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Hirata E, Sakata KT, Dearden GI, Noor F, Menon I, Chiduza GN, Menon AK. Molecular characterization of Rft1, an ER membrane protein associated with congenital disorder of glycosylation RFT1-CDG. J Biol Chem 2024; 300:107584. [PMID: 39025454 DOI: 10.1016/j.jbc.2024.107584] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2024] [Revised: 07/10/2024] [Accepted: 07/11/2024] [Indexed: 07/20/2024] Open
Abstract
The oligosaccharide needed for protein N-glycosylation is assembled on a lipid carrier via a multistep pathway. Synthesis is initiated on the cytoplasmic face of the endoplasmic reticulum (ER) and completed on the luminal side after transbilayer translocation of a heptasaccharide lipid intermediate. More than 30 congenital disorders of glycosylation (CDGs) are associated with this pathway, including RFT1-CDG which results from defects in the membrane protein Rft1. Rft1 is essential for the viability of yeast and mammalian cells and was proposed as the transporter needed to flip the heptasaccharide lipid intermediate across the ER membrane. However, other studies indicated that Rft1 is not required for heptasaccharide lipid flipping in microsomes or unilamellar vesicles reconstituted with ER membrane proteins, nor is it required for the viability of at least one eukaryote. It is therefore not known what essential role Rft1 plays in N-glycosylation. Here, we present a molecular characterization of human Rft1, using yeast cells as a reporter system. We show that it is a multispanning membrane protein located in the ER, with its N and C termini facing the cytoplasm. It is not N-glycosylated. The majority of RFT1-CDG mutations map to highly conserved regions of the protein. We identify key residues that are important for Rft1's ability to support N-glycosylation and cell viability. Our results provide a necessary platform for future work on this enigmatic protein.
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Affiliation(s)
- Eri Hirata
- Department of Biochemistry, Weill Cornell Medical College, New York, New York, USA
| | - Ken-Taro Sakata
- Department of Biochemistry, Weill Cornell Medical College, New York, New York, USA
| | - Grace I Dearden
- Department of Biochemistry, Weill Cornell Medical College, New York, New York, USA
| | - Faria Noor
- Department of Biochemistry, Weill Cornell Medical College, New York, New York, USA
| | - Indu Menon
- Department of Biochemistry, Weill Cornell Medical College, New York, New York, USA
| | - George N Chiduza
- Structure and Function of Biological Membranes - Chemistry Department, Université Libre de Bruxelles - Campus Plaine, Brussels, Belgium
| | - Anant K Menon
- Department of Biochemistry, Weill Cornell Medical College, New York, New York, USA.
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Hirata E, Sakata KT, Dearden GI, Noor F, Menon I, Chiduza GN, Menon AK. Molecular characterization of Rft1, an ER membrane protein associated with congenital disorder of glycosylation RFT1-CDG. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.04.03.587922. [PMID: 38617304 PMCID: PMC11014557 DOI: 10.1101/2024.04.03.587922] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/16/2024]
Abstract
The oligosaccharide needed for protein N-glycosylation is assembled on a lipid carrier via a multi-step pathway. Synthesis is initiated on the cytoplasmic face of the endoplasmic reticulum (ER) and completed on the luminal side after transbilayer translocation of a heptasaccharide lipid intermediate. More than 30 Congenital Disorders of Glycosylation (CDGs) are associated with this pathway, including RFT1-CDG which results from defects in the membrane protein Rft1. Rft1 is essential for the viability of yeast and mammalian cells and was proposed as the transporter needed to flip the heptasaccharide lipid intermediate across the ER membrane. However, other studies indicated that Rft1 is not required for heptasaccharide lipid flipping in microsomes or unilamellar vesicles reconstituted with ER membrane proteins, nor is it required for the viability of at least one eukaryote. It is therefore not known what essential role Rft1 plays in N-glycosylation. Here, we present a molecular characterization of human Rft1, using yeast cells as a reporter system. We show that it is a multi-spanning membrane protein located in the ER, with its N and C-termini facing the cytoplasm. It is not N-glycosylated. The majority of RFT1-CDG mutations map to highly conserved regions of the protein. We identify key residues that are important for Rft1's ability to support N-glycosylation and cell viability. Our results provide a necessary platform for future work on this enigmatic protein.
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Affiliation(s)
- Eri Hirata
- Department of Biochemistry, Weill Cornell Medical College, New York, NY 10065, USA
| | - Ken-taro Sakata
- Department of Biochemistry, Weill Cornell Medical College, New York, NY 10065, USA
| | - Grace I. Dearden
- Department of Biochemistry, Weill Cornell Medical College, New York, NY 10065, USA
| | - Faria Noor
- Department of Biochemistry, Weill Cornell Medical College, New York, NY 10065, USA
| | - Indu Menon
- Department of Biochemistry, Weill Cornell Medical College, New York, NY 10065, USA
| | - George N. Chiduza
- Structure and Function of Biological Membranes - Chemistry Department, Université Libre de Bruxelles - Campus Plaine, 1050 Brussels, Belgium
| | - Anant K. Menon
- Department of Biochemistry, Weill Cornell Medical College, New York, NY 10065, USA
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Chen YH, Shen HL, Chou SJ, Sato Y, Cheng WH. Interference of Arabidopsis N-Acetylglucosamine-1-P Uridylyltransferase Expression Impairs Protein N-Glycosylation and Induces ABA-Mediated Salt Sensitivity During Seed Germination and Early Seedling Development. FRONTIERS IN PLANT SCIENCE 2022; 13:903272. [PMID: 35747876 PMCID: PMC9210984 DOI: 10.3389/fpls.2022.903272] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 03/24/2022] [Accepted: 05/10/2022] [Indexed: 06/15/2023]
Abstract
N-acetylglucosamine (GlcNAc) is the fundamental amino sugar moiety that is essential for protein glycosylation. UDP-GlcNAc, an active form of GlcNAc, is synthesized through the hexosamine biosynthetic pathway (HBP). Arabidopsis N-acetylglucosamine-1-P uridylyltransferases (GlcNAc1pUTs), encoded by GlcNA.UTs, catalyze the last step in the HBP pathway, but their biochemical and molecular functions are less clear. In this study, the GlcNA.UT1 expression was knocked down by the double-stranded RNA interference (dsRNAi) in the glcna.ut2 null mutant background. The RNAi transgenic plants, which are referred to as iU1, displayed the reduced UDP-GlcNAc biosynthesis, altered protein N-glycosylation and induced an unfolded protein response under salt-stressed conditions. Moreover, the iU1 transgenic plants displayed sterility and salt hypersensitivity, including delay of both seed germination and early seedling establishment, which is associated with the induction of ABA biosynthesis and signaling. These salt hypersensitive phenotypes can be rescued by exogenous fluridone, an inhibitor of ABA biosynthesis, and by introducing an ABA-deficient mutant allele nced3 into iU1 transgenic plants. Transcriptomic analyses further supported the upregulated genes that were involved in ABA biosynthesis and signaling networks, and response to salt stress in iU1 plants. Collectively, these data indicated that GlcNAc1pUTs are essential for UDP-GlcNAc biosynthesis, protein N-glycosylation, fertility, and the response of plants to salt stress through ABA signaling pathways during seed germination and early seedling development.
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Affiliation(s)
- Ya-Huei Chen
- National Defense Medical Center, Graduate Institute of Life Sciences, Taipei, Taiwan
- Institute of Plant and Microbial Biology, Academia Sinica, Taipei, Taiwan
| | - Hwei-Ling Shen
- Institute of Plant and Microbial Biology, Academia Sinica, Taipei, Taiwan
| | - Shu-Jen Chou
- Institute of Plant and Microbial Biology, Academia Sinica, Taipei, Taiwan
| | - Yasushi Sato
- Biology and Environmental Science, Graduate School of Science and Engineering, Ehime University, Matsuyama, Japan
| | - Wan-Hsing Cheng
- National Defense Medical Center, Graduate Institute of Life Sciences, Taipei, Taiwan
- Institute of Plant and Microbial Biology, Academia Sinica, Taipei, Taiwan
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4
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Pejenaute-Ochoa MD, Santana-Molina C, Devos DP, Ibeas JI, Fernández-Álvarez A. Structural, Evolutionary, and Functional Analysis of the Protein O-Mannosyltransferase Family in Pathogenic Fungi. J Fungi (Basel) 2021; 7:jof7050328. [PMID: 33922798 PMCID: PMC8147084 DOI: 10.3390/jof7050328] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2021] [Revised: 04/19/2021] [Accepted: 04/20/2021] [Indexed: 12/27/2022] Open
Abstract
Protein O-mannosyltransferases (Pmts) comprise a group of proteins that add mannoses to substrate proteins at the endoplasmic reticulum. This post-translational modification is important for the faithful transfer of nascent glycoproteins throughout the secretory pathway. Most fungi genomes encode three O-mannosyltransferases, usually named Pmt1, Pmt2, and Pmt4. In pathogenic fungi, Pmts, especially Pmt4, are key factors for virulence. Although the importance of Pmts for fungal pathogenesis is well established in a wide range of pathogens, questions remain regarding certain features of Pmts. For example, why does the single deletion of each pmt gene have an asymmetrical impact on host colonization? Here, we analyse the origin of Pmts in fungi and review the most important phenotypes associated with Pmt mutants in pathogenic fungi. Hence, we highlight the enormous relevance of these glycotransferases for fungal pathogenic development.
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5
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Frank M, Kaulfürst-Soboll H, Fischer K, von Schaewen A. Complex-Type N-Glycans Influence the Root Hair Landscape of Arabidopsis Seedlings by Altering the Auxin Output. FRONTIERS IN PLANT SCIENCE 2021; 12:635714. [PMID: 33679849 PMCID: PMC7930818 DOI: 10.3389/fpls.2021.635714] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/30/2020] [Accepted: 01/27/2021] [Indexed: 05/03/2023]
Abstract
Roots supply plants with nutrients and water, besides anchoring them in the soil. The primary root with its lateral roots constitutes the central skeleton of the root system. In particular, root hairs increase the root surface, which is critical for optimizing uptake efficiency. During root-cell growth and development, many proteins that are components of, e.g., the cell wall and plasma membrane are constitutively transported through the secretory system and become posttranslationally modified. Here, the best-studied posttranslational modification is protein N-glycosylation. While alterations in the attachment/modification of N-glycans within the ER lumen results in severe developmental defects, the impact of Golgi-localized complex N-glycan modification, particularly on root development, has not been studied in detail. We report that impairment of complex-type N-glycosylation results in a differential response to synthetic phytohormones with earlier and increased root-hair elongation. Application of either the cytokinin BAP, the auxin NAA, or the ethylene precursor ACC revealed an interaction of auxin with complex N-glycosylation during root-hair development. Especially in gntI mutant seedlings, the early block of complex N-glycan formation resulted in an increased auxin sensitivity. RNA-seq experiments suggest that gntI roots have permanently elevated nutrient-, hypoxia-, and defense-stress responses, which might be a consequence of the altered auxin responsiveness.
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Affiliation(s)
- Manuel Frank
- Molecular Physiology of Plants, Institute of Plant Biology and Biotechnology, University of Münster (WWU Münster), Münster, Germany
- Department of Molecular Biology and Genetics, Aarhus University, Aarhus C, Denmark
| | - Heidi Kaulfürst-Soboll
- Molecular Physiology of Plants, Institute of Plant Biology and Biotechnology, University of Münster (WWU Münster), Münster, Germany
| | - Kerstin Fischer
- Molecular Physiology of Plants, Institute of Plant Biology and Biotechnology, University of Münster (WWU Münster), Münster, Germany
| | - Antje von Schaewen
- Molecular Physiology of Plants, Institute of Plant Biology and Biotechnology, University of Münster (WWU Münster), Münster, Germany
- *Correspondence: Antje von Schaewen,
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Mathieu-Rivet E, Lerouge P, Bardor M. Chlamydomonas reinhardtii: Protein Glycosylation and Production of Biopharmaceuticals. ACTA ACUST UNITED AC 2017. [DOI: 10.1007/978-3-319-66360-9_3] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
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7
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Vanier G, Lucas PL, Loutelier-Bourhis C, Vanier J, Plasson C, Walet-Balieu ML, Tchi-Song PC, Remy-Jouet I, Richard V, Bernard S, Driouich A, Afonso C, Lerouge P, Mathieu-Rivet E, Bardor M. Heterologous expression of the N-acetylglucosaminyltransferase I dictates a reinvestigation of the N-glycosylation pathway in Chlamydomonas reinhardtii. Sci Rep 2017; 7:10156. [PMID: 28860654 PMCID: PMC5578997 DOI: 10.1038/s41598-017-10698-z] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2017] [Accepted: 08/14/2017] [Indexed: 12/31/2022] Open
Abstract
Eukaryotic N-glycosylation pathways are dependent of N-acetylglucosaminyltransferase I (GnTI), a key glycosyltransferase opening the door to the formation of complex-type N-glycans by transferring a N-acetylglucosamine residue onto the Man5GlcNAc2 intermediate. In contrast, glycans N-linked to Chlamydomonas reinhardtii proteins arise from a GnTI-independent Golgi processing of oligomannosides giving rise to Man5GlcNAc2 substituted eventually with one or two xylose(s). Here, complementation of C. reinhardtii with heterologous GnTI was investigated by expression of GnTI cDNAs originated from Arabidopsis and the diatom Phaeodactylum tricornutum. No modification of the N-glycans was observed in the GnTI transformed cells. Consequently, the structure of the Man5GlcNAc2 synthesized by C. reinhardtii was reinvestigated. Mass spectrometry analyses combined with enzyme sequencing showed that C. reinhardtii proteins carry linear Man5GlcNAc2 instead of the branched structure usually found in eukaryotes. Moreover, characterization of the lipid-linked oligosaccharide precursor demonstrated that C. reinhardtii exhibit a Glc3Man5GlcNAc2 dolichol pyrophosphate precursor. We propose that this precursor is then trimmed into a linear Man5GlcNAc2 that is not substrate for GnTI. Furthermore, cells expressing GnTI exhibited an altered phenotype with large vacuoles, increase of ROS production and accumulation of starch granules, suggesting the activation of stress responses likely due to the perturbation of the Golgi apparatus.
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Affiliation(s)
- Gaëtan Vanier
- Normandie Univ, UNIROUEN, Laboratoire Glycobiologie et Matrice Extracellulaire végétale, EA 4358, 76000, Rouen, France.,UMR FARE 614, Fractionnement des AgroRessources et Environnement, Chaire AFERE, Université de Reims-Champagne-Ardenne, INRA, 51686, Reims Cedex, France
| | - Pierre-Louis Lucas
- Normandie Univ, UNIROUEN, Laboratoire Glycobiologie et Matrice Extracellulaire végétale, EA 4358, 76000, Rouen, France
| | - Corinne Loutelier-Bourhis
- Normandie Univ, UNIROUEN, COBRA, UMR 6014 et FR 3038, Université de Rouen, INSA de Rouen, CNRS, 76000, Rouen, France
| | - Jessica Vanier
- Normandie Univ, UNIROUEN, Laboratoire Glycobiologie et Matrice Extracellulaire végétale, EA 4358, 76000, Rouen, France
| | - Carole Plasson
- Normandie Univ, UNIROUEN, Laboratoire Glycobiologie et Matrice Extracellulaire végétale, EA 4358, 76000, Rouen, France
| | - Marie-Laure Walet-Balieu
- Normandie Univ, UNIROUEN, Plate-Forme de Protéomique PISSARO, 76000, Rouen, France.,Normandie Univ, UNIROUEN, Institut de Recherche et d'Innovation Biomédicale (IRIB), 76000, Rouen, France
| | - Philippe Chan Tchi-Song
- Normandie Univ, UNIROUEN, Plate-Forme de Protéomique PISSARO, 76000, Rouen, France.,Normandie Univ, UNIROUEN, Institut de Recherche et d'Innovation Biomédicale (IRIB), 76000, Rouen, France
| | - Isabelle Remy-Jouet
- Normandie Univ, UNIROUEN, Inserm UMR 1096, Plateforme BOSS, 76000, Rouen, France
| | - Vincent Richard
- Normandie Univ, UNIROUEN, Inserm UMR 1096, Plateforme BOSS, 76000, Rouen, France
| | - Sophie Bernard
- Normandie Univ, UNIROUEN, Laboratoire Glycobiologie et Matrice Extracellulaire végétale, EA 4358, 76000, Rouen, France.,Normandie Univ, UNIROUEN, Plate-forme, PRIMACEN, Cell Imaging Platform of Normandy, 76000, Rouen, France
| | - Azeddine Driouich
- Normandie Univ, UNIROUEN, Laboratoire Glycobiologie et Matrice Extracellulaire végétale, EA 4358, 76000, Rouen, France.,Normandie Univ, UNIROUEN, Plate-forme, PRIMACEN, Cell Imaging Platform of Normandy, 76000, Rouen, France
| | - Carlos Afonso
- Normandie Univ, UNIROUEN, COBRA, UMR 6014 et FR 3038, Université de Rouen, INSA de Rouen, CNRS, 76000, Rouen, France
| | - Patrice Lerouge
- Normandie Univ, UNIROUEN, Laboratoire Glycobiologie et Matrice Extracellulaire végétale, EA 4358, 76000, Rouen, France
| | - Elodie Mathieu-Rivet
- Normandie Univ, UNIROUEN, Laboratoire Glycobiologie et Matrice Extracellulaire végétale, EA 4358, 76000, Rouen, France
| | - Muriel Bardor
- Normandie Univ, UNIROUEN, Laboratoire Glycobiologie et Matrice Extracellulaire végétale, EA 4358, 76000, Rouen, France. .,Institut Universitaire de France (I.U.F.) 1, rue Descartes, 75231, Paris, Cedex 05, France.
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8
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Glycosylation of matrix metalloproteases and tissue inhibitors: present state, challenges and opportunities. Biochem J 2017; 473:1471-82. [PMID: 27234584 PMCID: PMC4888457 DOI: 10.1042/bj20151154] [Citation(s) in RCA: 43] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2015] [Accepted: 02/15/2016] [Indexed: 12/15/2022]
Abstract
Current knowledge about the glycosylation of matrix metalloproteinases (MMPs) and the inhibitors of metalloproteinases (TIMPs) is reviewed. Whereas structural and functional aspects of the glycobiology of many MMPs is unknown, research on MMP-9 and MMP-14 glycosylation reveals important functional implications, such as altered inhibitor binding and cellular localization. This, together with the fact that MMPs contain conserved and many potential attachment sites for N-linked and O-linked oligosaccharides, proves the need for further studies on MMP glycobiology. Matrix metalloproteases (MMPs) are crucial components of a complex and dynamic network of proteases. With a wide range of potential substrates, their production and activity are tightly controlled by a combination of signalling events, zymogen activation, post-translational modifications and extracellular inhibition. Slight imbalances may result in the initiation or progression of specific disease states, such as cancer and pathological inflammation. As glycosylation modifies the structures and functions of glycoproteins and many MMPs contain N- or O-linked oligosaccharides, we examine, compare and evaluate the evidence for whether glycosylation affects MMP catalytic activity and other functions. It is interesting that the catalytic sites of MMPs do not contain O-linked glycans, but instead possess a conserved N-linked glycosylation site. Both N- and O-linked oligosaccharides, attached to specific protein domains, endow these domains with novel functions such as the binding to lectins, cell-surface receptors and tissue inhibitors of metalloproteases (TIMPs). Validated glycobiological data on N- and O-linked oligosaccharides of gelatinase B/MMP-9 and on O-linked structures of membrane-type 1 MMP/MMP-14 indicate that in-depth research of other MMPs may yield important insights, e.g. about subcellular localizations and functions within macromolecular complexes.
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Comparative proteomic analyses reveal that Gnt2-mediated N-glycosylation affects cell wall glycans and protein content in Fusarium oxysporum. J Proteomics 2015; 128:189-202. [PMID: 26254006 DOI: 10.1016/j.jprot.2015.07.035] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2015] [Revised: 07/09/2015] [Accepted: 07/29/2015] [Indexed: 01/22/2023]
Abstract
Protein N-glycosylation is a ubiquitous post-translational modification that contributes to appropriate protein folding, stability, functionality and localization. N-glycosylation has been identified as an important process for morphogenesis and virulence in several fungal pathogens including Fusarium oxysporum. Here we conducted comparative chemical and proteome-based analyses to better understand the physiological changes associated with protein hypo-N-glycosylation in F. oxysporum N-glycosyltransferase Gnt2-deficient mutant. The results suggest that lack of functional Gnt2 alters the size of galactofuranose chains in cell wall glycans, resulting in polysaccharides with a broad range of polymerization degrees and differential protein glycosylation patterns. Functional Gnt2 is necessary for normal conidium size and morphology and wild-type hyphal fusion rates. Hypo-N-glycosylation in ∆gnt2 mutant results in enhanced oxidative stress resistance and reduced levels of proteins involved in cell wall organization, biogenesis and remodelling. Deletion of gnt2 gene led to accumulation of trafficking vesicles at hyphal tips, reduced secretion of extracellular proteins related to detoxification of antifungal compounds and degradation of plant cell walls, and lowered extracellular polygalacturonase activity. Altogether, the results confirm that Gnt2-mediated N-glycosylation plays a crucial role in morphogenesis and virulence, and demonstrate that Gnt2 is essential for protein function, transport and relative abundance in F. oxysporum.
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Tani Y, Omatsu K, Saito S, Miyake R, Kawabata H, Ueda M, Mihara H. Heterologous expression of l-lysine α-oxidase from Scomber japonicus in Pichia pastoris and functional characterization of the recombinant enzyme. J Biochem 2014; 157:201-10. [PMID: 25359785 DOI: 10.1093/jb/mvu064] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Fish have a complex self-defense mechanism against microbial invasion. Recently, l-lysine α-oxidases have been identified from a number of fish species as a novel type of antibacterial protein in the integument. These enzymes exhibit strict substrate specificity for l-lysine, but the underlying mechanisms and details of their catalytic properties remain unknown. In this study, a synthetic gene coding for Scomber japonicus l-lysine α-oxidase, originally termed AIP (for apoptosis-inducing protein), was expressed in Pichia pastoris, and the recombinant enzyme (rAIP) was purified and characterized. rAIP exhibited essentially the same substrate specificity as the native enzyme, catalyzing the oxidative deamination of l-lysine as an exclusive substrate. rAIP was N-glycosylated and remained active over a wide range of pH, with an optimal pH of 7.5. The enzyme was stable in the pH range from 4.5 to 10.0 and was thermally stable up to 60°C. A molecular modelling of rAIP and a comparative structure/sequence analysis with homologous enzymes indicate that Asp(220) and Asp(320) are the substrate-binding residues that are likely to confer exclusive substrate specificity for l-lysine on the fish enzymes.
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Affiliation(s)
- Yasushi Tani
- College of Life Sciences, Ritsumeikan University, Kusatsu, Shiga 525-8577, Japan; R-GIRO, Ritsumeikan University, Kusatsu, Shiga 525-8577, Japan; Mitsubishi Chemical Group Science and Technology Research Center, Inc., Yokohama, Kanagawa 227-8502, Japan; and API Corporation, Yokohama, Kanagawa 227-8502, Japan College of Life Sciences, Ritsumeikan University, Kusatsu, Shiga 525-8577, Japan; R-GIRO, Ritsumeikan University, Kusatsu, Shiga 525-8577, Japan; Mitsubishi Chemical Group Science and Technology Research Center, Inc., Yokohama, Kanagawa 227-8502, Japan; and API Corporation, Yokohama, Kanagawa 227-8502, Japan
| | - Koichiro Omatsu
- College of Life Sciences, Ritsumeikan University, Kusatsu, Shiga 525-8577, Japan; R-GIRO, Ritsumeikan University, Kusatsu, Shiga 525-8577, Japan; Mitsubishi Chemical Group Science and Technology Research Center, Inc., Yokohama, Kanagawa 227-8502, Japan; and API Corporation, Yokohama, Kanagawa 227-8502, Japan
| | - Shigeki Saito
- College of Life Sciences, Ritsumeikan University, Kusatsu, Shiga 525-8577, Japan; R-GIRO, Ritsumeikan University, Kusatsu, Shiga 525-8577, Japan; Mitsubishi Chemical Group Science and Technology Research Center, Inc., Yokohama, Kanagawa 227-8502, Japan; and API Corporation, Yokohama, Kanagawa 227-8502, Japan College of Life Sciences, Ritsumeikan University, Kusatsu, Shiga 525-8577, Japan; R-GIRO, Ritsumeikan University, Kusatsu, Shiga 525-8577, Japan; Mitsubishi Chemical Group Science and Technology Research Center, Inc., Yokohama, Kanagawa 227-8502, Japan; and API Corporation, Yokohama, Kanagawa 227-8502, Japan
| | - Ryoma Miyake
- College of Life Sciences, Ritsumeikan University, Kusatsu, Shiga 525-8577, Japan; R-GIRO, Ritsumeikan University, Kusatsu, Shiga 525-8577, Japan; Mitsubishi Chemical Group Science and Technology Research Center, Inc., Yokohama, Kanagawa 227-8502, Japan; and API Corporation, Yokohama, Kanagawa 227-8502, Japan College of Life Sciences, Ritsumeikan University, Kusatsu, Shiga 525-8577, Japan; R-GIRO, Ritsumeikan University, Kusatsu, Shiga 525-8577, Japan; Mitsubishi Chemical Group Science and Technology Research Center, Inc., Yokohama, Kanagawa 227-8502, Japan; and API Corporation, Yokohama, Kanagawa 227-8502, Japan
| | - Hiroshi Kawabata
- College of Life Sciences, Ritsumeikan University, Kusatsu, Shiga 525-8577, Japan; R-GIRO, Ritsumeikan University, Kusatsu, Shiga 525-8577, Japan; Mitsubishi Chemical Group Science and Technology Research Center, Inc., Yokohama, Kanagawa 227-8502, Japan; and API Corporation, Yokohama, Kanagawa 227-8502, Japan College of Life Sciences, Ritsumeikan University, Kusatsu, Shiga 525-8577, Japan; R-GIRO, Ritsumeikan University, Kusatsu, Shiga 525-8577, Japan; Mitsubishi Chemical Group Science and Technology Research Center, Inc., Yokohama, Kanagawa 227-8502, Japan; and API Corporation, Yokohama, Kanagawa 227-8502, Japan
| | - Makoto Ueda
- College of Life Sciences, Ritsumeikan University, Kusatsu, Shiga 525-8577, Japan; R-GIRO, Ritsumeikan University, Kusatsu, Shiga 525-8577, Japan; Mitsubishi Chemical Group Science and Technology Research Center, Inc., Yokohama, Kanagawa 227-8502, Japan; and API Corporation, Yokohama, Kanagawa 227-8502, Japan
| | - Hisaaki Mihara
- College of Life Sciences, Ritsumeikan University, Kusatsu, Shiga 525-8577, Japan; R-GIRO, Ritsumeikan University, Kusatsu, Shiga 525-8577, Japan; Mitsubishi Chemical Group Science and Technology Research Center, Inc., Yokohama, Kanagawa 227-8502, Japan; and API Corporation, Yokohama, Kanagawa 227-8502, Japan
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11
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Manat G, Roure S, Auger R, Bouhss A, Barreteau H, Mengin-Lecreulx D, Touzé T. Deciphering the metabolism of undecaprenyl-phosphate: the bacterial cell-wall unit carrier at the membrane frontier. Microb Drug Resist 2014; 20:199-214. [PMID: 24799078 DOI: 10.1089/mdr.2014.0035] [Citation(s) in RCA: 94] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
During the biogenesis of bacterial cell-wall polysaccharides, such as peptidoglycan, cytoplasmic synthesized precursors should be trafficked across the plasma membrane. This essential process requires a dedicated lipid, undecaprenyl-phosphate that is used as a glycan lipid carrier. The sugar is linked to the lipid carrier at the inner face of the membrane and is translocated toward the periplasm, where the glycan moiety is transferred to the growing polymer. Undecaprenyl-phosphate originates from the dephosphorylation of its precursor undecaprenyl-diphosphate, with itself generated by de novo synthesis or by recycling after the final glycan transfer. Undecaprenyl-diphosphate is de novo synthesized by the cytosolic cis-prenyltransferase undecaprenyl-diphosphate synthase, which has been structurally and mechanistically characterized in great detail highlighting the condensation process. In contrast, the next step toward the formation of the lipid carrier, the dephosphorylation step, which has been overlooked for many years, has only started revealing surprising features. In contrast to the previous step, two unrelated families of integral membrane proteins exhibit undecaprenyl-diphosphate phosphatase activity: BacA and members of the phosphatidic acid phosphatase type 2 super-family, raising the question of the significance of this multiplicity. Moreover, these enzymes establish an unexpected link between the synthesis of bacterial cell-wall polymers and other biological processes. In the present review, the current knowledge in the field of the bacterial lipid carrier, its mechanism of action, biogenesis, recycling, regulation, and future perspective works are presented.
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Affiliation(s)
- Guillaume Manat
- Laboratoire des Enveloppes Bactériennes et Antibiotiques, IBBMC, UMR 8619 CNRS, Université Paris Sud , Orsay Cedex, France
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12
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Cryptococcus neoformans dual GDP-mannose transporters and their role in biology and virulence. EUKARYOTIC CELL 2014; 13:832-42. [PMID: 24747214 DOI: 10.1128/ec.00054-14] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Cryptococcus neoformans is an opportunistic yeast responsible for lethal meningoencephalitis in humans. This pathogen elaborates a polysaccharide capsule, which is its major virulence factor. Mannose constitutes over one-half of the capsule mass and is also extensively utilized in cell wall synthesis and in glycosylation of proteins and lipids. The activated mannose donor for most biosynthetic reactions, GDP-mannose, is made in the cytosol, although it is primarily consumed in secretory organelles. This compartmentalization necessitates specific transmembrane transporters to make the donor available for glycan synthesis. We previously identified two cryptococcal GDP-mannose transporters, Gmt1 and Gmt2. Biochemical studies of each protein expressed in Saccharomyces cerevisiae showed that both are functional, with similar kinetics and substrate specificities in vitro. We have now examined these proteins in vivo and demonstrate that cells lacking Gmt1 show significant phenotypic differences from those lacking Gmt2 in terms of growth, colony morphology, protein glycosylation, and capsule phenotypes. Some of these observations may be explained by differential expression of the two genes, but others suggest that the two proteins play overlapping but nonidentical roles in cryptococcal biology. Furthermore, gmt1 gmt2 double mutant cells, which are unexpectedly viable, exhibit severe defects in capsule synthesis and protein glycosylation and are avirulent in mouse models of cryptococcosis.
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13
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Chen XL, Shi T, Yang J, Shi W, Gao X, Chen D, Xu X, Xu JR, Talbot NJ, Peng YL. N-glycosylation of effector proteins by an α-1,3-mannosyltransferase is required for the rice blast fungus to evade host innate immunity. THE PLANT CELL 2014; 26:1360-76. [PMID: 24642938 PMCID: PMC4001389 DOI: 10.1105/tpc.114.123588] [Citation(s) in RCA: 113] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/04/2023]
Abstract
Plant pathogenic fungi deploy secreted effectors to suppress plant immunity responses. These effectors operate either in the apoplast or within host cells, so they are putatively glycosylated, but the posttranslational regulation of their activities has not been explored. In this study, the ASPARAGINE-LINKED GLYCOSYLATION3 (ALG3)-mediated N-glycosylation of the effector, Secreted LysM Protein1 (Slp1), was found to be essential for its activity in the rice blast fungus Magnaporthe oryzae. ALG3 encodes an α-1,3-mannosyltransferase for protein N-glycosylation. Deletion of ALG3 resulted in the arrest of secondary infection hyphae and a significant reduction in virulence. We observed that Δalg3 mutants induced massive production of reactive oxygen species in host cells, in a similar manner to Δslp1 mutants, which is a key factor responsible for arresting infection hyphae of the mutants. Slp1 sequesters chitin oligosaccharides to avoid their recognition by the rice (Oryza sativa) chitin elicitor binding protein CEBiP and the induction of innate immune responses, including reactive oxygen species production. We demonstrate that Slp1 has three N-glycosylation sites and that simultaneous Alg3-mediated N-glycosylation of each site is required to maintain protein stability and the chitin binding activity of Slp1, which are essential for its effector function. These results indicate that Alg3-mediated N-glycosylation of Slp1 is required to evade host innate immunity.
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Affiliation(s)
- Xiao-Lin Chen
- State Key Laboratory of Agrobiotechnology and Ministry of Agriculture Key Laboratory of Plant Pathology, China Agricultural University, Beijing 100193, China
| | - Tao Shi
- State Key Laboratory of Agrobiotechnology and Ministry of Agriculture Key Laboratory of Plant Pathology, China Agricultural University, Beijing 100193, China
| | - Jun Yang
- State Key Laboratory of Agrobiotechnology and Ministry of Agriculture Key Laboratory of Plant Pathology, China Agricultural University, Beijing 100193, China
| | - Wei Shi
- State Key Laboratory of Agrobiotechnology and Ministry of Agriculture Key Laboratory of Plant Pathology, China Agricultural University, Beijing 100193, China
| | - Xusheng Gao
- State Key Laboratory of Agrobiotechnology and Ministry of Agriculture Key Laboratory of Plant Pathology, China Agricultural University, Beijing 100193, China
| | - Deng Chen
- State Key Laboratory of Agrobiotechnology and Ministry of Agriculture Key Laboratory of Plant Pathology, China Agricultural University, Beijing 100193, China
| | - Xiaowen Xu
- State Key Laboratory of Agrobiotechnology and Ministry of Agriculture Key Laboratory of Plant Pathology, China Agricultural University, Beijing 100193, China
| | - Jin-Rong Xu
- Department of Botany and Plant Pathology, Purdue University, West Lafayette, Indiana 47906
| | - Nicholas J. Talbot
- School of Biosciences, University of Exeter, Exeter EX4 4QD, United Kingdom
| | - You-Liang Peng
- State Key Laboratory of Agrobiotechnology and Ministry of Agriculture Key Laboratory of Plant Pathology, China Agricultural University, Beijing 100193, China
- Address correspondence to
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14
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Sweet taste of cell death: role of carbohydrate recognition systems. UKRAINIAN BIOCHEMICAL JOURNAL 2013. [DOI: 10.15407/ubj85.06.183] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
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15
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Costa AR, Rodrigues ME, Henriques M, Oliveira R, Azeredo J. Glycosylation: impact, control and improvement during therapeutic protein production. Crit Rev Biotechnol 2013; 34:281-99. [PMID: 23919242 DOI: 10.3109/07388551.2013.793649] [Citation(s) in RCA: 104] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
The emergence of the biopharmaceutical industry represented a major revolution for modern medicine, through the development of recombinant therapeutic proteins that brought new hope for many patients with previously untreatable diseases. There is a ever-growing demand for these therapeutics that forces a constant technological evolution to increase product yields while simultaneously reducing costs. However, the process changes made for this purpose may also affect the quality of the product, a factor that was initially overlooked but which is now a major focus of concern. Of the many properties determining product quality, glycosylation is regarded as one of the most important, influencing, for example, the biological activity, serum half-life and immunogenicity of the protein. Consequently, monitoring and control of glycosylation is now critical in biopharmaceutical manufacturing and a requirement of regulatory agencies. A rapid evolution is being observed in this context, concerning the influence of glycosylation in the efficacy of different therapeutic proteins, the impact on glycosylation of a diversity of parameters/processes involved in therapeutic protein production, the analytical methodologies employed for glycosylation monitoring and control, as well as strategies that are being explored to use this property to improve therapeutic protein efficacy (glycoengineering). This work reviews the main findings on these subjects, providing an up-to-date source of information to support further studies.
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Affiliation(s)
- Ana Rita Costa
- IBB - Institute for Biotechnology and Bioengineering, Centre of Biological Engineering, University of Minho, Campus de Gualtar , Braga , Portugal
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16
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Holtzman JL. Cellular and animal models for high-throughput screening of therapeutic agents for the treatment of the diseases of the elderly in general and Alzheimer's disease in particular(†). Front Pharmacol 2013; 4:59. [PMID: 23717280 PMCID: PMC3651961 DOI: 10.3389/fphar.2013.00059] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2012] [Accepted: 04/18/2013] [Indexed: 01/04/2023] Open
Abstract
It is currently thought that the dementia of Alzheimer's disease is due to the neurotoxicity of the deposits or aggregates of amyloid-β (Aβ) in the extracellular space of the cerebral cortex. This model has been widely criticized because there is a poor correlation between deposits and dementia. Others have questioned whether Aβ is truly neurotoxic. Yet, in spite of these concerns, the search for therapeutic agents has been based on the development of mouse models transfected with mutant genes associated in humans with early onset Alzheimer's disease. A major limitation of these models is that although they exhibit many of the pathological and clinical manifestation of the human disease, the bulk of individuals who develop the dementia of Alzheimer's disease have none of these mutant genes. Furthermore, nine clinical trials of drugs that were effective in transgenic mice failed to show any benefit in patients. Finally, a major unresolved issue with the Aβ model is that since Aβ is produced in everyone, why are deposits only seen in the elderly? This issue must be resolved if we are to understand the etiology of the disease and develop test systems for both diagnosis and drug discovery. Published studies from my laboratory demonstrate that in human cerebrospinal fluid immunoreactive Aβ is only present as a complex with two chaperones, ERp57 and calreticulin and is N-glycosylated. This complex formation is catalyzed by the posttranslational protein processing system of the endoplasmic reticulum (ER). Others have reported that in plaque Aβ is present only as the naked peptide. Together these results suggest that both plaque and dementia are secondary to an age related decline in the capacity of the ER to catalyze protein, posttranslational processing. Since the synaptic membrane proteins necessary for a functioning memory are also processed in the ER, these findings would suggest that the loss of cognition is due to a decline in the capacity of the neuron to produce and maintain functioning synapses. Work from my laboratory and from others further indicate that the components of the ER, posttranslational, protein processing pathway do dramatically decline with age. These data suggest that this decline may be found in all cells and could account not only for the dementia of Alzheimer's disease, but also for many of the other manifestations of the aging process. These observations also suggest that declining ER function has a role in two well-recognized phenomena associated with aging: a loss of mitochondrial function and a decrease in myelin. Finally, based on this paradigm I propose new cellular and animals models for high-throughput screening for drug discovery.
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Affiliation(s)
- Jordan L. Holtzman
- Department of Pharmacology, University of MinnesotaMinneapolis, MN, USA
- Department of Medicine, University of MinnesotaMinneapolis, MN, USA
- Department of Environmental Health Sciences, University of MinnesotaMinneapolis, MN, USA
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17
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Orlean P. Architecture and biosynthesis of the Saccharomyces cerevisiae cell wall. Genetics 2012; 192:775-818. [PMID: 23135325 PMCID: PMC3522159 DOI: 10.1534/genetics.112.144485] [Citation(s) in RCA: 296] [Impact Index Per Article: 24.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2012] [Accepted: 08/06/2012] [Indexed: 01/02/2023] Open
Abstract
The wall gives a Saccharomyces cerevisiae cell its osmotic integrity; defines cell shape during budding growth, mating, sporulation, and pseudohypha formation; and presents adhesive glycoproteins to other yeast cells. The wall consists of β1,3- and β1,6-glucans, a small amount of chitin, and many different proteins that may bear N- and O-linked glycans and a glycolipid anchor. These components become cross-linked in various ways to form higher-order complexes. Wall composition and degree of cross-linking vary during growth and development and change in response to cell wall stress. This article reviews wall biogenesis in vegetative cells, covering the structure of wall components and how they are cross-linked; the biosynthesis of N- and O-linked glycans, glycosylphosphatidylinositol membrane anchors, β1,3- and β1,6-linked glucans, and chitin; the reactions that cross-link wall components; and the possible functions of enzymatic and nonenzymatic cell wall proteins.
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Affiliation(s)
- Peter Orlean
- Department of Microbiology, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, USA.
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18
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Csala M, Kereszturi É, Mandl J, Bánhegyi G. The endoplasmic reticulum as the extracellular space inside the cell: role in protein folding and glycosylation. Antioxid Redox Signal 2012; 16:1100-8. [PMID: 22149109 DOI: 10.1089/ars.2011.4227] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
SIGNIFICANCE Proteins destined to secretion and exposure on the cell surface are synthesized and processed in the extracellular-like environment of the endoplasmic reticulum (ER) of higher eukaryotic cells. Compartmentation plays a crucial role in the post-translational modifications, such as oxidative folding and N-glycosylation in the ER lumen. Transport of the required intermediates across the ER membrane and maintenance of the luminal redox conditions and Ca(2+) ion concentration are indispensable for appropriate protein maturation. RECENT ADVANCES Cooperation of enzymes and transporters to maintain a thiol-oxidizing milieu in the ER lumen has been recently elucidated. Ca(2+)-dependence of certain ER chaperones is a subject of intensive research. CRITICAL ISSUES Mounting evidence supports the existence of a real barrier between the ER lumen and the cytosol. The unique set of enzymes, selection of metabolites, and characteristic ion and redox milieu of the luminal compartment strongly argue against the general permeability of the ER membrane. FUTURE DIRECTIONS Alterations in the luminal environment can trigger the unfolded protein response, a common event in a variety of pathological conditions. Therefore, redox and calcium homeostasis and protein glycosylation in the ER provide novel drug-targets for medical treatment in a wide array of diseases.
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Affiliation(s)
- Miklós Csala
- Department of Medical Chemistry, Molecular Biology and Pathobiochemistry, Semmelweis University, Budapest, Hungary.
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19
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Hanover JA, Krause MW, Love DC. linking metabolism to epigenetics through O-GlcNAcylation. Nat Rev Mol Cell Biol 2012; 13:312-21. [DOI: 10.1038/nrm3334] [Citation(s) in RCA: 319] [Impact Index Per Article: 26.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
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20
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Ruiz-May E, Kim SJ, Brandizzi F, Rose JKC. The secreted plant N-glycoproteome and associated secretory pathways. FRONTIERS IN PLANT SCIENCE 2012; 3:117. [PMID: 22685447 PMCID: PMC3368311 DOI: 10.3389/fpls.2012.00117] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/30/2012] [Accepted: 05/15/2012] [Indexed: 05/14/2023]
Abstract
N-Glycosylation is a common form of eukaryotic protein post-translational modification, and one that is particularly prevalent in plant cell wall proteins. Large scale and detailed characterization of N-glycoproteins therefore has considerable potential in better understanding the composition and functions of the cell wall proteome, as well as those proteins that reside in other compartments of the secretory pathway. While there have been numerous studies of mammalian and yeast N-glycoproteins, less is known about the population complexity, biosynthesis, structural variation, and trafficking of their plant counterparts. However, technical developments in the analysis of glycoproteins and the structures the glycans that they bear, as well as valuable comparative analyses with non-plant systems, are providing new insights into features that are common among eukaryotes and those that are specific to plants, some of which may reflect the unique nature of the plant cell wall. In this review we present an overview of the current knowledge of plant N-glycoprotein synthesis and trafficking, with particular reference to those that are cell wall localized.
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Affiliation(s)
- Eliel Ruiz-May
- Department of Plant Biology, Cornell UniversityIthaca, NY, USA
| | - Sang-Jin Kim
- Great Lakes Bioenergy Research Center, Michigan State UniversityEast Lansing, MI, USA
- DOE Plant Research Laboratory, Michigan State UniversityEast Lansing, MI, USA
| | - Federica Brandizzi
- Great Lakes Bioenergy Research Center, Michigan State UniversityEast Lansing, MI, USA
- DOE Plant Research Laboratory, Michigan State UniversityEast Lansing, MI, USA
| | - Jocelyn K. C. Rose
- Department of Plant Biology, Cornell UniversityIthaca, NY, USA
- *Correspondence: Jocelyn K. C. Rose, Department of Plant Biology, Cornell University, 412 Mann Library Building, Ithaca, NY 14853 USA. e-mail:
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21
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Valvano MA. Common themes in glycoconjugate assembly using the biogenesis of O-antigen lipopolysaccharide as a model system. BIOCHEMISTRY (MOSCOW) 2011; 76:729-35. [DOI: 10.1134/s0006297911070029] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
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22
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Membrane topology and identification of critical amino acid residues in the Wzx O-antigen translocase from Escherichia coli O157:H4. J Bacteriol 2010; 192:6160-71. [PMID: 20870764 DOI: 10.1128/jb.00141-10] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Wzx belongs to a family of membrane proteins involved in the translocation of isoprenoid lipid-linked glycans, which is loosely related to members of the major facilitator superfamily. Despite Wzx homologs performing a conserved function, it has been difficult to pinpoint specific motifs of functional significance in their amino acid sequences. Here, we elucidate the topology of the Escherichia coli O157 Wzx (Wzx(EcO157)) by a combination of bioinformatics and substituted cysteine scanning mutagenesis, as well as targeted deletion-fusions to green fluorescent protein and alkaline phosphatase. We conclude that Wzx(EcO157) consists of 12 transmembrane (TM) helices and six periplasmic and five cytosolic loops, with N and C termini facing the cytoplasm. Four TM helices (II, IV, X, and XI) contain polar residues (aspartic acid or lysine), and they may form part of a relatively hydrophilic core. Thirty-five amino acid replacements to alanine or serine were targeted to five native cysteines and most of the aspartic acid, arginine, and lysine residues. From these, only replacements of aspartic acid-85, aspartic acid-326, arginine-298, and lysine-419 resulted in a protein unable to support O-antigen production. Aspartic acid-85 and lysine-419 are located in TM helices II and XI, while arginine-298 and aspartic acid-326 are located in periplasmic and cytosolic loops 4, respectively. Further analysis revealed that the charge at these positions is required for Wzx function since conservative substitutions maintaining the same charge polarity resulted in a functional protein, whereas those reversing or eliminating polarity abolished function. We propose that the functional requirement of charged residues at both sides of the membrane and in two TM helices could be important to allow the passage of the Und-PP-linked saccharide substrate across the membrane.
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23
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Fernández-Alvarez A, Elías-Villalobos A, Ibeas JI. Protein glycosylation in the phytopathogen Ustilago maydis: From core oligosaccharide synthesis to the ER glycoprotein quality control system, a genomic analysis. Fungal Genet Biol 2010; 47:727-35. [PMID: 20554055 DOI: 10.1016/j.fgb.2010.06.004] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2010] [Revised: 05/28/2010] [Accepted: 06/01/2010] [Indexed: 01/21/2023]
Abstract
The corn smut fungus Ustilago maydis has, over recent decades, become established as a robust pathogenic model for studying fungi-plant relationships. This use of U. maydis can be attributed to its biotrophic host interaction, easy culture and genetic manipulation in the laboratory, and the severe disease symptoms it induces in infected maize. Recent studies have shown that normal protein glycosylation is essential for pathogenic development, but dispensable for the saprophytic growth or mating. Given the relevance of protein glycosylation for U. maydis virulence, and consequently its role in the plant pathogenesis, here we review the main actors and events implicated in protein glycosylation. Furthermore, we describe the results of an in silico search, where we identify all the conserved members of the N- and O-glycosylation pathways in U. maydis at each stage: core oligosaccharide synthesis, addition of the core oligosaccharide to nascent target proteins, maturation and extension of the core oligosaccharide, and the quality control system used by the cell to avoid the presence of unfolded glycoproteins. Finally, we discuss how these genes could affect U. maydis virulence and their biotechnological implications.
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Affiliation(s)
- Alfonso Fernández-Alvarez
- Centro Andaluz de Biología del Desarrollo, Universidad Pablo de Olavide - Consejo Superior de Investigaciones Científicas, Seville, Spain
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24
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Aebi M, Bernasconi R, Clerc S, Molinari M. N-glycan structures: recognition and processing in the ER. Trends Biochem Sci 2009; 35:74-82. [PMID: 19853458 DOI: 10.1016/j.tibs.2009.10.001] [Citation(s) in RCA: 339] [Impact Index Per Article: 22.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2009] [Revised: 09/30/2009] [Accepted: 10/01/2009] [Indexed: 11/26/2022]
Abstract
The processing of N-linked glycans determines secretory protein homeostasis in the eukaryotic cell. Folding and degradation of glycoproteins in the endoplasmic reticulum (ER) are regulated by molecular chaperones and enzymes recruited by specific oligosaccharide structures. Recent findings have identified several components of this protein quality control system that specifically modify N-linked glycans, thereby generating oligosaccharide structures recognized by carbohydrate-binding proteins, lectins. In turn, lectins direct newly synthesized polypeptides to the folding, secretion or degradation pathways. The "glyco-code of the ER" displays the folding status of a multitude of cargo proteins. Deciphering this code will be instrumental in understanding protein homeostasis regulation in eukaryotic cells and for intervention because such processes can have crucial importance for clinical and industrial applications.
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Affiliation(s)
- Markus Aebi
- Institute of Microbiology, Department of Biology, Eidgenössische Technische Hochschule (ETH) Zürich, CH-8093 Zürich, Switzerland.
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25
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Henquet M, Heinhuis B, Borst JW, Eigenhuijsen J, Schreuder M, Bosch D, van der Krol A. Differential effects of human and plant N-acetylglucosaminyltransferase I (GnTI) in plants. Transgenic Res 2009; 19:535-47. [PMID: 19826906 PMCID: PMC2902736 DOI: 10.1007/s11248-009-9331-7] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2009] [Accepted: 09/27/2009] [Indexed: 11/25/2022]
Abstract
In plants and animals, the first step in complex type N-glycan formation on glycoproteins is catalyzed by N-acetylglucosaminyltransferase I (GnTI). We show that the cgl1-1 mutant of Arabidopsis, which lacks GnTI activity, is fully complemented by YFP-labeled plant AtGnTI, but only partially complemented by YFP-labeled human HuGnTI and that this is due to post-transcriptional events. In contrast to AtGnTI-YFP, only low levels of HuGnTI-YFP protein was detected in transgenic plants. In protoplast co-transfection experiments all GnTI-YFP fusion proteins co-localized with a Golgi marker protein, but only limited co-localization of AtGnTI and HuGnTI in the same plant protoplast. The partial alternative targeting of HuGnTI in plant protoplasts was alleviated by exchanging the membrane-anchor domain with that of AtGnTI, but in stably transformed cgl1-1 plants this chimeric GnTI still did not lead to full complementation of the cgl1-1 phenotype. Combined, the results indicate that activity of HuGnTI in plants is limited by a combination of reduced protein stability, alternative protein targeting and possibly to some extend to lower enzymatic performance of the catalytic domain in the plant biochemical environment.
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Affiliation(s)
- Maurice Henquet
- Laboratory of Plant Physiology, Wageningen University, Droevendaalsesteeg 1, 6708 PB Wageningen, The Netherlands
| | - Bas Heinhuis
- Laboratory of Plant Physiology, Wageningen University, Droevendaalsesteeg 1, 6708 PB Wageningen, The Netherlands
| | - Jan Willem Borst
- Microspectroscopy Centre, Laboratory of Biochemistry, Wageningen University, Dreijenlaan 3, 6703 HA Wageningen, The Netherlands
| | - Jochem Eigenhuijsen
- Laboratory of Plant Physiology, Wageningen University, Droevendaalsesteeg 1, 6708 PB Wageningen, The Netherlands
| | - Mariëlle Schreuder
- Laboratory of Plant Physiology, Wageningen University, Droevendaalsesteeg 1, 6708 PB Wageningen, The Netherlands
| | - Dirk Bosch
- Business Unit Bioscience, Plant Research International BV, Wageningen University and Research Centre, Droevendaalsesteeg 1, 6700 AA Wageningen, The Netherlands
- Membrane Enzymology, Department of Chemistry, Utrecht University, Padualaan 8, 3584 CH Utrecht, The Netherlands
| | - Alexander van der Krol
- Laboratory of Plant Physiology, Wageningen University, Droevendaalsesteeg 1, 6708 PB Wageningen, The Netherlands
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Vasudevan P, McElligott J, Attkisson C, Betteken M, Popham DL. Homologues of the Bacillus subtilis SpoVB protein are involved in cell wall metabolism. J Bacteriol 2009; 191:6012-9. [PMID: 19648239 PMCID: PMC2747891 DOI: 10.1128/jb.00604-09] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2009] [Accepted: 07/24/2009] [Indexed: 11/20/2022] Open
Abstract
Members of the COG2244 protein family are integral membrane proteins involved in synthesis of a variety of extracellular polymers. In several cases, these proteins have been suggested to move lipid-linked oligomers across the membrane or, in the case of Escherichia coli MviN, to flip the lipid II peptidoglycan precursor. Bacillus subtilis SpoVB was the first member of this family implicated in peptidoglycan synthesis and is required for spore cortex polymerization. Three other COG2244 members with high similarity to SpoVB are encoded within the B. subtilis genome. Mutant strains lacking any or all of these genes (yabM, ykvU, and ytgP) in addition to spoVB are viable and produce apparently normal peptidoglycan, indicating that their function is not essential in B. subtilis. Phenotypic changes associated with loss of two of these genes suggest that they function in peptidoglycan synthesis. Mutants lacking YtgP produce long cells and chains of cells, suggesting a role in cell division. Mutants lacking YabM exhibit sensitivity to moenomycin, an antibiotic that blocks peptidoglycan polymerization by class A penicillin-binding proteins. This result suggests that YabM may function in a previously observed alternate pathway for peptidoglycan strand synthesis.
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Affiliation(s)
- Pradeep Vasudevan
- Department of Biological Sciences, Virginia Tech, Blacksburg, VA 24061, USA
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Specific transbilayer translocation of dolichol-linked oligosaccharides by an endoplasmic reticulum flippase. Proc Natl Acad Sci U S A 2009; 106:767-72. [PMID: 19129492 DOI: 10.1073/pnas.0810225106] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The oligosaccharide donor for protein N-glycosylation, Glc(3)Man(9)GlcNAc(2)-PP-dolichol, is synthesized via a multistep pathway that starts on the cytoplasmic face of the endoplasmic reticulum (ER) and ends in the lumen where the glycosylation reaction occurs. This necessitates transbilayer translocation or flipping of the lipid intermediate Man(5)GlcNAc(2)-PP-dolichol (M5-DLO) across the ER membrane. The mechanism by which M5-DLO-or any other lipid-is flipped across the ER is unknown, except that specific transport proteins or flippases are required. We recently demonstrated M5-DLO flipping activity in proteoliposomes reconstituted from detergent-solubilized ER membrane proteins and showed that it was ATP-independent and required a trypsin-sensitive protein that sedimented at approximately 4S. By using an activity-enriched fraction devoid of glycerophospholipid flippase activity, we now report that M5-DLO is rapidly flipped in the reconstituted system with a time constant tau <2 min, whereas its triantennary structural isomer is flipped slowly with tau >200 min. DLOs larger than M5-DLO are also poorly translocated, with tau ranging from approximately 10 min to >200 min. We conclude that (i) the number and arrangement of mannoses in the DLO glycan has a profound effect on the ability of the DLO to be translocated by the flippase, (ii) glycan size per se does not dictate whether a DLO will be flipped, and (iii) the flippase is highly specific for M5-DLO. Our results suggest a simple structural model for the interaction between the DLO head group and the flippase.
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Stern R, Jedrzejas MJ. Carbohydrate Polymers at the Center of Life’s Origins: The Importance of Molecular Processivity. Chem Rev 2008; 108:5061-85. [DOI: 10.1021/cr078240l] [Citation(s) in RCA: 88] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
Affiliation(s)
- Robert Stern
- Department of Pathology and Comprehensive Cancer Center, School of Medicine, University of California, San Francisco, California 94143, Microdesign Institute, 29 Kingwood Rd., Oakland, California 94619, and Center for Immunobiology and Vaccine Development, Children’s Hospital Oakland Research Institute, 5700 Martin Luther King, Jr. Way, Oakland, California 94609
| | - Mark J. Jedrzejas
- Department of Pathology and Comprehensive Cancer Center, School of Medicine, University of California, San Francisco, California 94143, Microdesign Institute, 29 Kingwood Rd., Oakland, California 94619, and Center for Immunobiology and Vaccine Development, Children’s Hospital Oakland Research Institute, 5700 Martin Luther King, Jr. Way, Oakland, California 94609
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Funakoshi Y, Suzuki T. Glycobiology in the cytosol: the bitter side of a sweet world. Biochim Biophys Acta Gen Subj 2008; 1790:81-94. [PMID: 18952151 DOI: 10.1016/j.bbagen.2008.09.009] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2008] [Revised: 08/03/2008] [Accepted: 09/11/2008] [Indexed: 01/11/2023]
Abstract
Progress in glycobiology has undergone explosive growth over the past decade with more of the researchers now realizing the importance of glycan chains in various inter- and intracellular processes. However, there is still an area of glycobiology awaiting exploration. This is especially the case for the field of "glycobiology in the cytosol" which remains rather poorly understood. Yet evidence is accumulating to demonstrate that the glycoconjugates and their recognition molecules (i.e. lectins) are often present in this subcellular compartment.
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Affiliation(s)
- Yoko Funakoshi
- Glycometabolome Team, Systems Glycobiology Research Group, RIKEN Advanced Science Institute, 2-1 Hirosawa, Wako Saitama, 351-0198, Japan
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de Kruijff B, van Dam V, Breukink E. Lipid II: a central component in bacterial cell wall synthesis and a target for antibiotics. Prostaglandins Leukot Essent Fatty Acids 2008; 79:117-21. [PMID: 19008088 DOI: 10.1016/j.plefa.2008.09.020] [Citation(s) in RCA: 86] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
The bacterial cell wall is mainly composed of peptidoglycan, which is a three-dimensional network of long aminosugar strands located on the exterior of the cytoplasmic membrane. These strands consist of alternating MurNAc and GlcNAc units and are interlinked to each other via peptide moieties that are attached to the MurNAc residues. Peptidoglycan subunits are assembled on the cytoplasmic side of the bacterial membrane on a polyisoprenoid anchor and one of the key components in the synthesis of peptidoglycan is Lipid II. Being essential for bacterial cell survival, it forms an attractive target for antibacterial compounds such as vancomycin and several lantibiotics. Lipid II consists of one GlcNAc-MurNAc-pentapeptide subunit linked to a polyiosoprenoid anchor 11 subunits long via a pyrophosphate linker. This review focuses on this special molecule and addresses three questions. First, why are special lipid carriers as polyprenols used in the assembly of peptidoglycan? Secondly, how is Lipid II translocated across the bacterial cytoplasmic membrane? And finally, how is Lipid II used as a receptor for lantibiotics to kill bacteria?
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Affiliation(s)
- Ben de Kruijff
- Chemical Biology and Organic Chemistry, Utrecht University, Padualaan 8, Utrecht, The Netherlands
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31
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Does Rft1 flip an N-glycan lipid precursor? Nature 2008; 454:E3-4; discussion E4-5. [PMID: 18668045 DOI: 10.1038/nature07165] [Citation(s) in RCA: 56] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2007] [Accepted: 06/03/2008] [Indexed: 11/09/2022]
Abstract
Protein N-glycosylation requires flipping of the glycolipid Man(5)GlcNAc(2)-diphosphate dolichol (Man(5)GlcNAc(2)-PP-Dol) across the endoplasmic reticulum (ER). Helenius et al. report genetic evidence suggesting that Rft1, an essential ER membrane protein in yeast, is required directly to translocate Man(5)GlcNAc(2)-PP-Dol. We now show that a specific ER protein(s), but not Rft1, is required to flip Man(5)GlcNAc(2)-PP-Dol in reconstituted vesicles. Rft1 may have a critical accessory role in translocating Man(5)GlcNAc(2)-PP-Dol in vivo, but the Man(5)GlcNAc(2)-PP-Dol flippase itself remains to be identified.
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Sanyal S, Frank CG, Menon AK. Distinct flippases translocate glycerophospholipids and oligosaccharide diphosphate dolichols across the endoplasmic reticulum. Biochemistry 2008; 47:7937-46. [PMID: 18597486 PMCID: PMC2646664 DOI: 10.1021/bi800723n] [Citation(s) in RCA: 69] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023]
Abstract
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Transbilayer movement, or flip-flop, of lipids across the endoplasmic reticulum (ER) is required for membrane biogenesis, protein glycosylation, and GPI anchoring. Specific ER membrane proteins, flippases, are proposed to facilitate lipid flip-flop, but no ER flippase has been biochemically identified. The glycolipid Glc3Man9GlcNAc2-PP-dolichol is the oligosaccharide donor for protein N-glycosylation reactions in the ER lumen. Synthesis of Glc3Man9GlcNAc2-PP-dolichol is initiated on the cytoplasmic side of the ER and completed on the lumenal side, requiring flipping of the intermediate Man5GlcNAc2-PP-dolichol (M5-DLO) across the ER. Here we report the reconstitution of M5-DLO flipping in proteoliposomes generated from Triton X-100-extracted Saccharomyces cerevisiae microsomal proteins. Flipping was assayed by using the lectin Concanavalin A to capture M5-DLOs that had been translocated from the inner to the outer leaflet of the vesicles. M5-DLO flipping in the reconstituted system was ATP-independent and trypsin-sensitive and required a membrane protein(s) that sedimented at ∼4 S. Man7GlcNAc2-PP-dolichol, a higher-order lipid intermediate, was flipped >10-fold more slowly than M5-DLO at 25 °C. Chromatography on Cibacron Blue dye resin enriched M5-DLO flippase activity ∼5-fold and resolved it from both the ER glycerophospholipid flippase activity and the genetically identified flippase candidate Rft1 [Helenius, J., et al. (2002) Nature 415, 447−450]. The latter result indicates that Rft1 is not the M5-DLO flippase. Our data (i) demonstrate that the ER has at least two distinct flippase proteins, each specifically capable of translocating a class of phospholipid, and (ii) provide, for the first time, a biochemical means of identifying the M5-DLO flippase.
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Affiliation(s)
- Sumana Sanyal
- Department of Biochemistry, Weill Cornell Medical College, 1300 York Avenue, New York, New York 10065, USA
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Urushibata Y, Ebisu S, Matsui I. A thermostable dolichol phosphoryl mannose synthase responsible for glycoconjugate synthesis of the hyperthermophilic archaeon Pyrococcus horikoshii. Extremophiles 2008; 12:665-76. [PMID: 18563288 DOI: 10.1007/s00792-008-0173-7] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2008] [Accepted: 05/08/2008] [Indexed: 11/28/2022]
Abstract
Dolichol phosphoryl mannose synthase (DPM synthase) is an essential enzyme in the synthesis of N- and O-linked glycoproteins and the glycosylphosphatidyl-inositol anchor. An open reading frame, PH0051, from the hyperthermophilic archaeon Pyrococcus horikoshii encodes a DPM synthase ortholog, PH0051p. A full-length version of PH0051p was produced using an E. coli in vitro translation system and its thermostable activity was confirmed with a DPM synthesis assay, although the in vitro productivity was not sufficient for further characterization. Then, a yeast expression vector coding for the N-terminal catalytic domain of PH0051p was constructed. The N-terminal domain, named DPM(1-237), was successfully expressed, and turned out to be a membrane-bound form in Saccharomyces cerevisiae cells, even without its hydrophobic C-terminal domain. The membrane-bound DPM(1-237) was solubilized with a detergent and purified to homogeneity. The purified DPM(1-237) showed thermostability at up to 75 degrees C and an optimum temperature of 60 degrees C. The truncated mutant DPM(1-237) required Mg(2+) and Mn(2+) ions as cofactors the same as eukaryotic DPM synthases. By site-directed mutagenesis, Asp(89) and Asp(91) located at the most conserved motif, DXD, were confirmed as the catalytic residues, the latter probably bound to a cofactor, Mg(2+). DPM(1-237) was able to utilize both acceptor lipids, dolichol phosphate and the prokaryotic carrier lipid C(55)-undecaprenyl phosphate, with Km values of 1.17 and 0.59 microM, respectively. The DPM synthase PH0051p seems to be a key component of the pathway supplying various lipid-linked phosphate sugars, since P. horikoshii could synthesize glycoproteins as well as the membrane-associated PH0051p in vivo.
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Affiliation(s)
- Yuji Urushibata
- Biological Information Research Center, National Institute of Advanced Industrial Science and Technology, Tsukuba, Ibaraki 305-8566, Japan
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Henquet M, Lehle L, Schreuder M, Rouwendal G, Molthoff J, Helsper J, van der Krol S, Bosch D. Identification of the gene encoding the alpha1,3-mannosyltransferase (ALG3) in Arabidopsis and characterization of downstream n-glycan processing. THE PLANT CELL 2008; 20:1652-64. [PMID: 18567790 PMCID: PMC2483356 DOI: 10.1105/tpc.108.060731] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/14/2008] [Revised: 05/28/2008] [Accepted: 06/05/2008] [Indexed: 05/18/2023]
Abstract
Glycosyltransferases are involved in the biosynthesis of lipid-linked N-glycans. Here, we identify and characterize a mannosyltransferase gene from Arabidopsis thaliana, which is the functional homolog of the ALG3 (Dol-P-Man:Man5GlcNAc2-PP-Dol alpha1,3-mannosyl transferase) gene in yeast. The At ALG3 protein can complement a Deltaalg3 yeast mutant and is localized to the endoplasmic reticulum in yeast and in plants. A homozygous T-DNA insertion mutant, alg3-2, was identified in Arabidopsis with residual levels of wild-type ALG3, derived from incidental splicing of the 11th intron carrying the T-DNAs. N-glycan analysis of alg3-2 and alg3-2 in the complex-glycan-less mutant background, which lacks N-acetylglucosaminyl-transferase I activity, reveals that when ALG3 activity is strongly reduced, almost all N-glycans transferred to proteins are aberrant, indicating that the Arabidopsis oligosaccharide transferase complex is remarkably substrate tolerant. In alg3-2 plants, the aberrant glycans on glycoproteins are recognized by endogenous mannosidase I and N-acetylglucosaminyltransferase I and efficiently processed into complex-type glycans. Although no high-mannose-type glycoproteins are detected in alg3-2 plants, these plants do not show a growth phenotype under normal growth conditions. However, the glycosylation abnormalities result in activation of marker genes diagnostic of the unfolded protein response.
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Affiliation(s)
- Maurice Henquet
- Laboratory of Plant Physiology, Wageningen University, 6703 BD Wageningen, The Netherlands
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Kajiwara K, Watanabe R, Pichler H, Ihara K, Murakami S, Riezman H, Funato K. Yeast ARV1 is required for efficient delivery of an early GPI intermediate to the first mannosyltransferase during GPI assembly and controls lipid flow from the endoplasmic reticulum. Mol Biol Cell 2008; 19:2069-82. [PMID: 18287539 DOI: 10.1091/mbc.e07-08-0740] [Citation(s) in RCA: 87] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
Glycosylphosphatidylinositol (GPI), covalently attached to many eukaryotic proteins, not only acts as a membrane anchor but is also thought to be a sorting signal for GPI-anchored proteins that are associated with sphingolipid and sterol-enriched domains. GPI anchors contain a core structure conserved among all species. The core structure is synthesized in two topologically distinct stages on the leaflets of the endoplasmic reticulum (ER). Early GPI intermediates are assembled on the cytoplasmic side of the ER and then are flipped into the ER lumen where a complete GPI precursor is synthesized and transferred to protein. The flipping process is predicted to be mediated by a protein referred as flippase; however, its existence has not been proven. Here we show that yeast Arv1p is an important protein required for the delivery of an early GPI intermediate, GlcN-acylPI, to the first mannosyltransferase of GPI synthesis in the ER lumen. We also provide evidence that ARV1 deletion and mutations in other proteins involved in GPI anchor synthesis affect inositol phosphorylceramide synthesis as well as the intracellular distribution and amounts of sterols, suggesting a role of GPI anchor synthesis in lipid flow from the ER.
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Affiliation(s)
- Kentaro Kajiwara
- Department of Bioresource Science and Technology, Graduate School of Biosphere Science, Hiroshima University, Higashi-Hiroshima 739-8528, Japan
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Brockhausen I, Larsson EA, Hindsgaul O. A very simple synthesis of GlcNAc-α-pyrophosphoryl-decanol: A substrate for the assay of a bacterial galactosyltransferase. Bioorg Med Chem Lett 2008; 18:804-7. [DOI: 10.1016/j.bmcl.2007.11.031] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2007] [Revised: 11/07/2007] [Accepted: 11/09/2007] [Indexed: 11/17/2022]
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Abstract
The recycling of the lipid carrier undecaprenyl-phosphate (Und-P) requires the dephosphorylation of Und-PP, a reaction proposed to occur at the external or periplasmic side of the bacterial cell membrane. In this issue of Molecular Microbiology, experiments based on the analysis of lipopolysaccharide modifications in Escherichia coli demonstrate that the phosphorylation of lipid A at position 1 is catalysed by the membrane enzyme LpxT (formerly YeiU). This enzyme specifically transfers the distal phosphate group from Und-PP to lipid A 1-phosphate to produce lipid A 1-diphosphate. Furthermore, this reaction requires a functionally intact MsbA protein, which catalyses the transfer of lipid A across the membrane, confirming that the LpxT-mediated lipid A modification occurs on the periplasmic side of the membrane. These observations provide a novel and unexpected link between periplasmic lipid A modifications and the Und-PP recycling pathway.
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Affiliation(s)
- Miguel A Valvano
- Siebens-Drake Research Institute, Department of Microbiology and Immunology, University of Western Ontario, London, Ontario, Canada N6A 5C1.
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Tatar LD, Marolda CL, Polischuk AN, van Leeuwen D, Valvano MA. An Escherichia coli undecaprenyl-pyrophosphate phosphatase implicated in undecaprenyl phosphate recycling. Microbiology (Reading) 2007; 153:2518-2529. [PMID: 17660416 DOI: 10.1099/mic.0.2007/006312-0] [Citation(s) in RCA: 81] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Undecaprenyl phosphate (Und-P) is a universal lipid carrier of glycan biosynthetic intermediates for carbohydrate polymers that are exported to the bacterial cell envelope. Und-P arises from the dephosphorylation of undecaprenyl pyrophosphate (Und-PP) molecules produced by de novo synthesis and also from the recycling of released Und-PP after the transfer of the glycan component to other acceptor molecules. The latter reactions take place at the periplasmic side of the plasma membrane, while cytoplasmic enzymes catalyse the de novo synthesis. Four Und-PP pyrophosphatases were recently identified in Escherichia coli. One of these, UppP (formerly BacA), accounts for 75 % of the total cellular Und-PP pyrophosphatase activity and has been suggested to participate in the Und-P de novo synthesis pathway. Unlike UppP, the other three pyrophosphatases (YbjG, YeiU and PgpB) have a typical acid phosphatase motif also found in eukaryotic dolichyl-pyrophosphate-recycling pyrophosphatases. This study shows that double and triple deletion mutants in the genes uppP and ybjG, and uppP, ybjG and yeiU, respectively, are supersensitive to the Und-P de novo biosynthesis inhibitor fosmidomycin. In contrast, single or combined deletions including pgpB have no effect on fosmidomycin supersensitivity. Experimental evidence is also presented that the acid phosphatase motifs of YbjG and YeiU face the periplasmic space. Furthermore, the quadruple deletion mutant DeltauppP-DeltaybjG-DeltayeiU-DeltawaaL has a growth defect and abnormal cell morphology, suggesting that accumulation of unprocessed Und-PP-linked O antigen polysaccharides is toxic for these cells. Together, the results support the notion that YbjG, and to a lesser extent YeiU, exert their enzymic activity on the periplasmic side of the plasma membrane and are implicated in the recycling of periplasmic Und-PP molecules.
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Affiliation(s)
- Laura D Tatar
- Department of Microbiology and Immunology, Infectious Diseases Research Group, Siebens Drake Research Institute, University of Western Ontario, London, Ontario N6A 5C1, Canada
| | - Cristina L Marolda
- Department of Microbiology and Immunology, Infectious Diseases Research Group, Siebens Drake Research Institute, University of Western Ontario, London, Ontario N6A 5C1, Canada
| | - Andrew N Polischuk
- Department of Microbiology and Immunology, Infectious Diseases Research Group, Siebens Drake Research Institute, University of Western Ontario, London, Ontario N6A 5C1, Canada
| | - Deborah van Leeuwen
- Department of Microbiology and Immunology, Infectious Diseases Research Group, Siebens Drake Research Institute, University of Western Ontario, London, Ontario N6A 5C1, Canada
| | - Miguel A Valvano
- Department of Medicine, University of Western Ontario, London, Ontario N6A 5C1, Canada
- Department of Microbiology and Immunology, Infectious Diseases Research Group, Siebens Drake Research Institute, University of Western Ontario, London, Ontario N6A 5C1, Canada
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Vehring S, Pakkiri L, Schröer A, Alder-Baerens N, Herrmann A, Menon AK, Pomorski T. Flip-flop of fluorescently labeled phospholipids in proteoliposomes reconstituted with Saccharomyces cerevisiae microsomal proteins. EUKARYOTIC CELL 2007; 6:1625-34. [PMID: 17616631 PMCID: PMC2043374 DOI: 10.1128/ec.00198-07] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
A phospholipid flippase activity from the endoplasmic reticulum (ER) of the model organism Saccharomyces cerevisiae has been characterized and functionally reconstituted into proteoliposomes. Analysis of the transbilayer movement of acyl-7-nitrobenz-2-oxa-1,3-diazol-4-yl (acyl-NBD)-labeled phosphatidylcholine in yeast microsomes using a fluorescence stopped-flow back exchange assay revealed a rapid, ATP-independent flip-flop (half-time, <2 min). Proteoliposomes prepared from a Triton X-100 extract of yeast microsomal membranes were also capable of flipping NBD-labeled phospholipid analogues rapidly in an ATP-independent fashion. Flippase activity was sensitive to the protein modification reagents N-ethylmaleimide and diethylpyrocarbonate. Resolution of the Triton X-100 extract by velocity gradient centrifugation resulted in the identification of a approximately 4S protein fraction enriched in flippase activity as well as of other fractions where flippase activity was depleted or undetectable. We estimate that flippase activity is due to a protein(s) representing approximately 2% (wt/wt) of proteins in the Triton X-100 extract. These results indicate that specific proteins are required to facilitate ATP-independent phospholipid flip-flop in the ER and that their identification is feasible. The architecture of the ER protein translocon suggests that it could account for the flippase activity in the ER. We tested this hypothesis using microsomes prepared from a temperature-sensitive yeast mutant in which the major translocon component, Sec61p, was quantitatively depleted. We found that the protein translocon is not required for transbilayer movement of phospholipids across the ER. Our work defines yeast as a promising model system for future attempts to identify the ER phospholipid flippase and to test and purify candidate flippases.
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Affiliation(s)
- Stefanie Vehring
- Institute of Biology/Biophysics, Humboldt University of Berlin, Invalidenstr. 42, 10115 Berlin, Germany
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Orlean P, Menon AK. Thematic review series: lipid posttranslational modifications. GPI anchoring of protein in yeast and mammalian cells, or: how we learned to stop worrying and love glycophospholipids. J Lipid Res 2007; 48:993-1011. [PMID: 17361015 DOI: 10.1194/jlr.r700002-jlr200] [Citation(s) in RCA: 273] [Impact Index Per Article: 16.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Glycosylphosphatidylinositol (GPI) anchoring of cell surface proteins is the most complex and metabolically expensive of the lipid posttranslational modifications described to date. The GPI anchor is synthesized via a membrane-bound multistep pathway in the endoplasmic reticulum (ER) requiring >20 gene products. The pathway is initiated on the cytoplasmic side of the ER and completed in the ER lumen, necessitating flipping of a glycolipid intermediate across the membrane. The completed GPI anchor is attached to proteins that have been translocated across the ER membrane and that display a GPI signal anchor sequence at the C terminus. GPI proteins transit the secretory pathway to the cell surface; in yeast, many become covalently attached to the cell wall. Genes encoding proteins involved in all but one of the predicted steps in the assembly of the GPI precursor glycolipid and its transfer to protein in mammals and yeast have now been identified. Most of these genes encode polytopic membrane proteins, some of which are organized in complexes. The steps in GPI assembly, and the enzymes that carry them out, are highly conserved. GPI biosynthesis is essential for viability in yeast and for embryonic development in mammals. In this review, we describe the biosynthesis of mammalian and yeast GPIs, their transfer to protein, and their subsequent processing.
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Affiliation(s)
- Peter Orlean
- Department of Microbiology, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA.
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Cottrell TR, Griffith CL, Liu H, Nenninger AA, Doering TL. The pathogenic fungus Cryptococcus neoformans expresses two functional GDP-mannose transporters with distinct expression patterns and roles in capsule synthesis. EUKARYOTIC CELL 2007; 6:776-85. [PMID: 17351078 PMCID: PMC1899245 DOI: 10.1128/ec.00015-07] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Cryptococcus neoformans is a fungal pathogen that is responsible for life-threatening disease, particularly in the context of compromised immunity. This organism makes extensive use of mannose in constructing its cell wall, glycoproteins, and glycolipids. Mannose also comprises up to two-thirds of the main cryptococcal virulence factor, a polysaccharide capsule that surrounds the cell. The glycosyltransfer reactions that generate cellular carbohydrate structures usually require activated donors such as nucleotide sugars. GDP-mannose, the mannose donor, is produced in the cytosol by the sequential actions of phosphomannose isomerase, phosphomannomutase, and GDP-mannose pyrophosphorylase. However, most mannose-containing glycoconjugates are synthesized within intracellular organelles. This topological separation necessitates a specific transport mechanism to move this key precursor across biological membranes to the appropriate site for biosynthetic reactions. We have discovered two GDP-mannose transporters in C. neoformans, in contrast to the single such protein reported previously for other fungi. Biochemical studies of each protein expressed in Saccharomyces cerevisiae show that both are functional, with similar kinetics and substrate specificities. Microarray experiments indicate that the two proteins Gmt1 and Gmt2 are transcribed with distinct patterns of expression in response to variations in growth conditions. Additionally, deletion of the GMT1 gene yields cells with small capsules and a defect in capsule induction, while deletion of GMT2 does not alter the capsule. We suggest that C. neoformans produces two GDP-mannose transporters to satisfy its enormous need for mannose utilization in glycan synthesis. Furthermore, we propose that the two proteins have distinct biological roles. This is supported by the different expression patterns of GMT1 and GMT2 in response to environmental stimuli and the dissimilar phenotypes that result when each gene is deleted.
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Affiliation(s)
- Tricia R Cottrell
- Department of Molecular Microbiology, Washington University School of Medicine, Campus Box 8230, 600 South Euclid Avenue, St. Louis, MO 63110, USA
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Orłowski J, Machula K, Janik A, Zdebska E, Palamarczyk G. Dissecting the role of dolichol in cell wall assembly in the yeast mutants impaired in early glycosylation reactions. Yeast 2007; 24:239-52. [PMID: 17397129 DOI: 10.1002/yea.1479] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
Evidence is presented that temperature-sensitive Saccharomyces cerevisiae mutants, impaired in dolichol kinase (Sec59p) or dolichyl phosphate mannose synthase (Dpm1p) activity have an aberrant cell wall composition and ultrastructure. The mutants were oversensitive to Calcofluor white, an agent interacting with the cell wall chitin. In accordance with this, chemical analysis of the cell wall alkali-insoluble fraction indicated an increased amount of chitin and changes in the quantity of beta1,6- and beta1,3-glucan in sec59-1 and dpm1-6 mutants. In order to unravel the link between the formation of dolichyl phosphate and dolichyl phosphate mannose and the cell wall assembly, we screened a yeast genomic library for a multicopy suppressors of the thermosensitive phenotype. The RER2 and SRT1 genes, encoding cis-prenyltransferases, were isolated. In addition, the ROT1 gene, encoding protein involved in beta1,6-glucan synthesis (Machi et al., 2004) and protein folding (Takeuchi et al., 2006) acted as a multicopy suppressor of the temperature-sensitive phenotype of the sec59-1 mutant. The cell wall of the mutants and of mutants bearing the multicopy suppressors was analysed for carbohydrate and mannoprotein content. We also examined the glycosylation status of the plasma membrane protein Gas1p, a beta1,3-glucan elongase, and the degree of phosphorylation of the Mpk1/Slt2 protein, involved in the cell wall integrity pathway.
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Affiliation(s)
- Jacek Orłowski
- Institute of Biochemistry and Biophysics, Polish Academy of Sciences, Pawinskiego 5a, Warsaw, Poland
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43
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Affiliation(s)
- David L Daleke
- Department of Biochemistry and Molecular Biology and the Medical Sciences Program, Indiana University School of Medicine, Bloomington, Indiana 47405, USA.
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Österberg M, Kim H, Warringer J, Melén K, Blomberg A, von Heijne G. Phenotypic effects of membrane protein overexpression in Saccharomyces cerevisiae. Proc Natl Acad Sci U S A 2006; 103:11148-53. [PMID: 16847257 PMCID: PMC1544056 DOI: 10.1073/pnas.0604078103] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Large-scale protein overexpression phenotype screens provide an important complement to the more common gene knockout screens. Here, we have targeted the so far poorly understood Saccharomyces cerevisiae membrane proteome and report growth phenotypes for a strain collection overexpressing approximately 600 C-terminally tagged integral membrane proteins grown both under normal and three different stress conditions. Although overexpression of most membrane proteins reduce the growth rate in synthetic defined medium, we identify a large number of proteins that, when overexpressed, confer specific resistance to various stress conditions. Our data suggest that regulation of glycosylphosphatidylinositol anchor biosynthesis and the Na(+)/K(+) homeostasis system constitute major downstream targets of the yeast PKA/RAS pathway and point to a possible connection between the early secretory pathway and the cells' response to oxidative stress. We also have quantified the expression levels for >550 membrane proteins, facilitating the choice of well expressing proteins for future functional and structural studies.
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Affiliation(s)
- Marie Österberg
- *Center for Biomembrane Research, Department of Biochemistry and Biophysics, Stockholm University, SE-106 91 Stockholm, Sweden
| | - Hyun Kim
- *Center for Biomembrane Research, Department of Biochemistry and Biophysics, Stockholm University, SE-106 91 Stockholm, Sweden
| | - Jonas Warringer
- Department of Cell and Molecular Biology, Göteborg University, SE-413 90 Göteborg, Sweden
| | - Karin Melén
- *Center for Biomembrane Research, Department of Biochemistry and Biophysics, Stockholm University, SE-106 91 Stockholm, Sweden
- Stockholm Bioinformatics Center, AlbaNova, SE-106 91 Stockholm, Sweden; and
| | - Anders Blomberg
- Department of Cell and Molecular Biology, Göteborg University, SE-413 90 Göteborg, Sweden
| | - Gunnar von Heijne
- *Center for Biomembrane Research, Department of Biochemistry and Biophysics, Stockholm University, SE-106 91 Stockholm, Sweden
- Stockholm Bioinformatics Center, AlbaNova, SE-106 91 Stockholm, Sweden; and
- To whom correspondence should be addressed. E-mail:
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Marolda CL, Tatar LD, Alaimo C, Aebi M, Valvano MA. Interplay of the Wzx translocase and the corresponding polymerase and chain length regulator proteins in the translocation and periplasmic assembly of lipopolysaccharide o antigen. J Bacteriol 2006; 188:5124-35. [PMID: 16816184 PMCID: PMC1539953 DOI: 10.1128/jb.00461-06] [Citation(s) in RCA: 76] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2006] [Accepted: 04/25/2006] [Indexed: 11/20/2022] Open
Abstract
Genetic evidence suggests that a family of bacterial and eukaryotic integral membrane proteins (referred to as Wzx and Rft1, respectively) mediates the transbilayer movement of isoprenoid lipid-linked glycans. Recent work in our laboratory has shown that Wzx proteins involved in O-antigen lipopolysaccharide (LPS) assembly have relaxed specificity for the carbohydrate structure of the O-antigen subunit. Furthermore, the proximal sugar bound to the isoprenoid lipid carrier, undecaprenyl-phosphate (Und-P), is the minimal structure required for translocation. In Escherichia coli K-12, N-acetylglucosamine (GlcNAc) is the proximal sugar of the O16 and enterobacterial common antigen (ECA) subunits. Both O16 and ECA systems have their respective translocases, WzxO16 and WzxE, and also corresponding polymerases (WzyO16 and WzyE) and O-antigen chain-length regulators (WzzO16 and WzzE), respectively. In this study, we show that the E. coli wzxE gene can fully complement a wzxO16 translocase deletion mutant only if the majority of the ECA gene cluster is deleted. In addition, we demonstrate that introduction of plasmids expressing either the WzyE polymerase or the WzzE chain-length regulator proteins drastically reduces the O16 LPS-complementing activity of WzxE. We also show that this property is not unique to WzxE, since WzxO16 and WzxO7 can cross-complement translocase defects in the O16 and O7 antigen clusters only in the absence of their corresponding Wzz and Wzy proteins. These genetic data are consistent with the notion that the translocation of O-antigen and ECA subunits across the plasma membrane and the subsequent assembly of periplasmic O-antigen and ECA Und-PP-linked polymers depend on interactions among Wzx, Wzz, and Wzy, which presumably form a multiprotein complex.
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Affiliation(s)
- Cristina L Marolda
- Department of Microbiology and Immunology, Dental Sciences Building, Rm. 3014, University of Western Ontario, London, Ontario, Canada, N6A 5C1
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Mitra N, Sinha S, Ramya TNC, Surolia A. N-linked oligosaccharides as outfitters for glycoprotein folding, form and function. Trends Biochem Sci 2006; 31:156-63. [PMID: 16473013 DOI: 10.1016/j.tibs.2006.01.003] [Citation(s) in RCA: 233] [Impact Index Per Article: 12.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2005] [Revised: 01/06/2006] [Accepted: 01/30/2006] [Indexed: 01/27/2023]
Abstract
Glycosylation, particularly N-linked glycosylation, profoundly affects protein folding, oligomerization and stability. The increased efficiency of folding of glycosylated proteins could be due to the chaperone-like activity of glycans, which is observed even when the glycan is not attached to the protein. Covalently linked glycans could also facilitate oligomerization by mediating inter-subunit interactions in the protein or stabilizing the oligomer in other ways. Glycosylation also affects the rate of fibril formation in prion proteins: N-glycans reduce the rate of fibril formation, and O-glycans affect the rate either way depending on factors such as position and orientation. It has yet to be determined whether there is any correlation among the sites of glycosylation and the ensuing effect in multiply glycosylated proteins. It is also not apparent whether there is a common pattern in the conservation of glycans in a related family of glycoproteins, but it is evident that glycosylation is a multifaceted post-translational modification. Indeed, glycosylation serves to "outfit" proteins for fold-function balance.
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Affiliation(s)
- Nivedita Mitra
- Molecular Biophysics Unit, Indian Institute of Science, Bangalore 560 012, India
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van Anken E, Braakman I. Versatility of the endoplasmic reticulum protein folding factory. Crit Rev Biochem Mol Biol 2005; 40:191-228. [PMID: 16126486 DOI: 10.1080/10409230591008161] [Citation(s) in RCA: 135] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
The endoplasmic reticulum (ER) is dedicated to import, folding and assembly of all proteins that travel along or reside in the secretory pathway of eukaryotic cells. Folding in the ER is special. For instance, newly synthesized proteins are N-glycosylated and by default form disulfide bonds in the ER, but not elsewhere in the cell. In this review, we discuss which features distinguish the ER as an efficient folding factory, how the ER monitors its output and how it disposes of folding failures.
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Affiliation(s)
- Eelco van Anken
- Department of Cellular Protein Chemistry, Bijvoet Center, Utrecht University, The Netherlands
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Abstract
One of the first hurdles to be negotiated in the postgenomic era involves the description of the entire protein content of the cell, the proteome. Such efforts are presently complicated by the various posttranslational modifications that proteins can experience, including glycosylation, lipid attachment, phosphorylation, methylation, disulfide bond formation, and proteolytic cleavage. Whereas these and other posttranslational protein modifications have been well characterized in Eucarya and Bacteria, posttranslational modification in Archaea has received far less attention. Although archaeal proteins can undergo posttranslational modifications reminiscent of what their eucaryal and bacterial counterparts experience, examination of archaeal posttranslational modification often reveals aspects not previously observed in the other two domains of life. In some cases, posttranslational modification allows a protein to survive the extreme conditions often encountered by Archaea. The various posttranslational modifications experienced by archaeal proteins, the molecular steps leading to these modifications, and the role played by posttranslational modification in Archaea form the focus of this review.
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Affiliation(s)
- Jerry Eichler
- Dept. of Life Sciences, Ben Gurion University, P.O. Box 653, Beersheva 84105, Israel.
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Jones J, Viswanathan K, Krag SS, Betenbaugh MJ. Polyprenyl lipid synthesis in mammalian cells expressing human cis-prenyl transferase. Biochem Biophys Res Commun 2005; 331:379-83. [PMID: 15850770 DOI: 10.1016/j.bbrc.2005.03.181] [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] [Received: 03/22/2005] [Indexed: 10/25/2022]
Abstract
The level of cis-prenyl transferase activity has been implicated in controlling the level of biosynthesis of dolichol and dolichol intermediates. In this study, we isolated a cDNA encoding a human CPT (GenBank Accession No. ), which had substantial homology to other CPT isolated from human brain, bacteria, Arabidopsis, and Saccharomyces cerevisiae. Expression of this cDNA in two different insect cell lines confirmed the functionality of the protein in an in vitro assay. Western blot analysis revealed an expressed protein of approximately 38 kDa in HEK293 cells. Overexpression of the protein in HEK293 cells resulted in an increase in the level of total prenol in vivo. Furthermore, product characterization by thin layer chromatography (TLC) confirmed that the major product was a long-chain prenol with a chain length of 95 carbons. These results suggest a regulatory relationship between CPT activity and dolichol biosynthesis, and may implicate CPT in the levels of dolichol-oligosaccharide intermediate biosynthesis.
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Affiliation(s)
- Jullian Jones
- Department of Chemical and Biomolecular Engineering, Baltimore, MD 21218, USA.
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Frank CG, Aebi M. ALG9 mannosyltransferase is involved in two different steps of lipid-linked oligosaccharide biosynthesis. Glycobiology 2005; 15:1156-63. [PMID: 15987956 DOI: 10.1093/glycob/cwj002] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
N-linked protein glycosylation follows a conserved pathway in eukaryotic cells. The assembly of the lipid-linked core oligosaccharide Glc3Man9GlcNAc2, the substrate for the oligosaccharyltransferase (OST), is catalyzed by different glycosyltransferases located at the membrane of the endoplasmic reticulum (ER). The substrate specificity of the different glycosyltransferase guarantees the ordered assembly of the branched oligosaccharide and ensures that only completely assembled oligosaccharide is transferred to protein. The glycosyltransferases involved in this pathway are highly specific, catalyzing the addition of one single hexose unit to the lipid-linked oligosaccharide (LLO). Here, we show that the dolichylphosphomannose-dependent ALG9 mannosyltransferase is the exception from this rule and is required for the addition of two different alpha-1,2-linked mannose residues to the LLO. This report completes the list of lumen-oriented glycosyltransferases required for the assembly of the LLO.
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Affiliation(s)
- Christian G Frank
- Institute of Microbiology, Department of Biology, Swiss Federal Institute of Technology Zürich, ETH Hönggerberg, CH-8093 Zürich, Switzerland
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