1
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Ahn SY, Lee SJ, Yoon SI. Structural and biochemical analysis of the unique interactions of the Campylobacter jejuni CorA channel protein with divalent cations. Biochem Biophys Res Commun 2024; 723:150166. [PMID: 38810321 DOI: 10.1016/j.bbrc.2024.150166] [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: 05/17/2024] [Accepted: 05/22/2024] [Indexed: 05/31/2024]
Abstract
CorA is a Mg2+ channel that plays a key role in the homeostasis of intracellular Mg2+ in bacteria and archaea. CorA consists of a cytoplasmic domain and a transmembrane domain and generates a Mg2+ pathway by forming a pentamer in the cell membrane. CorA gating is regulated via negative feedback by Mg2+, which is accommodated by the pentamerization interface of the CorA cytoplasmic domain (CorACD). The Mg2+-binding sites of CorACD differ depending on the species, suggesting that the Mg2+-binding modes and Mg2+-mediated gating mechanisms of CorA vary across prokaryotes. To define the Mg2+-binding mechanism of CorA in the Campylobacter jejuni pathogen, we structurally and biochemically characterized C. jejuni CorACD (cjCorACD). cjCorACD adopts a three-layered α/β/α structure as observed in other CorA orthologs. Interestingly, cjCorACD exhibited enhanced thermostability in the presence of Ca2+, Ni2+, Zn2+, or Mn2+ in addition to Mg2+, indicating that cjCorACD interacts with diverse divalent cations. This cjCorACD stabilization is mediated by divalent cation accommodation by negatively charged residues located at the bottom of the cjCorACD structure away from the pentamerization interface. Consistently, cjCorACD exists as a monomer irrespective of the presence of divalent cations. We concluded that cjCorACD binds divalent cations in a unique pentamerization-independent manner.
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Affiliation(s)
- Si Yeon Ahn
- Division of Biomedical Convergence, College of Biomedical Science, Kangwon National University, Chuncheon, 24341, Republic of Korea
| | - Su-Jin Lee
- Division of Biomedical Convergence, College of Biomedical Science, Kangwon National University, Chuncheon, 24341, Republic of Korea
| | - Sung-Il Yoon
- Division of Biomedical Convergence, College of Biomedical Science, Kangwon National University, Chuncheon, 24341, Republic of Korea.
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2
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Uthayabalan S, Lake T, Stathopulos PB. MRS2 missense variation at Asp216 abrogates inhibitory Mg 2+ binding, potentiating cell migration and apoptosis resistance. Protein Sci 2024; 33:e5108. [PMID: 38989547 PMCID: PMC11237551 DOI: 10.1002/pro.5108] [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: 02/23/2024] [Revised: 06/06/2024] [Accepted: 06/24/2024] [Indexed: 07/12/2024]
Abstract
Mitochondrial magnesium (Mg2+) is a crucial modulator of protein stability, enzymatic activity, ATP synthesis, and cell death. Mitochondrial RNA splicing protein 2 (MRS2) is the main Mg2+ channel in the inner mitochondrial membrane that mediates influx into the matrix. Recent cryo-electron microscopy (cryo-EM) human MRS2 structures exhibit minimal conformational changes at high and low Mg2+, yet the regulation of human MRS2 and orthologues by Mg2+ binding to analogous matrix domains has been well established. Further, a missense variation at D216 has been identified associated with malignant melanoma and MRS2 expression and activity is implicated in gastric cancer. Thus, to gain more mechanistic and functional insight into Mg2+ sensing by the human MRS2 matrix domain and the association with proliferative disease, we assessed the structural, biophysical, and functional effects of a D216Q mutant. We show that the D216Q mutation is sufficient to abrogate Mg2+-binding and associated conformational changes including increased α-helicity, stability, and monomerization. Further, we reveal that the MRS2 matrix domains interact with ~μM affinity, which is weakened by up to two orders of magnitude in the presence of Mg2+ for wild-type but unaffected for D216Q. Finally, we demonstrate the importance of Mg2+ sensing by MRS2 to prevent matrix Mg2+ overload as HeLa cells overexpressing MRS2 show enhanced Mg2+ uptake, cell migration, and resistance to apoptosis while MRS2 D216Q robustly potentiates these cancer phenotypes. Collectively, our findings further define the MRS2 matrix domain as a critical Mg2+ sensor that undergoes conformational and assembly changes upon Mg2+ interactions dependent on D216 to temper matrix Mg2+ overload.
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Affiliation(s)
- Sukanthathulse Uthayabalan
- Department of Physiology and Pharmacology, Schulich School of Medicine and Dentistry, University of Western Ontario, London, Ontario, Canada
| | - Taylor Lake
- Department of Physiology and Pharmacology, Schulich School of Medicine and Dentistry, University of Western Ontario, London, Ontario, Canada
| | - Peter B Stathopulos
- Department of Physiology and Pharmacology, Schulich School of Medicine and Dentistry, University of Western Ontario, London, Ontario, Canada
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3
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Nies DH, Schleuder G, Galea D, Herzberg M. A flow equilibrium of zinc in cells of Cupriavidus metallidurans. J Bacteriol 2024; 206:e0008024. [PMID: 38661374 PMCID: PMC11112998 DOI: 10.1128/jb.00080-24] [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: 02/28/2024] [Accepted: 04/03/2024] [Indexed: 04/26/2024] Open
Abstract
The hypothesis was tested that a kinetical flow equilibrium of uptake and efflux reactions is responsible for balancing the cellular zinc content. The experiments were done with the metal-resistant bacterium Cupriavidus metallidurans. In pulse-chase experiments, the cells were loaded with radioactive 65Zn and chased with the 100-fold concentration of non-radioactive zinc chloride. In parallel, the cells were loaded with isotope-enriched stable 67Zn and chased with non-enriched zinc to differentiate between zinc pools in the cell. The experiments demonstrated the existence of a kinetical flow equilibrium, resulting in a constant turnover of cell-bound zinc ions. The absence of the metal-binding cytoplasmic components, polyphosphate and glutathione, metal uptake, and metal efflux systems influenced the flow equilibrium. The experiments also revealed that not all zinc uptake and efflux systems are known in C. metallidurans. Cultivation of the cells under zinc-replete, zinc-, and zinc-magnesium-starvation conditions influenced zinc import and export rates. Here, magnesium starvation had a stronger influence compared to zinc starvation. Other metal cations, especially cobalt, affected the cellular zinc pools and zinc export during the chase reaction. In summary, the experiments with 65Zn and 67Zn demonstrated a constant turnover of cell-bound zinc. This indicated that simultaneously occurring import and export reactions in combination with cytoplasmic metal-binding components resulted in a kinetical flow equilibrium that was responsible for the adjustment of the cellular zinc content. IMPORTANCE Understanding the biochemical action of a single enzyme or transport protein is the pre-requisite to obtain insight into its cellular function but this is only one half of the coin. The other side concerns the question of how central metabolic functions of a cell emerge from the interplay of different proteins and other macromolecules. This paper demonstrates that a flow equilibrium of zinc uptake and efflux reactions is at the core of cellular zinc homeostasis and identifies the most important contributors to this flow equilibrium: the uptake and efflux systems and metal-binding components of the cytoplasm.
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Affiliation(s)
- Dietrich H. Nies
- Martin-Luther-University Halle-Wittenberg, Institute for Biology/Microbiology, Halle (Saale), Germany
| | - Grit Schleuder
- Martin-Luther-University Halle-Wittenberg, Institute for Biology/Microbiology, Halle (Saale), Germany
| | - Diana Galea
- Martin-Luther-University Halle-Wittenberg, Institute for Biology/Microbiology, Halle (Saale), Germany
| | - Martin Herzberg
- Martin-Luther-University Halle-Wittenberg, Institute for Biology/Microbiology, Halle (Saale), Germany
- Department of Analytical Chemistry, Helmholtz Centre for Environmental Research – UFZ, Leipzig, Germany
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4
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Ponnusamy T, Velusamy P, Shanmughapriya S. Mrs2-mediated mitochondrial magnesium uptake is essential for the regulation of MCU-mediated mitochondrial Ca 2+ uptake and viability. Mitochondrion 2024; 76:101877. [PMID: 38599304 DOI: 10.1016/j.mito.2024.101877] [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: 12/27/2023] [Revised: 03/07/2024] [Accepted: 04/07/2024] [Indexed: 04/12/2024]
Abstract
Mitochondrial Ca2+ uptake is essential in regulating bioenergetics, cell death, and cytosolic Ca2+ transients. Mitochondrial Calcium Uniporter (MCU) mediates the mitochondrial Ca2+ uptake. Though MCU regulation by MICUs is unequivocally established, there needs to be more knowledge of whether divalent cations regulate MCU. Here, we set out to understand the mitochondrial matrix Mg2+-dependent regulation of MCU activity. We showed that decreased matrix [Mg2+] is associated with increased MCU activity and significantly prompted mitochondrial permeability transition pore opening. Our findings support the critical role of mMg2+ in regulating MCU activity.
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Affiliation(s)
- Thiruvelselvan Ponnusamy
- Heart and Vascular Institute, Department of Medicine, Department of Cellular and Molecular Physiology, Pennsylvania State University, College of Medicine, Hershey, PA 17033, USA
| | - Prema Velusamy
- Heart and Vascular Institute, Department of Medicine, Department of Cellular and Molecular Physiology, Pennsylvania State University, College of Medicine, Hershey, PA 17033, USA
| | - Santhanam Shanmughapriya
- Heart and Vascular Institute, Department of Medicine, Department of Cellular and Molecular Physiology, Pennsylvania State University, College of Medicine, Hershey, PA 17033, USA.
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5
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Zeinert R, Zhou F, Franco P, Zöller J, Lessen HJ, Aravind L, Langer JD, Sodt AJ, Storz G, Matthies D. Magnesium Transporter MgtA revealed as a Dimeric P-type ATPase. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.02.28.582502. [PMID: 38464158 PMCID: PMC10925321 DOI: 10.1101/2024.02.28.582502] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 03/12/2024]
Abstract
Magnesium (Mg2+) uptake systems are present in all domains of life given the vital role of this ion. Bacteria acquire Mg2+ via conserved Mg2+ channels and transporters. The transporters are required for growth when Mg2+ is limiting or during bacterial pathogenesis, but, despite their significance, there are no known structures for these transporters. Here we report the first structure of the Mg2+ transporter MgtA solved by single particle cryo-electron microscopy (cryo-EM). Using mild membrane extraction, we obtained high resolution structures of both a homodimeric form (2.9 Å), the first for a P-type ATPase, and a monomeric form (3.6 Å). Each monomer unit of MgtA displays a structural architecture that is similar to other P-type ATPases with a transmembrane domain and two soluble domains. The dimer interface consists of contacts between residues in adjacent soluble nucleotide binding and phosphotransfer regions of the haloacid dehalogenase (HAD) domain. We suggest oligomerization is a conserved structural feature of the diverse family of P-type ATPase transporters. The ATP binding site and conformational dynamics upon nucleotide binding to MgtA were characterized using a combination of cryo-EM, molecular dynamics simulations, hydrogen-deuterium exchange mass spectrometry, and mutagenesis. Our structure also revealed a Mg2+ ion in the transmembrane segments, which, when combined with sequence conservation and mutagenesis studies, allowed us to propose a model for Mg2+ transport across the lipid bilayer. Finally, our work revealed the N-terminal domain structure and cytoplasmic Mg2+ binding sites, which have implications for related P-type ATPases defective in human disease.
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Affiliation(s)
- Rilee Zeinert
- Division of Molecular and Cellular Biology, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda MD 20892, USA
| | - Fei Zhou
- Unit on Structural Biology, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda MD 20892, USA
| | - Pedro Franco
- Max Planck Institute of Biophysics, 60438 Frankfurt am Main, Germany
| | - Jonathan Zöller
- Max Planck Institute of Biophysics, 60438 Frankfurt am Main, Germany
| | - Henry J. Lessen
- Unit on Membrane Chemical Physics, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda MD 20892, USA
| | - L. Aravind
- National Center for Biotechnology Information, National Institutes of Health, Bethesda MD 20892, USA
| | - Julian D. Langer
- Max Planck Institute of Biophysics, 60438 Frankfurt am Main, Germany
| | - Alexander J. Sodt
- Unit on Membrane Chemical Physics, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda MD 20892, USA
| | - Gisela Storz
- Division of Molecular and Cellular Biology, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda MD 20892, USA
| | - Doreen Matthies
- Unit on Structural Biology, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda MD 20892, USA
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6
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Lai LTF, Balaraman J, Zhou F, Matthies D. Cryo-EM structures of human magnesium channel MRS2 reveal gating and regulatory mechanisms. Nat Commun 2023; 14:7207. [PMID: 37938562 PMCID: PMC10632456 DOI: 10.1038/s41467-023-42599-3] [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: 08/22/2023] [Accepted: 10/16/2023] [Indexed: 11/09/2023] Open
Abstract
Magnesium ions (Mg2+) play an essential role in cellular physiology. In mitochondria, protein and ATP synthesis and various metabolic pathways are directly regulated by Mg2+. MRS2, a magnesium channel located in the inner mitochondrial membrane, mediates the influx of Mg2+ into the mitochondrial matrix and regulates Mg2+ homeostasis. Knockdown of MRS2 in human cells leads to reduced uptake of Mg2+ into mitochondria and disruption of the mitochondrial metabolism. Despite the importance of MRS2, the Mg2+ translocation and regulation mechanisms of MRS2 are still unclear. Here, using cryo-EM we report the structures of human MRS2 in the presence and absence of Mg2+ at 2.8 Å and 3.3 Å, respectively. From the homo-pentameric structures, we identify R332 and M336 as major gating residues, which are then tested using mutagenesis and two cellular divalent ion uptake assays. A network of hydrogen bonds is found connecting the gating residue R332 to the soluble domain, potentially regulating the gate. Two Mg2+-binding sites are identified in the MRS2 soluble domain, distinct from the two sites previously reported in CorA, a homolog of MRS2 in prokaryotes. Altogether, this study provides the molecular basis for understanding the Mg2+ translocation and regulatory mechanisms of MRS2.
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Affiliation(s)
- Louis Tung Faat Lai
- Unit on Structural Biology, Division of Basic and Translational Biophysics, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD, 20892, USA
| | - Jayashree Balaraman
- Unit on Structural Biology, Division of Basic and Translational Biophysics, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD, 20892, USA
| | - Fei Zhou
- Unit on Structural Biology, Division of Basic and Translational Biophysics, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD, 20892, USA
| | - Doreen Matthies
- Unit on Structural Biology, Division of Basic and Translational Biophysics, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD, 20892, USA.
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7
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Elston R, Mulligan C, Thomas GH. Flipping the switch: dynamic modulation of membrane transporter activity in bacteria. MICROBIOLOGY (READING, ENGLAND) 2023; 169. [PMID: 37948297 DOI: 10.1099/mic.0.001412] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/12/2023]
Abstract
The controlled entry and expulsion of small molecules across the bacterial cytoplasmic membrane is essential for efficient cell growth and cellular homeostasis. While much is known about the transcriptional regulation of genes encoding transporters, less is understood about how transporter activity is modulated once the protein is functional in the membrane, a potentially more rapid and dynamic level of control. In this review, we bring together literature from the bacterial transport community exemplifying the extensive and diverse mechanisms that have evolved to rapidly modulate transporter function, predominantly by switching activity off. This includes small molecule feedback, inhibition by interaction with small peptides, regulation through binding larger signal transduction proteins and, finally, the emerging area of controlled proteolysis. Many of these examples have been discovered in the context of metal transport, which has to finely balance active accumulation of elements that are essential for growth but can also quickly become toxic if intracellular homeostasis is not tightly controlled. Consistent with this, these transporters appear to be regulated at multiple levels. Finally, we find common regulatory themes, most often through the fusion of additional regulatory domains to transporters, which suggest the potential for even more widespread regulation of transporter activity in biology.
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Affiliation(s)
- Rory Elston
- Department of Biology, University of York, York, UK
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8
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Takayanagi H, Bardaud JX, Hirata K, Brenner V, Gloaguen E, Ishiuchi SI, Fujii M. Stepwise hydration of [CH 3COOMg] + studied by cold ion trap infrared spectroscopy: insights into interactions in the magnesium channel selection filters. Phys Chem Chem Phys 2023; 25:23923-23928. [PMID: 37642502 DOI: 10.1039/d3cp00992k] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 08/31/2023]
Abstract
The magnesium channel controls Mg2+ concentration in the cell and plays an indispensable role in biological functions. The crystal structure of the Magnesium Transport E channel suggested that Mg2+ hydrated by 6 water molecules is transported through a selection filter consisting of COO- groups on two Asp residues. This Mg2+ motion implies successive pairing with -OOC-R and dissociation mediated by water molecules. For another divalent ion, however, it is known that RCOO-⋯Ca2+ cannot be separated even with 12 water molecules. From this discrepancy, we probe the structure of Mg2+(CH3COO-)(H2O)4-17 clusters by measuring the infrared spectra and monitoring the vibrational frequencies of COO- with the help of quantum chemistry calculations. The hydration by (H2O)6 is not enough to induce ion separation, and partially-separated or separated pairs are formed from 10 water molecules at least. These results suggest that the ion separation between Mg2+ and carboxylate ions in the selection-filter of the MgtE channel not only results from water molecules in their first hydration shell, but also from additional factors including water molecules and protein groups in the second solvation shell of Mg2+.
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Affiliation(s)
- Hikaru Takayanagi
- Laboratory for Chemistry and Life Science, Institute of Innovative Research, Tokyo Institute of Technology, 4259 Nagatsuta-cho, Midori-ku, Yokohama, 226-8503, Japan.
- School of Life Science and Technology, Tokyo Institute of Technology, 4259 Nagatsuta-cho, Midori-ku, Yokohama, Kanagawa, 226-8503, Japan
| | - Jean-Xavier Bardaud
- LIDYL, CEA, CNRS, Université Paris Saclay, CEA Saclay, Bât 522, Gif-sur-Yvette 91191, France.
| | - Keisuke Hirata
- Laboratory for Chemistry and Life Science, Institute of Innovative Research, Tokyo Institute of Technology, 4259 Nagatsuta-cho, Midori-ku, Yokohama, 226-8503, Japan.
- Department of Chemistry, School of Science, Tokyo Institute of Technology, 2-12-1 Ookayama, Meguro-ku, Tokyo 152-8550, Japan
| | - Valérie Brenner
- LIDYL, CEA, CNRS, Université Paris Saclay, CEA Saclay, Bât 522, Gif-sur-Yvette 91191, France.
| | - Eric Gloaguen
- LIDYL, CEA, CNRS, Université Paris Saclay, CEA Saclay, Bât 522, Gif-sur-Yvette 91191, France.
| | - Shun-Ichi Ishiuchi
- Laboratory for Chemistry and Life Science, Institute of Innovative Research, Tokyo Institute of Technology, 4259 Nagatsuta-cho, Midori-ku, Yokohama, 226-8503, Japan.
- Department of Chemistry, School of Science, Tokyo Institute of Technology, 2-12-1 Ookayama, Meguro-ku, Tokyo 152-8550, Japan
| | - Masaaki Fujii
- Laboratory for Chemistry and Life Science, Institute of Innovative Research, Tokyo Institute of Technology, 4259 Nagatsuta-cho, Midori-ku, Yokohama, 226-8503, Japan.
- School of Life Science and Technology, Tokyo Institute of Technology, 4259 Nagatsuta-cho, Midori-ku, Yokohama, Kanagawa, 226-8503, Japan
- IRFI/IPWR, Institute of Innovative Research, Tokyo Institute of Technology, 4259 Nagatsuta-cho, Midori-ku, Yokohama, 226-8503, Japan
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9
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Erramilli SK, Dominik PK, Deneka D, Tokarz P, Kim SS, Reddy BG, Skrobek BM, Dalmas O, Perozo E, Kossiakoff AA. Conformation-specific Synthetic Antibodies Discriminate Multiple Functional States of the Ion Channel CorA. J Mol Biol 2023; 435:168192. [PMID: 37394032 PMCID: PMC10529903 DOI: 10.1016/j.jmb.2023.168192] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2023] [Revised: 06/20/2023] [Accepted: 06/26/2023] [Indexed: 07/04/2023]
Abstract
CorA, the primary magnesium ion channel in prokaryotes and archaea, is a prototypical homopentameric ion channel that undergoes ion-dependent conformational transitions. CorA adopts five-fold symmetric non-conductive states in the presence of high concentrations of Mg2+, and highly asymmetric flexible states in its complete absence. However, the latter were of insufficient resolution to be thoroughly characterized. In order to gain additional insights into the relationship between asymmetry and channel activation, we exploited phage display selection strategies to generate conformation-specific synthetic antibodies (sABs) against CorA in the absence of Mg2+. Two sABs from these selections, C12 and C18, showed different degrees of Mg2+-sensitivity. Through structural, biochemical, and biophysical characterization, we found the sABs are both conformation-specific but probe different features of the channel under open-like conditions. C18 is highly specific to the Mg2+-depleted state of CorA and through negative-stain electron microscopy (ns-EM), we show sAB binding reflects the asymmetric arrangement of CorA protomers in Mg2+-depleted conditions. We used X-ray crystallography to determine a structure at 2.0 Å resolution of sAB C12 bound to the soluble N-terminal regulatory domain of CorA. The structure shows C12 is a competitive inhibitor of regulatory magnesium binding through its interaction with the divalent cation sensing site. We subsequently exploited this relationship to capture and visualize asymmetric CorA states in different [Mg2+] using ns-EM. We additionally utilized these sABs to provide insights into the energy landscape that governs the ion-dependent conformational transitions of CorA.
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Affiliation(s)
- Satchal K Erramilli
- Department of Biochemistry and Molecular Biology, The University of Chicago, Chicago, IL, USA
| | - Pawel K Dominik
- Department of Biochemistry and Molecular Biology, The University of Chicago, Chicago, IL, USA
| | - Dawid Deneka
- Department of Biochemistry and Molecular Biology, The University of Chicago, Chicago, IL, USA
| | - Piotr Tokarz
- Department of Biochemistry and Molecular Biology, The University of Chicago, Chicago, IL, USA
| | - Sangwoo S Kim
- Department of Biochemistry and Molecular Biology, The University of Chicago, Chicago, IL, USA
| | - Bharat G Reddy
- Department of Biochemistry and Molecular Biology, The University of Chicago, Chicago, IL, USA
| | - Blazej M Skrobek
- Department of Biochemistry and Molecular Biology, The University of Chicago, Chicago, IL, USA; Intercollegiate Faculty of Biotechnology of University of Gdansk and Medical University of Gdansk, Gdansk, Poland
| | - Olivier Dalmas
- Department of Biochemistry and Molecular Biology, The University of Chicago, Chicago, IL, USA
| | - Eduardo Perozo
- Department of Biochemistry and Molecular Biology, The University of Chicago, Chicago, IL, USA; Grossman Institute for Neuroscience, Quantitative Biology and Human Behavior, The University of Chicago, Chicago, IL, USA
| | - Anthony A Kossiakoff
- Department of Biochemistry and Molecular Biology, The University of Chicago, Chicago, IL, USA; Institute for Biophysical Dynamics, The University of Chicago, Chicago, IL, USA.
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10
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Dukic E, van Maldegem KA, Shaikh KM, Fukuda K, Töpel M, Solymosi K, Hellsten J, Hansen TH, Husted S, Higgins J, Sano S, Ishijima S, Spetea C. Chloroplast magnesium transporters play essential but differential roles in maintaining magnesium homeostasis. FRONTIERS IN PLANT SCIENCE 2023; 14:1221436. [PMID: 37692441 PMCID: PMC10484576 DOI: 10.3389/fpls.2023.1221436] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/12/2023] [Accepted: 07/07/2023] [Indexed: 09/12/2023]
Abstract
Magnesium (Mg2+) is essential for photosynthesis in the chloroplasts of land plants and algae. Being the central ion of chlorophyll, cofactor and activator of many photosynthetic enzymes including RuBisCO, magnesium-deficient plants may suffer from leaf chlorosis symptoms and retarded growth. Therefore, the chloroplast Mg2+ concentration is tightly controlled by magnesium transport proteins. Recently, three different transporters from two distinct families have been identified in the chloroplast inner envelope of the model plant Arabidopsis thaliana: MGT10, MGR8, and MGR9. Here, we assess the individual roles of these three proteins in maintaining chloroplast Mg2+ homeostasis and regulating photosynthesis, and if their role is conserved in the model green alga Chlamydomonas reinhardtii. Phylogenetic analysis and heterologous expression revealed that the CorC-like MGR8 and MGR9 transport Mg2+ by a different mechanism than the CorA-like MGT10. MGR8 and MGT10 genes are highest expressed in leaves, indicating a function in chloroplast Mg2+ transport. MGR9 is important for chloroplast function and plant adaptation in conditions of deficiency or excess of Mg2+. Transmission electron microscopy indicated that MGT10 plays a differential role in thylakoid stacking than MGR8 and MGR9. Furthermore, we report that MGR8, MGR9, and MGT10 are involved in building up the pH gradient across the thylakoid membrane and activating photoprotection in conditions of excess light, however the mechanism has not been resolved yet. While there are no chloroplast MGR-like transporters in Chlamydomonas, we show that MRS4 is a homolog of MGT10, that is required for photosynthesis and cell growth. Taken together, our findings reveal that the studied Mg2+ transporters play essential but differential roles in maintaining chloroplast Mg2+ homeostasis.
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Affiliation(s)
- Emilija Dukic
- Department of Biological and Environmental Sciences, University of Gothenburg, Gothenburg, Sweden
| | - Kim A. van Maldegem
- Department of Biological and Environmental Sciences, University of Gothenburg, Gothenburg, Sweden
| | - Kashif Mohd Shaikh
- Department of Biological and Environmental Sciences, University of Gothenburg, Gothenburg, Sweden
| | - Kento Fukuda
- Graduate School of Life and Environmental Sciences, Kyoto Prefectural University, Kyoto, Japan
| | - Mats Töpel
- Department of Marine Sciences, University of Gothenburg, Gothenburg, Sweden
- IVL Swedish Environmental Research Institute, Gothenburg, Sweden
| | - Katalin Solymosi
- Department of Plant Anatomy, ELTE Eötvös Loránd University, Budapest, Hungary
| | - Jonna Hellsten
- Department of Biological and Environmental Sciences, University of Gothenburg, Gothenburg, Sweden
| | - Thomas Hesselhøj Hansen
- Copenhagen Plant Science Centre, Department of Plant and Environmental Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Søren Husted
- Copenhagen Plant Science Centre, Department of Plant and Environmental Sciences, University of Copenhagen, Copenhagen, Denmark
| | - John Higgins
- Department of Geosciences, Princeton University, Princeton, NJ, United States
| | - Satoshi Sano
- Graduate School of Life and Environmental Sciences, Kyoto Prefectural University, Kyoto, Japan
| | - Sumio Ishijima
- Graduate School of Life and Environmental Sciences, Kyoto Prefectural University, Kyoto, Japan
| | - Cornelia Spetea
- Department of Biological and Environmental Sciences, University of Gothenburg, Gothenburg, Sweden
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11
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Lai LTF, Balaraman J, Zhou F, Matthies D. Cryo-EM structures of human magnesium channel MRS2 reveal gating and regulatory mechanisms. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.08.22.553867. [PMID: 37662257 PMCID: PMC10473633 DOI: 10.1101/2023.08.22.553867] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 09/05/2023]
Abstract
Magnesium ions (Mg2+) play an essential role in cellular physiology. In mitochondria, protein and ATP synthesis and various metabolic pathways are directly regulated by Mg2+. MRS2, a magnesium channel located in the inner mitochondrial membrane, mediates the influx of Mg2+ into the mitochondrial matrix and regulates Mg2+ homeostasis. Knockdown of MRS2 in human cells leads to reduced uptake of Mg2+ into mitochondria and disruption of the mitochondrial metabolism. Despite the importance of MRS2, the Mg2+ translocation and regulation mechanisms of MRS2 are still unclear. Here, using cryo-EM we determined the structure of human MRS2 in the presence and absence of Mg2+ at 2.8 Å and 3.3 Å, respectively. From the homo-pentameric structures, we identified R332 and M336 as major gating residues, which were then tested using mutagenesis and two cellular divalent ion uptake assays. A network of hydrogen bonds was found connecting the gating residue R332 to the soluble domain, potentially regulating the gate. Two Mg2+-binding sites were identified in the MRS2 soluble domain, distinct from the two sites previously reported in CorA, a homolog of MRS2 in prokaryotes. Altogether, this study provides the molecular basis for understanding the Mg2+ translocation and regulatory mechanisms of MRS2.
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Affiliation(s)
- Louis Tung Faat Lai
- Unit on Structural Biology, Division of Basic and Translational Biophysics, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda MD 20892, USA
| | - Jayashree Balaraman
- Unit on Structural Biology, Division of Basic and Translational Biophysics, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda MD 20892, USA
| | - Fei Zhou
- Unit on Structural Biology, Division of Basic and Translational Biophysics, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda MD 20892, USA
| | - Doreen Matthies
- Unit on Structural Biology, Division of Basic and Translational Biophysics, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda MD 20892, USA
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12
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He Z, Tu YC, Tsai CW, Mount J, Zhang J, Tsai MF, Yuan P. Structure and function of the human mitochondrial MRS2 channel. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.08.12.553106. [PMID: 37645897 PMCID: PMC10462007 DOI: 10.1101/2023.08.12.553106] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 08/31/2023]
Abstract
The human Mitochondrial RNA Splicing 2 protein (MRS2) has been implicated in Mg2+ transport across mitochondrial inner membranes, thus playing an important role in Mg2+ homeostasis critical for mitochondrial integrity and function. However, the molecular mechanisms underlying its fundamental channel properties such as ion selectivity and regulation remain unclear. Here, we present structural and functional investigation of MRS2. Cryo-electron microscopy structures in various ionic conditions reveal a pentameric channel architecture and the molecular basis of ion permeation and potential regulation mechanisms. Electrophysiological analyses demonstrate that MRS2 is a Ca2+-regulated, non-selective channel permeable to Mg2+, Ca2+, Na+ and K+, which contrasts with its prokaryotic ortholog, CorA, operating as a Mg2+-gated Mg2+ channel. Moreover, a conserved arginine ring within the pore of MRS2 functions to restrict cation movements, likely preventing the channel from collapsing the proton motive force that drives mitochondrial ATP synthesis. Together, our results provide a molecular framework for further understanding MRS2 in mitochondrial function and disease.
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Affiliation(s)
- Zhihui He
- Department of Cell Biology and Physiology, Washington University School of Medicine, Saint Louis, MO, USA
- These authors contributed equally to this work
| | - Yung-Chi Tu
- Department of Physiology and Biophysics, University of Colorado Anschutz Medical Campus, Aurora, CO, USA
- These authors contributed equally to this work
| | - Chen-Wei Tsai
- Department of Physiology and Biophysics, University of Colorado Anschutz Medical Campus, Aurora, CO, USA
| | - Jonathan Mount
- Department of Cell Biology and Physiology, Washington University School of Medicine, Saint Louis, MO, USA
- Department of Pharmacological Sciences, Icahn School of Medicine at Mount Sinai, New York, NY, USA
| | - Jingying Zhang
- Department of Cell Biology and Physiology, Washington University School of Medicine, Saint Louis, MO, USA
- Department of Pharmacological Sciences, Icahn School of Medicine at Mount Sinai, New York, NY, USA
| | - Ming-Feng Tsai
- Department of Physiology and Biophysics, University of Colorado Anschutz Medical Campus, Aurora, CO, USA
| | - Peng Yuan
- Department of Cell Biology and Physiology, Washington University School of Medicine, Saint Louis, MO, USA
- Department of Pharmacological Sciences, Icahn School of Medicine at Mount Sinai, New York, NY, USA
- Department of Neuroscience, Icahn School of Medicine at Mount Sinai, New York, NY, USA
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13
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Li M, Li Y, Lu Y, Li J, Lu X, Ren Y, Wen T, Wang Y, Chang S, Zhang X, Yang X, Shen Y. Molecular basis of Mg 2+ permeation through the human mitochondrial Mrs2 channel. Nat Commun 2023; 14:4713. [PMID: 37543649 PMCID: PMC10404273 DOI: 10.1038/s41467-023-40516-2] [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: 03/21/2023] [Accepted: 07/25/2023] [Indexed: 08/07/2023] Open
Abstract
Mitochondrial RNA splicing 2 (Mrs2), a eukaryotic CorA ortholog, enables Mg2+ to permeate the inner mitochondrial membrane and plays an important role in mitochondrial metabolic function. However, the mechanism by which Mrs2 permeates Mg2+ remains unclear. Here, we report four cryo-electron microscopy (cryo-EM) reconstructions of Homo sapiens Mrs2 (hMrs2) under various conditions. All of these hMrs2 structures form symmetrical pentamers with very similar pentamer and protomer conformations. A special structural feature of Cl--bound R-ring, which consists of five Arg332 residues, was found in the hMrs2 structure. Molecular dynamics simulations and mitochondrial Mg2+ uptake assays show that the R-ring may function as a charge repulsion barrier, and Cl- may function as a ferry to jointly gate Mg2+ permeation in hMrs2. In addition, the membrane potential is likely to be the driving force for Mg2+ permeation. Our results provide insights into the channel assembly and Mg2+ permeation of hMrs2.
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Affiliation(s)
- Ming Li
- State Key Laboratory of Medicinal Chemical Biology and Frontiers Science Center for Cell Responses, College of Life Sciences, Nankai University, Tianjin, 300350, China
| | - Yang Li
- State Key Laboratory of Medicinal Chemical Biology and Frontiers Science Center for Cell Responses, College of Life Sciences, Nankai University, Tianjin, 300350, China
| | - Yue Lu
- State Key Laboratory of Medicinal Chemical Biology and Frontiers Science Center for Cell Responses, College of Life Sciences, Nankai University, Tianjin, 300350, China
| | - Jianhui Li
- State Key Laboratory of Medicinal Chemical Biology and Frontiers Science Center for Cell Responses, College of Life Sciences, Nankai University, Tianjin, 300350, China
| | - Xuhang Lu
- State Key Laboratory of Medicinal Chemical Biology and Frontiers Science Center for Cell Responses, College of Life Sciences, Nankai University, Tianjin, 300350, China
| | - Yue Ren
- State Key Laboratory of Medicinal Chemical Biology and Frontiers Science Center for Cell Responses, College of Life Sciences, Nankai University, Tianjin, 300350, China
| | - Tianlei Wen
- State Key Laboratory of Medicinal Chemical Biology and Frontiers Science Center for Cell Responses, College of Life Sciences, Nankai University, Tianjin, 300350, China
| | - Yaojie Wang
- State Key Laboratory of Medicinal Chemical Biology and Frontiers Science Center for Cell Responses, College of Life Sciences, Nankai University, Tianjin, 300350, China
| | - Shenghai Chang
- Department of Biophysics and Department of Pathology of Sir Run Run Shaw Hospital, School of Medicine, Zhejiang University, Hangzhou, 310058, China
- Center of Cryo Electron Microscopy, Zhejiang University, Hangzhou, 310058, China
| | - Xing Zhang
- Department of Biophysics and Department of Pathology of Sir Run Run Shaw Hospital, School of Medicine, Zhejiang University, Hangzhou, 310058, China
- Center of Cryo Electron Microscopy, Zhejiang University, Hangzhou, 310058, China
| | - Xue Yang
- State Key Laboratory of Medicinal Chemical Biology and Frontiers Science Center for Cell Responses, College of Life Sciences, Nankai University, Tianjin, 300350, China.
| | - Yuequan Shen
- State Key Laboratory of Medicinal Chemical Biology and Frontiers Science Center for Cell Responses, College of Life Sciences, Nankai University, Tianjin, 300350, China.
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14
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Ponnusamy T, Velusamy P, Kumar A, Morris D, Zhang X, Ning G, Klinger M, Copper JE, Rajan S, Cheung JY, Natarajaseenivasan K, Mnatsakanyan N, Shanmughapriya S. Mitochondrial Magnesium is the cationic rheostat for MCU-mediated mitochondrial Ca 2+ uptake. RESEARCH SQUARE 2023:rs.3.rs-3088175. [PMID: 37502932 PMCID: PMC10371168 DOI: 10.21203/rs.3.rs-3088175/v1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 07/29/2023]
Abstract
Calcium (Ca2+) uptake by mitochondria is essential in regulating bioenergetics, cell death, and cytosolic Ca2+ transients. Mitochondrial Calcium Uniporter (MCU) mediates the mitochondrial Ca2+ uptake. MCU is a heterooligomeric complex with a pore-forming component and accessory proteins required for channel activity. Though MCU regulation by MICUs is unequivocally established, there needs to be more knowledge of whether divalent cations regulate MCU. Here we set out to understand the mitochondrial matrix Mg2+-dependent regulation of MCU activity. We showed Mrs2 as the authentic mammalian mitochondrial Mg2+ channel using the planar lipid bilayer recordings. Using a liver-specific Mrs2 KO mouse model, we showed that decreased matrix [Mg2+] is associated with increased MCU activity and matrix Ca2+ overload. The disruption of Mg2+dependent MCU regulation significantly prompted mitochondrial permeability transition pore opening-mediated cell death during tissue IR injury. Our findings support a critical role for mMg2+ in regulating MCU activity and attenuating mCa2+ overload.
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Affiliation(s)
- Thiruvelselvan Ponnusamy
- Heart and Vascular Institute, Department of Medicine, Department of Cellular and Molecular Physiology, Pennsylvania State University, College of Medicine, Hershey, PA 17033, USA
| | - Prema Velusamy
- Heart and Vascular Institute, Department of Medicine, Department of Cellular and Molecular Physiology, Pennsylvania State University, College of Medicine, Hershey, PA 17033, USA
| | - Amrendra Kumar
- Department of Cellular and Molecular Physiology, Pennsylvania State University, College of Medicine, Hershey, PA 17033, USA
| | - Daniel Morris
- Department of Cellular and Molecular Physiology, Pennsylvania State University, College of Medicine, Hershey, PA 17033, USA
| | - Xueqian Zhang
- Cardiovascular Medicine, Department of Medicine, UMass Chan Medical School, Worcester, MA 01655, USA
| | - Gang Ning
- Microscopy Core Facility, Penn State Huck Institutes of the Life Sciences, University Park, PA 16802, USA
| | - Marianne Klinger
- Department of Pathology, Pennsylvania State University, College of Medicine, Hershey, PA 17033, USA
| | - Jean E. Copper
- Department of Pathology, Pennsylvania State University, College of Medicine, Hershey, PA 17033, USA
| | - Sudarsan Rajan
- Center for Translational Medicine, Lewis Katz School of Medicine, Temple University, Philadelphia, PA 19140, USA
| | - Joseph Y Cheung
- Department of Renal Medicine, Brigham & Women’s Hospital, Harvard Medical School, Boston, MA 02115, USA
| | | | - Nelli Mnatsakanyan
- Department of Cellular and Molecular Physiology, Pennsylvania State University, College of Medicine, Hershey, PA 17033, USA
| | - Santhanam Shanmughapriya
- Heart and Vascular Institute, Department of Medicine, Department of Cellular and Molecular Physiology, Pennsylvania State University, College of Medicine, Hershey, PA 17033, USA
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15
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Erramilli SK, Dominik PK, Deneka D, Tokarz P, Kim SS, Reddy BG, Skrobek BM, Dalmas O, Perozo E, Kossiakoff AA. Conformation-specific synthetic antibodies discriminate multiple functional states of the ion channel CorA. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.05.07.539746. [PMID: 37205530 PMCID: PMC10187328 DOI: 10.1101/2023.05.07.539746] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/21/2023]
Abstract
CorA, the primary magnesium ion channel in prokaryotes and archaea, is a prototypical homopentameric ion channel that undergoes ion-dependent conformational transitions. CorA adopts five-fold symmetric non-conductive states in the presence of high concentrations of Mg 2+ , and highly asymmetric flexible states in its complete absence. However, the latter were of insufficient resolution to be thoroughly characterized. In order to gain additional insights into the relationship between asymmetry and channel activation, we exploited phage display selection strategies to generate conformation-specific synthetic antibodies (sABs) against CorA in the absence of Mg 2+ . Two sABs from these selections, C12 and C18, showed different degrees of Mg 2+ -sensitivity. Through structural, biochemical, and biophysical characterization, we found the sABs are both conformation-specific but probe different features of the channel under open-like conditions. C18 is highly specific to the Mg 2+ -depleted state of CorA and through negative-stain electron microscopy (ns-EM), we show sAB binding reflects the asymmetric arrangement of CorA protomers in Mg 2+ -depleted conditions. We used X-ray crystallography to determine a structure at 2.0 Å resolution of sAB C12 bound to the soluble N-terminal regulatory domain of CorA. The structure shows C12 is a competitive inhibitor of regulatory magnesium binding through its interaction with the divalent cation sensing site. We subsequently exploited this relationship to capture and visualize asymmetric CorA states in different [Mg 2+ ] using ns-EM. We additionally utilized these sABs to provide insights into the energy landscape that governs the ion-dependent conformational transitions of CorA.
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16
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Uthayabalan S, Vishnu N, Madesh M, Stathopulos PB. The human MRS2 magnesium-binding domain is a regulatory feedback switch for channel activity. Life Sci Alliance 2023; 6:e202201742. [PMID: 36754568 PMCID: PMC9909464 DOI: 10.26508/lsa.202201742] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2022] [Revised: 01/25/2023] [Accepted: 01/26/2023] [Indexed: 02/10/2023] Open
Abstract
Mitochondrial RNA splicing 2 (MRS2) forms a magnesium (Mg2+) entry protein channel in mitochondria. Whereas MRS2 contains two transmembrane domains constituting a pore on the inner mitochondrial membrane, most of the protein resides within the matrix. Yet, the precise structural and functional role of this obtrusive amino terminal domain (NTD) in human MRS2 is unknown. Here, we show that the MRS2 NTD self-associates into a homodimer, contrasting the pentameric assembly of CorA, an orthologous bacterial channel. Mg2+ and calcium suppress lower and higher order oligomerization of MRS2 NTD, whereas cobalt has no effect on the NTD but disassembles full-length MRS2. Mutating-pinpointed residues-mediating Mg2+ binding to the NTD not only selectively decreases Mg2+-binding affinity ∼sevenfold but also abrogates Mg2+ binding-induced secondary, tertiary, and quaternary structure changes. Disruption of NTD Mg2+ binding strikingly potentiates mitochondrial Mg2+ uptake in WT and Mrs2 knockout cells. Our work exposes a mechanism for human MRS2 autoregulation by negative feedback from the NTD and identifies a novel gain of function mutant with broad applicability to future Mg2+ signaling research.
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Affiliation(s)
- Sukanthathulse Uthayabalan
- Department of Physiology and Pharmacology, Schulich School of Medicine and Dentistry, University of Western Ontario, London, Canada
| | - Neelanjan Vishnu
- Center for Mitochondrial Medicine, Department of Medicine, University of Texas Health San Antonio, San Antonio, TX, USA
| | - Muniswamy Madesh
- Center for Mitochondrial Medicine, Department of Medicine, University of Texas Health San Antonio, San Antonio, TX, USA
| | - Peter B Stathopulos
- Department of Physiology and Pharmacology, Schulich School of Medicine and Dentistry, University of Western Ontario, London, Canada
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17
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Zhu Y, Wang Y, Zhang Y, Pu M, Miao W, Bai M, Bao R, Geng J. Ion selectivity and gating behavior of the CorA-type channel Bpss1228. Front Chem 2022; 10:998075. [PMID: 36171999 PMCID: PMC9511408 DOI: 10.3389/fchem.2022.998075] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2022] [Accepted: 08/25/2022] [Indexed: 11/24/2022] Open
Abstract
Magnesium is an essential element to sustain all forms of life. Total intracellular magnesium content is determined by the balance of magnesium influx and efflux. CorA is a divalent selective channel in the metal ion transport superfamily and is the major Mg2+ uptake pathway in prokaryotes and eukaryotic mitochondria. Previous studies have demonstrated that CorA showed distinct magnesium bound closed conformation and Mg2+-free states. In addition, CorA is regulated by cytoplasmic magnesium ions and its gating mechanism has been investigated by electron paramagnetic resonance technique and molecular dynamic simulations. Here, we report a study of the putative CorA-type channel Bpss1228 from Burkholderia pseudomallei, which has been shown to be significantly associated with pseudomallei infection. We expressed and purified the Bpss1228 in full-length. Subsequently, electrophysiological experiments further investigated the electrical characteristics of Bpss1228 and revealed that it was a strictly cation-selective channel. We also proved that Bpss1228 not only possessed magnesium-mediated regulatory property a remarkable ability to be modulated by magnesium ions. Finally, we observed the three-step gating behavior of Bpss1228 on planar lipid bilayer, and further proposed a synergistic gating mechanism by which CorA family channels control intracellular magnesium homeostasis.
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Affiliation(s)
| | | | | | | | | | | | - Rui Bao
- *Correspondence: Rui Bao, ; Jia Geng,
| | - Jia Geng
- *Correspondence: Rui Bao, ; Jia Geng,
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18
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Jin F, Huang Y, Hattori M. Recent Advances in the Structural Biology of Mg 2+ Channels and Transporters. J Mol Biol 2022; 434:167729. [PMID: 35841930 DOI: 10.1016/j.jmb.2022.167729] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/29/2021] [Revised: 07/06/2022] [Accepted: 07/07/2022] [Indexed: 10/17/2022]
Abstract
Magnesium ions (Mg2+) are the most abundant divalent cations in living organisms and are essential for various physiological processes, including ATP utilization and the catalytic activity of numerous enzymes. Therefore, the homeostatic mechanisms associated with cellular Mg2+ are crucial for both eukaryotic and prokaryotic organisms and are thus strictly controlled by Mg2+ channels and transporters. Technological advances in structural biology, such as the expression screening of membrane proteins, in meso phase crystallization, and recent cryo-EM techniques, have enabled the structure determination of numerous Mg2+ channels and transporters. In this review article, we provide an overview of the families of Mg2+ channels and transporters (MgtE/SLC41, TRPM6/7, CorA/Mrs2, CorC/CNNM), and discuss the structural biology prospects based on the known structures of MgtE, TRPM7, CorA and CorC.
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Affiliation(s)
- Fei Jin
- State Key Laboratory of Genetic Engineering, Shanghai Key Laboratory of Bioactive Small Molecules, Collaborative Innovation Center of Genetics and Development, Department of Physiology and Neurobiology, School of Life Sciences, Fudan University, Shanghai 200438, China
| | - Yichen Huang
- State Key Laboratory of Genetic Engineering, Shanghai Key Laboratory of Bioactive Small Molecules, Collaborative Innovation Center of Genetics and Development, Department of Physiology and Neurobiology, School of Life Sciences, Fudan University, Shanghai 200438, China
| | - Motoyuki Hattori
- State Key Laboratory of Genetic Engineering, Shanghai Key Laboratory of Bioactive Small Molecules, Collaborative Innovation Center of Genetics and Development, Department of Physiology and Neurobiology, School of Life Sciences, Fudan University, Shanghai 200438, China.
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19
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Johansen NT, Bonaccorsi M, Bengtsen T, Larsen AH, Tidemand FG, Pedersen MC, Huda P, Berndtsson J, Darwish T, Yepuri NR, Martel A, Pomorski TG, Bertarello A, Sansom MS, Rapp M, Crehuet R, Schubeis T, Lindorff-Larsen K, Pintacuda G, Arleth L. Mg 2+-dependent conformational equilibria in CorA and an integrated view on transport regulation. eLife 2022; 11:71887. [PMID: 35129435 PMCID: PMC8865849 DOI: 10.7554/elife.71887] [Citation(s) in RCA: 12] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2021] [Accepted: 02/04/2022] [Indexed: 11/13/2022] Open
Abstract
The CorA family of proteins regulates the homeostasis of divalent metal ions in many bacteria, archaea, and eukaryotic mitochondria, making it an important target in the investigation of the mechanisms of transport and its functional regulation. Although numerous structures of open and closed channels are now available for the CorA family, the mechanism of the transport regulation remains elusive. Here, we investigated the conformational distribution and associated dynamic behaviour of the pentameric Mg2+ channel CorA at room temperature using small-angle neutron scattering (SANS) in combination with molecular dynamics (MD) simulations and solid-state nuclear magnetic resonance spectroscopy (NMR). We find that neither the Mg2+-bound closed structure nor the Mg2+-free open forms are sufficient to explain the average conformation of CorA. Our data support the presence of conformational equilibria between multiple states, and we further find a variation in the behaviour of the backbone dynamics with and without Mg2+. We propose that CorA must be in a dynamic equilibrium between different non-conducting states, both symmetric and asymmetric, regardless of bound Mg2+ but that conducting states become more populated in Mg2+-free conditions. These properties are regulated by backbone dynamics and are key to understanding the functional regulation of CorA.
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Affiliation(s)
| | - Marta Bonaccorsi
- Centre de RMN à Très hauts Champs de Lyon, UMR 5280, CNRS, University of Lyon, Villeurbanne, France
| | - Tone Bengtsen
- Department of Biology, University of Copenhagen, Copenhagen N, Denmark
| | - Andreas Haahr Larsen
- Condensed Matter Physics, Niels Bohr Institute, University of Copenhagen, Copenhagen E, Denmark
| | | | - Martin Cramer Pedersen
- Condensed Matter Physics, Niels Bohr Institute, University of Copenhagen, Copenhagen E, Denmark
| | - Pie Huda
- Australian Institute for Bioengineering and Nanotechnology, University of Queensland, Brisbane, Australia
| | - Jens Berndtsson
- Department of Biochemistry and Biophysics, Stockholm University, Stockholm, Sweden
| | - Tamim Darwish
- National Deuteration Facility, Australian Nuclear Science and Technology Organization, Lucas Heights, Australia
| | - Nageshewar Rao Yepuri
- National Deuteration Facility, Australian Nuclear Science and Technology Organization, Lucas Heights, Australia
| | | | - Thomas Günther Pomorski
- Department of Plant and Environmental Sciences, University of Copenhagen, Frederiksberg, Denmark
| | - Andrea Bertarello
- Centre de RMN à Très hauts Champs de Lyon, UMR 5280, CNRS, University of Lyon, Villeurbanne, France
| | - Mark Sp Sansom
- Department of Biochemistry, University of Oxford, Oxford, United Kingdom
| | - Mikaela Rapp
- Department of Biochemistry and Biophysics, Stockholm University, Stockholm, Sweden
| | - Ramon Crehuet
- Department of Biology, University of Copenhagen, Copenhagen N, Denmark
| | - Tobias Schubeis
- Centre de RMN à Très hauts Champs de Lyon, UMR 5280, CNRS, University of Lyon, Villeurbanne, France
| | | | - Guido Pintacuda
- Centre de RMN à Très hauts Champs de Lyon, UMR 5280, CNRS, University of Lyon, Villeurbanne, France
| | - Lise Arleth
- Condensed Matter Physics, Niels Bohr Institute, University of Copenhagen, Copenhagen, Denmark
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20
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Ramanadane K, Straub MS, Dutzler R, Manatschal C. Structural and functional properties of a magnesium transporter of the SLC11/NRAMP family. eLife 2022; 11:74589. [PMID: 35001872 PMCID: PMC8806188 DOI: 10.7554/elife.74589] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2021] [Accepted: 12/17/2021] [Indexed: 11/13/2022] Open
Abstract
Members of the ubiquitous SLC11/NRAMP family catalyze the uptake of divalent transition metal ions into cells. They have evolved to efficiently select these trace elements from a large pool of Ca2+ and Mg2+, which are both orders of magnitude more abundant, and to concentrate them in the cytoplasm aided by the cotransport of H+ serving as energy source. In the present study, we have characterized a member of a distant clade of the family found in prokaryotes, termed NRMTs, that were proposed to function as transporters of Mg2+. The protein transports Mg2+ and Mn2+ but not Ca2+ by a mechanism that is not coupled to H+. Structures determined by cryo-EM and X-ray crystallography revealed a generally similar protein architecture compared to classical NRAMPs, with a restructured ion binding site whose increased volume provides suitable interactions with ions that likely have retained much of their hydration shell.
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Affiliation(s)
| | - Monique S Straub
- Department of Biochemistry, University of Zurich, Zürich, Switzerland
| | - Raimund Dutzler
- Department of Biochemistry, University of Zurich, Zürich, Switzerland
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21
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Chen Y, Zhu Z, Tian Y, Jiang L. Rational ion transport management mediated through membrane structures. EXPLORATION 2021; 1:20210101. [PMCID: PMC10190948 DOI: 10.1002/exp.20210101] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/06/2021] [Accepted: 09/13/2021] [Indexed: 06/14/2023]
Affiliation(s)
- Yupeng Chen
- Key Laboratory of Bio‐Inspired Smart Interfacial Science and Technology of Ministry of Education, School of Chemistry Beihang University Beijing P. R. China
| | - Zhongpeng Zhu
- Key Laboratory of Bio‐Inspired Smart Interfacial Science and Technology of Ministry of Education, School of Chemistry Beihang University Beijing P. R. China
| | - Ye Tian
- CAS Key Laboratory of Bio‐Inspired Materials and Interfacial Science CAS Center for Excellence in Nanoscience Technical Institute of Physics and Chemistry, Chinese Academy of Sciences Beijing P. R. China
- University of Chinese Academy of Sciences Beijing P. R. China
| | - Lei Jiang
- Key Laboratory of Bio‐Inspired Smart Interfacial Science and Technology of Ministry of Education, School of Chemistry Beihang University Beijing P. R. China
- CAS Key Laboratory of Bio‐Inspired Materials and Interfacial Science CAS Center for Excellence in Nanoscience Technical Institute of Physics and Chemistry, Chinese Academy of Sciences Beijing P. R. China
- University of Chinese Academy of Sciences Beijing P. R. China
- School of Future Technology University of Chinese Academy of Sciences Beijing P. R. China
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22
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Abstract
CNNM/CorB proteins are a broadly conserved family of integral membrane proteins with close to 90,000 protein sequences known. They are associated with Mg2+ transport but it is not known if they mediate transport themselves or regulate other transporters. Here, we determine the crystal structure of an archaeal CorB protein in two conformations (apo and Mg2+-ATP bound). The transmembrane DUF21 domain exists in an inward-facing conformation with a Mg2+ ion coordinated by a conserved π-helix. In the absence of Mg2+-ATP, the CBS-pair domain adopts an elongated dimeric configuration with previously unobserved domain-domain contacts. Hydrogen-deuterium exchange mass spectrometry, analytical ultracentrifugation, and molecular dynamics experiments support a role of the structural rearrangements in mediating Mg2+-ATP sensing. Lastly, we use an in vitro, liposome-based assay to demonstrate direct Mg2+ transport by CorB proteins. These structural and functional insights provide a framework for understanding function of CNNMs in Mg2+ transport and associated diseases.
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23
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Stetsenko A, Stehantsev P, Dranenko NO, Gelfand MS, Guskov A. Structural and biochemical characterization of a novel ZntB (CmaX) transporter protein from Pseudomonas aeruginosa. Int J Biol Macromol 2021; 184:760-767. [PMID: 34175341 DOI: 10.1016/j.ijbiomac.2021.06.130] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2021] [Revised: 06/16/2021] [Accepted: 06/18/2021] [Indexed: 11/19/2022]
Abstract
The 2-TM-GxN family of membrane proteins is widespread in prokaryotes and plays an important role in transport of divalent cations. The canonical signature motif, which is also a selectivity filter, has a composition of Gly-Met-Asn. Some members though deviate from this composition, however no data are available as to whether this has any functional implications. Here we report the functional and structural analysis of CmaX protein from a pathogenic Pseudomonas aeruginosa bacterium, which has a Gly-Ile-Asn signature motif. CmaX readily transports Zn2+, Mg2+, Cd2+, Ni2+ and Co2+ ions, but it does not utilize proton-symport as does ZntB from Escherichia coli. Together with the bioinformatics analysis, our data suggest that deviations from the canonical signature motif do not reveal any changes in substrate selectivity or transport and easily alter in course of evolution.
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Affiliation(s)
- Artem Stetsenko
- Groningen Biomolecular Sciences and Biotechnology Institute, University of Groningen, the Netherlands
| | - Pavlo Stehantsev
- Groningen Biomolecular Sciences and Biotechnology Institute, University of Groningen, the Netherlands
| | - Natalia O Dranenko
- Institute for Information Transmission Problems (Kharkevich Institute) RAS, Moscow, Russia
| | - Mikhail S Gelfand
- Institute for Information Transmission Problems (Kharkevich Institute) RAS, Moscow, Russia; Skolkovo Institute of Science and Technology, Moscow, Russia
| | - Albert Guskov
- Groningen Biomolecular Sciences and Biotechnology Institute, University of Groningen, the Netherlands; Moscow Institute of Physics and Technology, Dolgoprudny, Russia.
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24
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Nemchinova M, Melcr J, Wassenaar TA, Marrink SJ, Guskov A. Asymmetric CorA Gating Mechanism as Observed by Molecular Dynamics Simulations. J Chem Inf Model 2021; 61:2407-2417. [PMID: 33886304 PMCID: PMC8154316 DOI: 10.1021/acs.jcim.1c00261] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
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The CorA family of
proteins plays a housekeeping role in the homeostasis
of divalent metal ions in many bacteria and archaea as well as in
mitochondria of eukaryotes, rendering it an important target to study
the mechanisms of divalent transport and regulation across different
life domains. Despite numerous studies, the mechanistic details of
the channel gating and the transport of the metal ions are still not
entirely understood. Here, we use all-atom and coarse-grained molecular
dynamics simulations combined with in vitro experiments
to investigate the influence of divalent cations on the function of
CorA. Simulations reveal pronounced asymmetric movements of monomers
that enable the rotation of the α7 helix and the cytoplasmic
subdomain with the subsequent formation of new interactions and the
opening of the channel. These computational results are functionally
validated using site-directed mutagenesis of the intracellular cytoplasmic
domain residues and biochemical assays. The obtained results infer
a complex network of interactions altering the structure of CorA to
allow gating. Furthermore, we attempt to reconcile the existing gating
hypotheses for CorA to conclude the mechanism of transport of divalent
cations via these proteins.
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Affiliation(s)
- Mariia Nemchinova
- Groningen Institute for Biomolecular Sciences and Biotechnology, University of Groningen, 9747AG Groningen, The Netherlands
| | - Josef Melcr
- Groningen Institute for Biomolecular Sciences and Biotechnology, University of Groningen, 9747AG Groningen, The Netherlands
| | - Tsjerk A Wassenaar
- Groningen Institute for Biomolecular Sciences and Biotechnology, University of Groningen, 9747AG Groningen, The Netherlands
| | - Siewert J Marrink
- Groningen Institute for Biomolecular Sciences and Biotechnology, University of Groningen, 9747AG Groningen, The Netherlands
| | - Albert Guskov
- Groningen Institute for Biomolecular Sciences and Biotechnology, University of Groningen, 9747AG Groningen, The Netherlands
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25
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Fu T, Cai Z, Yue Z, Yang H, Fang B, Zhang X, Fan Z, Pan X, Yang F, Jin Y, Cheng Z, Wu W, Sun B, Huigens RW, Yang L, Bai F. Evolution of Resistance to Phenazine Antibiotics in Staphylococcus aureus and Its Role During Coinfection with Pseudomonas aeruginosa. ACS Infect Dis 2021; 7:636-649. [PMID: 33650853 DOI: 10.1021/acsinfecdis.0c00837] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
In the niches that Staphylococcus aureus and Pseudomonas aeruginosa coinhabit, the later pathogen produces phenazine antibiotics to inhibit the growth of S. aureus. Recently, a group of halogenated phenazines (HPs) has been shown to have potent antimicrobial activities against Staphylococci; however, no HP-resistant mutant has been reported. Here, we demonstrate that S. aureus develops HP-resistance via single amino acid change (Arg116Cys) in a transcriptional repressor TetR21. RNA-seq analysis showed that the TetR21R116C variation caused drastic up-regulation of an adjacent gene hprS (halogenated phenazine resistance protein of S. aureus). Deletion of the hprS in the TetR21R116C background restored bacterial susceptibility to HP, while hprS overexpression in S. aureus conferred HP-resistance. The expression of HprS is under tight transcriptional control of the TetR21 via direct binding to the promoter region of hprS. The R116C mutation in TetR21 significantly reduced its DNA binding affinity. Moreover, natural phenazine antibiotics (phenazine-1-carboxylic acid and pyocyanin) and a HP analog (HP-22) are ligands for the TetR21, regulating its repressor activity. Combining homology analysis and LC-MS/MS assay we demonstrated that HprS is a phenazine efflux pump. To the best of our knowledge, we provide the first report of phenazine efflux pump in S. aureus. Interestingly, the TetR21R116C variation has been found in some clinical S. aureus isolates, and a laboratory strain of S. aureus with TetR21R116C variation showed enhanced growth competitiveness toward P. aeruginosa and promoted coinfection with P. aeruginosa in the host environment, demonstrating significance of the mutation in host infections.
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Affiliation(s)
- Tongtong Fu
- State Key Laboratory of Medicinal Chemical Biology, Key Laboratory of Molecular Microbiology and Technology of the Ministry of Education, College of Life Sciences, Nankai University, Tianjin, 300071, China
| | - Zhao Cai
- School of Medicine, Southern University of Science and Technology (SUSTec), Shenzhen 518055, China
| | - Zhuo Yue
- State Key Laboratory of Medicinal Chemical Biology, Key Laboratory of Molecular Microbiology and Technology of the Ministry of Education, College of Life Sciences, Nankai University, Tianjin, 300071, China
| | - Hongfen Yang
- Department of Medicinal Chemistry & Center for Natural Products, Drug Discovery and Development (CNPD3), College of Pharmacy, University of Florida, Gainesville, Florida 32610, United States
| | - Bo Fang
- School of Life Sciences and Medical Center, University of Science and Technology of China, Hefei, Anhui 230027, China
| | - Xinwen Zhang
- State Key Laboratory of Medicinal Chemical Biology, Key Laboratory of Molecular Microbiology and Technology of the Ministry of Education, College of Life Sciences, Nankai University, Tianjin, 300071, China
| | - Zheng Fan
- State Key Laboratory of Medicinal Chemical Biology, Key Laboratory of Molecular Microbiology and Technology of the Ministry of Education, College of Life Sciences, Nankai University, Tianjin, 300071, China
| | - Xiaolei Pan
- State Key Laboratory of Medicinal Chemical Biology, Key Laboratory of Molecular Microbiology and Technology of the Ministry of Education, College of Life Sciences, Nankai University, Tianjin, 300071, China
| | - Fan Yang
- State Key Laboratory of Medicinal Chemical Biology, Key Laboratory of Molecular Microbiology and Technology of the Ministry of Education, College of Life Sciences, Nankai University, Tianjin, 300071, China
| | - Yongxin Jin
- State Key Laboratory of Medicinal Chemical Biology, Key Laboratory of Molecular Microbiology and Technology of the Ministry of Education, College of Life Sciences, Nankai University, Tianjin, 300071, China
| | - Zhihui Cheng
- State Key Laboratory of Medicinal Chemical Biology, Key Laboratory of Molecular Microbiology and Technology of the Ministry of Education, College of Life Sciences, Nankai University, Tianjin, 300071, China
| | - Wuihui Wu
- State Key Laboratory of Medicinal Chemical Biology, Key Laboratory of Molecular Microbiology and Technology of the Ministry of Education, College of Life Sciences, Nankai University, Tianjin, 300071, China
| | - Baolin Sun
- School of Life Sciences and Medical Center, University of Science and Technology of China, Hefei, Anhui 230027, China
| | - Robert W. Huigens
- Department of Medicinal Chemistry & Center for Natural Products, Drug Discovery and Development (CNPD3), College of Pharmacy, University of Florida, Gainesville, Florida 32610, United States
| | - Liang Yang
- School of Medicine, Southern University of Science and Technology (SUSTec), Shenzhen 518055, China
| | - Fang Bai
- State Key Laboratory of Medicinal Chemical Biology, Key Laboratory of Molecular Microbiology and Technology of the Ministry of Education, College of Life Sciences, Nankai University, Tianjin, 300071, China
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26
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Huang Y, Jin F, Funato Y, Xu Z, Zhu W, Wang J, Sun M, Zhao Y, Yu Y, Miki H, Hattori M. Structural basis for the Mg 2+ recognition and regulation of the CorC Mg 2+ transporter. SCIENCE ADVANCES 2021; 7:7/7/eabe6140. [PMID: 33568487 PMCID: PMC7875539 DOI: 10.1126/sciadv.abe6140] [Citation(s) in RCA: 33] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/02/2020] [Accepted: 12/23/2020] [Indexed: 05/05/2023]
Abstract
The CNNM/CorC family proteins are Mg2+ transporters that are widely distributed in all domains of life. In bacteria, CorC has been implicated in the survival of pathogenic microorganisms. In humans, CNNM proteins are involved in various biological events, such as body absorption/reabsorption of Mg2+ and genetic disorders. Here, we determined the crystal structure of the Mg2+-bound CorC TM domain dimer. Each protomer has a single Mg2+ binding site with a fully dehydrated Mg2+ ion. The residues at the Mg2+ binding site are strictly conserved in both human CNNM2 and CNNM4, and many of these residues are associated with genetic diseases. Furthermore, we determined the structures of the CorC cytoplasmic region containing its regulatory ATP-binding domain. A combination of structural and functional analyses not only revealed the potential interface between the TM and cytoplasmic domains but also showed that ATP binding is important for the Mg2+ export activity of CorC.
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Affiliation(s)
- Yichen Huang
- State Key Laboratory of Genetic Engineering, Shanghai Key Laboratory of Bioactive Small Molecules, Collaborative Innovation Center of Genetics and Development, and Department of Physiology and Biophysics, School of Life Sciences, Fudan University, 2005 Songhu Road, Yangpu District, Shanghai 200438, China
| | - Fei Jin
- State Key Laboratory of Genetic Engineering, Shanghai Key Laboratory of Bioactive Small Molecules, Collaborative Innovation Center of Genetics and Development, and Department of Physiology and Biophysics, School of Life Sciences, Fudan University, 2005 Songhu Road, Yangpu District, Shanghai 200438, China
| | - Yosuke Funato
- Department of Cellular Regulation, Research Institute for Microbial Diseases, Osaka University, 3-1 Yamadaoka, Suita, Osaka 565-0871, Japan
| | - Zhijian Xu
- CAS Key Laboratory of Receptor Research and Drug Discovery and Design Center, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, 555 Zuchongzhi Road, Pudong New Area, Shanghai 201203, China
| | - Weiliang Zhu
- CAS Key Laboratory of Receptor Research and Drug Discovery and Design Center, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, 555 Zuchongzhi Road, Pudong New Area, Shanghai 201203, China
| | - Jing Wang
- School of Basic Medicine and Clinical Pharmacy, China Pharmaceutical University, Medical Building, Room 128, 639 Long-Mian Road, Nanjing 200098, China
| | - Minxuan Sun
- State Key Laboratory of Genetic Engineering, Shanghai Key Laboratory of Bioactive Small Molecules, Collaborative Innovation Center of Genetics and Development, and Department of Physiology and Biophysics, School of Life Sciences, Fudan University, 2005 Songhu Road, Yangpu District, Shanghai 200438, China
| | - Yimeng Zhao
- State Key Laboratory of Genetic Engineering, Shanghai Key Laboratory of Bioactive Small Molecules, Collaborative Innovation Center of Genetics and Development, and Department of Physiology and Biophysics, School of Life Sciences, Fudan University, 2005 Songhu Road, Yangpu District, Shanghai 200438, China
| | - Ye Yu
- School of Basic Medicine and Clinical Pharmacy, China Pharmaceutical University, Medical Building, Room 128, 639 Long-Mian Road, Nanjing 200098, China
| | - Hiroaki Miki
- Department of Cellular Regulation, Research Institute for Microbial Diseases, Osaka University, 3-1 Yamadaoka, Suita, Osaka 565-0871, Japan.
| | - Motoyuki Hattori
- State Key Laboratory of Genetic Engineering, Shanghai Key Laboratory of Bioactive Small Molecules, Collaborative Innovation Center of Genetics and Development, and Department of Physiology and Biophysics, School of Life Sciences, Fudan University, 2005 Songhu Road, Yangpu District, Shanghai 200438, China.
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27
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Functional analysis of whether the glycine residue of the GMN motif of the Arabidopsis MRS2/MGT/CorA-type Mg 2+ channel protein AtMRS2-11 is critical for Mg 2+ transport activity. Arch Biochem Biophys 2020; 697:108673. [PMID: 33217378 DOI: 10.1016/j.abb.2020.108673] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2020] [Revised: 10/09/2020] [Accepted: 11/08/2020] [Indexed: 11/21/2022]
Abstract
Magnesium (Mg2+) plays a critical role in many physiological processes. The AtMRS2/MGT family, which contains nine Arabidopsis genes (and two pseudogenes), belongs to a eukaryotic subset of the CorA superfamily of divalent cation transporters. AtMRS2-11/MGT10 possesses the signature GlyMetAsn sequence (the GMN motif) conserved in the CorA superfamily; however, little is known about the role of the GMN motif in AtMRS2. Direct measurement using the fluorescent dye mag-fura-2 revealed that reconstituted AtMRS2-11 mediated rapid Mg2+ uptake into proteoliposomes at extraliposomal Mg2+ concentrations of 10 and 20 mM. Mutations in the GMN motif, G417 to A, S or V, did not show a significant change in Mg2+ uptake relative to the wild-type protein. The G417W mutant exhibited a significant increase in Mg2+ uptake. The functional complementation assay in Escherichia coli strain TM2 showed that E. coli cells expressing AtMRS2-11 with mutations in G of the GMN motif did not grow in LB medium without Mg2+ supplementation, while growth was observed in LB medium supplemented with 0.5 mM Mg2+; no difference was observed between the growth of TM2 cells expressing the AtMRS2-11 G417W mutant and that of cells expressing wild-type AtMRS2-11. These results suggested that the Mg2+ transport activity of the AtMRS2-11 GMN-motif mutants was low at low physiological Mg2+ concentrations; thus, the Gly residue is critical for Mg2+ transport, and the Mg2+ transport activity of the GMN-motif mutants was increased at high Mg2+ concentrations.
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28
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Abstract
CorA proteins belong to 2-TM-GxN family of membrane proteins, and play a major role in Mg2+ transport in prokaryotes and eukaryotic mitochondria. The selection of substrate is believed to occur via the signature motif GxN, however there is no consensus how strict this selection within the family. To answer this question, we employed fluorescence-based transport assays on three different family members, namely CorA from bacterium Thermotoga maritima, CorA from the archeon Methanocaldococcus jannaschii and ZntB from bacterium Escherichia coli, reconstituted into proteoliposomes. Our results show that all three proteins readily transport Mg2+, Co2+, Ni2+ and Zn2+, but not Al3+. Despite the similarity in cation specificity, ZntB differs from the CorA proteins, as in the former transport is stimulated by a proton gradient, but in the latter by the membrane potential, confirming the hypothesis that CorA and ZntB proteins diverged to different transport mechanisms within the same protein scaffold.
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29
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Rangl M, Schmandt N, Perozo E, Scheuring S. Real time dynamics of Gating-Related conformational changes in CorA. eLife 2019; 8:47322. [PMID: 31774394 PMCID: PMC6927688 DOI: 10.7554/elife.47322] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2019] [Accepted: 11/26/2019] [Indexed: 01/01/2023] Open
Abstract
CorA, a divalent-selective channel in the metal ion transport superfamily, is the major Mg2+-influx pathway in prokaryotes. CorA structures in closed (Mg2+-bound), and open (Mg2+-free) states, together with functional data showed that Mg2+-influx inhibits further Mg2+-uptake completing a regulatory feedback loop. While the closed state structure is a symmetric pentamer, the open state displayed unexpected asymmetric architectures. Using high-speed atomic force microscopy (HS-AFM), we explored the Mg2+-dependent gating transition of single CorA channels: HS-AFM movies during Mg2+-depletion experiments revealed the channel’s transition from a stable Mg2+-bound state over a highly mobile and dynamic state with fluctuating subunits to asymmetric structures with varying degree of protrusion heights from the membrane. Our data shows that at Mg2+-concentration below Kd, CorA adopts a dynamic (putatively open) state of multiple conformations that imply structural rearrangements through hinge-bending in TM1. We discuss how these structural dynamics define the functional behavior of this ligand-dependent channel.
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Affiliation(s)
- Martina Rangl
- Department of Anesthesiology, Weill Cornell Medical College, New York, United States.,Department of Physiology and Biophysics, Weill Cornell Medical College, New York, United States
| | - Nicolaus Schmandt
- Department of Biochemistry and Molecular Biophysics, The University of Chicago, Chicago, United States
| | - Eduardo Perozo
- Department of Biochemistry and Molecular Biophysics, The University of Chicago, Chicago, United States
| | - Simon Scheuring
- Department of Anesthesiology, Weill Cornell Medical College, New York, United States.,Department of Physiology and Biophysics, Weill Cornell Medical College, New York, United States
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30
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Trachsel E, Redder P, Linder P, Armitano J. Genetic screens reveal novel major and minor players in magnesium homeostasis of Staphylococcus aureus. PLoS Genet 2019; 15:e1008336. [PMID: 31415562 PMCID: PMC6711546 DOI: 10.1371/journal.pgen.1008336] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2019] [Revised: 08/27/2019] [Accepted: 07/29/2019] [Indexed: 12/19/2022] Open
Abstract
Magnesium is one of the most abundant metal ions in living cells. Very specific and devoted transporters have evolved for transporting Mg2+ ions across the membrane and maintain magnesium homeostasis. Using genetic screens, we were able to identify the main players in magnesium homeostasis in the opportunistic pathogen Staphylococcus aureus. Here, we show that import of magnesium relies on the redundant activity of either CorA2 or MgtE since in absence of these two importers, bacteria require increased amounts of magnesium in the medium. A third CorA-like importer seems to play a minor role, at least under laboratory conditions. For export of magnesium, we identified two proteins, MpfA and MpfB. MpfA, is the main actor since it is essential for growth in high magnesium concentrations. We show that gain of function mutations or overexpression of the minor factor, MpfB, which is part of a sigmaB controlled stress response regulon, can compensate for the absence of MpfA.
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Affiliation(s)
- Emilie Trachsel
- Department of Microbiology and Molecular Medicine, CMU, Faculty of Medicine, University of Geneva, Geneva, Switzerland
| | - Peter Redder
- Department of Microbiology and Molecular Medicine, CMU, Faculty of Medicine, University of Geneva, Geneva, Switzerland
- LMGM UMR5100, Centre de Biologie Integrative, Paul Sabatier University, Toulouse, France
| | - Patrick Linder
- Department of Microbiology and Molecular Medicine, CMU, Faculty of Medicine, University of Geneva, Geneva, Switzerland
| | - Joshua Armitano
- Department of Microbiology and Molecular Medicine, CMU, Faculty of Medicine, University of Geneva, Geneva, Switzerland
- * E-mail:
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31
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Emerging structural biology of TRPM subfamily channels. Cell Calcium 2019; 79:75-79. [DOI: 10.1016/j.ceca.2019.02.011] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2019] [Revised: 02/28/2019] [Accepted: 02/28/2019] [Indexed: 12/20/2022]
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32
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Ishijima S, Manabe Y, Shinkawa Y, Hotta A, Tokumasu A, Ida M, Sagami I. The homologous Arabidopsis MRS2/MGT/CorA-type Mg2+ channels, AtMRS2-10 and AtMRS2-1 exhibit different aluminum transport activity. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2018; 1860:2184-2191. [DOI: 10.1016/j.bbamem.2018.08.016] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/24/2018] [Revised: 08/24/2018] [Accepted: 08/29/2018] [Indexed: 11/30/2022]
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33
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Structure of the mammalian TRPM7, a magnesium channel required during embryonic development. Proc Natl Acad Sci U S A 2018; 115:E8201-E8210. [PMID: 30108148 PMCID: PMC6126765 DOI: 10.1073/pnas.1810719115] [Citation(s) in RCA: 83] [Impact Index Per Article: 13.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
The transient receptor potential ion channel subfamily M, member 7 (TRPM7), is a ubiquitously expressed protein that is required for mouse embryonic development. TRPM7 contains both an ion channel and an α-kinase. The channel domain comprises a nonselective cation channel with notable permeability to Mg2+ and Zn2+ Here, we report the closed state structures of the mouse TRPM7 channel domain in three different ionic conditions to overall resolutions of 3.3, 3.7, and 4.1 Å. The structures reveal key residues for an ion binding site in the selectivity filter, with proposed partially hydrated Mg2+ ions occupying the center of the conduction pore. In high [Mg2+], a prominent external disulfide bond is found in the pore helix, which is essential for ion channel function. Our results provide a structural framework for understanding the TRPM1/3/6/7 subfamily and extend the knowledge base upon which to study the diversity and evolution of TRP channels.
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34
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Niitsu A, Heal JW, Fauland K, Thomson AR, Woolfson DN. Membrane-spanning α-helical barrels as tractable protein-design targets. Philos Trans R Soc Lond B Biol Sci 2018. [PMID: 28630153 DOI: 10.1098/rstb.2016.0213] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
The rational (de novo) design of membrane-spanning proteins lags behind that for water-soluble globular proteins. This is due to gaps in our knowledge of membrane-protein structure, and experimental difficulties in studying such proteins compared to water-soluble counterparts. One limiting factor is the small number of experimentally determined three-dimensional structures for transmembrane proteins. By contrast, many tens of thousands of globular protein structures provide a rich source of 'scaffolds' for protein design, and the means to garner sequence-to-structure relationships to guide the design process. The α-helical coiled coil is a protein-structure element found in both globular and membrane proteins, where it cements a variety of helix-helix interactions and helical bundles. Our deep understanding of coiled coils has enabled a large number of successful de novo designs. For one class, the α-helical barrels-that is, symmetric bundles of five or more helices with central accessible channels-there are both water-soluble and membrane-spanning examples. Recent computational designs of water-soluble α-helical barrels with five to seven helices have advanced the design field considerably. Here we identify and classify analogous and more complicated membrane-spanning α-helical barrels from the Protein Data Bank. These provide tantalizing but tractable targets for protein engineering and de novo protein design.This article is part of the themed issue 'Membrane pores: from structure and assembly, to medicine and technology'.
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Affiliation(s)
- Ai Niitsu
- School of Chemistry, University of Bristol, Cantock's Close, Bristol BS8 1TS, UK
| | - Jack W Heal
- School of Chemistry, University of Bristol, Cantock's Close, Bristol BS8 1TS, UK
| | - Kerstin Fauland
- School of Chemistry, University of Bristol, Cantock's Close, Bristol BS8 1TS, UK
| | - Andrew R Thomson
- School of Chemistry, University of Bristol, Cantock's Close, Bristol BS8 1TS, UK
| | - Derek N Woolfson
- School of Chemistry, University of Bristol, Cantock's Close, Bristol BS8 1TS, UK .,School of Biochemistry, University of Bristol, Medical Sciences Building, University Walk, Bristol BS8 1TD, UK.,BrisSynBio, University of Bristol, Life Sciences Building, Tyndall Avenue, Bristol BS8 1TQ, UK
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35
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Pravda L, Sehnal D, Svobodová Vařeková R, Navrátilová V, Toušek D, Berka K, Otyepka M, Koča J. ChannelsDB: database of biomacromolecular tunnels and pores. Nucleic Acids Res 2018; 46:D399-D405. [PMID: 29036719 PMCID: PMC5753359 DOI: 10.1093/nar/gkx868] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2017] [Revised: 09/08/2017] [Accepted: 09/28/2017] [Indexed: 01/21/2023] Open
Abstract
ChannelsDB (http://ncbr.muni.cz/ChannelsDB) is a database providing information about the positions, geometry and physicochemical properties of channels (pores and tunnels) found within biomacromolecular structures deposited in the Protein Data Bank. Channels were deposited from two sources; from literature using manual deposition and from a software tool automatically detecting tunnels leading to the enzymatic active sites and selected cofactors, and transmembrane pores. The database stores information about geometrical features (e.g. length and radius profile along a channel) and physicochemical properties involving polarity, hydrophobicity, hydropathy, charge and mutability. The stored data are interlinked with available UniProt annotation data mapping known mutation effects to channel-lining residues. All structures with channels are displayed in a clear interactive manner, further facilitating data manipulation and interpretation. As such, ChannelsDB provides an invaluable resource for research related to deciphering the biological function of biomacromolecular channels.
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Affiliation(s)
- Lukáš Pravda
- CEITEC - Central European Institute of Technology, Masaryk University Brno, Kamenice 5, 625 00 Brno-Bohunice, Czech Republic
- National Centre for Biomolecular Research, Faculty of Science, Kamenice 5, 625 00 Brno-Bohunice, Czech Republic
| | - David Sehnal
- CEITEC - Central European Institute of Technology, Masaryk University Brno, Kamenice 5, 625 00 Brno-Bohunice, Czech Republic
- National Centre for Biomolecular Research, Faculty of Science, Kamenice 5, 625 00 Brno-Bohunice, Czech Republic
| | - Radka Svobodová Vařeková
- CEITEC - Central European Institute of Technology, Masaryk University Brno, Kamenice 5, 625 00 Brno-Bohunice, Czech Republic
- National Centre for Biomolecular Research, Faculty of Science, Kamenice 5, 625 00 Brno-Bohunice, Czech Republic
| | - Veronika Navrátilová
- Regional Centre of Advanced Technologies and Materials, Department of Physical Chemistry, Faculty of Science, Palacký University, tř. 17. listopadu 12, 771 46 Olomouc, Czech Republic
| | - Dominik Toušek
- CEITEC - Central European Institute of Technology, Masaryk University Brno, Kamenice 5, 625 00 Brno-Bohunice, Czech Republic
- Regional Centre of Advanced Technologies and Materials, Department of Physical Chemistry, Faculty of Science, Palacký University, tř. 17. listopadu 12, 771 46 Olomouc, Czech Republic
| | - Karel Berka
- Regional Centre of Advanced Technologies and Materials, Department of Physical Chemistry, Faculty of Science, Palacký University, tř. 17. listopadu 12, 771 46 Olomouc, Czech Republic
| | - Michal Otyepka
- Regional Centre of Advanced Technologies and Materials, Department of Physical Chemistry, Faculty of Science, Palacký University, tř. 17. listopadu 12, 771 46 Olomouc, Czech Republic
| | - Jaroslav Koča
- CEITEC - Central European Institute of Technology, Masaryk University Brno, Kamenice 5, 625 00 Brno-Bohunice, Czech Republic
- National Centre for Biomolecular Research, Faculty of Science, Kamenice 5, 625 00 Brno-Bohunice, Czech Republic
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36
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Nies DH. The biological chemistry of the transition metal "transportome" of Cupriavidus metallidurans. Metallomics 2017; 8:481-507. [PMID: 27065183 DOI: 10.1039/c5mt00320b] [Citation(s) in RCA: 43] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
This review tries to illuminate how the bacterium Cupriavidus metallidurans CH34 is able to allocate essential transition metal cations to their target proteins although these metals have similar charge-to-surface ratios and chemical features, exert toxic effects, compete with each other, and occur in the bacterial environment over a huge range of concentrations and speciations. Central to this ability is the "transportome", the totality of all interacting metal import and export systems, which, as an emergent feature, transforms the environmental metal content and speciation into the cellular metal mélange. In a kinetic flow equilibrium resulting from controlled uptake and efflux reactions, the periplasmic and cytoplasmic metal content is adjusted in a way that minimizes toxic effects. A central core function of the transportome is to shape the metal ion composition using high-rate and low-specificity reactions to avoid time and/or energy-requiring metal discrimination reactions. This core is augmented by metal-specific channels that may even deliver metals all the way from outside of the cell to the cytoplasm. This review begins with a description of the basic chemical features of transition metal cations and the biochemical consequences of these attributes, and which transition metals are available to C. metallidurans. It then illustrates how the environment influences the metal content and speciation, and how the transportome adjusts this metal content. It concludes with an outlook on the fate of metals in the cytoplasm. By generalization, insights coming from C. metallidurans shed light on multiple transition metal homoeostatic mechanisms in all kinds of bacteria including pathogenic species, where the "battle" for metals is an important part of the host-pathogen interaction.
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Affiliation(s)
- Dietrich H Nies
- Molecular Microbiology, Institute for Biology/Microbiology, Martin-Luther-University Halle-Wittenberg, Germany.
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37
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The structural basis of proton driven zinc transport by ZntB. Nat Commun 2017; 8:1313. [PMID: 29101379 PMCID: PMC5670123 DOI: 10.1038/s41467-017-01483-7] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2017] [Accepted: 09/18/2017] [Indexed: 01/09/2023] Open
Abstract
Zinc is an essential microelement to sustain all forms of life. However, excess of zinc is toxic, therefore dedicated import, export and storage proteins for tight regulation of the zinc concentration have evolved. In Enterobacteriaceae, several membrane transporters are involved in zinc homeostasis and linked to virulence. ZntB has been proposed to play a role in the export of zinc, but the transport mechanism of ZntB is poorly understood and based only on experimental characterization of its distant homologue CorA magnesium channel. Here, we report the cryo-electron microscopy structure of full-length ZntB from Escherichia coli together with the results of isothermal titration calorimetry, and radio-ligand uptake and fluorescent transport assays on ZntB reconstituted into liposomes. Our results show that ZntB mediates Zn2+ uptake, stimulated by a pH gradient across the membrane, using a transport mechanism that does not resemble the one proposed for homologous CorA channels. The bacterial zinc transporter ZntB is important for maintaining zinc homeostasis and is mechanistically not well understood. Here, the authors present the cryo-EM structure of ZntB at 4.2 Å resolution, perform transport assays and propose a model for its Zn2+ transport mechanism.
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38
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Zhu Y, Ruan Y, Zhang Y, Chen Y, Lu X, Lu L. Mg 2+-Channel-Inspired Nanopores for Mg 2+/Li + Separation: The Effect of Coordination on the Ionic Hydration Microstructures. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2017; 33:9201-9210. [PMID: 28803477 DOI: 10.1021/acs.langmuir.7b01249] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
The separation behaviors of Mg2+ and Li+ were investigated using molecular dynamics. Two functionalized graphene nanopore models (i.e., co_5 and coo_5) inspired by the characteristic structural features of Mg2+ channels were used. Both nanopores exhibited a higher preference to Mg2+ than to Li+, and the selectivity ratios were higher for coo_5 than for co_5 under all the studied transmembrane voltages. An evaluation of the effect of coordination on the ionic hydration microstructures for both nanopores showed that the positioning of the modified groups could better fit a hydrated Mg2+ than a hydrated Li+, as if Mg2+ was not dehydrated according to hydrogen bond analysis of the ionic hydration shells. This condition led to a lower resistance for Mg2+ than for Li+ when traveling through the nanopores. Moreover, a distinct increase in hydrogen bonds occurred with coo_5 compared with co_5 for hydrated Li+, which made it more difficult for Li+ to pass through coo_5. Thus, a higher Mg2+/Li+ selectivity was found in for coo_5 than for co_5. These findings provide some design principles for developing artificial Mg2+ channels, which have potential applications as Mg2+ sensors and novel devices for Mg2+/Li+ separation.
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Affiliation(s)
- Yudan Zhu
- College of Chemical Engineering, State Key Laboratory of Materials-oriented Chemical Engineering, Nanjing Tech University , Nanjing 210009, P.R. China
| | - Yang Ruan
- College of Chemical Engineering, State Key Laboratory of Materials-oriented Chemical Engineering, Nanjing Tech University , Nanjing 210009, P.R. China
| | - Yumeng Zhang
- College of Chemical Engineering, State Key Laboratory of Materials-oriented Chemical Engineering, Nanjing Tech University , Nanjing 210009, P.R. China
| | - Yaojia Chen
- College of Chemical Engineering, State Key Laboratory of Materials-oriented Chemical Engineering, Nanjing Tech University , Nanjing 210009, P.R. China
| | - Xiaohua Lu
- College of Chemical Engineering, State Key Laboratory of Materials-oriented Chemical Engineering, Nanjing Tech University , Nanjing 210009, P.R. China
| | - Linghong Lu
- College of Chemical Engineering, State Key Laboratory of Materials-oriented Chemical Engineering, Nanjing Tech University , Nanjing 210009, P.R. China
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39
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Lerche M, Sandhu H, Flöckner L, Högbom M, Rapp M. Structure and Cooperativity of the Cytosolic Domain of the CorA Mg 2+ Channel from Escherichia coli. Structure 2017; 25:1175-1186.e4. [PMID: 28669631 DOI: 10.1016/j.str.2017.05.024] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2016] [Revised: 03/24/2017] [Accepted: 05/25/2017] [Indexed: 01/04/2023]
Abstract
Structures of the Mg2+ bound (closed) and apo (open) states of CorA suggests that channel gating is accomplished by rigid-body motions between symmetric and asymmetric assemblies of the cytosolic portions of the five subunits in response to ligand (Mg2+) binding/unbinding at interfacial sites. Here, we structurally and biochemically characterize the isolated cytosolic domain from Escherichia coli CorA. The data reveal an Mg2+-ligand binding site located in a novel position between each of the five subunits and two Mg2+ ions trapped inside the pore. Soaking experiments show that cobalt hexammine outcompetes Mg2+ at the pore site closest to the membrane. This represents the first structural information of how an analog of hexa-hydrated Mg2+ (and competitive inhibitor of CorA) associates to the CorA pore. Biochemical data on the isolated cytoplasmic domain and full-length protein suggests that gating of the CorA channel is governed cooperatively.
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Affiliation(s)
- Michael Lerche
- Department of Biochemistry and Biophysics, Center for Biomembrane Research, Stockholm University, 106 91 Stockholm, Sweden
| | - Hena Sandhu
- Department of Biochemistry and Biophysics, Center for Biomembrane Research, Stockholm University, 106 91 Stockholm, Sweden
| | - Lukas Flöckner
- Department of Biochemistry and Biophysics, Center for Biomembrane Research, Stockholm University, 106 91 Stockholm, Sweden
| | - Martin Högbom
- Department of Biochemistry and Biophysics, Center for Biomembrane Research, Stockholm University, 106 91 Stockholm, Sweden
| | - Mikaela Rapp
- Department of Biochemistry and Biophysics, Center for Biomembrane Research, Stockholm University, 106 91 Stockholm, Sweden.
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40
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Altier A, Jiménez-Piedrahita M, Rey-Castro C, Cecilia J, Galceran J, Puy J. Accumulation of Mg to Diffusive Gradients in Thin Films (DGT) Devices: Kinetic and Thermodynamic Effects of the Ionic Strength. Anal Chem 2016; 88:10245-10251. [PMID: 27660851 DOI: 10.1021/acs.analchem.6b02961] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Affiliation(s)
- Alexandra Altier
- Departament de Química and ‡Departament de Matemàtica, Universitat de Lleida and AGROTECNIO, Rovira Roure 191, 25198, Lleida, Spain
| | - Martín Jiménez-Piedrahita
- Departament de Química and ‡Departament de Matemàtica, Universitat de Lleida and AGROTECNIO, Rovira Roure 191, 25198, Lleida, Spain
| | - Carlos Rey-Castro
- Departament de Química and ‡Departament de Matemàtica, Universitat de Lleida and AGROTECNIO, Rovira Roure 191, 25198, Lleida, Spain
| | - Joan Cecilia
- Departament de Química and ‡Departament de Matemàtica, Universitat de Lleida and AGROTECNIO, Rovira Roure 191, 25198, Lleida, Spain
| | - Josep Galceran
- Departament de Química and ‡Departament de Matemàtica, Universitat de Lleida and AGROTECNIO, Rovira Roure 191, 25198, Lleida, Spain
| | - Jaume Puy
- Departament de Química and ‡Departament de Matemàtica, Universitat de Lleida and AGROTECNIO, Rovira Roure 191, 25198, Lleida, Spain
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41
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Abstract
Ligand binding usually moves the target protein from an ensemble of inactive states to a well-defined active conformation. Matthies et al. flip this scheme around, finding that, for the magnesium channel CorA, loss of ligand binding induces an ensemble of conformations that turn the channel on.
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Affiliation(s)
- Daniel L Minor
- Cardiovascular Research Institute, Departments of Biochemistry and Biophysics and Cellular and Molecular Pharmacology, and California Institute for Quantitative Biomedical Research, University of California, San Francisco, San Francisco, California 94158 USA; Physical Biosciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720 USA.
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42
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Matthies D, Dalmas O, Borgnia MJ, Dominik PK, Merk A, Rao P, Reddy BG, Islam S, Bartesaghi A, Perozo E, Subramaniam S. Cryo-EM Structures of the Magnesium Channel CorA Reveal Symmetry Break upon Gating. Cell 2016; 164:747-56. [PMID: 26871634 DOI: 10.1016/j.cell.2015.12.055] [Citation(s) in RCA: 94] [Impact Index Per Article: 11.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2015] [Revised: 11/10/2015] [Accepted: 12/23/2015] [Indexed: 11/30/2022]
Abstract
CorA, the major Mg(2+) uptake system in prokaryotes, is gated by intracellular Mg(2+) (KD ∼ 1-2 mM). X-ray crystallographic studies of CorA show similar conformations under Mg(2+)-bound and Mg(2+)-free conditions, but EPR spectroscopic studies reveal large Mg(2+)-driven quaternary conformational changes. Here, we determined cryo-EM structures of CorA in the Mg(2+)-bound closed conformation and in two open Mg(2+)-free states at resolutions of 3.8, 7.1, and 7.1 Å, respectively. In the absence of bound Mg(2+), four of the five subunits are displaced to variable extents (∼ 10-25 Å) by hinge-like motions as large as ∼ 35° at the stalk helix. The transition between a single 5-fold symmetric closed state and an ensemble of low Mg(2+), open, asymmetric conformational states is, thus, the key structural signature of CorA gating. This mechanism is likely to apply to other structurally similar divalent ion channels.
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Affiliation(s)
- Doreen Matthies
- Laboratory of Cell Biology, Center for Cancer Research, National Cancer Institute, NIH, Bethesda, MD 20892, USA
| | - Olivier Dalmas
- Department of Biochemistry and Molecular Biology, Institute for Biophysical Dynamics, The University of Chicago, Chicago, IL 60637, USA
| | - Mario J Borgnia
- Laboratory of Cell Biology, Center for Cancer Research, National Cancer Institute, NIH, Bethesda, MD 20892, USA
| | - Pawel K Dominik
- Department of Biochemistry and Molecular Biology, Institute for Biophysical Dynamics, The University of Chicago, Chicago, IL 60637, USA
| | - Alan Merk
- Laboratory of Cell Biology, Center for Cancer Research, National Cancer Institute, NIH, Bethesda, MD 20892, USA
| | - Prashant Rao
- Laboratory of Cell Biology, Center for Cancer Research, National Cancer Institute, NIH, Bethesda, MD 20892, USA
| | - Bharat G Reddy
- Department of Biochemistry and Molecular Biology, Institute for Biophysical Dynamics, The University of Chicago, Chicago, IL 60637, USA
| | - Shahidul Islam
- Department of Biochemistry and Molecular Biology, Institute for Biophysical Dynamics, The University of Chicago, Chicago, IL 60637, USA
| | - Alberto Bartesaghi
- Laboratory of Cell Biology, Center for Cancer Research, National Cancer Institute, NIH, Bethesda, MD 20892, USA
| | - Eduardo Perozo
- Department of Biochemistry and Molecular Biology, Institute for Biophysical Dynamics, The University of Chicago, Chicago, IL 60637, USA.
| | - Sriram Subramaniam
- Laboratory of Cell Biology, Center for Cancer Research, National Cancer Institute, NIH, Bethesda, MD 20892, USA.
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43
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Oxenoid K, Dong Y, Cao C, Cui T, Sancak Y, Markhard AL, Grabarek Z, Kong L, Liu Z, Ouyang B, Cong Y, Mootha VK, Chou JJ. Architecture of the mitochondrial calcium uniporter. Nature 2016; 533:269-73. [PMID: 27135929 PMCID: PMC4874835 DOI: 10.1038/nature17656] [Citation(s) in RCA: 233] [Impact Index Per Article: 29.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2015] [Accepted: 03/08/2016] [Indexed: 01/12/2023]
Abstract
Mitochondria from multiple, eukaryotic clades uptake and buffer large amounts of calcium (Ca2+) via an inner membrane transporter called the uniporter. Early studies demonstrated that this transport requires a mitochondrial membrane potential and that the uniporter is itself Ca2+ activated, and blocked by ruthenium red or Ru3601. Later, electrophysiological studies demonstrated that the uniporter is an ion channel with remarkably high conductance and selectivity2. Ca2+ entry into mitochondria is also known to activate the TCA cycle and appears to be critical for matching ATP production in mitochondria with its cytosolic demand3. MCU (mitochondrial calcium uniporter) is the pore forming and Ca2+ conducting subunit of the uniporter, but its primary sequence does not resemble any calcium channel known to date. Here, we report the structure of the core region of MCU, determined using nuclear magnetic resonance (NMR) and electron microscopy (EM). MCU is a homo-oligomer with the second transmembrane helix forming a hydrophilic pore across the membrane. The channel assembly represents a new solution of ion channel architecture and is stabilized by a coiled coil motif protruding in the mitochondrial matrix. The critical DxxE motif forms the pore entrance featuring two carboxylate rings, which appear to be the selectivity filter based on the ring dimensions and functional mutagenesis. To our knowledge, this is one of the largest structures characterized by NMR, which provides a structural blueprint for understanding the function of this channel.
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Affiliation(s)
- Kirill Oxenoid
- Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, Massachusetts 02115, USA
| | - Ying Dong
- State Key Laboratory of Molecular Biology, National Center for Protein Science Shanghai, Shanghai Institute of Biochemistry and Cell Biology, Shanghai Science Research Center, Chinese Academy of Sciences, Shanghai 200031, China
| | - Chan Cao
- Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, Massachusetts 02115, USA.,State Key Laboratory of Elemento-Organic Chemistry and College of Chemistry, Nankai University, Tianjin 300071, China
| | - Tanxing Cui
- Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, Massachusetts 02115, USA
| | - Yasemin Sancak
- Department of Molecular Biology and Howard Hughes Medical Institute, Massachusetts General Hospital, Boston, Massachusetts 02114, USA
| | - Andrew L Markhard
- Department of Molecular Biology and Howard Hughes Medical Institute, Massachusetts General Hospital, Boston, Massachusetts 02114, USA
| | - Zenon Grabarek
- Department of Molecular Biology and Howard Hughes Medical Institute, Massachusetts General Hospital, Boston, Massachusetts 02114, USA
| | - Liangliang Kong
- State Key Laboratory of Molecular Biology, National Center for Protein Science Shanghai, Shanghai Institute of Biochemistry and Cell Biology, Shanghai Science Research Center, Chinese Academy of Sciences, Shanghai 200031, China
| | - Zhijun Liu
- State Key Laboratory of Molecular Biology, National Center for Protein Science Shanghai, Shanghai Institute of Biochemistry and Cell Biology, Shanghai Science Research Center, Chinese Academy of Sciences, Shanghai 200031, China
| | - Bo Ouyang
- State Key Laboratory of Molecular Biology, National Center for Protein Science Shanghai, Shanghai Institute of Biochemistry and Cell Biology, Shanghai Science Research Center, Chinese Academy of Sciences, Shanghai 200031, China
| | - Yao Cong
- State Key Laboratory of Molecular Biology, National Center for Protein Science Shanghai, Shanghai Institute of Biochemistry and Cell Biology, Shanghai Science Research Center, Chinese Academy of Sciences, Shanghai 200031, China
| | - Vamsi K Mootha
- Department of Molecular Biology and Howard Hughes Medical Institute, Massachusetts General Hospital, Boston, Massachusetts 02114, USA
| | - James J Chou
- Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, Massachusetts 02115, USA.,State Key Laboratory of Molecular Biology, National Center for Protein Science Shanghai, Shanghai Institute of Biochemistry and Cell Biology, Shanghai Science Research Center, Chinese Academy of Sciences, Shanghai 200031, China
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44
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Kitjaruwankul S, Wapeesittipan P, Boonamnaj P, Sompornpisut P. Inner and Outer Coordination Shells of Mg(2+) in CorA Selectivity Filter from Molecular Dynamics Simulations. J Phys Chem B 2016; 120:406-17. [PMID: 26727882 DOI: 10.1021/acs.jpcb.5b10925] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
Structural data of CorA Mg(2+) channels show that the five Gly-Met-Asn (GMN) motifs at the periplasmic loop of the pentamer structure form a molecular scaffold serving as a selectivity filter. Unfortunately, knowledge about the cation selectivity of Mg(2+) channels remains limited. Since Mg(2+) in aqueous solution has a strong first hydration shell and apparent second hydration sphere, the coordination structure of Mg(2+) in a CorA selectivity filter is expected to be different from that in bulk water. Hence, this study investigated the hydration structure and ligand coordination of Mg(2+) in a selectivity filter of CorA using molecular dynamics (MD) simulations. The simulations reveal that the inner-shell structure of Mg(2+) in the filter is not significantly different from that in aqueous solution. The major difference is the characteristic structural features of the outer shell. The GMN residues engage indirectly in the interactions with the metal ion as ligands in the second shell of Mg(2+). Loss of hydrogen bonds between inner- and outer-shell waters observed from Mg(2+) in bulk water is mostly compensated by interactions between waters in the first solvation shell and the GMN motif. Some water molecules in the second shell remain in the selectivity filter and become less mobile to support the metal binding. Removal of Mg(2+) from the divalent cation sensor sites of the protein had an impact on the structure and metal binding of the filter. From the results, it can be concluded that the GMN motif enhances the affinity of the metal binding site in the CorA selectivity filter by acting as an outer coordination ligand.
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Affiliation(s)
- Sunan Kitjaruwankul
- Graduate School of Nanoscience and Technology, Chulalongkorn University , Bangkok 10330, Thailand.,Department of Chemistry, Faculty of Science, Chulalongkorn University , Bangkok 10330, Thailand
| | - Pattama Wapeesittipan
- Department of Chemistry, Faculty of Science, Chulalongkorn University , Bangkok 10330, Thailand
| | - Panisak Boonamnaj
- Department of Chemistry, Faculty of Science, Chulalongkorn University , Bangkok 10330, Thailand
| | - Pornthep Sompornpisut
- Department of Chemistry, Faculty of Science, Chulalongkorn University , Bangkok 10330, Thailand
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45
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Herzberg M, Bauer L, Kirsten A, Nies DH. Interplay between seven secondary metal uptake systems is required for full metal resistance of Cupriavidus metallidurans. Metallomics 2016; 8:313-26. [DOI: 10.1039/c5mt00295h] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
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46
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Cleverley RM, Kean J, Shintre CA, Baldock C, Derrick JP, Ford RC, Prince SM. The Cryo-EM structure of the CorA channel from Methanocaldococcus jannaschii in low magnesium conditions. BIOCHIMICA ET BIOPHYSICA ACTA 2015; 1848:2206-15. [PMID: 26051127 PMCID: PMC4579555 DOI: 10.1016/j.bbamem.2015.06.002] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 02/24/2015] [Revised: 05/20/2015] [Accepted: 06/01/2015] [Indexed: 01/04/2023]
Abstract
CorA channels are responsible for the uptake of essential magnesium ions by bacteria. X-ray crystal structures have been resolved for two full-length CorA channels, each in a non-conducting state with magnesium ions bound to the protein: These structures reveal a homo-pentameric quaternary structure with approximate 5-fold rotational symmetry about a central pore axis. We report the structure of the detergent solubilized Methanocaldococcus jannaschii CorA channel determined by Cryo-Electron Microscopy and Single Particle Averaging, supported by Small Angle X-ray Scattering and X-ray crystallography. This structure also shows a pentameric channel but with a highly asymmetric domain structure. The asymmetry of the domains includes differential separations between the trans-membrane segments, which reflects mechanical coupling of the cytoplasmic domain to the trans-membrane domain. This structure therefore reveals an important aspect of the gating mechanism of CorA channels by providing an indication of how the absence of magnesium ions leads to major structural changes.
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Affiliation(s)
- Robert M Cleverley
- Faculty of Life Sciences, University of Manchester, Oxford Road, Manchester M13 9PL, UK
| | - James Kean
- Faculty of Life Sciences, University of Manchester, Oxford Road, Manchester M13 9PL, UK
| | - Chitra A Shintre
- Faculty of Life Sciences, University of Manchester, Oxford Road, Manchester M13 9PL, UK
| | - Clair Baldock
- Faculty of Life Sciences, University of Manchester, Oxford Road, Manchester M13 9PL, UK
| | - Jeremy P Derrick
- Faculty of Life Sciences, University of Manchester, Oxford Road, Manchester M13 9PL, UK
| | - Robert C Ford
- Faculty of Life Sciences, University of Manchester, Oxford Road, Manchester M13 9PL, UK
| | - Stephen M Prince
- Faculty of Life Sciences, University of Manchester, Oxford Road, Manchester M13 9PL, UK.
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47
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Kobayashi NI, Tanoi K. Critical Issues in the Study of Magnesium Transport Systems and Magnesium Deficiency Symptoms in Plants. Int J Mol Sci 2015; 16:23076-93. [PMID: 26404266 PMCID: PMC4613352 DOI: 10.3390/ijms160923076] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2015] [Revised: 08/27/2015] [Accepted: 09/06/2015] [Indexed: 12/16/2022] Open
Abstract
Magnesium (Mg) is the second most abundant cation in living cells. Over 300 enzymes are known to be Mg-dependent, and changes in the Mg concentration significantly affects the membrane potential. As Mg becomes deficient, starch accumulation and chlorosis, bridged by the generation of reactive oxygen species, are commonly found in Mg-deficient young mature leaves. These defects further cause the inhibition of photosynthesis and finally decrease the biomass. Recently, transcriptome analysis has indicated the transcriptinal downregulation of chlorophyll apparatus at the earlier stages of Mg deficiency, and also the potential involvement of complicated networks relating to hormonal signaling and circadian oscillation. However, the processes of the common symptoms as well as the networks between Mg deficiency and signaling are not yet fully understood. Here, for the purpose of defining the missing pieces, several problems are considered and explained by providing an introduction to recent reports on physiological and transcriptional responses to Mg deficiency. In addition, it has long been unclear whether the Mg deficiency response involves the modulation of Mg2+ transport system. In this review, the current status of research on Mg2+ transport and the relating transporters are also summarized. Especially, the rapid progress in physiological characterization of the plant MRS2 gene family as well as the fundamental investigation about the molecular mechanism of the action of bacterial CorA proteins are described.
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Affiliation(s)
- Natsuko I Kobayashi
- Graduate School of Agricultural and Life Sciences, the University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo 113-8657, Japan.
| | - Keitaro Tanoi
- Graduate School of Agricultural and Life Sciences, the University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo 113-8657, Japan.
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48
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Yan M, Lu Y, Gao Y, Benedetti MF, Korshin GV. In-Situ Investigation of Interactions between Magnesium Ion and Natural Organic Matter. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2015; 49:8323-8329. [PMID: 26090773 DOI: 10.1021/acs.est.5b00003] [Citation(s) in RCA: 40] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
Natural organic matter (NOM) generated in all niches of the environment constitutes a large fraction of the global pool of organic carbon while magnesium is one of the most abundant elements that has multiple roles in both biotic and abiotic processes. Although interactions between Mg(2+) and NOM have been recognized to affect many environmental processes, little is understood about relevant mechanisms and equilibria. This study addressed this deficiency and quantified Mg(2+)-NOM interactions using differential absorbance spectroscopy (DAS) in combination with the NICA-Donnan speciation model. DAS data were obtained for varying total Mg concentrations, pHs from 5.0 to 11.0 and ionic strengths from 0.001 to 0.3 mol L(-1). DAS results demonstrated the existence of strong interactions between magnesium and NOM at all examined conditions and demonstrated that the binding of Mg(2+) by NOM was accompanied by the replacement of protons in the protonation-active phenolic and carboxylic groups. The slope of the log-transformed absorbance spectra of NOM in the range of wavelength 350-400 nm was found to be indicative of the extent of Mg(2+)-NOM binding. The differential and absolute values of the spectral slopes were strongly correlated with the amount of NOM-bound Mg(2+) ions and with the concentrations of NOM-bound protons.
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Affiliation(s)
- Mingquan Yan
- †Department of Environmental Engineering, The Key Laboratory of Water and Sediment Sciences, Ministry of Education, Peking University, Beijing 100871, China
| | - Yujuan Lu
- ‡College of Chemistry and Chemical Engineering, Shenzhen University, Shenzhen 518060, China
| | - Yuan Gao
- §Department of Civil and Environmental Engineering, University of Washington, Box 352700, Seattle, Washington 98195-2700, United States
| | - Marc F Benedetti
- ∥Institut de Physique du Globe de Paris-Sorbonne Paris Cité-Université Paris-Diderot, UMR CNRS 7154, Paris, France
| | - Gregory V Korshin
- §Department of Civil and Environmental Engineering, University of Washington, Box 352700, Seattle, Washington 98195-2700, United States
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49
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Neale C, Chakrabarti N, Pomorski P, Pai EF, Pomès R. Hydrophobic Gating of Ion Permeation in Magnesium Channel CorA. PLoS Comput Biol 2015; 11:e1004303. [PMID: 26181442 PMCID: PMC4504495 DOI: 10.1371/journal.pcbi.1004303] [Citation(s) in RCA: 40] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2014] [Accepted: 04/28/2015] [Indexed: 12/17/2022] Open
Abstract
Ion channels catalyze ionic permeation across membranes via water-filled pores. To understand how changes in intracellular magnesium concentration regulate the influx of Mg2+ into cells, we examine early events in the relaxation of Mg2+ channel CorA toward its open state using massively-repeated molecular dynamics simulations conducted either with or without regulatory ions. The pore of CorA contains a 2-nm-long hydrophobic bottleneck which remained dehydrated in most simulations. However, rapid hydration or “wetting” events concurrent with small-amplitude fluctuations in pore diameter occurred spontaneously and reversibly. In the absence of regulatory ions, wetting transitions are more likely and include a wet state that is significantly more stable and more hydrated. The free energy profile for Mg2+ permeation presents a barrier whose magnitude is anticorrelated to pore diameter and the extent of hydrophobic hydration. These findings support an allosteric mechanism whereby wetting of a hydrophobic gate couples changes in intracellular magnesium concentration to the onset of ionic conduction. This study shows how rapid wetting/dewetting transitions in the pores of ion channels participate in the control of biological ion permeation. Ion channels catalyze ionic permeation across non-polar membranes via water-filled pores. However, non-polar stretches or hydrophobic bottlenecks are present in the pores of many ion channels. To clarify the relationship between channel regulation, pore hydration, and ion permeation, we examine how the slow relaxation of magnesium channel CorA from its closed state towards its open state modulates wetting of its hydrophobic bottleneck. Results provide a quantitative description of wetting and dewetting probabilities and kinetics and a quantitative relationship between the extent of pore hydration and the energetics of ion permeation, consistent with a mechanism of hydrophobic gating.
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Affiliation(s)
- Chris Neale
- Molecular Structure and Function, The Hospital for Sick Children, Toronto, Ontario, Canada
- Department of Biochemistry, University of Toronto, Toronto, Ontario, Canada
| | - Nilmadhab Chakrabarti
- Molecular Structure and Function, The Hospital for Sick Children, Toronto, Ontario, Canada
| | - Pawel Pomorski
- Shared Hierarchical Academic Research Computing Network, Department of Physics and Astronomy, University of Waterloo, Waterloo, Ontario, Canada
| | - Emil F. Pai
- Department of Biochemistry, University of Toronto, Toronto, Ontario, Canada
- Department of Medical Biophysics, University of Toronto, Toronto, Ontario, Canada
- Department of Molecular Genetics, University of Toronto, Toronto, Ontario, Canada
- Ontario Cancer Institute/Princess Margaret Cancer Centre, Campbell Family Institute for Cancer Research, Toronto, Ontario, Canada
| | - Régis Pomès
- Molecular Structure and Function, The Hospital for Sick Children, Toronto, Ontario, Canada
- Department of Biochemistry, University of Toronto, Toronto, Ontario, Canada
- * E-mail:
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Rengel Z, Bose J, Chen Q, Tripathi BN. Magnesium alleviates plant toxicity of aluminium and heavy metals. CROP AND PASTURE SCIENCE 2015; 66:1298. [PMID: 0 DOI: 10.1071/cp15284] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/25/2023]
Abstract
Magnesium (Mg) is an essential nutrient that can alleviate soilborne toxicity of many ions. This review paper critically assesses the literature on interactions and mechanisms influencing Mg alleviation of aluminium (Al) and heavy metal toxicity. Hydrated radii of Mg2+ and Al3+ are similar; therefore, these two ions compete for binding to ion transporters and other important biological molecules. In monocotyledonous species such as rice and wheat, millimolar concentrations of Mg alleviate Al toxicity, mainly by decreasing Al saturation and activity at cell wall and plasma membrane binding sites. In dicotyledonous legume species such as soybean (Glycine max), rice bean (Vigna umbellata) and broad bean (Vicia faba), micromolar concentrations of Mg may enhance biosynthesis of organic ligands and thus underpin alleviation of Al toxicity. Resistance to Al may be enhanced by increased expression of the genes coding for Mg transporters, as well as by upregulation of activity of Mg-transport proteins; intracellular Mg2+ activity may thus be increased under Al stress, which may increase the activity of H+-ATPases. In Vicia faba, Mg-related enhancement in the activity of plasma membrane H+-ATPase under Al stress was found to be due to post-translational modification (increased phosphorylation of the penultimate threonine as well as association with regulatory 14-3-3 proteins), resulting in increased resistance to Al stress. Magnesium can alleviate heavy metal stress by decreasing negative electrical potential and thus metal ion activities at the plasma membrane surface (physico-chemical competition), by enhancing activities of enzymes involved in biosynthesis of organic ligands, and by increasing vacuolar sequestration of heavy metals via increasing H+-pumping activity at the tonoplast. Future work should concentrate on characterising the role of intracellular Mg2+ homeostasis and Mg transporters in alleviating metal stress as well as in transcriptional, translational and post-translational regulation of H+-pumps and enzymes involved in biosynthesis and exudation of organic ligands.
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