1
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Gemmer M, Chaillet ML, Förster F. Exploring the molecular composition of the multipass translocon in its native membrane environment. Life Sci Alliance 2024; 7:e202302496. [PMID: 38866426 PMCID: PMC11169918 DOI: 10.26508/lsa.202302496] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2023] [Revised: 05/22/2024] [Accepted: 05/23/2024] [Indexed: 06/14/2024] Open
Abstract
Multispanning membrane proteins are inserted into the endoplasmic reticulum membrane by the ribosome-bound multipass translocon (MPT) machinery. Based on cryo-electron tomography and extensive subtomogram analysis, we reveal the composition and arrangement of ribosome-bound MPT components in their native membrane environment. The intramembrane chaperone complex PAT and the translocon-associated protein (TRAP) complex associate substoichiometrically with the MPT in a translation-dependent manner. Although PAT is preferentially part of MPTs bound to translating ribosomes, the abundance of TRAP is highest in MPTs associated with non-translating ribosomes. The subtomogram average of the TRAP-containing MPT reveals intermolecular contacts between the luminal domains of TRAP and an unknown subunit of the back-of-Sec61 complex. AlphaFold modeling suggests this protein is nodal modulator, bridging the luminal domains of nicalin and TRAPα. Collectively, our results visualize the variability of MPT factors in the native membrane environment dependent on the translational activity of the bound ribosome.
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Affiliation(s)
- Max Gemmer
- https://ror.org/04pp8hn57 Structural Biochemistry, Bijvoet Center for Biomolecular Research, Utrecht University, Utrecht, Netherlands
| | - Marten L Chaillet
- https://ror.org/04pp8hn57 Structural Biochemistry, Bijvoet Center for Biomolecular Research, Utrecht University, Utrecht, Netherlands
| | - Friedrich Förster
- https://ror.org/04pp8hn57 Structural Biochemistry, Bijvoet Center for Biomolecular Research, Utrecht University, Utrecht, Netherlands
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2
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Hendershot LM, Buck TM, Brodsky JL. The Essential Functions of Molecular Chaperones and Folding Enzymes in Maintaining Endoplasmic Reticulum Homeostasis. J Mol Biol 2024; 436:168418. [PMID: 38143019 DOI: 10.1016/j.jmb.2023.168418] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2023] [Revised: 12/18/2023] [Accepted: 12/19/2023] [Indexed: 12/26/2023]
Abstract
It has been estimated that up to one-third of the proteins encoded by the human genome enter the endoplasmic reticulum (ER) as extended polypeptide chains where they undergo covalent modifications, fold into their native structures, and assemble into oligomeric protein complexes. The fidelity of these processes is critical to support organellar, cellular, and organismal health, and is perhaps best underscored by the growing number of disease-causing mutations that reduce the fidelity of protein biogenesis in the ER. To meet demands encountered by the diverse protein clientele that mature in the ER, this organelle is populated with a cadre of molecular chaperones that prevent protein aggregation, facilitate protein disulfide isomerization, and lower the activation energy barrier of cis-trans prolyl isomerization. Components of the lectin (glycan-binding) chaperone system also reside within the ER and play numerous roles during protein biogenesis. In addition, the ER houses multiple homologs of select chaperones that can recognize and act upon diverse peptide signatures. Moreover, redundancy helps ensure that folding-compromised substrates are unable to overwhelm essential ER-resident chaperones and enzymes. In contrast, the ER in higher eukaryotic cells possesses a single member of the Hsp70, Hsp90, and Hsp110 chaperone families, even though several homologs of these molecules reside in the cytoplasm. In this review, we discuss specific functions of the many factors that maintain ER quality control, highlight some of their interactions, and describe the vulnerabilities that arise from the absence of multiple members of some chaperone families.
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Affiliation(s)
- Linda M Hendershot
- Department of Tumor Cell Biology, St. Jude Children's Research Hospital, Memphis, TN 38105, United States.
| | - Teresa M Buck
- Department of Biological Sciences, University of Pittsburgh, Pittsburgh, PA 15260, United States
| | - Jeffrey L Brodsky
- Department of Biological Sciences, University of Pittsburgh, Pittsburgh, PA 15260, United States
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3
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Piniello B, Macías-León J, Miyazaki S, García-García A, Compañón I, Ghirardello M, Taleb V, Veloz B, Corzana F, Miyagawa A, Rovira C, Hurtado-Guerrero R. Molecular basis for bacterial N-glycosylation by a soluble HMW1C-like N-glycosyltransferase. Nat Commun 2023; 14:5785. [PMID: 37723184 PMCID: PMC10507012 DOI: 10.1038/s41467-023-41238-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2023] [Accepted: 08/24/2023] [Indexed: 09/20/2023] Open
Abstract
Soluble HMW1C-like N-glycosyltransferases (NGTs) catalyze the glycosylation of Asn residues in proteins, a process fundamental for bacterial autoaggregation, adhesion and pathogenicity. However, our understanding of their molecular mechanisms is hindered by the lack of structures of enzymatic complexes. Here, we report structures of binary and ternary NGT complexes of Aggregatibacter aphrophilus NGT (AaNGT), revealing an essential dyad of basic/acidic residues located in the N-terminal all α-domain (AAD) that intimately recognizes the Thr residue within the conserved motif Asn0-X+1-Ser/Thr+2. Poor substrates and inhibitors such as UDP-galactose and UDP-glucose mimetics adopt non-productive conformations, decreasing or impeding catalysis. QM/MM simulations rationalize these results, showing that AaNGT follows a SN2 reaction mechanism in which the acceptor asparagine uses its imidic form for catalysis and the UDP-glucose phosphate group acts as a general base. These findings provide key insights into the mechanism of NGTs and will facilitate the design of structure-based inhibitors to treat diseases caused by non-typeable H. influenzae or other Gram-negative bacteria.
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Affiliation(s)
- Beatriz Piniello
- Departament de Química Inorgànica i Orgànica (Secció de Química Orgànica) and Institut de Química Teòrica i Computacional (IQTCUB), Universitat de Barcelona, Martí i Franquès 1, 08028, Barcelona, Spain
| | - Javier Macías-León
- Institute of Biocomputation and Physics of Complex Systems, University of Zaragoza, Mariano Esquillor s/n, Campus Rio Ebro, Edificio I+D, Zaragoza, Spain
| | - Shun Miyazaki
- Department of Life Science and Applied Chemistry, Nagoya Institute of Technology, Gokiso-cho, Showa-ku, Nagoya, 466-8555, Japan
| | - Ana García-García
- Institute of Biocomputation and Physics of Complex Systems, University of Zaragoza, Mariano Esquillor s/n, Campus Rio Ebro, Edificio I+D, Zaragoza, Spain
| | - Ismael Compañón
- Departamento de Química, Universidad de La Rioja, Centro de Investigación en Síntesis Química, E-26006, Logroño, Spain
| | - Mattia Ghirardello
- Departamento de Química, Universidad de La Rioja, Centro de Investigación en Síntesis Química, E-26006, Logroño, Spain
| | - Víctor Taleb
- Institute of Biocomputation and Physics of Complex Systems, University of Zaragoza, Mariano Esquillor s/n, Campus Rio Ebro, Edificio I+D, Zaragoza, Spain
| | - Billy Veloz
- Institute of Biocomputation and Physics of Complex Systems, University of Zaragoza, Mariano Esquillor s/n, Campus Rio Ebro, Edificio I+D, Zaragoza, Spain
| | - Francisco Corzana
- Departamento de Química, Universidad de La Rioja, Centro de Investigación en Síntesis Química, E-26006, Logroño, Spain
| | - Atsushi Miyagawa
- Department of Life Science and Applied Chemistry, Nagoya Institute of Technology, Gokiso-cho, Showa-ku, Nagoya, 466-8555, Japan
| | - Carme Rovira
- Departament de Química Inorgànica i Orgànica (Secció de Química Orgànica) and Institut de Química Teòrica i Computacional (IQTCUB), Universitat de Barcelona, Martí i Franquès 1, 08028, Barcelona, Spain.
- Institució Catalana de Recerca i Estudis Avançats (ICREA), Passeig Lluís Companys 23, 08010, Barcelona, Spain.
| | - Ramon Hurtado-Guerrero
- Institute of Biocomputation and Physics of Complex Systems, University of Zaragoza, Mariano Esquillor s/n, Campus Rio Ebro, Edificio I+D, Zaragoza, Spain.
- Copenhagen Center for Glycomics, Department of Cellular and Molecular Medicine, University of Copenhagen, Copenhagen, Denmark.
- Fundación ARAID, 50018, Zaragoza, Spain.
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4
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Bai L, Li H. Structural insights into the membrane chaperones for multi-pass membrane protein biogenesis. Curr Opin Struct Biol 2023; 79:102563. [PMID: 36863267 DOI: 10.1016/j.sbi.2023.102563] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2022] [Revised: 01/22/2023] [Accepted: 01/28/2023] [Indexed: 03/04/2023]
Abstract
Certain transmembrane α-helices of multi-pass membrane proteins line substrate transport paths or catalytic pockets and, therefore, are partially hydrophilic. Sec61 alone is insufficient to insert these less hydrophobic segments into the membrane and needs to work with dedicated membrane chaperones. Three such membrane chaperones have been described in the literature-the endoplasmic reticulum membrane protein complex (EMC), the TMCO1 complex, and the PAT complex. Recent structural studies on these membrane chaperones have revealed their overall architecture, multi-subunit assembly, putative substrate transmembrane helix-binding pockets, and cooperative mechanisms with the ribosome and Sec61 translocon. These structures are providing initial insights into the poorly understood processes of multi-pass membrane protein biogenesis.
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Affiliation(s)
- Lin Bai
- Department of Biochemistry and Biophysics, School of Basic Medical Sciences, Peking University, Beijing, 100083, China.
| | - Huilin Li
- Department of Structural Biology, Van Andel Institute, Grand Rapids, MI, 49503, United States.
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5
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Liu D, De Schutter K, Chen P, Smagghe G. The N-glycosylation-related genes as potential targets for RNAi-mediated pest control of the Colorado potato beetle (Leptinotarsa decemlineata). PEST MANAGEMENT SCIENCE 2022; 78:3815-3822. [PMID: 34821017 DOI: 10.1002/ps.6732] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/17/2021] [Revised: 11/09/2021] [Accepted: 11/25/2021] [Indexed: 06/13/2023]
Abstract
BACKGROUND N-glycosylation is one of the most common and important post-translational modifications in the eukaryotic cell. The study of protein N-glycosylation in several model insects confirmed the importance of this process in insect development, immunity, survival and fertility. The Colorado potato beetle (Leptinotarsa decemlineata) (CPB) is a common pest of Solanaceae crops. With the infamous title of champion of insecticide resistance, novel pest control strategies for this insect are needed. Luckily this pest insect is reported as very sensitive for the post-genomic technology of RNA interference (RNAi). RESULTS In this project, we investigated the importance of N-glycosylation in the survival and development of CPB using RNAi-mediated gene silencing of N-glycosylation-related genes (NGRGs) during the different transition steps from the larva, through the pupa to the adult stage. High mortality was observed in the larval stage with the silencing of early NGRGs, as STT3a, DAD1 and GCS1. With dsRNA against middle NGRGs, abnormal phenotypes at the ecdysis process and adult formation were observed, while the silencing of late NGRGs did not cause mortality. CONCLUSION The lethal phenotypes observed on silencing of the genes involved in the early processing steps of the N-glycosylation pathway suggest these genes are good candidates for RNAi-mediated control of CPB. Next to the gene-specific mechanism of RNAi for biosafety and possible implementation in integrated pest management, we believe these early NGRGs provide a possible alternative to the well-known target genes Snf7 and vacuolar ATPases that are now used in the first commercial RNAi-based products and thus they may be useful in the context of proactive resistance management. © 2021 Society of Chemical Industry.
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Affiliation(s)
- Dongdong Liu
- Laboratory of Agrozoology, Department Plants and Crops, Faculty of Bioscience Engineering, Ghent University, Ghent, Belgium
| | - Kristof De Schutter
- Laboratory of Agrozoology, Department Plants and Crops, Faculty of Bioscience Engineering, Ghent University, Ghent, Belgium
| | - Pengyu Chen
- Laboratory of Agrozoology, Department Plants and Crops, Faculty of Bioscience Engineering, Ghent University, Ghent, Belgium
| | - Guy Smagghe
- Laboratory of Agrozoology, Department Plants and Crops, Faculty of Bioscience Engineering, Ghent University, Ghent, Belgium
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6
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Li H, Lee WS, Feng X, Bai L, Jennings BC, Liu L, Doray B, Canfield WM, Kornfeld S, Li H. Structure of the human GlcNAc-1-phosphotransferase αβ subunits reveals regulatory mechanism for lysosomal enzyme glycan phosphorylation. Nat Struct Mol Biol 2022; 29:348-356. [PMID: 35332324 PMCID: PMC9018626 DOI: 10.1038/s41594-022-00748-0] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2021] [Accepted: 02/16/2022] [Indexed: 02/07/2023]
Abstract
Vertebrates use the mannose 6-phosphate (M6P)-recognition system to deliver lysosomal hydrolases to lysosomes. Key to this pathway is N-acetylglucosamine (GlcNAc)-1-phosphotransferase (PTase) that selectively adds GlcNAc-phosphate (P) to mannose residues of hydrolases. Human PTase is an α2β2γ2 heterohexamer with a catalytic core and several peripheral domains that recognize and bind substrates. Here we report a cryo-EM structure of the catalytic core of human PTase and the identification of a hockey stick-like motif that controls activation of the enzyme. Movement of this motif out of the catalytic pocket is associated with a rearrangement of part of the peripheral domains that unblocks hydrolase glycan access to the catalytic site, thereby activating PTase. We propose that PTase fluctuates between inactive and active states in solution, and selective substrate binding of a lysosomal hydrolase through its protein-binding determinant to PTase locks the enzyme in the active state to permit glycan phosphorylation. This mechanism would help ensure that only N-linked glycans of lysosomal enzymes are phosphorylated.
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Affiliation(s)
- Hua Li
- Department of Structural Biology, Van Andel Institute, Grand Rapids, MI, USA
| | - Wang-Sik Lee
- Department of Internal Medicine, Washington University School of Medicine, St. Louis, MO, USA
| | - Xiang Feng
- Department of Structural Biology, Van Andel Institute, Grand Rapids, MI, USA
| | - Lin Bai
- Department of Structural Biology, Van Andel Institute, Grand Rapids, MI, USA
- Department of Biochemistry and Biophysics, School of Basic Medical Sciences, Peking University, Beijing, China
| | - Benjamin C Jennings
- Department of Internal Medicine, Washington University School of Medicine, St. Louis, MO, USA
| | - Lin Liu
- Department of Internal Medicine, Washington University School of Medicine, St. Louis, MO, USA
- M6P Therapeutics, St. Louis, MO, USA
| | - Balraj Doray
- Department of Internal Medicine, Washington University School of Medicine, St. Louis, MO, USA
| | | | - Stuart Kornfeld
- Department of Internal Medicine, Washington University School of Medicine, St. Louis, MO, USA.
| | - Huilin Li
- Department of Structural Biology, Van Andel Institute, Grand Rapids, MI, USA.
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7
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Bai L, Li H. Protein N-glycosylation and O-mannosylation are catalyzed by two evolutionarily related GT-C glycosyltransferases. Curr Opin Struct Biol 2021; 68:66-73. [PMID: 33445129 PMCID: PMC8222153 DOI: 10.1016/j.sbi.2020.12.009] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2020] [Revised: 12/14/2020] [Accepted: 12/23/2020] [Indexed: 11/30/2022]
Abstract
The structural folds of glycosyltransferases are categorized into three superfamilies: GT-A, GT-B, and GT-C. Few structures of GT-C fold existed in the Protein Data Bank prior to the recent advent of high-resolution cryo-EM, because the glycosyltransferases are large membrane proteins that are difficult to crystallize. The use of cryo-EM has resulted in the structures of several key GT-C glycosyltransferases. Here we summarize the latest structural features of and mechanistic insights into these membrane enzyme complexes.
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Affiliation(s)
- Lin Bai
- Department of Biochemistry and Biophysics, School of Basic Medical Sciences, Peking University, Beijing 100083, PR China.
| | - Huilin Li
- Department of Structural Biology, Van Andel Institute, Grand Rapids, MI 49503, United States.
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8
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Kerselidou D, Dohai BS, Nelson DR, Daakour S, De Cock N, Hassoun ZAO, Kim DK, Olivet J, El Assal DC, Jaiswal A, Alzahmi A, Saha D, Pain C, Matthijssens F, Lemaitre P, Herfs M, Chapuis J, Ghesquiere B, Vertommen D, Kriechbaumer V, Knoops K, Lopez-Iglesias C, van Zandvoort M, Lambert JC, Hanson J, Desmet C, Thiry M, Lauersen KJ, Vidal M, Van Vlierberghe P, Dequiedt F, Salehi-Ashtiani K, Twizere JC. Alternative glycosylation controls endoplasmic reticulum dynamics and tubular extension in mammalian cells. SCIENCE ADVANCES 2021; 7:7/19/eabe8349. [PMID: 33962942 PMCID: PMC8104865 DOI: 10.1126/sciadv.abe8349] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/27/2020] [Accepted: 03/18/2021] [Indexed: 05/28/2023]
Abstract
The endoplasmic reticulum (ER) is a central eukaryotic organelle with a tubular network made of hairpin proteins linked by hydrolysis of guanosine triphosphate nucleotides. Among posttranslational modifications initiated at the ER level, glycosylation is the most common reaction. However, our understanding of the impact of glycosylation on the ER structure remains unclear. Here, we show that exostosin-1 (EXT1) glycosyltransferase, an enzyme involved in N-glycosylation, is a key regulator of ER morphology and dynamics. We have integrated multiomics and superresolution imaging to characterize the broad effect of EXT1 inactivation, including the ER shape-dynamics-function relationships in mammalian cells. We have observed that inactivating EXT1 induces cell enlargement and enhances metabolic switches such as protein secretion. In particular, suppressing EXT1 in mouse thymocytes causes developmental dysfunctions associated with the ER network extension. Last, our data illuminate the physical and functional aspects of the ER proteome-glycome-lipidome structure axis, with implications in biotechnology and medicine.
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Affiliation(s)
- Despoina Kerselidou
- Laboratory of Viral Interactomes, GIGA Institute, University of Liege, Liege, Belgium
- Laboratory of Gene expression and Cancer, GIGA Institute, University of Liege, Liege, Belgium
| | - Bushra Saeed Dohai
- Division of Science and Math, New York University Abu Dhabi, Abu Dhabi, UAE
| | - David R Nelson
- Center for Genomics and Systems Biology (CGSB), New York University Abu Dhabi, Abu Dhabi, UAE
| | - Sarah Daakour
- Center for Genomics and Systems Biology (CGSB), New York University Abu Dhabi, Abu Dhabi, UAE
| | - Nicolas De Cock
- TERRA Teaching and Research Centre, University of Liege, Liege, Belgium
| | - Zahra Al Oula Hassoun
- Laboratory of Gene expression and Cancer, GIGA Institute, University of Liege, Liege, Belgium
| | - Dae-Kyum Kim
- The Donnelly Centre, University of Toronto, Toronto, ON, Canada
- Department of Molecular Genetics, University of Toronto, Toronto, ON, Canada
- Lunenfeld Tanenbaum Research Institute, Mount Sinai Hospital, Toronto, ON, Canada
| | - Julien Olivet
- Laboratory of Viral Interactomes, GIGA Institute, University of Liege, Liege, Belgium
| | - Diana C El Assal
- Division of Science and Math, New York University Abu Dhabi, Abu Dhabi, UAE
| | - Ashish Jaiswal
- Center for Genomics and Systems Biology (CGSB), New York University Abu Dhabi, Abu Dhabi, UAE
| | - Amnah Alzahmi
- Center for Genomics and Systems Biology (CGSB), New York University Abu Dhabi, Abu Dhabi, UAE
| | - Deeya Saha
- Laboratory of Viral Interactomes, GIGA Institute, University of Liege, Liege, Belgium
- Laboratory of Gene expression and Cancer, GIGA Institute, University of Liege, Liege, Belgium
| | - Charlotte Pain
- Plant Cell Biology, Biological and Medical Sciences, Oxford Brookes University, Oxford, UK
| | - Filip Matthijssens
- Department of Biomolecular Medicine and Center for Medical Genetics, Ghent University, Ghent, Belgium
- Cancer Research Institute Ghent (CRIG), Ghent, Belgium
| | - Pierre Lemaitre
- GIGA-I3 Unit, GIGA Institute, University of Liege, Liege, Belgium
| | - Michael Herfs
- GIGA-Cancer Unit, GIGA Institute, University of Liege, Liege, Belgium
| | - Julien Chapuis
- Laboratory of Excellence Distalz, INSERM Unit 1167, Pasteur Institute of Lille, Lille, France
| | - Bart Ghesquiere
- Metabolomics Expertise Center, Center for Cancer Biology, VIB Center for Cancer Biology, Leuven, Belgium
| | - Didier Vertommen
- de Duve Institute, Catholic University of Louvain, Brussels, Belgium
| | - Verena Kriechbaumer
- Plant Cell Biology, Biological and Medical Sciences, Oxford Brookes University, Oxford, UK
| | - Kèvin Knoops
- Microscopy CORE Lab, Maastricht Multimodal Molecular Imaging Institute, Maastricht University, Maastricht, Netherlands
| | - Carmen Lopez-Iglesias
- Microscopy CORE Lab, Maastricht Multimodal Molecular Imaging Institute, Maastricht University, Maastricht, Netherlands
| | - Marc van Zandvoort
- Department of Cell Biology, School for Cardiovascular Diseases (CARIM), School for Nutrition and Translational Research in Metabolism (NUTRIM), School for Mental health and Neuroscience (MHeNS), and School for Oncology and Developmental Biology (GROW), Maastricht University, Maastricht, Netherlands
| | - Jean-Charles Lambert
- Laboratory of Excellence Distalz, INSERM Unit 1167, Pasteur Institute of Lille, Lille, France
| | - Julien Hanson
- GIGA-Molecular Pharmacology, University of Liege, Liege, Belgium
| | | | - Marc Thiry
- Laboratory of cell and tissue Biology, GIGA-Neurosciences, University of Liege, Liege, Belgium
| | - Kyle J Lauersen
- Biological and Environmental Sciences and Engineering Division (BESE), King Abdullah University of Science and Technology (KAUST), Thuwal, Kingdom of Saudi Arabia
| | - Marc Vidal
- Center for Cancer Systems Biology (CCSB), Dana-Farber Cancer Institute, Boston, MA, USA
- Department of Genetics, Blavatnik Institute, Harvard Medical School, Boston, MA, USA
| | - Pieter Van Vlierberghe
- Department of Biomolecular Medicine and Center for Medical Genetics, Ghent University, Ghent, Belgium
- Cancer Research Institute Ghent (CRIG), Ghent, Belgium
| | - Franck Dequiedt
- Laboratory of Gene expression and Cancer, GIGA Institute, University of Liege, Liege, Belgium.
| | - Kourosh Salehi-Ashtiani
- Division of Science and Math, New York University Abu Dhabi, Abu Dhabi, UAE.
- Center for Genomics and Systems Biology (CGSB), New York University Abu Dhabi, Abu Dhabi, UAE
| | - Jean-Claude Twizere
- Laboratory of Viral Interactomes, GIGA Institute, University of Liege, Liege, Belgium.
- TERRA Teaching and Research Centre, University of Liege, Liege, Belgium
- Center for Cancer Systems Biology (CCSB), Dana-Farber Cancer Institute, Boston, MA, USA
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9
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Bohl H, Bai L, Li H. Recent Progress in Structural Studies on the GT-C Superfamily of Protein Glycosyltransferases. Subcell Biochem 2021; 96:259-271. [PMID: 33252732 DOI: 10.1007/978-3-030-58971-4_6] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
Protein glycosylation is an essential covalent modification involved in protein secretion, stability, binding, folding, and activity. One or more sugars may be O-, N-, S-, or C-linked to specific amino acids by glycosyltransferases, which catalyze the transfer of these sugars from a phosphate-containing carrier molecule. Most glycosyltransferases are members of the GT-A, GT-B, or GT-C structural superfamilies. GT-C enzymes are integral membrane proteins that utilize a phospho-isoprenoid carrier for sugar transfer. To-date, two families of GT-Cs involved in protein glycosylation have been structurally characterized: the family represented by PglB, AglB, and Stt3, which catalyzes oligosaccharide transfer to Asn, and the family represented by Pmt1 and Pmt2, which catalyzes mannose transfer to Thr or Ser. This chapter reviews progress made over recent years on the structure and function of these two GT-C families.
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Affiliation(s)
- Heather Bohl
- Structural Biology Program, Van Andel Institute, Grand Rapids, Michigan, 49503, USA
| | - Lin Bai
- Department of Biochemistry and Biophysics, School of Basic Medical Sciences, Peking University, 100083, Beijing, P. R. China
| | - Huilin Li
- Structural Biology Program, Van Andel Institute, Grand Rapids, Michigan, 49503, USA.
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10
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Emerging structural insights into glycosyltransferase-mediated synthesis of glycans. Nat Chem Biol 2019; 15:853-864. [PMID: 31427814 DOI: 10.1038/s41589-019-0350-2] [Citation(s) in RCA: 108] [Impact Index Per Article: 21.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2019] [Accepted: 07/17/2019] [Indexed: 12/27/2022]
Abstract
Glycans linked to proteins and lipids play key roles in biology; thus, accurate replication of cellular glycans is crucial for maintaining function following cell division. The fact that glycans are not copied from genomic templates suggests that fidelity is provided by the catalytic templates of glycosyltransferases that accurately add sugars to specific locations on growing oligosaccharides. To form new glycosidic bonds, glycosyltransferases bind acceptor substrates and orient a specific hydroxyl group, frequently one of many, for attack of the donor sugar anomeric carbon. Several recent crystal structures of glycosyltransferases with bound acceptor substrates reveal that these enzymes have common core structures that function as scaffolds upon which variable loops are inserted to confer substrate specificity and correctly orient the nucleophilic hydroxyl group. The varied approaches for acceptor binding site assembly suggest an ongoing evolution of these loop regions provides templates for assembly of the diverse glycan structures observed in biology.
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11
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Bai L, Kovach A, You Q, Kenny A, Li H. Structure of the eukaryotic protein O-mannosyltransferase Pmt1-Pmt2 complex. Nat Struct Mol Biol 2019; 26:704-711. [PMID: 31285605 PMCID: PMC6684406 DOI: 10.1038/s41594-019-0262-6] [Citation(s) in RCA: 30] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2019] [Accepted: 05/29/2019] [Indexed: 12/24/2022]
Abstract
In eukaryotes, a nascent peptide entering the endoplasmic reticulum (ER) is scanned by two Sec61-translocon-associated large membrane machines for protein N-glycosylation and protein O-mannosylation, respectively. While the structure of the eight-protein oligosaccharyltransferase complex has been determined recently, the structures of mannosyltransferases of the PMT family, which are an integral part of ER protein homeostasis, are still unknown. Here we report cryo-EM structures of the S. cerevisiae Pmt1–Pmt2 complex bound to a donor and an acceptor peptide at 3.2-Å resolution, showing that each subunit contains 11 transmembrane helices and a lumenal β-trefoil fold termed the MIR domain. The structures reveal the substrate recognition model and confirm an inverting mannosyl-transferring reaction mechanism by the enzyme complex. Furthermore, we found that the transmembrane domains of Pmt1 and Pmt2 share a structural fold with the catalytic subunits of oligosaccharyltransferases, confirming a previously proposed evolutionary relationship between protein O-mannosylation and protein N-glycosylation.
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Affiliation(s)
- Lin Bai
- Structural Biology Program, Van Andel Research Institute, Grand Rapids, MI, USA
| | - Amanda Kovach
- Structural Biology Program, Van Andel Research Institute, Grand Rapids, MI, USA
| | - Qinglong You
- Structural Biology Program, Van Andel Research Institute, Grand Rapids, MI, USA
| | - Alanna Kenny
- Structural Biology Program, Van Andel Research Institute, Grand Rapids, MI, USA
| | - Huilin Li
- Structural Biology Program, Van Andel Research Institute, Grand Rapids, MI, USA.
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