1
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Gao Y, Zhang Y, Hakke S, Mohren R, Sijbers LJPM, Peters PJ, Ravelli RBG. Cryo-EM structure of cytochrome bo 3 quinol oxidase assembled in peptidiscs reveals an "open" conformation for potential ubiquinone-8 release. BIOCHIMICA ET BIOPHYSICA ACTA. BIOENERGETICS 2024; 1865:149045. [PMID: 38614453 DOI: 10.1016/j.bbabio.2024.149045] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/01/2023] [Revised: 04/03/2024] [Accepted: 04/07/2024] [Indexed: 04/15/2024]
Abstract
Cytochrome bo3 quinol oxidase belongs to the heme‑copper-oxidoreductase (HCO) superfamily, which is part of the respiratory chain and essential for cell survival. While the reaction mechanism of cyt bo3 has been studied extensively over the last decades, specific details about its substrate binding and product release have remained unelucidated due to the lack of structural information. Here, we report a 2.8 Å cryo-electron microscopy structure of cyt bo3 from Escherichia coli assembled in peptidiscs. Our structural model shows a conformation for amino acids 1-41 of subunit I different from all previously published structures while the remaining parts of this enzyme are similar. Our new conformation shows a "U-shape" assembly in contrast to the transmembrane helix, named "TM0", in other reported structural models. However, TM0 blocks ubiquinone-8 (reaction product) release, suggesting that other cyt bo3 conformations should exist. Our structural model presents experimental evidence for an "open" conformation to facilitate substrate/product exchange. This work helps further understand the reaction cycle of this oxidase, which could be a benefit for potential drug/antibiotic design for health science.
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Affiliation(s)
- Ye Gao
- Division of Nanoscopy, Maastricht Multimodal Molecular Imaging Institute, Maastricht University, Maastricht, the Netherlands; Division of Imaging Mass Spectrometry, Maastricht Multimodal Molecular Imaging Institute, Maastricht University, Maastricht, the Netherlands.
| | - Yue Zhang
- Division of Nanoscopy, Maastricht Multimodal Molecular Imaging Institute, Maastricht University, Maastricht, the Netherlands; Division of Imaging Mass Spectrometry, Maastricht Multimodal Molecular Imaging Institute, Maastricht University, Maastricht, the Netherlands
| | - Sneha Hakke
- Division of Nanoscopy, Maastricht Multimodal Molecular Imaging Institute, Maastricht University, Maastricht, the Netherlands; Division of Imaging Mass Spectrometry, Maastricht Multimodal Molecular Imaging Institute, Maastricht University, Maastricht, the Netherlands
| | - Ronny Mohren
- Division of Nanoscopy, Maastricht Multimodal Molecular Imaging Institute, Maastricht University, Maastricht, the Netherlands; Division of Imaging Mass Spectrometry, Maastricht Multimodal Molecular Imaging Institute, Maastricht University, Maastricht, the Netherlands
| | - Lyanne J P M Sijbers
- Division of Nanoscopy, Maastricht Multimodal Molecular Imaging Institute, Maastricht University, Maastricht, the Netherlands; Division of Imaging Mass Spectrometry, Maastricht Multimodal Molecular Imaging Institute, Maastricht University, Maastricht, the Netherlands
| | - Peter J Peters
- Division of Nanoscopy, Maastricht Multimodal Molecular Imaging Institute, Maastricht University, Maastricht, the Netherlands; Division of Imaging Mass Spectrometry, Maastricht Multimodal Molecular Imaging Institute, Maastricht University, Maastricht, the Netherlands.
| | - Raimond B G Ravelli
- Division of Nanoscopy, Maastricht Multimodal Molecular Imaging Institute, Maastricht University, Maastricht, the Netherlands; Division of Imaging Mass Spectrometry, Maastricht Multimodal Molecular Imaging Institute, Maastricht University, Maastricht, the Netherlands
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2
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Thévenod F, Lee WK. Cadmium transport by mammalian ATP-binding cassette transporters. Biometals 2024; 37:697-719. [PMID: 38319451 PMCID: PMC11101381 DOI: 10.1007/s10534-024-00582-5] [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: 09/15/2023] [Accepted: 01/04/2024] [Indexed: 02/07/2024]
Abstract
Cellular responses to toxic metals depend on metal accessibility to intracellular targets, reaching interaction sites, and the intracellular metal concentration, which is mainly determined by uptake pathways, binding/sequestration and efflux pathways. ATP-binding cassette (ABC) transporters are ubiquitous in the human body-usually in epithelia-and are responsible for the transfer of indispensable physiological substrates (e.g. lipids and heme), protection against potentially toxic substances, maintenance of fluid composition, and excretion of metabolic waste products. Derailed regulation and gene variants of ABC transporters culminate in a wide array of pathophysiological disease states, such as oncogenic multidrug resistance or cystic fibrosis. Cadmium (Cd) has no known physiological role in mammalians and poses a health risk due to its release into the environment as a result of industrial activities, and eventually passes into the food chain. Epithelial cells, especially within the liver, lungs, gastrointestinal tract and kidneys, are particularly susceptible to the multifaceted effects of Cd because of the plethora of uptake pathways available. Pertinent to their broad substrate spectra, ABC transporters represent a major cellular efflux pathway for Cd and Cd complexes. In this review, we summarize current knowledge concerning transport of Cd and its complexes (mainly Cd bound to glutathione) by the ABC transporters ABCB1 (P-glycoprotein, MDR1), ABCB6, ABCC1 (multidrug resistance related protein 1, MRP1), ABCC7 (cystic fibrosis transmembrane regulator, CFTR), and ABCG2 (breast cancer related protein, BCRP). Potential detoxification strategies underlying ABC transporter-mediated efflux of Cd and Cd complexes are discussed.
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Affiliation(s)
- Frank Thévenod
- Institute for Physiology, Pathophysiology and Toxicology & ZBAF, Witten/Herdecke University, 58453, Witten, Germany
- Physiology and Pathophysiology of Cells and Membranes, Medical School OWL, Bielefeld University, Morgenbreede 1, 33615, Bielefeld, Germany
| | - Wing-Kee Lee
- Physiology and Pathophysiology of Cells and Membranes, Medical School OWL, Bielefeld University, Morgenbreede 1, 33615, Bielefeld, Germany.
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3
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Choi SH, Lee SS, Lee HY, Kim S, Kim JW, Jin MS. Cryo-EM structure of cadmium-bound human ABCB6. Commun Biol 2024; 7:672. [PMID: 38822018 PMCID: PMC11143254 DOI: 10.1038/s42003-024-06377-1] [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: 09/22/2023] [Accepted: 05/23/2024] [Indexed: 06/02/2024] Open
Abstract
ATP-binding cassette transporter B6 (ABCB6), a protein essential for heme biosynthesis in mitochondria, also functions as a heavy metal efflux pump. Here, we present cryo-electron microscopy structures of human ABCB6 bound to a cadmium Cd(II) ion in the presence of antioxidant thiol peptides glutathione (GSH) and phytochelatin 2 (PC2) at resolutions of 3.2 and 3.1 Å, respectively. The overall folding of the two structures resembles the inward-facing apo state but with less separation between the two halves of the transporter. Two GSH molecules are symmetrically bound to the Cd(II) ion in a bent conformation, with the central cysteine protruding towards the metal. The N-terminal glutamate and C-terminal glycine of GSH do not directly interact with Cd(II) but contribute to neutralizing positive charges of the binding cavity by forming hydrogen bonds and van der Waals interactions with nearby residues. In the presence of PC2, Cd(II) binding to ABCB6 is similar to that observed with GSH, except that two cysteine residues of each PC2 molecule participate in Cd(II) coordination to form a tetrathiolate. Structural comparison of human ABCB6 and its homologous Atm-type transporters indicate that their distinct substrate specificity might be attributed to variations in the capping residues situated at the top of the substrate-binding cavity.
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Affiliation(s)
- Seung Hun Choi
- School of Life Sciences, GIST, 123 Cheomdangwagi-ro, Buk-gu, Gwangju, Republic of Korea
| | - Sang Soo Lee
- School of Life Sciences, GIST, 123 Cheomdangwagi-ro, Buk-gu, Gwangju, Republic of Korea
| | - Hyeon You Lee
- School of Life Sciences, GIST, 123 Cheomdangwagi-ro, Buk-gu, Gwangju, Republic of Korea
| | - Subin Kim
- School of Life Sciences, GIST, 123 Cheomdangwagi-ro, Buk-gu, Gwangju, Republic of Korea
| | - Ji Won Kim
- Department of Life Sciences, POSTECH, 77 Cheongam-Ro, Nam-gu, Pohang, Republic of Korea
| | - Mi Sun Jin
- School of Life Sciences, GIST, 123 Cheomdangwagi-ro, Buk-gu, Gwangju, Republic of Korea.
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4
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Villa M, Wu J, Hansen S, Pahnke J. Emerging Role of ABC Transporters in Glia Cells in Health and Diseases of the Central Nervous System. Cells 2024; 13:740. [PMID: 38727275 PMCID: PMC11083179 DOI: 10.3390/cells13090740] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2024] [Revised: 04/15/2024] [Accepted: 04/20/2024] [Indexed: 05/13/2024] Open
Abstract
ATP-binding cassette (ABC) transporters play a crucial role for the efflux of a wide range of substrates across different cellular membranes. In the central nervous system (CNS), ABC transporters have recently gathered significant attention due to their pivotal involvement in brain physiology and neurodegenerative disorders, such as Alzheimer's disease (AD). Glial cells are fundamental for normal CNS function and engage with several ABC transporters in different ways. Here, we specifically highlight ABC transporters involved in the maintenance of brain homeostasis and their implications in its metabolic regulation. We also show new aspects related to ABC transporter function found in less recognized diseases, such as Huntington's disease (HD) and experimental autoimmune encephalomyelitis (EAE), as a model for multiple sclerosis (MS). Understanding both their impact on the physiological regulation of the CNS and their roles in brain diseases holds promise for uncovering new therapeutic options. Further investigations and preclinical studies are warranted to elucidate the complex interplay between glial ABC transporters and physiological brain functions, potentially leading to effective therapeutic interventions also for rare CNS disorders.
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Affiliation(s)
- Maria Villa
- Translational Neurodegeneration Research and Neuropathology Lab, Department of Clinical Medicine (KlinMed), Medical Faculty, University of Oslo (UiO) and Section of Neuropathology Research, Department of Pathology (PAT), Clinics for Laboratory Medicine (KLM), Oslo University Hospital (OUS), Sognsvannsveien 20, NO-0372 Oslo, Norway
| | - Jingyun Wu
- Translational Neurodegeneration Research and Neuropathology Lab, Department of Clinical Medicine (KlinMed), Medical Faculty, University of Oslo (UiO) and Section of Neuropathology Research, Department of Pathology (PAT), Clinics for Laboratory Medicine (KLM), Oslo University Hospital (OUS), Sognsvannsveien 20, NO-0372 Oslo, Norway
| | - Stefanie Hansen
- Translational Neurodegeneration Research and Neuropathology Lab, Department of Clinical Medicine (KlinMed), Medical Faculty, University of Oslo (UiO) and Section of Neuropathology Research, Department of Pathology (PAT), Clinics for Laboratory Medicine (KLM), Oslo University Hospital (OUS), Sognsvannsveien 20, NO-0372 Oslo, Norway
| | - Jens Pahnke
- Translational Neurodegeneration Research and Neuropathology Lab, Department of Clinical Medicine (KlinMed), Medical Faculty, University of Oslo (UiO) and Section of Neuropathology Research, Department of Pathology (PAT), Clinics for Laboratory Medicine (KLM), Oslo University Hospital (OUS), Sognsvannsveien 20, NO-0372 Oslo, Norway
- Institute of Nutritional Medicine (INUM)/Lübeck Institute of Dermatology (LIED), University of Lübeck (UzL) and University Medical Center Schleswig-Holstein (UKSH), Ratzeburger Allee 160, D-23538 Lübeck, Germany
- Department of Pharmacology, Faculty of Medicine, University of Latvia (LU), Jelgavas iela 3, LV-1004 Rīga, Latvia
- School of Neurobiology, Biochemistry and Biophysics, The Georg S. Wise Faculty of Life Sciences, Tel Aviv University (TAU), Tel Aviv IL-6997801, Israel
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5
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Jandu RS, Yu H, Zhao Z, Le HT, Kim S, Huan T, Duong van Hoa F. Capture of endogenous lipids in peptidiscs and effect on protein stability and activity. iScience 2024; 27:109382. [PMID: 38577106 PMCID: PMC10993126 DOI: 10.1016/j.isci.2024.109382] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2023] [Revised: 12/17/2023] [Accepted: 02/27/2024] [Indexed: 04/06/2024] Open
Abstract
Compared to protein-protein and protein-nucleic acid interactions, our knowledge of protein-lipid interactions remains limited. This is primarily due to the inherent insolubility of membrane proteins (MPs) in aqueous solution. The traditional use of detergents to overcome the solubility barrier destabilizes MPs and strips away certain lipids that are increasingly recognized as crucial for protein function. Recently, membrane mimetics have been developed to circumvent the limitations. In this study, using the peptidisc, we find that MPs in different lipid states can be isolated based on protein purification and reconstitution methods, leading to observable effects on MP activity and stability. Peptidisc also enables re-incorporating specific lipids to fine-tune the protein microenvironment and assess the impact on downstream protein associations. This study offers a first look at the illusive protein-lipid interaction specificity, laying the path for a systematic evaluation of lipid identity and contributions to membrane protein function.
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Affiliation(s)
- Rupinder Singh Jandu
- Department of Biochemistry and Molecular Biology, Faculty of Medicine, Life Sciences Institute, University of British Columbia, Vancouver, BC V6T 1Z3, Canada
| | - Huaxu Yu
- Department of Chemistry, Faculty of Science, University of British Columbia, Vancouver, BC V6T 1Z3, Canada
| | - Zhiyu Zhao
- Department of Biochemistry and Molecular Biology, Faculty of Medicine, Life Sciences Institute, University of British Columbia, Vancouver, BC V6T 1Z3, Canada
| | - Hai Tuong Le
- Department of Biochemistry and Molecular Biology, Faculty of Medicine, Life Sciences Institute, University of British Columbia, Vancouver, BC V6T 1Z3, Canada
| | - Sehyeon Kim
- Department of Chemistry, Faculty of Science, University of British Columbia, Vancouver, BC V6T 1Z3, Canada
| | - Tao Huan
- Department of Chemistry, Faculty of Science, University of British Columbia, Vancouver, BC V6T 1Z3, Canada
| | - Franck Duong van Hoa
- Department of Biochemistry and Molecular Biology, Faculty of Medicine, Life Sciences Institute, University of British Columbia, Vancouver, BC V6T 1Z3, Canada
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6
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Fan W, Shao K, Luo M. Structural View of Cryo-Electron Microscopy-Determined ATP-Binding Cassette Transporters in Human Multidrug Resistance. Biomolecules 2024; 14:231. [PMID: 38397468 PMCID: PMC10886794 DOI: 10.3390/biom14020231] [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: 12/19/2023] [Revised: 02/01/2024] [Accepted: 02/15/2024] [Indexed: 02/25/2024] Open
Abstract
ATP-binding cassette (ABC) transporters, acting as cellular "pumps," facilitate solute translocation through membranes via ATP hydrolysis. Their overexpression is closely tied to multidrug resistance (MDR), a major obstacle in chemotherapy and neurological disorder treatment, hampering drug accumulation and delivery. Extensive research has delved into the intricate interplay between ABC transporter structure, function, and potential inhibition for MDR reversal. Cryo-electron microscopy has been instrumental in unveiling structural details of various MDR-causing ABC transporters, encompassing ABCB1, ABCC1, and ABCG2, as well as the recently revealed ABCC3 and ABCC4 structures. The newly obtained structural insight has deepened our understanding of substrate and drug binding, translocation mechanisms, and inhibitor interactions. Given the growing body of structural information available for human MDR transporters and their associated mechanisms, we believe it is timely to compile a comprehensive review of these transporters and compare their functional mechanisms in the context of multidrug resistance. Therefore, this review primarily focuses on the structural aspects of clinically significant human ABC transporters linked to MDR, with the aim of providing valuable insights to enhance the effectiveness of MDR reversal strategies in clinical therapies.
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Affiliation(s)
| | | | - Min Luo
- Department of Biological Sciences, Faculty of Science, National University of Singapore, Singapore 117543, Singapore; (W.F.); (K.S.)
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7
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Bloch M, Raj I, Pape T, Taylor NMI. Structural and mechanistic basis of substrate transport by the multidrug transporter MRP4. Structure 2023; 31:1407-1418.e6. [PMID: 37683641 DOI: 10.1016/j.str.2023.08.014] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2022] [Revised: 05/31/2023] [Accepted: 08/14/2023] [Indexed: 09/10/2023]
Abstract
Multidrug resistance-associated protein 4 (MRP4) is an ATP-binding cassette (ABC) transporter expressed at multiple tissue barriers where it actively extrudes a wide variety of drug compounds. Overexpression of MRP4 provides resistance to clinically used antineoplastic agents, making it a highly attractive therapeutic target for countering multidrug resistance. Here, we report cryo-EM structures of multiple physiologically relevant states of lipid bilayer-embedded human MRP4, including complexes between MRP4 and two widely used chemotherapeutic agents and a complex between MRP4 and its native substrate. The structures display clear similarities and distinct differences in the coordination of these chemically diverse substrates and, in combination with functional and mutational analysis, reveal molecular details of the transport mechanism. Our study provides key insights into the unusually broad substrate specificity of MRP4 and constitutes an important contribution toward a general understanding of multidrug transporters.
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Affiliation(s)
- Magnus Bloch
- Structural Biology of Molecular Machines Group, Protein Structure & Function Program, Novo Nordisk Foundation Center for Protein Research, Faculty of Health and Medical Sciences, University of Copenhagen, Blegdamsvej 3B, 2200 Copenhagen, Denmark
| | - Isha Raj
- Structural Biology of Molecular Machines Group, Protein Structure & Function Program, Novo Nordisk Foundation Center for Protein Research, Faculty of Health and Medical Sciences, University of Copenhagen, Blegdamsvej 3B, 2200 Copenhagen, Denmark
| | - Tillmann Pape
- Structural Molecular Biology Group, Protein Structure & Function Program, Novo Nordisk Foundation Center for Protein Research, Faculty of Health and Medical Sciences, University of Copenhagen, Blegdamsvej 3B, 2200 Copenhagen, Denmark; Core Facility for Integrated Microscopy (CFIM), Faculty of Health and Medical Sciences, University of Copenhagen, Nørre Allé 20, 2200 Copenhagen, Denmark
| | - Nicholas M I Taylor
- Structural Biology of Molecular Machines Group, Protein Structure & Function Program, Novo Nordisk Foundation Center for Protein Research, Faculty of Health and Medical Sciences, University of Copenhagen, Blegdamsvej 3B, 2200 Copenhagen, Denmark.
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8
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Stewart GW, Gibson JS, Rees DC. The cation-leaky hereditary stomatocytosis syndromes: A tale of six proteins. Br J Haematol 2023; 203:509-522. [PMID: 37679660 DOI: 10.1111/bjh.19093] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2023] [Revised: 08/13/2023] [Accepted: 08/22/2023] [Indexed: 09/09/2023]
Abstract
This review concerns a series of dominantly inherited haemolytic anaemias in which the membrane of the erythrocyte 'leaks' the univalent cations, compromising the osmotic stability of the cell. The majority of the conditions are explained by mutations in one of six genes, coding for multispanning membrane proteins of different structure and function. These are: RhAG, coding for an ammonium carrier; SLC4A1, coding for the band 3 anion exchanger; PIEZO1, coding for a mechanosensitive cation channel; GLUT1, coding for a glucose transporter; KCNN4, coding for an internal-calcium-activated potassium channel; and ABCB6, coding for a porphyrin transporter. This review describes the five clinical syndromes associated with genetic defects in these genes and their variable genotype/phenotype relationships.
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Affiliation(s)
- Gordon W Stewart
- Division of Medicine, Faculty of Medical Sciences, University College London, London, UK
| | - John S Gibson
- Department of Veterinary Medicine, University of Cambridge, Cambridge, UK
| | - David C Rees
- Haematological Medicine, Kings College London, London, UK
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9
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Lee D, Lee H, Lee J, Roh SH, Ha NC. Copper Oxide Spike Grids for Enhanced Solution Transfer in Cryogenic Electron Microscopy. Mol Cells 2023; 46:538-544. [PMID: 37528647 PMCID: PMC10495688 DOI: 10.14348/molcells.2023.0058] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2023] [Revised: 06/27/2023] [Accepted: 06/27/2023] [Indexed: 08/03/2023] Open
Abstract
The formation of uniform vitreous ice is a crucial step in the preparation of samples for cryogenic electron microscopy (cryo-EM). Despite the rapid technological progress in EM, controlling the thickness of vitreous ice on sample grids with reproducibility remains a major obstacle to obtaining high-quality data in cryo-EM imaging. The commonly employed classical blotting process faces the problem of excess water that cannot be absorbed by the filter paper, resulting in the formation of thick and heterogeneous ice. In this study, we propose a novel approach that combines the recently developed nanowire self-wicking technique with the classical blotting method to effectively control the thickness and homogeneity of vitrified ice. With simple procedures, we generated a copper oxide spike (COS) grid by inducing COSs on commercially available copper grids, which can effectively remove excess water during the blotting procedure without damaging the holey carbon membrane. The ice thickness could be controlled with good reproducibility compared to non-oxidized grids. Incorporated into other EM techniques, our new modification method is an effective option for obtaining high-quality data during cryo-EM imaging.
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Affiliation(s)
- Dukwon Lee
- Research Institute of Agriculture and Life Sciences, Center for Food and Bioconvergence, Department of Agricultural Biotechnology, Interdisciplinary Programs in Agricultural Genomics, College of Agriculture and Life Sciences (CALS), Seoul National University, Seoul 08826, Korea
| | - Hansol Lee
- School of Biological Sciences, Seoul National University, Seoul 08826, Korea
- Institute of Molecular Biology and Genetics, Seoul National University, Seoul 08826, Korea
| | - Jinwook Lee
- Research Institute of Agriculture and Life Sciences, Center for Food and Bioconvergence, Department of Agricultural Biotechnology, Interdisciplinary Programs in Agricultural Genomics, College of Agriculture and Life Sciences (CALS), Seoul National University, Seoul 08826, Korea
| | - Soung-Hun Roh
- School of Biological Sciences, Seoul National University, Seoul 08826, Korea
- Institute of Molecular Biology and Genetics, Seoul National University, Seoul 08826, Korea
| | - Nam-Chul Ha
- Research Institute of Agriculture and Life Sciences, Center for Food and Bioconvergence, Department of Agricultural Biotechnology, Interdisciplinary Programs in Agricultural Genomics, College of Agriculture and Life Sciences (CALS), Seoul National University, Seoul 08826, Korea
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10
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Lee SS, Park JG, Jang E, Choi SH, Kim S, Kim JW, Jin MS. W546 stacking disruption traps the human porphyrin transporter ABCB6 in an outward-facing transient state. Commun Biol 2023; 6:960. [PMID: 37735522 PMCID: PMC10514269 DOI: 10.1038/s42003-023-05339-3] [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: 03/16/2023] [Accepted: 09/11/2023] [Indexed: 09/23/2023] Open
Abstract
Human ATP-binding cassette transporter subfamily B6 (ABCB6) is a mitochondrial ATP-driven pump that translocates porphyrins from the cytoplasm into mitochondria for heme biosynthesis. Within the transport pathway, a conserved aromatic residue W546 located in each monomer plays a pivotal role in stabilizing the occluded conformation via π-stacking interactions. Herein, we employed cryo-electron microscopy to investigate the structural consequences of a single W546A mutation in ABCB6, both in detergent micelles and nanodiscs. The results demonstrate that the W546A mutation alters the conformational dynamics of detergent-purified ABCB6, leading to entrapment of the transporter in an outward-facing transient state. However, in the nanodisc system, we observed a direct interaction between the transporter and a phospholipid molecule that compensates for the absence of the W546 residue, thereby facilitating the normal conformational transition of the transporter toward the occluded state following ATP hydrolysis. The findings also reveal that adoption of the outward-facing conformation causes charge repulsion between ABCB6 and the bound substrate, and rearrangement of key interacting residues at the substrate-binding site. Consequently, the affinity for the substrate is significantly reduced, facilitating its release from the transporter.
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Affiliation(s)
- Sang Soo Lee
- School of Life Sciences, GIST, 123 Cheomdan-gwagiro, Buk-gu, Gwangju, 61005, Republic of Korea
| | - Jun Gyou Park
- School of Life Sciences, GIST, 123 Cheomdan-gwagiro, Buk-gu, Gwangju, 61005, Republic of Korea
| | - Eunhong Jang
- School of Life Sciences, GIST, 123 Cheomdan-gwagiro, Buk-gu, Gwangju, 61005, Republic of Korea
| | - Seung Hun Choi
- School of Life Sciences, GIST, 123 Cheomdan-gwagiro, Buk-gu, Gwangju, 61005, Republic of Korea
| | - Subin Kim
- School of Life Sciences, GIST, 123 Cheomdan-gwagiro, Buk-gu, Gwangju, 61005, Republic of Korea
| | - Ji Won Kim
- Department of Life Sciences, POSTECH, 77 Cheongam-Ro, Nam-gu, Pohang, 37673, Republic of Korea
| | - Mi Sun Jin
- School of Life Sciences, GIST, 123 Cheomdan-gwagiro, Buk-gu, Gwangju, 61005, Republic of Korea.
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