycosylated proteins. In eukaryotes, all mannose residues attached to glycoproteins from the luminal side of the endoplasmic reticulum (ER) derive from the polyprenyl monosaccharide carrier, dolichol P-mannose (Dol-P-Man), which is flipped across the ER membrane to the lumen. We show that in plants, Dol-P-Man is synthesized when Dol-P-Man synthase1 (DPMS1), the catalytic core, interacts with two binding proteins, DPMS2 and DPMS3, that may serve as membrane anchors for DPMS1 or provide catalytic assistance. This configuration is reminiscent of that observed in mammals but is distinct from the single DPMS protein catalyzing Dol-P-Man biosynthesis in bakers' yeast and protozoan parasites. Overexpression of DPMS1 in Arabidopsis thaliana results in disorganized stem morphology and vascular bundle arrangements, wrinkled seed coat, and constitutive ER stress response. Loss-of-function mutations and RNA interference-mediated reduction of DPMS1 expression in Arabidopsis also caused a wrinkled seed coat phenotype and most remarkably enhanced hypersensitivity to ammonium that was manifested by extensive chlorosis and a strong reduction of root growth. Collectively, these data reveal a previously unsuspected role of the prenyl-linked carrier pathway for plant development and physiology that may help integrate several aspects of candidate susceptibility genes to ammonium stress.
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Affiliation(s)
- Nurul Jadid
- Institut de Biologie Moléculaire des Plantes du Centre National de la Recherche Scientifique, Université de Strasbourg, 67084 Strasbourg Cedex, France
- Department of Biology, Botanical and Plant Tissue Culture Laboratory, Sepuluh Nopember Institut of Technology (Its), Gedung H Kampus Its Sukolilo, Surabaya 60111, East-Java, Indonesia
| | - Alexis Samba Mialoundama
- Institut de Biologie Moléculaire des Plantes du Centre National de la Recherche Scientifique, Université de Strasbourg, 67084 Strasbourg Cedex, France
| | - Dimitri Heintz
- Institut de Biologie Moléculaire des Plantes du Centre National de la Recherche Scientifique, Université de Strasbourg, 67084 Strasbourg Cedex, France
| | - Daniel Ayoub
- Laboratoire de Spectrométrie de Masse Bio-Organique, Département des Sciences Analytiques, Institut Pluridisciplinaire Hubert Curien du Centre National de la Recherche Scientifique, Unité Mixte de Recherche 7178, Université de Strasbourg, 67087 Strasbourg Cedex, France
| | - Mathieu Erhardt
- Institut de Biologie Moléculaire des Plantes du Centre National de la Recherche Scientifique, Université de Strasbourg, 67084 Strasbourg Cedex, France
| | - Jérôme Mutterer
- Institut de Biologie Moléculaire des Plantes du Centre National de la Recherche Scientifique, Université de Strasbourg, 67084 Strasbourg Cedex, France
| | - Denise Meyer
- Institut de Biologie Moléculaire des Plantes du Centre National de la Recherche Scientifique, Université de Strasbourg, 67084 Strasbourg Cedex, France
| | - Abdelmalek Alioua
- Institut de Biologie Moléculaire des Plantes du Centre National de la Recherche Scientifique, Université de Strasbourg, 67084 Strasbourg Cedex, France
| | - Alain Van Dorsselaer
- Laboratoire de Spectrométrie de Masse Bio-Organique, Département des Sciences Analytiques, Institut Pluridisciplinaire Hubert Curien du Centre National de la Recherche Scientifique, Unité Mixte de Recherche 7178, Université de Strasbourg, 67087 Strasbourg Cedex, France
| | - Alain Rahier
- Institut de Biologie Moléculaire des Plantes du Centre National de la Recherche Scientifique, Université de Strasbourg, 67084 Strasbourg Cedex, France
| | - Bilal Camara
- Institut de Biologie Moléculaire des Plantes du Centre National de la Recherche Scientifique, Université de Strasbourg, 67084 Strasbourg Cedex, France
| | - Florence Bouvier
- Institut de Biologie Moléculaire des Plantes du Centre National de la Recherche Scientifique, Université de Strasbourg, 67084 Strasbourg Cedex, France
- Address correspondence to
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4
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Lamani E, Mewbourne RB, Fletcher DS, Maltsev SD, Danilov LL, Veselovsky VV, Lozanova AV, Grigorieva NY, Pinsker OA, Xing J, Forsee WT, Cheung HC, Schutzbach JS, Shibaev VN, Jedrzejas MJ. Structural studies and mechanism of Saccharomyces cerevisiae dolichyl-phosphate-mannose synthase: insights into the initial step of synthesis of dolichyl-phosphate-linked oligosaccharide chains in membranes of endoplasmic reticulum. Glycobiology 2006; 16:666-78. [PMID: 16549409 DOI: 10.1093/glycob/cwj104] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Dolichyl-phosphate-mannose (Dol-P-Man) synthase catalyzes the reversible formation of a key intermediate that is involved as a mannosyl donor in at least three different pathways for the synthesis of glycoconjugates important for eukaryotic development and viability. The enzyme is found associated with membranes of the endoplasmic reticulum (ER), where it transfers mannose from the water soluble cytoplasmic donor, guanosine 5'-diphosphate (GDP)-Man, to the membrane-bound, extremely hydrophobic, and long-chain polyisoprenoid acceptor, dolichyl-phosphate (Dol-P). The enzyme from Saccharomyces cerevisiae has been utilized to investigate the structure and activity of the protein and interactions of the enzyme with Dol-P and synthetic Dol-P analogs containing fluorescent probes. These interactions have been explored utilizing fluorescence resonance energy transfer (FRET) to establish intramolecular distances within the protein molecule as well as intermolecular distances to determine the localization of the active site and the hydrophobic substrate on the enzyme's surface. A three-dimensional (3D) model of the enzyme was produced with bound substrates, Dol-P, GDP-Man, and divalent cations to delineate the binding sites for these substrates as well as the catalytic site. The FRET analysis was used to characterize the functional properties of the enzyme and to evaluate its modeled structure. The data allowed for proposing a molecular mechanism of catalysis as an inverting mechanism of mannosyl residue transfer.
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Affiliation(s)
- Ejvis Lamani
- Children's Hospital Oakland Research Institute, CA 94609, USA
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5
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Sprung I, Carmès L, Watt GM, Flitsch SL. Synthesis of novel acceptor substrates for the dolichyl phosphate mannose synthase from yeast. Chembiochem 2003; 4:319-32. [PMID: 12672111 DOI: 10.1002/cbic.200390052] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Dolichols are polyisoprenoid lipid components of mammalian membranes consisting of an average of 20 head-to-tail linked isoprene units of which the first isoprene is fully saturated. The unusual size of these lipids is intriguing and poses questions about the role of dolichol structure in biological processes. In order to probe structure and function we have synthesised potential dolichyl analogues that retain only the first two isoprene units and carry a second functional group within the terminal lipid chain. Such analogues were evaluated as substrates for a key enzyme in the dolichyl-dependent pathway of glycan biosynthesis, dolichyl phosphate mannose (Dol-P-Man) synthase. It was shown that some functional groups, including labels such as biotin, could be tolerated. When the synthetic analogues were attached to a solid support they were still substrates for the Dol-P-Man system and thus allowed the enzymatic solid-phase synthesis of glycolipids.
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Affiliation(s)
- Ines Sprung
- School of Chemistry, Centre for Protein Technology, The University of Edinburgh King's Buildings, West Mains Road Edinburgh EH9 3JJ, UK
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6
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Sprung I, Ziegler A, Flitsch SL. Enzymatic synthesis of beta-mannosyl phosphates on solid support. Chem Commun (Camb) 2002:2676-7. [PMID: 12510294 DOI: 10.1039/b206451k] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Synthetic bifunctional analogues 4a, b and 14 of dolichol phosphate 1 were attached to solid support and were shown to be substrates for Dol-P-Man synthase.
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Affiliation(s)
- Ines Sprung
- School of Chemistry, Edinburgh Protein Interaction Centre, University of Edinburgh, King's Buildings, West Mains Road, Edinburgh, UK EH9 3JJ
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7
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Revers L, Bill RM, Wilson IB, Watt GM, Flitsch SL. Development of recombinant, immobilised beta-1,4-mannosyltransferase for use as an efficient tool in the chemoenzymatic synthesis of N-linked oligosaccharides. BIOCHIMICA ET BIOPHYSICA ACTA 1999; 1428:88-98. [PMID: 10366763 DOI: 10.1016/s0304-4165(99)00048-3] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
The preparation of the conserved core structure of asparagine-linked oligosaccharides found in eukaryotic glycoproteins is an important step towards the synthesis of homogeneous neoglycoproteins. So far, however, the convenient generation of the Manbeta4GlcNAcbeta4GlcNAc (Gn2M) core trisaccharide has proved to be a major obstacle because of the inherent difficulties associated with the synthesis of beta-mannosides. Here we report the overproduction in Escherichia coli of full-length and transmembrane-deleted yeast beta-1, 4-mannosyltransferases as novel N-terminal fusions bearing a decahistidinyl sequence and the minimal human Myc epitope. The recombinant enzymes were highly active and were amenable to immobilisation by nickel(II) chelation and to immunodetection with an anti-Myc monoclonal antibody. The immobilised, transmembrane-deleted enzyme exhibited an apparent Km of 14 microM for the synthetic acceptor substrate analogue, phytanyl-pyrophosphoryl-alpha-N,N'-diacetylchitobioside (PPGn2), under saturating donor conditions. This figure is comparable to those previously reported for native and recombinant yeast beta-1, 4-mannosyltransferases with, respectively, the natural dolichyl-linked acceptor and PPGn2. The validity of the reaction product was confirmed by chromatographic and spectroscopic analysis.
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Affiliation(s)
- L Revers
- The Edinburgh Centre for Protein Technology, Department of Chemistry, University of Edinburgh, King's Buildings, West Mains Road, Edinburgh EH9 3JJ, UK
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8
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The cofactor Mg2+—a key switch for effective continuous enzymatic production of GDP-mannose using recombinant GDP-mannose pyrophosphorylase. Carbohydr Res 1997. [DOI: 10.1016/s0008-6215(97)10095-7] [Citation(s) in RCA: 25] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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9
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Vimr E, Steenbergen S, Cieslewicz M. Biosynthesis of the polysialic acid capsule in Escherichia coli K1. JOURNAL OF INDUSTRIAL MICROBIOLOGY 1995; 15:352-60. [PMID: 8605072 DOI: 10.1007/bf01569991] [Citation(s) in RCA: 47] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
The extracellular polysaccharides elaborated by most or all bacterial species function in cell-to-cell and cell-substratum adhesion, cell signaling, and avoidance or inhibition of noxious agents in animal hosts or free-living environments. Recent advances in our understanding of exopolysaccharide synthesis have been facilitated by comparative approaches in both plant and animal pathogens, as well as in microorganisms of industrial importance. One of the best understood of these systems is the kps locus for polysialic acid synthesis in Escherichia coli K1. The genes for sialic acid synthesis, activation, polymerization and translocation have been identified and assigned at least tentative functions in the synthetic and export pathways. Initial studies of kps thermoregulation suggest that genetic control mechanisms will be involved which are distinct from those already described for several other exopolysaccharides. Information about the common as well as unique features of polysialic acid biosynthesis will increase our knowledge of microbial cell surfaces which in turn may suggest novel targets for therapeutic or industrial interventions.
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Affiliation(s)
- E Vimr
- Department of Veterinary Pathobiology, University of Illinois at Urbana-Champaign 61801, USA
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10
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Wilson IB, Webberley MC, Revers L, Flitsch SL. Dolichol is not a necessary moiety for lipid-linked oligosaccharide substrates of the mannosyltransferases involved in in vitro N-linked-oligosaccharide assembly. Biochem J 1995; 310 ( Pt 3):909-16. [PMID: 7575426 PMCID: PMC1135982 DOI: 10.1042/bj3100909] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
Dolichol is utilized in vivo as an unusually large anchor on which the precursor for N-linked oligosaccharides is assembled by a series of glycosyltransferases. The role of dolichol in enzyme substrate recognition is investigated. Thus the biosynthetic intermediate NN'-diacetylchitobiose was chemically linked to either dolichol or the much shorter fully saturated tetraisoprenoid phytanol. Both lipids were used as substrates by a recombinant, soluble beta-1,4-mannosyltransferase. beta-[3H]Mannosylated lipids from this reaction were then used as substrates for the subsequent mannosyltransferases from yeast or rat liver microsomes. It was found that both the dolichyl- and phytanyl-linked substrates were easily mannosylated to form Man5GlcNAc2, with some further mannosylation to Man7GlcNAc2 and Man9GlcNAc2 at low concentrations of lipid-linked substrate. It is concluded that dolichol is not necessary in vitro as part of the substrate for the mannosyltransferases in the biosynthetic pathway for N-glycosylation.
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Affiliation(s)
- I B Wilson
- Dyson Perrins Laboratory, University of Oxford, U.K
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11
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Chapter 5 Biosynthesis 2a. The Coenzymic Role of Phosphodolichols. ACTA ACUST UNITED AC 1995. [DOI: 10.1016/s0167-7306(08)60590-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register]
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12
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Flitsch SL, Goodridge DM, Guilbert B, Revers L, Webberley MC, Wilson IB. The chemoenzymatic synthesis of neoglycolipids and lipid-linked oligosaccharides using glycosyltransferases. Bioorg Med Chem 1994; 2:1243-50. [PMID: 7757420 DOI: 10.1016/s0968-0896(00)82075-1] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
The application of glycosyltransferases to the chemoenzymatic synthesis of neoglycosphingolipids and lipid-linked oligosaccharides allows the regio- and stereoselective formation of glycosidic bonds. In our laboratory galactosyl-, sialyl-, and fucosyltransferases have been used to assemble oligosaccharide headgroups directly on a sphingosine derivative without the need for any protection group strategies, including the Lewisx antigen. In complementary studies on N-linked oligosaccharide biosynthesis, chemically phosphorylated dolichol analogues have been tested as substrates for Dol-P-Man synthetase. Also, the substrate recognition of the core beta-1,4-mannosyltransferase from yeast has been investigated using a range of chitobiose derivatives as potential substrates.
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13
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Revers L, Wilson IB, Webberley MC, Flitsch SL. The potential dolichol recognition sequence of beta-1,4-mannosyltransferase is not required for enzymic activity using phytanyl-pyrophosphoryl-alpha-N,N'- diacetylchitobioside as acceptor. Biochem J 1994; 299 ( Pt 1):23-7. [PMID: 8166646 PMCID: PMC1138015 DOI: 10.1042/bj2990023] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
The ALG1 gene of Saccharomyces cerevisiae encodes beta-1,4-mannosyltransferase, an essential membrane-associated enzyme involved in the assembly of dolichyl-linked oligosaccharide precursors for N-glycosylation [Albright and Robbins (1990) J. Biol. Chem. 265, 7042-7049], which catalyses the transfer of a mannose residue from GDP-mannose to dolichyl-pyrophosphoryl-alpha-N,N'- diacetylchitobioside; it also possesses a putative transmembrane domain, bearing an 11-amino-acid consensus sequence, which has been proposed to mediate dolichol recognition. Here we report the construction and bacterial expression of a mutant beta-1,4-mannosyltransferase derived from ALG1, which carries a 34-amino-acid deletion resulting in the absence of the entire N-terminal transmembrane domain. This truncated enzyme has an apparent Km value of 17 microM for phytanyl-pyrophosphoryl-alpha-N,N'-diacetylchitobioside, a known acceptor for beta-1,4-mannosyltransferase [Flitsch, Pinches, Taylor and Turner (1992) J. Chem. Soc., Perkin Trans. 1, 2087-2093]. The intact enzyme, expressed in the same system, has an apparent Km value of 25 microM. These figures are in good agreement with previously reported values for wild-type beta-1,4-mannosyl-transferase incubated with the natural dolichyl-linked substrate. Gel-filtration chromatography (before and after beta-mannosidase digestion) of the products of both forms of the enzyme verifies the formation of Man beta 1-->4GlcNAc beta 1-->4GlcNAc. We therefore conclude that the putative dolichol recognition sequence is not necessary for recognition of the phytanyl analogue of its natural dolichol substrate and suggest it probably also is not needed for its natural substrate.
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Affiliation(s)
- L Revers
- Dyson Perrins Laboratory, University of Oxford, U.K
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