1
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Ongey EL, Banerjee A. In vitro reconstitution of transition metal transporters. J Biol Chem 2024:107589. [PMID: 39032653 DOI: 10.1016/j.jbc.2024.107589] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2024] [Revised: 06/28/2024] [Accepted: 07/03/2024] [Indexed: 07/23/2024] Open
Abstract
Transition metal ions are critically important across all kingdoms of life. The chemical properties of iron, copper, zinc, manganese, cobalt, and nickel make them very attractive for use as cofactors in metalloenzymes and/or metalloproteins. Their versatile chemistry in aqueous solution enables them to function both as an electron donors and acceptors, and thus participate in both reduction and oxidation reactions respectively. Transition metal ions can also function as nonredox mutidentate coordination sites that play essential roles in macromolecular structure and function. Malfunction in transition metal transport and homeostasis has been linked to a wide number of human diseases including cancer, diabetes and neurodegenerative disorders. Transition metal transporters are central players in the physiology of transition metals whereby they move transition metals in and out of cellular compartments. In this review, we provide a comprehensive overview of in vitro reconstitution of the activity of integral membrane transition metal transporters and discuss strategies that have been successfully implemented to overcome the challenges. We also discuss recent advances in our understanding of transition metal transport mechanisms and the techniques that are currently employed to decipher the molecular basis of transport activities of these proteins. Deep mechanistic insights into transition metal transport systems will be essential to understand their malfunction in human diseases and target them for potential therapeutic strategies.
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Affiliation(s)
- Elvis L Ongey
- Cell Biology and Neurobiology Branch, National Institutes of Child Health and Human, Development, National Institutes of Health, Bethesda, MD-20892
| | - Anirban Banerjee
- Cell Biology and Neurobiology Branch, National Institutes of Child Health and Human, Development, National Institutes of Health, Bethesda, MD-20892.
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2
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Azzollini L, Prete DD, Wolf G, Klimek C, Saggioro M, Ricci F, Christodoulaki E, Wiedmer T, Ingles-Prieto A, Superti-Furga G, Scarabottolo L. Development of a live cell assay for the zinc transporter ZnT8. SLAS DISCOVERY : ADVANCING LIFE SCIENCES R & D 2024; 29:100166. [PMID: 38848895 DOI: 10.1016/j.slasd.2024.100166] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/30/2024] [Revised: 05/27/2024] [Accepted: 06/04/2024] [Indexed: 06/09/2024]
Abstract
Zinc is an essential trace element that is involved in many biological processes and in cellular homeostasis. In pancreatic β-cells, zinc is crucial for the synthesis, processing, and secretion of insulin, which plays a key role in glucose homeostasis and which deficiency is the cause of diabetes. The accumulation of zinc in pancreatic cells is regulated by the solute carrier transporter SLC30A8 (or Zinc Transporter 8, ZnT8), which transports zinc from cytoplasm in intracellular vesicles. Allelic variants of SLC30A8 gene have been linked to diabetes. Given the physiological intracellular localization of SLC30A8 in pancreatic β-cells and the ubiquitous endogenous expression of other Zinc transporters in different cell lines that could be used as cellular model for SLC30A8 recombinant over-expression, it is challenging to develop a functional assay to measure SLC30A8 activity. To achieve this goal, we have firstly generated a HEK293 cell line stably overexpressing SLC30A8, where the over-expression favors the partial localization of SLC30A8 on the plasma membrane. Then, we used the combination of this cell model, commercial FluoZin-3 cell permeant zinc dye and live cell imaging approach to follow zinc flux across SLC30A8 over-expressed on plasma membrane, thus developing a novel functional imaging- based assay specific for SLC30A8. Our novel approach can be further explored and optimized, paving the way for future small molecule medium-throughput screening.
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Affiliation(s)
- Lucia Azzollini
- Axxam SpA, Openzone, Via Meucci 3 20091 Bresso, Milan, Italy.
| | | | - Gernot Wolf
- CeMM Research Center for Molecular Medicine of the Austrian Academy of Sciences, Vienna, Austria
| | - Christoph Klimek
- CeMM Research Center for Molecular Medicine of the Austrian Academy of Sciences, Vienna, Austria
| | - Mattia Saggioro
- Axxam SpA, Openzone, Via Meucci 3 20091 Bresso, Milan, Italy
| | - Fernanda Ricci
- Axxam SpA, Openzone, Via Meucci 3 20091 Bresso, Milan, Italy
| | - Eirini Christodoulaki
- CeMM Research Center for Molecular Medicine of the Austrian Academy of Sciences, Vienna, Austria
| | - Tabea Wiedmer
- CeMM Research Center for Molecular Medicine of the Austrian Academy of Sciences, Vienna, Austria
| | - Alvaro Ingles-Prieto
- CeMM Research Center for Molecular Medicine of the Austrian Academy of Sciences, Vienna, Austria
| | - Giulio Superti-Furga
- CeMM Research Center for Molecular Medicine of the Austrian Academy of Sciences, Vienna, Austria; Center for Physiology and Pharmacology, Medical University of Vienna, Vienna, Austria
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3
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Sun C, He B, Gao Y, Wang X, Liu X, Sun L. Structural insights into the calcium-coupled zinc export of human ZnT1. SCIENCE ADVANCES 2024; 10:eadk5128. [PMID: 38669333 PMCID: PMC11051671 DOI: 10.1126/sciadv.adk5128] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/28/2023] [Accepted: 03/27/2024] [Indexed: 04/28/2024]
Abstract
Cellular zinc (Zn2+) homeostasis is essential to human health and is under tight regulations. Human zinc transporter 1 (hZnT1) is a plasma membrane-localized Zn2+ exporter belonging to the ZnT family, and its functional aberration is associated with multiple diseases. Here, we show that hZnT1 works as a Zn2+/Ca2+ exchanger. We determine the structure of hZnT1 using cryo-electron microscopy (cryo-EM) single particle analysis. hZnT1 adopts a homodimeric structure, and each subunit contains a transmembrane domain consisting of six transmembrane segments, a cytosolic domain, and an extracellular domain. The transmembrane region displays an outward-facing conformation. On the basis of structural and functional analysis, we propose a model for the hZnT1-mediated Zn2+/Ca2+ exchange. Together, these results facilitate our understanding of the biological functions of hZnT1 and provide a basis for further investigations of the ZnT family transporters.
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Affiliation(s)
- Chunqiao Sun
- Department of Neurology, The First Affiliated Hospital of USTC, MOE Key Laboratory for Membraneless Organelles and Cellular Dynamics, Hefei National Research Center for Physical Sciences at the Microscale, Division of Life Sciences and Medicine, University of Science and Technology of China, Hefei 230027, China
| | - Bangguo He
- Department of Neurology, The First Affiliated Hospital of USTC, MOE Key Laboratory for Membraneless Organelles and Cellular Dynamics, Hefei National Research Center for Physical Sciences at the Microscale, Division of Life Sciences and Medicine, University of Science and Technology of China, Hefei 230027, China
- Department of Hematology, The First Affiliated Hospital of USTC, Division of Life Sciences and Medicine, University of Science and Technology of China, Hefei 230001, China
| | - Yongxiang Gao
- Department of Neurology, The First Affiliated Hospital of USTC, MOE Key Laboratory for Membraneless Organelles and Cellular Dynamics, Hefei National Research Center for Physical Sciences at the Microscale, Division of Life Sciences and Medicine, University of Science and Technology of China, Hefei 230027, China
- Cryo-EM Center, Core Facility Center for Life Sciences, University of Science and Technology of China, Hefei 230027, China
| | - Xingbing Wang
- Department of Hematology, The First Affiliated Hospital of USTC, Division of Life Sciences and Medicine, University of Science and Technology of China, Hefei 230001, China
| | - Xin Liu
- Department of Neurology, The First Affiliated Hospital of USTC, MOE Key Laboratory for Membraneless Organelles and Cellular Dynamics, Hefei National Research Center for Physical Sciences at the Microscale, Division of Life Sciences and Medicine, University of Science and Technology of China, Hefei 230027, China
| | - Linfeng Sun
- Department of Neurology, The First Affiliated Hospital of USTC, MOE Key Laboratory for Membraneless Organelles and Cellular Dynamics, Hefei National Research Center for Physical Sciences at the Microscale, Division of Life Sciences and Medicine, University of Science and Technology of China, Hefei 230027, China
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4
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Bui HB, Inaba K. Structures, Mechanisms, and Physiological Functions of Zinc Transporters in Different Biological Kingdoms. Int J Mol Sci 2024; 25:3045. [PMID: 38474291 DOI: 10.3390/ijms25053045] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2024] [Revised: 02/29/2024] [Accepted: 03/03/2024] [Indexed: 03/14/2024] Open
Abstract
Zinc transporters take up/release zinc ions (Zn2+) across biological membranes and maintain intracellular and intra-organellar Zn2+ homeostasis. Since this process requires a series of conformational changes in the transporters, detailed information about the structures of different reaction intermediates is required for a comprehensive understanding of their Zn2+ transport mechanisms. Recently, various Zn2+ transport systems have been identified in bacteria, yeasts, plants, and humans. Based on structural analyses of human ZnT7, human ZnT8, and bacterial YiiP, we propose updated models explaining their mechanisms of action to ensure efficient Zn2+ transport. We place particular focus on the mechanistic roles of the histidine-rich loop shared by several zinc transporters, which facilitates Zn2+ recruitment to the transmembrane Zn2+-binding site. This review provides an extensive overview of the structures, mechanisms, and physiological functions of zinc transporters in different biological kingdoms.
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Affiliation(s)
- Han Ba Bui
- Institute of Multidisciplinary Research for Advanced Materials, Tohoku University, Sendai 980-8577, Japan
- Department of Molecular and Chemical Life Sciences, Graduate School of Life Sciences, Tohoku University, Sendai 980-8577, Japan
- Medical Institute of Bioregulation, Kyushu University, Fukuoka 812-8582, Japan
| | - Kenji Inaba
- Institute of Multidisciplinary Research for Advanced Materials, Tohoku University, Sendai 980-8577, Japan
- Department of Molecular and Chemical Life Sciences, Graduate School of Life Sciences, Tohoku University, Sendai 980-8577, Japan
- Medical Institute of Bioregulation, Kyushu University, Fukuoka 812-8582, Japan
- Department of Chemistry, Graduate School of Science, Tohoku University, Sendai 980-8578, Japan
- Core Research for Evolutional Science and Technology (CREST), Japan Agency for Medical Research and Development (AMED), Chiyoda-ku, Tokyo 100-0004, Japan
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5
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Kambe T, Wagatsuma T. Metalation and activation of Zn 2+ enzymes via early secretory pathway-resident ZNT proteins. BIOPHYSICS REVIEWS 2023; 4:041302. [PMID: 38510844 PMCID: PMC10903440 DOI: 10.1063/5.0176048] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/11/2023] [Accepted: 11/21/2023] [Indexed: 03/22/2024]
Abstract
Zinc (Zn2+), an essential trace element, binds to various proteins, including enzymes, transcription factors, channels, and signaling molecules and their receptors, to regulate their activities in a wide range of physiological functions. Zn2+ proteome analyses have indicated that approximately 10% of the proteins encoded by the human genome have potential Zn2+ binding sites. Zn2+ binding to the functional site of a protein (for enzymes, the active site) is termed Zn2+ metalation. In eukaryotic cells, approximately one-third of proteins are targeted to the endoplasmic reticulum; therefore, a considerable number of proteins mature by Zn2+ metalation in the early secretory pathway compartments. Failure to capture Zn2+ in these compartments results in not only the inactivation of enzymes (apo-Zn2+ enzymes), but also their elimination via degradation. This process deserves attention because many Zn2+ enzymes that mature during the secretory process are associated with disease pathogenesis. However, how Zn2+ is mobilized via Zn2+ transporters, particularly ZNTs, and incorporated in enzymes has not been fully elucidated from the cellular perspective and much less from the biophysical perspective. This review focuses on Zn2+ enzymes that are activated by Zn2+ metalation via Zn2+ transporters during the secretory process. Further, we describe the importance of Zn2+ metalation from the physiopathological perspective, helping to reveal the importance of understanding Zn2+ enzymes from a biophysical perspective.
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Affiliation(s)
- Taiho Kambe
- Division of Integrated Life Science, Graduate School of Biostudies, Kyoto University, Kyoto 606-8502, Japan
| | - Takumi Wagatsuma
- Division of Integrated Life Science, Graduate School of Biostudies, Kyoto University, Kyoto 606-8502, Japan
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6
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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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7
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Hussein A, Fan S, Lopez-Redondo M, Kenney I, Zhang X, Beckstein O, Stokes DL. Energy coupling and stoichiometry of Zn 2+/H + antiport by the prokaryotic cation diffusion facilitator YiiP. eLife 2023; 12:RP87167. [PMID: 37906094 PMCID: PMC10617992 DOI: 10.7554/elife.87167] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2023] Open
Abstract
YiiP from Shewanella oneidensis is a prokaryotic Zn2+/H+ antiporter that serves as a model for the Cation Diffusion Facilitator (CDF) superfamily, members of which are generally responsible for homeostasis of transition metal ions. Previous studies of YiiP as well as related CDF transporters have established a homodimeric architecture and the presence of three distinct Zn2+ binding sites named A, B, and C. In this study, we use cryo-EM, microscale thermophoresis and molecular dynamics simulations to address the structural and functional roles of individual sites as well as the interplay between Zn2+ binding and protonation. Structural studies indicate that site C in the cytoplasmic domain is primarily responsible for stabilizing the dimer and that site B at the cytoplasmic membrane surface controls the structural transition from an inward facing conformation to an occluded conformation. Binding data show that intramembrane site A, which is directly responsible for transport, has a dramatic pH dependence consistent with coupling to the proton motive force. A comprehensive thermodynamic model encompassing Zn2+ binding and protonation states of individual residues indicates a transport stoichiometry of 1 Zn2+ to 2-3 H+ depending on the external pH. This stoichiometry would be favorable in a physiological context, allowing the cell to use the proton gradient as well as the membrane potential to drive the export of Zn2+.
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Affiliation(s)
- Adel Hussein
- Department of Biochemistry and Molecular Pharmacology, NYU School of MedicineNew YorkUnited States
| | - Shujie Fan
- Department of Physics, Arizona State UniversityTempeUnited States
| | - Maria Lopez-Redondo
- Department of Biochemistry and Molecular Pharmacology, NYU School of MedicineNew YorkUnited States
| | - Ian Kenney
- Department of Physics, Arizona State UniversityTempeUnited States
| | - Xihui Zhang
- Department of Biochemistry and Molecular Pharmacology, NYU School of MedicineNew YorkUnited States
| | - Oliver Beckstein
- Department of Physics, Arizona State UniversityTempeUnited States
| | - David L Stokes
- Department of Biochemistry and Molecular Pharmacology, NYU School of MedicineNew YorkUnited States
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8
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Aikawa C, Shimizu A, Nakakido M, Murase K, Nozawa T, Tsumoto K, Nakagawa I. Group A Streptococcus cation diffusion facilitator proteins contribute to immune evasion by regulating intracellular metal concentrations. Biochem Biophys Res Commun 2023; 676:141-148. [PMID: 37516031 DOI: 10.1016/j.bbrc.2023.07.052] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2023] [Accepted: 07/23/2023] [Indexed: 07/31/2023]
Abstract
Cation diffusion facilitators (CDFs) are a large family of divalent metal transporters with broad specificities that contribute to intracellular metal homeostasis and toxicity in bacterial pathogens. Streptococcus pyogenes (Group A Streptococcus [GAS]) expresses two homologous CDF efflux transporters, MntE and CzcD, which selectively transport Mn and Zn, respectively. We discovered that the MntE- and CzcD-deficient strains exhibited a marked decrease in the viability of macrophage-differentiated THP-1 cells and neutrophils. In addition, the viability of mice infected with both deficient strains markedly increased. Consistent with a previous study, our results suggest that MntE regulates the PerR-dependent oxidative stress response by maintaining intracellular Mn levels and contributing to the growth of GAS. The maturation and proteolytic activity of streptococcal cysteine protease (SpeB), an important virulence factor in GAS, has been reported to be abrogated by zinc and copper. Zn inhibited the maturation and proteolytic activity of SpeB in the culture supernatant of the CzcD-deficient strain. Furthermore, Mn inhibited SpeB maturation and proteolytic activity in a MntE-deficient strain. Since the host pathogenicity of the SpeB-deficient strain was significantly reduced, maintenance of intracellular manganese and zinc levels in the GAS via MntE and CzcD may not only confer metal resistance to the bacterium, but may also play an essential role in its virulence. These findings provide new insights into the molecular mechanisms of pathogenicity, which allow pathogens to survive under stressful conditions associated with elevated metal ion concentrations during host infection.
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Affiliation(s)
- Chihiro Aikawa
- Department of Microbiology, Graduate School of Medicine, Kyoto University, Kyoto, 606-8501, Japan.
| | - Akihide Shimizu
- Department of Microbiology, Graduate School of Medicine, Kyoto University, Kyoto, 606-8501, Japan
| | - Makoto Nakakido
- Department of Bioengineering, School of Engineering, The University of Tokyo, Tokyo, 108-8639, Japan; Department of Chemistry and Biotechnology, School of Engineering, The University of Tokyo, Tokyo, 108-8639, Japan
| | - Kazunori Murase
- Department of Microbiology, Graduate School of Medicine, Kyoto University, Kyoto, 606-8501, Japan
| | - Takashi Nozawa
- Department of Microbiology, Graduate School of Medicine, Kyoto University, Kyoto, 606-8501, Japan
| | - Kouhei Tsumoto
- Department of Bioengineering, School of Engineering, The University of Tokyo, Tokyo, 108-8639, Japan; Department of Chemistry and Biotechnology, School of Engineering, The University of Tokyo, Tokyo, 108-8639, Japan; Laboratory of Medical Proteomics, The Institute of Medical Science, The University of Tokyo, Tokyo, 108-8639, Japan
| | - Ichiro Nakagawa
- Department of Microbiology, Graduate School of Medicine, Kyoto University, Kyoto, 606-8501, Japan.
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Bui HB, Watanabe S, Nomura N, Liu K, Uemura T, Inoue M, Tsutsumi A, Fujita H, Kinoshita K, Kato Y, Iwata S, Kikkawa M, Inaba K. Cryo-EM structures of human zinc transporter ZnT7 reveal the mechanism of Zn 2+ uptake into the Golgi apparatus. Nat Commun 2023; 14:4770. [PMID: 37553324 PMCID: PMC10409766 DOI: 10.1038/s41467-023-40521-5] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2022] [Accepted: 07/27/2023] [Indexed: 08/10/2023] Open
Abstract
Zinc ions (Zn2+) are vital to most cells, with the intracellular concentrations of Zn2+ being tightly regulated by multiple zinc transporters located at the plasma and organelle membranes. We herein present the 2.2-3.1 Å-resolution cryo-EM structures of a Golgi-localized human Zn2+/H+ antiporter ZnT7 (hZnT7) in Zn2+-bound and unbound forms. Cryo-EM analyses show that hZnT7 exists as a dimer via tight interactions in both the cytosolic and transmembrane (TM) domains of two protomers, each of which contains a single Zn2+-binding site in its TM domain. hZnT7 undergoes a TM-helix rearrangement to create a negatively charged cytosolic cavity for Zn2+ entry in the inward-facing conformation and widens the luminal cavity for Zn2+ release in the outward-facing conformation. An exceptionally long cytosolic histidine-rich loop characteristic of hZnT7 binds two Zn2+ ions, seemingly facilitating Zn2+ recruitment to the TM metal transport pathway. These structures permit mechanisms of hZnT7-mediated Zn2+ uptake into the Golgi to be proposed.
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Affiliation(s)
- Han Ba Bui
- Institute of Multidisciplinary Research for Advanced Materials, Tohoku University, Sendai, Miyagi, 980-8577, Japan
- Department of Molecular and Chemical Life Sciences, Graduate School of Life Sciences, Tohoku University, Sendai, Miyagi, 980-8577, Japan
| | - Satoshi Watanabe
- Institute of Multidisciplinary Research for Advanced Materials, Tohoku University, Sendai, Miyagi, 980-8577, Japan
- Department of Molecular and Chemical Life Sciences, Graduate School of Life Sciences, Tohoku University, Sendai, Miyagi, 980-8577, Japan
- Department of Chemistry, Graduate School of Science, Tohoku University, Sendai, Miyagi, 980-8578, Japan
| | - Norimichi Nomura
- Department of Cell Biology, Graduate School of Medicine, Kyoto University, Kyoto, 606-8501, Japan
| | - Kehong Liu
- Department of Cell Biology, Graduate School of Medicine, Kyoto University, Kyoto, 606-8501, Japan
| | - Tomoko Uemura
- Department of Cell Biology, Graduate School of Medicine, Kyoto University, Kyoto, 606-8501, Japan
| | - Michio Inoue
- Institute of Multidisciplinary Research for Advanced Materials, Tohoku University, Sendai, Miyagi, 980-8577, Japan
| | - Akihisa Tsutsumi
- Graduate School of Medicine, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-0033, Japan
| | - Hiroyuki Fujita
- Advanced Research Laboratory, Canon Medical Systems Corporation, Otawara, 324-8550, Japan
| | - Kengo Kinoshita
- Department of System Bioinformatics, Graduate School of Information Sciences, Tohoku University, Sendai, Miyagi, 980-8579, Japan
- Department of Integrative Genomics, Tohoku Medical Megabank Organization, Tohoku University, Sendai, Miyagi, 980-8573, Japan
| | - Yukinari Kato
- Graduate School of Medicine, Tohoku University, Sendai, 980-8575, Japan
| | - So Iwata
- Department of Cell Biology, Graduate School of Medicine, Kyoto University, Kyoto, 606-8501, Japan
| | - Masahide Kikkawa
- Graduate School of Medicine, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-0033, Japan
| | - Kenji Inaba
- Institute of Multidisciplinary Research for Advanced Materials, Tohoku University, Sendai, Miyagi, 980-8577, Japan.
- Department of Molecular and Chemical Life Sciences, Graduate School of Life Sciences, Tohoku University, Sendai, Miyagi, 980-8577, Japan.
- Department of Chemistry, Graduate School of Science, Tohoku University, Sendai, Miyagi, 980-8578, Japan.
- Medical Institute of Bioregulation, Kyushu University, Fukuoka, 812-8582, Japan.
- Core Research for Evolutional Science and Technology (CREST), Japan Agency for Medical Research and Development (AMED), Chiyoda-ku, Tokyo, Japan.
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10
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Hussein A, Fan S, Lopez-Redondo M, Kenney I, Zhang X, Beckstein O, Stokes DL. Energy Coupling and Stoichiometry of Zn 2+/H + Antiport by the Cation Diffusion Facilitator YiiP. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.02.23.529644. [PMID: 36865113 PMCID: PMC9980050 DOI: 10.1101/2023.02.23.529644] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/25/2023]
Abstract
YiiP is a prokaryotic Zn2+/H+ antiporter that serves as a model for the Cation Diffusion Facilitator (CDF) superfamily, members of which are generally responsible for homeostasis of transition metal ions. Previous studies of YiiP as well as related CDF transporters have established a homodimeric architecture and the presence of three distinct Zn2+ binding sites named A, B, and C. In this study, we use cryo-EM, microscale thermophoresis and molecular dynamics simulations to address the structural and functional roles of individual sites as well as the interplay between Zn2+ binding and protonation. Structural studies indicate that site C in the cytoplasmic domain is primarily responsible for stabilizing the dimer and that site B at the cytoplasmic membrane surface controls the structural transition from an inward facing conformation to an occluded conformation. Binding data show that intramembrane site A, which is directly responsible for transport, has a dramatic pH dependence consistent with coupling to the proton motive force. A comprehensive thermodynamic model encompassing Zn2+ binding and protonation states of individual residues indicates a transport stoichiometry of 1 Zn2+ to 2-3 H+ depending on the external pH. This stoichiometry would be favorable in a physiological context, allowing the cell to use the proton gradient as well as the membrane potential to drive the export of Zn2+.
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Affiliation(s)
- Adel Hussein
- Dept. of Cell Biology, NYU School of Medicine, New York, NY 10016 USA
| | - Shujie Fan
- Dept. of Physics, Arizona State University, Tempe AZ
| | | | - Ian Kenney
- Dept. of Physics, Arizona State University, Tempe AZ
| | - Xihui Zhang
- Dept. of Cell Biology, NYU School of Medicine, New York, NY 10016 USA
| | | | - David L Stokes
- Dept. of Cell Biology, NYU School of Medicine, New York, NY 10016 USA
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11
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Sharma G, Jafari M, Merz KM. Getting zinc into and out of cells. Methods Enzymol 2023; 687:263-278. [PMID: 37666635 DOI: 10.1016/bs.mie.2023.05.003] [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] [Indexed: 09/06/2023]
Abstract
Ion channels are specialized proteins located on the plasma membrane and control the movement of ions across the membrane. Zn ion plays an indispensable role as a structural constituent of various proteins, moreover, it plays an important dynamic role in cell signaling. In this chapter, we discuss computational insights into zinc efflux and influx mechanism through YiiP (from Escherichia coli and Shewanella oneidensis) and BbZIP (Bordetella bronchiseptica) transporters, respectively. Gaining knowledge about the mechanism of zinc transport at the molecular level can aid in developing treatments for conditions such as diabetes and cancer by manipulating extracellular and intracellular levels of zinc ions.
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Affiliation(s)
- Gaurav Sharma
- Department of Chemistry, Michigan State University, East Lansing, MI, United States
| | - Majid Jafari
- Department of Chemistry, Michigan State University, East Lansing, MI, United States
| | - Kenneth M Merz
- Department of Chemistry, Michigan State University, East Lansing, MI, United States; Department of Biochemistry and Molecular Biology, Michigan State University, East Lansing, MI, United States.
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12
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Zhang S, Fu C, Luo Y, Xie Q, Xu T, Sun Z, Su Z, Zhou X. Cryo-EM structure of a eukaryotic zinc transporter at a low pH suggests its Zn 2+-releasing mechanism. J Struct Biol 2023; 215:107926. [PMID: 36464198 DOI: 10.1016/j.jsb.2022.107926] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2022] [Revised: 11/10/2022] [Accepted: 11/28/2022] [Indexed: 12/04/2022]
Abstract
Zinc transporter 8 (ZnT8) is mainly expressed in pancreatic islet β cells and is responsible for H+-coupled uptake (antiport) of Zn2+ into the lumen of insulin secretory granules. Structures of human ZnT8 and its prokaryotic homolog YiiP have provided structural basis for constructing a plausible transport cycle for Zn2+. However, the mechanistic role that protons play in the transport process remains unclear. Here we present a lumen-facing cryo-EM structure of ZnT8 from Xenopus tropicalis (xtZnT8) in the presence of Zn2+ at a luminal pH (5.5). Compared to a Zn2+-bound xtZnT8 structure at a cytosolic pH (7.5), the low-pH structure displays an empty transmembrane Zn2+-binding site with a disrupted coordination geometry. Combined with a Zn2+-binding assay our data suggest that protons may disrupt Zn2+ coordination at the transmembrane Zn2+-binding site in the lumen-facing state, thus facilitating Zn2+ release from ZnT8 into the lumen.
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Affiliation(s)
- Senfeng Zhang
- Department of Integrated Traditional Chinese and Western Medicine, Rare Diseases Center, State Key Laboratory of Biotherapy, West China Hospital, Sichuan University, Chengdu, Sichuan 610041, China
| | - Chunting Fu
- Department of Integrated Traditional Chinese and Western Medicine, Rare Diseases Center, State Key Laboratory of Biotherapy, West China Hospital, Sichuan University, Chengdu, Sichuan 610041, China
| | - Yongbo Luo
- The State Key Laboratory of Biotherapy, Department of Geriatrics and National Clinical Research Center for Geriatrics, West China Hospital, Sichuan University, Chengdu, Sichuan 610041, China
| | - Qingrong Xie
- Department of Integrated Traditional Chinese and Western Medicine, Rare Diseases Center, State Key Laboratory of Biotherapy, West China Hospital, Sichuan University, Chengdu, Sichuan 610041, China
| | - Tong Xu
- Department of Integrated Traditional Chinese and Western Medicine, Rare Diseases Center, State Key Laboratory of Biotherapy, West China Hospital, Sichuan University, Chengdu, Sichuan 610041, China
| | - Ziyi Sun
- Department of Integrated Traditional Chinese and Western Medicine, Rare Diseases Center, State Key Laboratory of Biotherapy, West China Hospital, Sichuan University, Chengdu, Sichuan 610041, China.
| | - Zhaoming Su
- The State Key Laboratory of Biotherapy, Department of Geriatrics and National Clinical Research Center for Geriatrics, West China Hospital, Sichuan University, Chengdu, Sichuan 610041, China.
| | - Xiaoming Zhou
- Department of Integrated Traditional Chinese and Western Medicine, Rare Diseases Center, State Key Laboratory of Biotherapy, West China Hospital, Sichuan University, Chengdu, Sichuan 610041, China.
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13
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Zhang Y, Jiang Y, Gao K, Sui D, Yu P, Su M, Wei GW, Hu J. Structural insights into the elevator-type transport mechanism of a bacterial ZIP metal transporter. Nat Commun 2023; 14:385. [PMID: 36693843 PMCID: PMC9873690 DOI: 10.1038/s41467-023-36048-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2022] [Accepted: 01/13/2023] [Indexed: 01/26/2023] Open
Abstract
The Zrt-/Irt-like protein (ZIP) family consists of ubiquitously expressed divalent metal transporters critically involved in maintaining systemic and cellular homeostasis of zinc, iron, and manganese. Here, we present a study on a prokaryotic ZIP from Bordetella bronchiseptica (BbZIP) by combining structural biology, evolutionary covariance, computational modeling, and a variety of biochemical assays to tackle the issue of the transport mechanism which has not been established for the ZIP family. The apo state structure in an inward-facing conformation revealed a disassembled transport site, altered inter-helical interactions, and importantly, a rigid body movement of a 4-transmembrane helix (TM) bundle relative to the other TMs. The computationally generated and biochemically validated outward-facing conformation model revealed a slide of the 4-TM bundle, which carries the transport site(s), by approximately 8 Å toward the extracellular side against the static TMs which mediate dimerization. These findings allow us to conclude that BbZIP is an elevator-type transporter.
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Affiliation(s)
- Yao Zhang
- Department of Biochemistry and Molecular Biology, Michigan State University, East Lansing, MI, USA
| | - Yuhan Jiang
- Department of Chemistry, Michigan State University, East Lansing, MI, USA
| | - Kaifu Gao
- Department of Mathematics, Michigan State University, East Lansing, MI, USA
| | - Dexin Sui
- Department of Biochemistry and Molecular Biology, Michigan State University, East Lansing, MI, USA
| | - Peixuan Yu
- Department of Biochemistry and Molecular Biology, Michigan State University, East Lansing, MI, USA
| | - Min Su
- Life Sciences Institute, University of Michigan, Ann Arbor, MI, USA
| | - Guo-Wei Wei
- Department of Biochemistry and Molecular Biology, Michigan State University, East Lansing, MI, USA
- Department of Mathematics, Michigan State University, East Lansing, MI, USA
| | - Jian Hu
- Department of Biochemistry and Molecular Biology, Michigan State University, East Lansing, MI, USA.
- Department of Chemistry, Michigan State University, East Lansing, MI, USA.
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14
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Bhatt M, Gauthier-Manuel L, Lazzarin E, Zerlotti R, Ziegler C, Bazzone A, Stockner T, Bossi E. A comparative review on the well-studied GAT1 and the understudied BGT-1 in the brain. Front Physiol 2023; 14:1145973. [PMID: 37123280 PMCID: PMC10137170 DOI: 10.3389/fphys.2023.1145973] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2023] [Accepted: 03/30/2023] [Indexed: 05/02/2023] Open
Abstract
γ-aminobutyric acid (GABA) is the primary inhibitory neurotransmitter in the central nervous system (CNS). Its homeostasis is maintained by neuronal and glial GABA transporters (GATs). The four GATs identified in humans are GAT1 (SLC6A1), GAT2 (SLC6A13), GAT3 (SLC6A11), and betaine/GABA transporter-1 BGT-1 (SLC6A12) which are all members of the solute carrier 6 (SLC6) family of sodium-dependent transporters. While GAT1 has been investigated extensively, the other GABA transporters are less studied and their role in CNS is not clearly defined. Altered GABAergic neurotransmission is involved in different diseases, but the importance of the different transporters remained understudied and limits drug targeting. In this review, the well-studied GABA transporter GAT1 is compared with the less-studied BGT-1 with the aim to leverage the knowledge on GAT1 to shed new light on the open questions concerning BGT-1. The most recent knowledge on transporter structure, functions, expression, and localization is discussed along with their specific role as drug targets for neurological and neurodegenerative disorders. We review and discuss data on the binding sites for Na+, Cl-, substrates, and inhibitors by building on the recent cryo-EM structure of GAT1 to highlight specific molecular determinants of transporter functions. The role of the two proteins in GABA homeostasis is investigated by looking at the transport coupling mechanism, as well as structural and kinetic transport models. Furthermore, we review information on selective inhibitors together with the pharmacophore hypothesis of transporter substrates.
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Affiliation(s)
- Manan Bhatt
- Department of Biotechnology and Life Sciences, University of Insubria, Varese, Italy
- Centre for Neuroscience—University of Insubria, Varese, Italy
| | - Laure Gauthier-Manuel
- Department of Biophysics II/Structural Biology, University of Regensburg, Regensburg, Germany
| | - Erika Lazzarin
- Center for Physiology and Pharmacology, Institute of Pharmacology, Medical University of Vienna, Waehringerstr, Vienna
| | - Rocco Zerlotti
- Department of Biophysics II/Structural Biology, University of Regensburg, Regensburg, Germany
- Nanion Technologies GmbH, Munich, Germany
| | - Christine Ziegler
- Department of Biophysics II/Structural Biology, University of Regensburg, Regensburg, Germany
| | | | - Thomas Stockner
- Center for Physiology and Pharmacology, Institute of Pharmacology, Medical University of Vienna, Waehringerstr, Vienna
- *Correspondence: Thomas Stockner, ; Elena Bossi,
| | - Elena Bossi
- Department of Biotechnology and Life Sciences, University of Insubria, Varese, Italy
- Centre for Neuroscience—University of Insubria, Varese, Italy
- *Correspondence: Thomas Stockner, ; Elena Bossi,
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15
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Wang X, Wang C, Zhang Z, Shi G. Genome-wide Identification of Metal Tolerance Protein Genes in Peanut: Differential Expression in the Root of Two Contrasting Cultivars Under Metal Stresses. FRONTIERS IN PLANT SCIENCE 2022; 13:791200. [PMID: 35432419 PMCID: PMC9011049 DOI: 10.3389/fpls.2022.791200] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/08/2021] [Accepted: 03/15/2022] [Indexed: 05/23/2023]
Abstract
Metal tolerance proteins (MTP) are Me2+/H+(K+) antiporters that play important roles in the transport of divalent cations in plants. However, their functions in peanut are unknown. In the present study, a total of 24 AhMTP genes were identified in peanut, which were divided into seven groups belonging to three substrate-specific clusters (Zn-CDFs, Zn/Fe-CDFs, and Mn-CDFs). All AhMTP genes underwent whole genome or segmental gene duplication events except AhMTP12. Most AhMTP members within the same subfamily or group generally have similar gene and protein structural characteristics. However, some genes, such as AhMTP1.3, AhMTP2.4, and AhMTP12, showed wide divergences. Most of AhMTP genes preferentially expressed in reproductive tissues, suggesting that these genes might play roles in metal transport during the pod and seed development stages. Excess metal exposure induced expressions for most of AhMTP genes in peanut roots depending on cultivars. By contrast, AhMTP genes in the root of Fenghua 1 were more sensitive to excess Fe, Cd, and Zn exposure than that of Silihong. Stepwise linear regression analysis showed that the percentage of Fe in shoots significantly and positively correlated with the expression of AhMTP4.1, AhMTP9.1, and AhMTPC4.1, but negatively correlated with that of AhMTPC2.1 and AhMTP12. The expression of AhMTP1.1 showed a significant and negative correlation with the percentage of Mn in shoots. The percentage of Zn in shoots was significantly and positively correlated with the expression of AhMTP2.1 but was negatively correlated with that of AhMTPC2.1. The differential responses of AhMTP genes to metal exposure might be, at least partially, responsible for the different metal translocation from roots to shoots between Fenghua 1 and Silihong.
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16
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Yin S, Duan M, Fang B, Zhao G, Leng X, Zhang T. Zinc homeostasis and regulation: Zinc transmembrane transport through transporters. Crit Rev Food Sci Nutr 2022; 63:7627-7637. [PMID: 35258351 DOI: 10.1080/10408398.2022.2048292] [Citation(s) in RCA: 11] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
Abstract
The second abundant micronutrient, zinc, is attracting more and more attention for it performs essential functions in living organisms and bears close relationships with the occurrence of diseases. However, excess zinc is toxic to cells. Ensuring a balanced zinc state for organisms is essential. Zinc transporters, including ZIPs and ZnTs, are pivotal in regulating zinc homeostasis. Benefiting from zinc transporter structures determination and their transporting dynamic revelation, the clarification of detailed mechanisms of zinc trafficking and the maintenance of zinc homeostasis by transporters in the human body are getting more and more evident. The present review gives a detailed description of the structural basis of zinc transport through ZIP and ZnT, through which the molecular mechanism of zinc binding and transport was illustrated. Then the motive force that drives zinc transmembrane transport and finally a generalization for the regulation models of zinc transporters were summarized.
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Affiliation(s)
- Shuhua Yin
- Key Laboratory of Precision Nutrition and Food Quality, Ministry of Education, College of Food Science and Nutritional Engineering, China Agricultural University, Beijing, China
| | - Maoping Duan
- Key Laboratory of Precision Nutrition and Food Quality, Ministry of Education, College of Food Science and Nutritional Engineering, China Agricultural University, Beijing, China
| | - Bing Fang
- Department of Nutrition and Health, China Agricultural University, Beijing, China
| | - Guanghua Zhao
- Key Laboratory of Precision Nutrition and Food Quality, Ministry of Education, College of Food Science and Nutritional Engineering, China Agricultural University, Beijing, China
| | - Xiaojing Leng
- Key Laboratory of Precision Nutrition and Food Quality, Ministry of Education, College of Food Science and Nutritional Engineering, China Agricultural University, Beijing, China
| | - Tuo Zhang
- Key Laboratory of Precision Nutrition and Food Quality, Ministry of Education, College of Food Science and Nutritional Engineering, China Agricultural University, Beijing, China
- Department of Nutrition and Health, China Agricultural University, Beijing, China
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17
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Sharma G, Merz KM. Mechanism of Zinc Transport through the Zinc Transporter YiiP. J Chem Theory Comput 2022; 18:2556-2568. [PMID: 35226479 DOI: 10.1021/acs.jctc.1c00927] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Zinc is an essential transition metal ion that plays as a structural, functional (catalytic), and a signaling molecule regulating cellular function. Unbalanced levels of zinc in cells can result in various pathological conditions. In the current work, all-atom molecular dynamics simulations were used to study the structure-function correlation between different YiiP states embedded in a lipid bilayer. This study enabled us to develop a hypothesis on the zinc efflux mechanism of YiiP. We have created six different models of YiiP representing the stages of the ion-transport process. We found that zinc ion plays a crucial role in restraining the transmembrane domains (TMDs) of the protein. In addition, H153, located in the TMD, has been proposed to guide the zinc ion toward the ZnA site of the YiiP transporter. Understanding the molecular-level Zn2+-transport process sheds light on the strategies affecting intracellular transition-metal ion concentrations in order to treat diseases like diabetes and cancer.
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Affiliation(s)
- Gaurav Sharma
- Department of Chemistry, Michigan State University, East Lansing, Michigan 48824, United States
| | - Kenneth M Merz
- Department of Chemistry, Michigan State University, East Lansing, Michigan 48824, United States.,Department of Biochemistry and Molecular Biology, Michigan State University, East Lansing, Michigan 48824, United States
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18
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Fujishiro H, Kambe T. Manganese transport in mammals by zinc transporter family proteins, ZNT and ZIP. J Pharmacol Sci 2021; 148:125-133. [PMID: 34924116 DOI: 10.1016/j.jphs.2021.10.011] [Citation(s) in RCA: 16] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2021] [Revised: 10/07/2021] [Accepted: 10/07/2021] [Indexed: 12/14/2022] Open
Abstract
Manganese (Mn) is an essential trace element required for various biological processes. However, excess Mn causes serious side effects in humans, including parkinsonism. Thus, elucidation of Mn homeostasis at the systemic, cellular, and molecular levels is important. Many metal transporters and channels can be involved in the transport and homeostasis of Mn, and an increasing body of evidence shows that several zinc (Zn) transporters belonging to the ZIP and ZNT families, specifically, ZNT10, ZIP8, and ZIP14, play pivotal roles in Mn metabolism. Mutations in the genes encoding these transporter proteins are associated with congenital disorders related to dysregulated Mn homeostasis in humans. Moreover, single nucleotide polymorphisms of ZIP8 are associated with multiple clinical phenotypes. In this review, we discuss the recent literature on the structural and biochemical features of ZNT10, ZIP8, and ZIP14, including transport mechanisms, regulation of expression, and pathophysiological functions. Because a disturbance in Mn homeostasis is closely associated with a variety of phenotypes and risk of human diseases, these transporters constitute a significant target for drug development. An understanding of the roles of these key transporters in Mn metabolism should provide new insights into pharmacological applications of their inhibitors and enhancers in human diseases.
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Affiliation(s)
- Hitomi Fujishiro
- Faculty of Pharmaceutical Sciences, Tokushima Bunri University, Tokushima, 770-8514, Japan.
| | - Taiho Kambe
- Division of Integrated Life Science, Graduate School of Biostudies, Kyoto University, Kyoto, 606-8502, Japan.
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19
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Yang F, Gao Y, Liu J, Chen Z, de Dios VR, Gao Q, Zhang M, Peng Z, Yao Y. Metal tolerance protein MTP6 is involved in Mn and Co distribution in poplar. ECOTOXICOLOGY AND ENVIRONMENTAL SAFETY 2021; 226:112868. [PMID: 34619477 DOI: 10.1016/j.ecoenv.2021.112868] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/28/2021] [Revised: 09/27/2021] [Accepted: 10/01/2021] [Indexed: 06/13/2023]
Abstract
With the booming demand of the electric vehicle industry, the concentration of manganese (Mn) and cobalt (Co) flowing into land ecosystems has also increased significantly. While these transition metals can promote the growth and development of plants, they may become toxic under high concentrations. It is thus important to understand how Mn and Co are distributed in plants to develop novel germplasms for the remediation of these heavy metals in contaminated soils. Here, an MTP gene that encodes the CDF (cation diffusion facilitator) protein in Populus trichocarpa, PtrMTP6, was screened as the key gene involved in the distribution of both Mn and Co in poplar. The PtrMTP6-GFP fusion protein was co-localized with the mRFP-VSR2, showing that PtrMTP6 proteins are present at the pre-vacuolar compartment (PVC). Yeast mutant complementation assays further identified that PtrMTP6 serves as a Mn and Co transporter, reducing yeast cell toxicity after exposure to excessive Mn or Co. Histochemical analyses showed that PtrMTP6 was mainly expressed in phloem, suggesting that PtrMTP6 probably involved in the Mn and Co transport via phloem in plants. Under excess Co, PtrMTP6 overexpressing poplar lines were more severely damaged than the control due to higher Co accumulations in young tissue. PtrMTP6 overexpressing lines showed little change in their tolerance to excess Mn, although young tissues also accumulated more Mn. PtrMTP6 play important roles in Mn and Co distribution in poplar and further research on its regulation will be important to increase bioremediation in Mn and Co polluted ecosystems.
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Affiliation(s)
- Fengming Yang
- School of Life Science and Engineering, Southwest University of Science and Technology, Mianyang 621010, China
| | - Yongfeng Gao
- School of Life Science and Engineering, Southwest University of Science and Technology, Mianyang 621010, China.
| | - Jikai Liu
- School of Life Science and Engineering, Southwest University of Science and Technology, Mianyang 621010, China
| | - Zihao Chen
- School of Life Science and Engineering, Southwest University of Science and Technology, Mianyang 621010, China
| | - Víctor Resco de Dios
- School of Life Science and Engineering, Southwest University of Science and Technology, Mianyang 621010, China; Department of Crop and Forest Sciences & Joint Research Unit CTFC-AGROTECNIO-CERCA Center, Universitat de Lleida, 25198 Lleida, Spain
| | - Qian Gao
- School of Life Science and Engineering, Southwest University of Science and Technology, Mianyang 621010, China
| | - Meng Zhang
- School of Life Science and Engineering, Southwest University of Science and Technology, Mianyang 621010, China
| | - Zhuoxi Peng
- School of Life Science and Engineering, Southwest University of Science and Technology, Mianyang 621010, China
| | - Yinan Yao
- School of Life Science and Engineering, Southwest University of Science and Technology, Mianyang 621010, China.
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20
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Brown JB, Lee MA, Smith AT. Ins and Outs: Recent Advancements in Membrane Protein-Mediated Prokaryotic Ferrous Iron Transport. Biochemistry 2021; 60:3277-3291. [PMID: 34670078 DOI: 10.1021/acs.biochem.1c00586] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
Abstract
Iron is an essential nutrient for virtually every living organism, especially pathogenic prokaryotes. Despite its importance, however, both the acquisition and the export of this element require dedicated pathways that are dependent on oxidation state. Due to its solubility and kinetic lability, reduced ferrous iron (Fe2+) is useful to bacteria for import, chaperoning, and efflux. Once imported, ferrous iron may be loaded into apo and nascent enzymes and even sequestered into storage proteins under certain conditions. However, excess labile ferrous iron can impart toxicity as it may spuriously catalyze Fenton chemistry, thereby generating reactive oxygen species and leading to cellular damage. In response, it is becoming increasingly evident that bacteria have evolved Fe2+ efflux pumps to deal with conditions of ferrous iron excess and to prevent intracellular oxidative stress. In this work, we highlight recent structural and mechanistic advancements in our understanding of prokaryotic ferrous iron import and export systems, with a focus on the connection of these essential transport systems to pathogenesis. Given the connection of these pathways to the virulence of many increasingly antibiotic resistant bacterial strains, a greater understanding of the mechanistic details of ferrous iron cycling in pathogens could illuminate new pathways for future therapeutic developments.
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Affiliation(s)
- Janae B Brown
- Department of Chemistry and Biochemistry, University of Maryland, Baltimore County, Baltimore, Maryland 21250, United States
| | - Mark A Lee
- Department of Chemistry and Biochemistry, University of Maryland, Baltimore County, Baltimore, Maryland 21250, United States
| | - Aaron T Smith
- Department of Chemistry and Biochemistry, University of Maryland, Baltimore County, Baltimore, Maryland 21250, United States
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21
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Zhang Y, Watanabe S, Tsutsumi A, Kadokura H, Kikkawa M, Inaba K. Cryo-EM analysis provides new mechanistic insight into ATP binding to Ca 2+ -ATPase SERCA2b. EMBO J 2021; 40:e108482. [PMID: 34459010 DOI: 10.15252/embj.2021108482] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2021] [Revised: 08/02/2021] [Accepted: 08/04/2021] [Indexed: 12/31/2022] Open
Abstract
Sarco/endoplasmic reticulum Ca2+ -ATPase (SERCA) 2b is a ubiquitous SERCA family member that conducts Ca2+ uptake from the cytosol to the ER. Herein, we present a 3.3 Å resolution cryo-electron microscopy (cryo-EM) structure of human SERCA2b in the E1·2Ca2+ state, revealing a new conformation for Ca2+ -bound SERCA2b with a much closer arrangement of cytosolic domains than in the previously reported crystal structure of Ca2+ -bound SERCA1a. Multiple conformations generated by 3D classification of cryo-EM maps reflect the intrinsically dynamic nature of the cytosolic domains in this state. Notably, ATP binding residues of SERCA2b in the E1·2Ca2+ state are located at similar positions to those in the E1·2Ca2+ -ATP state; hence, the cryo-EM structure likely represents a preformed state immediately prior to ATP binding. Consistently, a SERCA2b mutant with an interdomain disulfide bridge that locks the closed cytosolic domain arrangement displayed significant autophosphorylation activity in the presence of Ca2+ . We propose a novel mechanism of ATP binding to SERCA2b.
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Affiliation(s)
- Yuxia Zhang
- Institute of Multidisciplinary Research for Advanced Materials, Tohoku University, Sendai, Japan
| | - Satoshi Watanabe
- Institute of Multidisciplinary Research for Advanced Materials, Tohoku University, Sendai, Japan
| | - Akihisa Tsutsumi
- Graduate School of Medicine, The University of Tokyo, Tokyo, Japan
| | - Hiroshi Kadokura
- Institute of Multidisciplinary Research for Advanced Materials, Tohoku University, Sendai, Japan
| | - Masahide Kikkawa
- Graduate School of Medicine, The University of Tokyo, Tokyo, Japan
| | - Kenji Inaba
- Institute of Multidisciplinary Research for Advanced Materials, Tohoku University, Sendai, Japan
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22
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Lopez-Redondo M, Fan S, Koide A, Koide S, Beckstein O, Stokes DL. Zinc binding alters the conformational dynamics and drives the transport cycle of the cation diffusion facilitator YiiP. J Gen Physiol 2021; 153:212464. [PMID: 34254979 PMCID: PMC8282283 DOI: 10.1085/jgp.202112873] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2021] [Accepted: 06/14/2021] [Indexed: 11/20/2022] Open
Abstract
YiiP is a secondary transporter that couples Zn2+ transport to the proton motive force. Structural studies of YiiP from prokaryotes and Znt8 from humans have revealed three different Zn2+ sites and a conserved homodimeric architecture. These structures define the inward-facing and outward-facing states that characterize the archetypal alternating access mechanism of transport. To study the effects of Zn2+ binding on the conformational transition, we use cryo-EM together with molecular dynamics simulation to compare structures of YiiP from Shewanella oneidensis in the presence and absence of Zn2+. To enable single-particle cryo-EM, we used a phage-display library to develop a Fab antibody fragment with high affinity for YiiP, thus producing a YiiP/Fab complex. To perform MD simulations, we developed a nonbonded dummy model for Zn2+ and validated its performance with known Zn2+-binding proteins. Using these tools, we find that, in the presence of Zn2+, YiiP adopts an inward-facing conformation consistent with that previously seen in tubular crystals. After removal of Zn2+ with high-affinity chelators, YiiP exhibits enhanced flexibility and adopts a novel conformation that appears to be intermediate between inward-facing and outward-facing states. This conformation involves closure of a hydrophobic gate that has been postulated to control access to the primary transport site. Comparison of several independent cryo-EM maps suggests that the transition from the inward-facing state is controlled by occupancy of a secondary Zn2+ site at the cytoplasmic membrane interface. This work enhances our understanding of individual Zn2+ binding sites and their role in the conformational dynamics that govern the transport cycle.
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Affiliation(s)
- Maria Lopez-Redondo
- Skirball Institute of Biomolecular Medicine, Department of Cell Biology, New York University School of Medicine, New York, NY
| | - Shujie Fan
- Department of Physics, Arizona State University, Tempe, AZ
| | - Akiko Koide
- Perlmutter Cancer Center, Department of Medicine, New York University School of Medicine, New York, NY
| | - Shohei Koide
- Perlmutter Cancer Center, Department of Biochemistry and Molecular Pharmacology, New York University School of Medicine, New York, NY
| | | | - David L Stokes
- Skirball Institute of Biomolecular Medicine, Department of Cell Biology, New York University School of Medicine, New York, NY
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23
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Väth K, Mattes C, Reinhard J, Covino R, Stumpf H, Hummer G, Ernst R. Cysteine cross-linking in native membranes establishes the transmembrane architecture of Ire1. J Cell Biol 2021; 220:212449. [PMID: 34196665 PMCID: PMC8256922 DOI: 10.1083/jcb.202011078] [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] [Received: 11/12/2020] [Revised: 04/28/2021] [Accepted: 05/19/2021] [Indexed: 02/06/2023] Open
Abstract
The ER is a key organelle of membrane biogenesis and crucial for the folding of both membrane and secretory proteins. Sensors of the unfolded protein response (UPR) monitor the unfolded protein load in the ER and convey effector functions for maintaining ER homeostasis. Aberrant compositions of the ER membrane, referred to as lipid bilayer stress, are equally potent activators of the UPR. How the distinct signals from lipid bilayer stress and unfolded proteins are processed by the conserved UPR transducer Ire1 remains unknown. Here, we have generated a functional, cysteine-less variant of Ire1 and performed systematic cysteine cross-linking experiments in native membranes to establish its transmembrane architecture in signaling-active clusters. We show that the transmembrane helices of two neighboring Ire1 molecules adopt an X-shaped configuration independent of the primary cause for ER stress. This suggests that different forms of stress converge in a common, signaling-active transmembrane architecture of Ire1.
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Affiliation(s)
- Kristina Väth
- Medical Biochemistry and Molecular Biology, Medical Faculty, Saarland University, Homburg, Germany.,Preclinical Center for Molecular Signaling, Medical Faculty, Saarland University, Homburg, Germany
| | - Carsten Mattes
- Medical Biochemistry and Molecular Biology, Medical Faculty, Saarland University, Homburg, Germany.,Preclinical Center for Molecular Signaling, Medical Faculty, Saarland University, Homburg, Germany
| | - John Reinhard
- Medical Biochemistry and Molecular Biology, Medical Faculty, Saarland University, Homburg, Germany.,Preclinical Center for Molecular Signaling, Medical Faculty, Saarland University, Homburg, Germany
| | - Roberto Covino
- Frankfurt Institute of Advanced Sciences, Goethe-University, Frankfurt, Germany
| | - Heike Stumpf
- Medical Biochemistry and Molecular Biology, Medical Faculty, Saarland University, Homburg, Germany.,Preclinical Center for Molecular Signaling, Medical Faculty, Saarland University, Homburg, Germany
| | - Gerhard Hummer
- Department of Theoretical Biophysics, Max Planck Institute of Biophysics, Frankfurt, Germany.,Institute of Biophysics, Goethe-University, Frankfurt, Germany
| | - Robert Ernst
- Medical Biochemistry and Molecular Biology, Medical Faculty, Saarland University, Homburg, Germany.,Preclinical Center for Molecular Signaling, Medical Faculty, Saarland University, Homburg, Germany
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24
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Ma C, Gong C. Expression, Purification and Characterization of a ZIP Family Transporter from Desulfovibrio vulgaris. Protein J 2021; 40:776-785. [PMID: 34101092 DOI: 10.1007/s10930-021-10008-7] [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] [Accepted: 06/03/2021] [Indexed: 10/21/2022]
Abstract
The ZIP family transport zinc ions from the extracellular medium across the plasma membrane or from the intracellular compartments across endomembranes, which play fundamental roles in metal homeostasis and are broadly involved in physiological and pathological processes. Desulfovibrio is the predominant sulphate-reducing bacteria in human colonic microbiota, but also a potential choice for metal bioremediation. while, there are no published studies describing the zinc transporters from Desulfovibrio up to now. In this study, we obtained for the first time a heterologously expressed ZIP homolog from Desulfovibrio vulgaris, termed dvZip. The purified dvZip was reconstituted into proteoliposomes, and confirmed its zinc transport ability in vitro. By combining topology prediction, homology modeling and phylogenetic approaches, we also noticed that dvZip belongs to the GufA and probably have 8 transmembrane α-helical segments (TM 1-8) in which both termini are located on the extracellular, with TM2, 4, 5 and 7 create an inner bundle. We believe that purification and characterization of zinc (probably also cadmium) transporters from Desulfovibrio vulgaris such as dvZip could shed light on understanding of metal homeostasis of Desulfovibrio and provided protein products for future detailed function and structural studies.
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Affiliation(s)
- Cheng Ma
- Protein Facility, Zhejiang University School of Medicine, Zhejiang University, Hangzhou, 310058, China.
| | - Caixia Gong
- Department of Geriatrics, the First Affiliated Hospital, School of Medicine, Zhejiang University, Hangzhou, 310058, China
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25
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Laws M, Jin P, Rahman KM. Efflux pumps in Mycobacterium tuberculosis and their inhibition to tackle antimicrobial resistance. Trends Microbiol 2021; 30:57-68. [PMID: 34052094 DOI: 10.1016/j.tim.2021.05.001] [Citation(s) in RCA: 21] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2021] [Revised: 05/04/2021] [Accepted: 05/05/2021] [Indexed: 02/08/2023]
Abstract
Tuberculosis (TB), an infectious disease caused by the bacterium Mycobacterium tuberculosis, was the leading cause of mortality worldwide in 2019 due to a single infectious agent. The growing threat of strains of M. tuberculosis untreatable by modern antibiotic regimens only exacerbates this problem. In response to this continued public health emergency, research into methods of potentiating currently approved antimicrobial agents against resistant strains of M. tuberculosis is an urgent priority, and a key strategy in this regard is the design of mycobacterial efflux pump inhibitors (EPIs). This review summarises the current state of knowledge surrounding drug-related efflux pumps in M. tuberculosis and presents recent updates within the field of mycobacterial EPIs with a view to aiding the design of an effective adjunct therapy to overcome efflux-mediated resistance in TB.
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Affiliation(s)
- Mark Laws
- School of Cancer and Pharmaceutical Sciences, King's College London, Franklin-Wilkins Building, 150 Stamford Street, London SE1 9NH, UK
| | - Peiqin Jin
- School of Cancer and Pharmaceutical Sciences, King's College London, Franklin-Wilkins Building, 150 Stamford Street, London SE1 9NH, UK
| | - Khondaker Miraz Rahman
- School of Cancer and Pharmaceutical Sciences, King's College London, Franklin-Wilkins Building, 150 Stamford Street, London SE1 9NH, UK.
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26
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Cotrim CA, Jarrott RJ, Whitten AE, Choudhury HG, Drew D, Martin JL. Heterologous Expression and Biochemical Characterization of the Human Zinc Transporter 1 (ZnT1) and Its Soluble C-Terminal Domain. Front Chem 2021; 9:667803. [PMID: 33996761 PMCID: PMC8120272 DOI: 10.3389/fchem.2021.667803] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2021] [Accepted: 03/31/2021] [Indexed: 11/13/2022] Open
Abstract
Human zinc transporter 1 (hZnT1) belongs to the cation diffusion facilitator (CDF) family. It plays a major role in transporting zinc (Zn2+) from the cytoplasm across the plasma membrane and into the extracellular space thereby protecting cells from Zn2+ toxicity. Through homology with other CDF family members, ZnT1 is predicted to contain a transmembrane region and a soluble C-terminal domain though little is known about its biochemistry. Here, we demonstrate that human ZnT1 and a variant can be produced by heterologous expression in Saccharomyces cerevisiae cells and purified in the presence of detergent and cholesteryl hemisuccinate. We show that the purified hZnT1 variant has Zn2+/H+ antiporter activity. Furthermore, we expressed, purified and characterized the soluble C-terminal domain of hZnT1 (hZnT1-CTD) in a bacterial expression system. We found that the hZnT1-CTD melting temperature increases at acidic pH, thus, we used an acetate buffer at pH 4.5 for purifications and concentration of the protein up to 12 mg/mL. Small-angle X-ray scattering analysis of hZnT1-CTD is consistent with the formation of a dimer in solution with a V-shaped core.
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Affiliation(s)
- Camila A. Cotrim
- Griffith Institute for Drug Discovery, Griffith University, Nathan, QLD, Australia
| | - Russell J. Jarrott
- Griffith Institute for Drug Discovery, Griffith University, Nathan, QLD, Australia
| | - Andrew E. Whitten
- Australian Nuclear Science and Technology Organisation, Lucas Heights, NSW, Australia
| | - Hassanul G. Choudhury
- Institute for Molecular Bioscience, University of Queensland, St Lucia, QLD, Australia
| | - David Drew
- Department of Biochemistry and Biophysics, Stockholm University, Stockholm, Sweden
| | - Jennifer L. Martin
- Griffith Institute for Drug Discovery, Griffith University, Nathan, QLD, Australia
- Vice-Chancellor's Unit, University of Wollongong, Wollongong, NSW, Australia
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27
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Barber-Zucker S, Moran A, Zarivach R. Metal transport mechanism of the cation diffusion facilitator (CDF) protein family - a structural perspective on human CDF (ZnT)-related diseases. RSC Chem Biol 2021; 2:486-498. [PMID: 34458794 PMCID: PMC8341793 DOI: 10.1039/d0cb00181c] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2020] [Accepted: 12/26/2020] [Indexed: 11/21/2022] Open
Abstract
Divalent d-block metal cations (DDMCs) participate in many cellular functions; however, their accumulation in cells can be cytotoxic. The cation diffusion facilitator (CDF) family is a ubiquitous family of transmembrane DDMC exporters that ensures their homeostasis. Severe diseases, such as type II diabetes, Parkinson's and Alzheimer's disease, were linked to dysfunctional human CDF proteins, ZnT-1-10 (SLC30A1-10). Each member of the CDF family reduces the cytosolic concentration of a specific DDMC by transporting it from the cytoplasm to the extracellular environment or into intracellular compartments. This process is usually achieved by utilizing the proton motive force. In addition to their activity as DDMC transporters, CDFs also have other cellular functions such as the regulation of ion channels and enzymatic activity. The combination of structural and biophysical studies of different bacterial and eukaryotic CDF proteins led to significant progress in the understanding of the mutual interaction among CDFs and DDMCs, their involvement in ion binding and selectivity, conformational changes and the consequent transporting mechanisms. Here, we review these studies, provide our mechanistic interpretation of CDF proteins based on the current literature and relate the above to known human CDF-related diseases. Our analysis provides a common structure-function relationship to this important protein family and closes the gap between eukaryote and prokaryote CDFs.
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Affiliation(s)
- Shiran Barber-Zucker
- Department of Life Sciences, the National Institute for Biotechnology in the Negev and Ilse Katz Institute for Nanoscale Science and Technology, Ben-Gurion University of the Negev P.O.B. 653 Beer Sheva 8410501 Israel +972-8-6472970 +972-8-6472970 +972-8-6428447 +972-8-6461999
| | - Arie Moran
- Department of Physiology and Cell Biology, Faculty of Health Sciences, Ben-Gurion University of the Negev P.O.B. 653 Beer Sheva 8410501 Israel
| | - Raz Zarivach
- Department of Life Sciences, the National Institute for Biotechnology in the Negev and Ilse Katz Institute for Nanoscale Science and Technology, Ben-Gurion University of the Negev P.O.B. 653 Beer Sheva 8410501 Israel +972-8-6472970 +972-8-6472970 +972-8-6428447 +972-8-6461999
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28
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Amphipathic environments for determining the structure of membrane proteins by single-particle electron cryo-microscopy. Q Rev Biophys 2021; 54:e6. [PMID: 33785082 DOI: 10.1017/s0033583521000044] [Citation(s) in RCA: 15] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Over the past decade, the structural biology of membrane proteins (MPs) has taken a new turn thanks to epoch-making technical progress in single-particle electron cryo-microscopy (cryo-EM) as well as to improvements in sample preparation. The present analysis provides an overview of the extent and modes of usage of the various types of surfactants for cryo-EM studies. Digitonin, dodecylmaltoside, protein-based nanodiscs, lauryl maltoside-neopentyl glycol, glyco-diosgenin, and amphipols (APols) are the most popular surfactants at the vitrification step. Surfactant exchange is frequently used between MP purification and grid preparation, requiring extensive optimization each time the study of a new MP is undertaken. The variety of both the surfactants and experimental approaches used over the past few years bears witness to the need to continue developing innovative surfactants and optimizing conditions for sample preparation. The possibilities offered by novel APols for EM applications are discussed.
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29
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Sala D, Giachetti A, Rosato A. Insights into the Dynamics of the Human Zinc Transporter ZnT8 by MD Simulations. J Chem Inf Model 2021; 61:901-912. [PMID: 33508935 PMCID: PMC8023586 DOI: 10.1021/acs.jcim.0c01139] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2020] [Indexed: 02/07/2023]
Abstract
ZnT8 is a human zinc(II) transporter expressed at the membrane of secretory granules where it contributes to insulin storage importing zinc ions from the cytosol. In the human population, the two most common ZnT8 variants carry an arginine (R325) or a tryptophan (W325) in position 325. The former variant has the most efficient kinetics in zinc transport and has been correlated to a higher risk of developing insulin resistance. On the contrary, the W325 variant is less active and protects against type-2-diabetes. Here, we used molecular dynamics (MD) simulations to investigate the main differences between the R325 and W325 variants in the interaction with zinc(II) ions. Our simulations suggested that the position of the metal ion within the transport site was not the same for the two variants, underlying a different rearrangement of the transmembrane (TM) helices in the channel. The W325 variant featured a peculiar zinc environment not detected in the experimental structures. With respect to conformational dynamics, we observed that the R325 variant was significantly more flexible than W325, with the main role played by the transmembrane domain (TMD) and the C-terminal domain (CTD). This dynamics affected the packing of the TM helices and thus the channel accessibility from the cytosol. The dimer interface that keeps the two TM channels in contact became looser in both variants upon zinc binding to the transport site, suggesting that this may be an important step toward the switch from the inward- to the outward-facing state of the protein.
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Affiliation(s)
- Davide Sala
- Magnetic
Resonance Center (CERM), University of Florence, Via Luigi Sacconi 6, 50019 Sesto Fiorentino, Italy
| | - Andrea Giachetti
- Consorzio
Interuniversitario di Risonanze Magnetiche di Metallo Proteine, Via Luigi Sacconi 6, 50019 Sesto Fiorentino, Italy
| | - Antonio Rosato
- Magnetic
Resonance Center (CERM), University of Florence, Via Luigi Sacconi 6, 50019 Sesto Fiorentino, Italy
- Department
of Chemistry, University of Florence, Via della Lastruccia 3, 50019 Sesto Fiorentino, Italy
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Kambe T, Taylor KM, Fu D. Zinc transporters and their functional integration in mammalian cells. J Biol Chem 2021; 296:100320. [PMID: 33485965 PMCID: PMC7949119 DOI: 10.1016/j.jbc.2021.100320] [Citation(s) in RCA: 99] [Impact Index Per Article: 33.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2020] [Revised: 01/15/2021] [Accepted: 01/20/2021] [Indexed: 12/14/2022] Open
Abstract
Zinc is a ubiquitous biological metal in all living organisms. The spatiotemporal zinc dynamics in cells provide crucial cellular signaling opportunities, but also challenges for intracellular zinc homeostasis with broad disease implications. Zinc transporters play a central role in regulating cellular zinc balance and subcellular zinc distributions. The discoveries of two complementary families of mammalian zinc transporters (ZnTs and ZIPs) in the mid-1990s spurred much speculation on their metal selectivity and cellular functions. After two decades of research, we have arrived at a biochemical description of zinc transport. However, in vitro functions are fundamentally different from those in living cells, where mammalian zinc transporters are directed to specific subcellular locations, engaged in dedicated macromolecular machineries, and connected with diverse cellular processes. Hence, the molecular functions of individual zinc transporters are reshaped and deeply integrated in cells to promote the utilization of zinc chemistry to perform enzymatic reactions, tune cellular responsiveness to pathophysiologic signals, and safeguard cellular homeostasis. At present, the underlying mechanisms driving the functional integration of mammalian zinc transporters are largely unknown. This knowledge gap has motivated a shift of the research focus from in vitro studies of purified zinc transporters to in cell studies of mammalian zinc transporters in the context of their subcellular locations and protein interactions. In this review, we will outline how knowledge of zinc transporters has been accumulated from in-test-tube to in-cell studies, highlighting new insights and paradigm shifts in our understanding of the molecular and cellular basis of mammalian zinc transporter functions.
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Affiliation(s)
- Taiho Kambe
- Division of Integrated Life Science, Graduate School of Biostudies, Kyoto University, Kyoto, Japan
| | - Kathryn M Taylor
- School of Pharmacy and Pharmaceutical Sciences, Cardiff University, Cardiff, United Kingdom
| | - Dax Fu
- Department of Physiology, Johns Hopkins School of Medicine, Johns Hopkins University, Baltimore, Maryland, USA.
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31
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Barber-Zucker S, Hall J, Froes A, Kolusheva S, MacMillan F, Zarivach R. The cation diffusion facilitator protein MamM's cytoplasmic domain exhibits metal-type dependent binding modes and discriminates against Mn 2. J Biol Chem 2020; 295:16614-16629. [PMID: 32967967 PMCID: PMC7864060 DOI: 10.1074/jbc.ra120.014145] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2020] [Revised: 09/11/2020] [Indexed: 12/20/2022] Open
Abstract
Cation diffusion facilitator (CDF) proteins are a conserved family of divalent transition metal cation transporters. CDF proteins are usually composed of two domains: the transmembrane domain, in which the metal cations are transported through, and a regulatory cytoplasmic C-terminal domain (CTD). Each CDF protein transports either one specific metal or multiple metals from the cytoplasm, and it is not known whether the CTD takes an active regulatory role in metal recognition and discrimination during cation transport. Here, the model CDF protein MamM, an iron transporter from magnetotactic bacteria, was used to probe the role of the CTD in metal recognition and selectivity. Using a combination of biophysical and structural approaches, the binding of different metals to MamM CTD was characterized. Results reveal that different metals bind distinctively to MamM CTD in terms of their binding sites, thermodynamics, and binding-dependent conformations, both in crystal form and in solution, which suggests a varying level of functional discrimination between CDF domains. Furthermore, these results provide the first direct evidence that CDF CTDs play a role in metal selectivity. We demonstrate that MamM's CTD can discriminate against Mn2+, supporting its postulated role in preventing magnetite formation poisoning in magnetotactic bacteria via Mn2+ incorporation.
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Affiliation(s)
- Shiran Barber-Zucker
- Department of Life Sciences, Ben-Gurion University of the Negev, Beer Sheva, Israel; The National Institute for Biotechnology in the Negev, Ben-Gurion University of the Negev, Beer Sheva, Israel; Ilse Katz Institute for Nanoscale Science and Technology, Ben-Gurion University of the Negev, Beer Sheva, Israel
| | - Jenny Hall
- Henry Wellcome Unit for Biological EPR, School of Chemistry, University of East Anglia, Norwich, United Kingdom
| | - Afonso Froes
- Henry Wellcome Unit for Biological EPR, School of Chemistry, University of East Anglia, Norwich, United Kingdom
| | - Sofiya Kolusheva
- Ilse Katz Institute for Nanoscale Science and Technology, Ben-Gurion University of the Negev, Beer Sheva, Israel
| | - Fraser MacMillan
- Henry Wellcome Unit for Biological EPR, School of Chemistry, University of East Anglia, Norwich, United Kingdom.
| | - Raz Zarivach
- Department of Life Sciences, Ben-Gurion University of the Negev, Beer Sheva, Israel; The National Institute for Biotechnology in the Negev, Ben-Gurion University of the Negev, Beer Sheva, Israel; Ilse Katz Institute for Nanoscale Science and Technology, Ben-Gurion University of the Negev, Beer Sheva, Israel.
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32
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Barber-Zucker S, Shahar A, Kolusheva S, Zarivach R. The metal binding site composition of the cation diffusion facilitator protein MamM cytoplasmic domain impacts its metal responsivity. Sci Rep 2020; 10:14022. [PMID: 32820200 PMCID: PMC7441159 DOI: 10.1038/s41598-020-71036-4] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2020] [Accepted: 07/29/2020] [Indexed: 11/09/2022] Open
Abstract
The cation diffusion facilitator (CDF) is a conserved family of divalent d-block metal cation transporters that extrude these cations selectively from the cytoplasm. CDF proteins are composed of two domains: the transmembrane domain, through which the cations are transported, and a regulatory cytoplasmic C-terminal domain (CTD). It was recently shown that the CTD of the CDF protein MamM from magnetotactic bacteria has a role in metal selectivity, as binding of different metal cations exhibits distinctive affinities and conformations. It is yet unclear whether the composition of the CTD binding sites can impact metal selectivity and if we can manipulate the CTD to response to other non-native metals in CDF proteins. Here we performed a mutational study of the model protein MamM CTD, where we exchanged the native metal binding residues with different metal-binding amino acids. Using X-ray crystallography and Trp-fluorescence spectrometry, we studied the impact of these mutations on the CTD conformation in the presence of non-native metals. Our results reveal that the incorporation of such mutations alters the domain response to metals in vitro, as mutant forms of the CTD bind metals differently in terms of the composition of the binding sites and the CTD conformation. Therefore, the results demonstrate the direct influence of the CTD binding site composition on CDF proteins structure and hence, function, and constitute a first step for rational design of MamM for transporting different metals in vivo.
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Affiliation(s)
- Shiran Barber-Zucker
- Department of Life Sciences, Ben-Gurion University of the Negev, P.O.B. 653, 8410501, Beer Sheva, Israel
- The National Institute for Biotechnology in the Negev, Ben-Gurion University of the Negev, 8410501, Beer Sheva, Israel
- Ilse Katz Institute for Nanoscale Science and Technology, Ben-Gurion University of the Negev, 8410501, Beer Sheva, Israel
| | - Anat Shahar
- The National Institute for Biotechnology in the Negev, Ben-Gurion University of the Negev, 8410501, Beer Sheva, Israel
| | - Sofiya Kolusheva
- Ilse Katz Institute for Nanoscale Science and Technology, Ben-Gurion University of the Negev, 8410501, Beer Sheva, Israel
| | - Raz Zarivach
- Department of Life Sciences, Ben-Gurion University of the Negev, P.O.B. 653, 8410501, Beer Sheva, Israel.
- The National Institute for Biotechnology in the Negev, Ben-Gurion University of the Negev, 8410501, Beer Sheva, Israel.
- Ilse Katz Institute for Nanoscale Science and Technology, Ben-Gurion University of the Negev, 8410501, Beer Sheva, Israel.
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33
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Xue J, Xie T, Zeng W, Jiang Y, Bai XC. Cryo-EM structures of human ZnT8 in both outward- and inward-facing conformations. eLife 2020; 9:e58823. [PMID: 32723473 PMCID: PMC7428307 DOI: 10.7554/elife.58823] [Citation(s) in RCA: 36] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2020] [Accepted: 07/28/2020] [Indexed: 01/02/2023] Open
Abstract
ZnT8 is a Zn2+/H+ antiporter that belongs to SLC30 family and plays an essential role in regulating Zn2+ accumulation in the insulin secretory granules of pancreatic β cells. However, the Zn2+/H+ exchange mechanism of ZnT8 remains unclear due to the lack of high-resolution structures. Here, we report the cryo-EM structures of human ZnT8 (HsZnT8) in both outward- and inward-facing conformations. HsZnT8 forms a dimeric structure with four Zn2+ binding sites within each subunit: a highly conserved primary site in transmembrane domain (TMD) housing the Zn2+ substrate; an interfacial site between TMD and C-terminal domain (CTD) that modulates the Zn2+ transport activity of HsZnT8; and two adjacent sites buried in the cytosolic domain and chelated by conserved residues from CTD and the His-Cys-His (HCH) motif from the N-terminal segment of the neighboring subunit. A comparison of the outward- and inward-facing structures reveals that the TMD of each HsZnT8 subunit undergoes a large structural rearrangement, allowing for alternating access to the primary Zn2+ site during the transport cycle. Collectively, our studies provide the structural insights into the Zn2+/H+ exchange mechanism of HsZnT8.
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Affiliation(s)
- Jing Xue
- Howard Hughes Medical Institute and Department of Physiology, University of Texas Southwestern Medical CenterDallasUnited States
- Department of Biophysics, University of Texas Southwestern Medical CenterDallasUnited States
| | - Tian Xie
- Department of Biophysics, University of Texas Southwestern Medical CenterDallasUnited States
- Department of Cell Biology, University of Texas Southwestern Medical CenterDallasUnited States
| | - Weizhong Zeng
- Howard Hughes Medical Institute and Department of Physiology, University of Texas Southwestern Medical CenterDallasUnited States
- Department of Biophysics, University of Texas Southwestern Medical CenterDallasUnited States
| | - Youxing Jiang
- Howard Hughes Medical Institute and Department of Physiology, University of Texas Southwestern Medical CenterDallasUnited States
- Department of Biophysics, University of Texas Southwestern Medical CenterDallasUnited States
| | - Xiao-chen Bai
- Department of Biophysics, University of Texas Southwestern Medical CenterDallasUnited States
- Department of Cell Biology, University of Texas Southwestern Medical CenterDallasUnited States
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Abstract
The integral membrane protein heme A synthase (HAS) catalyzes the biosynthesis of heme A, which is a prerequisite for cellular respiration in a wide range of aerobic organisms. Previous studies have revealed that HAS can form homo-oligomeric complexes, and this oligomerization appears to be evolutionarily conserved among prokaryotes and eukaryotes and is shown to be essential for the biological function of eukaryotic HAS. Despite its importance, little is known about the detailed structural properties of HAS oligomers. Here, we aimed to address this critical issue by analyzing the oligomeric state of HAS from Aquifex aeolicus (AaHAS) using a combination of techniques, including size exclusion chromatography coupled with multiangle light scattering (SEC-MALS), cross-linking, laser-induced liquid bead ion desorption mass spectrometry (LILBID-MS), and single-particle electron cryomicroscopy (cryo-EM). Our results show that HAS forms a thermostable trimeric complex. A cryo-EM density map provides information on the oligomerization interface of the AaHAS trimer. These results provide structural insights into HAS multimerization and expand our knowledge of this important enzyme.IMPORTANCE Heme A is a vital redox cofactor unique for the terminal cytochrome c oxidase in mitochondria and many microorganisms. It plays a key role in oxygen reduction by serving as an electron carrier and as the oxygen-binding site. Heme A is synthesized from heme O by an integral membrane protein, heme A synthase (HAS). Defects in HAS impair cellular respiration and have been linked to various human diseases, e.g., fatal infantile hypertrophic cardiomyopathy and Leigh syndrome. HAS exists as a stable oligomeric complex, and studies have shown that oligomerization of eukaryotic HAS is necessary for its proper function. However, the molecular architecture of the HAS oligomeric complex has remained uncharacterized. The present study shows that HAS forms trimers and reveals how the oligomeric arrangement contributes to the complex stability and flexibility, enabling HAS to perform its catalytic function effectively. This work provides the basic understanding for future studies on heme A biosynthesis.
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35
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Daniels MJ, Jagielnicki M, Yeager M. Structure/Function Analysis of human ZnT8 (SLC30A8): A Diabetes Risk Factor and Zinc Transporter. Curr Res Struct Biol 2020; 2:144-155. [PMID: 34235474 PMCID: PMC8244513 DOI: 10.1016/j.crstbi.2020.06.001] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2020] [Revised: 06/15/2020] [Accepted: 06/22/2020] [Indexed: 12/17/2022] Open
Abstract
The human zinc transporter ZnT8 (SLC30A8) is expressed primarily in pancreatic β-cells and plays a key function in maintaining the concentration of blood glucose through its role in insulin storage, maturation and secretion. ZnT8 is an autoantigen for Type 1 diabetes (T1D) and is associated with Type 2 diabetes (T2D) through its risk allele that encodes a major non-synonymous single nucleotide polymorphism (SNP) at Arg325. Loss of function mutations improve insulin secretion and are protective against diabetes. Despite its role in diabetes and concomitant potential as a drug target, little is known about the structure or mechanism of ZnT8. To this end, we expressed ZnT8 in Pichia pastoris yeast and Sf9 insect cells. Guided by a rational screen of 96 detergents, we developed a method to solubilize and purify recombinant ZnT8. An in vivo transport assay in Pichia and a liposome-based uptake assay for insect-cell derived ZnT8 showed that the protein is functionally active in both systems. No significant difference in activity was observed between full-length ZnT8 (ZnT8A) and the amino-terminally truncated ZnT8B isoform. A fluorescence-based in vitro transport assay using proteoliposomes indicated that human ZnT8 functions as a Zn2+/H+ antiporter. We also purified E. coli-expressed amino- and carboxy-terminal cytoplasmic domains of ZnT8A. Circular dichroism spectrometry suggested that the amino-terminal domain contains predominantly α-helical structure, and indicated that the carboxy-terminal domain has a mixed α/β structure. Negative-stain electron microscopy and single-particle image analysis yielded a density map of ZnT8B at 20 Å resolution, which revealed that ZnT8 forms a dimer in detergent micelles. Two prominent lobes are ascribed to the transmembrane domains, and the molecular envelope recapitulates that of the bacterial zinc transporter YiiP. These results provide a foundation for higher resolution structural studies and screening experiments to identify compounds that modulate ZnT8 activity.
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Affiliation(s)
- Mark J. Daniels
- Department of Molecular Physiology and Biological Physics, University of Virginia School of Medicine, Charlottesville, VA, 22908, USA
| | - Maciej Jagielnicki
- Department of Molecular Physiology and Biological Physics, University of Virginia School of Medicine, Charlottesville, VA, 22908, USA
- Department of Biochemistry, University of Toronto, Toronto, ON, M5G 1M1, Canada
| | - Mark Yeager
- Department of Molecular Physiology and Biological Physics, University of Virginia School of Medicine, Charlottesville, VA, 22908, USA
- Department of Medicine, Division of Cardiovascular Medicine, University of Virginia Health System, Charlottesville, VA, 22908, USA
- Center for Membrane and Cell Physiology, University of Virginia School of Medicine, Charlottesville, VA, 22908, USA
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36
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Udagedara SR, La Porta DM, Spehar C, Purohit G, Hein MJA, Fatmous ME, Casas Garcia GP, Ganio K, McDevitt CA, Maher MJ. Structural and functional characterizations of the C-terminal domains of CzcD proteins. J Inorg Biochem 2020; 208:111087. [PMID: 32505855 DOI: 10.1016/j.jinorgbio.2020.111087] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2020] [Revised: 04/11/2020] [Accepted: 04/15/2020] [Indexed: 12/15/2022]
Abstract
Zinc is a potent antimicrobial component of the innate immune response at the host-pathogen interface. Bacteria subvert or resist host zinc insults by metal efflux pathways that include cation diffusion facilitator (CDF) proteins. The structural and functional examination of this protein class has been limited, with only the structures of the zinc transporter YiiP proteins from E. coli and Shewanella oneidensis described to date. Here, we determine the metal binding properties, solution quaternary structures and three dimensional architectures of the C-terminal domains of the metal transporter CzcD proteins from Cupriavidus metallidurans, Pseudomonas aeruginosa and Thermotoga maritima. We reveal significant diversity in the metal-binding properties and structures of these proteins and discover a potential novel mechanism for metal-promoted dimerization for the Cupriavidus metallidurans and Pseudomonas aeruginosa proteins.
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Affiliation(s)
- Saumya R Udagedara
- Department of Biochemistry and Genetics, La Trobe Institute for Molecular Science, La Trobe University, Melbourne 3083, Australia
| | - Daniel M La Porta
- Department of Biochemistry and Genetics, La Trobe Institute for Molecular Science, La Trobe University, Melbourne 3083, Australia
| | - Christian Spehar
- Department of Biochemistry and Genetics, La Trobe Institute for Molecular Science, La Trobe University, Melbourne 3083, Australia
| | - Ghruta Purohit
- Department of Biochemistry and Genetics, La Trobe Institute for Molecular Science, La Trobe University, Melbourne 3083, Australia
| | - Matthew J A Hein
- Department of Biochemistry and Genetics, La Trobe Institute for Molecular Science, La Trobe University, Melbourne 3083, Australia
| | - Monique E Fatmous
- Department of Biochemistry and Genetics, La Trobe Institute for Molecular Science, La Trobe University, Melbourne 3083, Australia
| | - G Patricia Casas Garcia
- Department of Biochemistry and Genetics, La Trobe Institute for Molecular Science, La Trobe University, Melbourne 3083, Australia
| | - Katherine Ganio
- Department of Microbiology and Immunology, The Peter Doherty Institute for Infection and Immunity, The University of Melbourne, Melbourne 3000, Australia
| | - Christopher A McDevitt
- Department of Microbiology and Immunology, The Peter Doherty Institute for Infection and Immunity, The University of Melbourne, Melbourne 3000, Australia
| | - Megan J Maher
- Department of Biochemistry and Genetics, La Trobe Institute for Molecular Science, La Trobe University, Melbourne 3083, Australia; School of Chemistry, The Bio21 Molecular Science and Biotechnology Institute, The University of Melbourne, Melbourne 3010, Australia.
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Keren-Khadmy N, Zeytuni N, Kutnowski N, Perriere G, Monteil C, Zarivach R. From conservation to structure, studies of magnetosome associated cation diffusion facilitators (CDF) proteins in Proteobacteria. PLoS One 2020; 15:e0231839. [PMID: 32310978 PMCID: PMC7170241 DOI: 10.1371/journal.pone.0231839] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2020] [Accepted: 04/01/2020] [Indexed: 12/24/2022] Open
Abstract
Magnetotactic bacteria (MTB) are prokaryotes that sense the geomagnetic field lines to geolocate and navigate in aquatic sediments. They are polyphyletically distributed in several bacterial divisions but are mainly represented in the Proteobacteria. In this phylum, magnetotactic Deltaproteobacteria represent the most ancestral class of MTB. Like all MTB, they synthesize membrane-enclosed magnetic nanoparticles, called magnetosomes, for magnetic sensing. Magnetosome biogenesis is a complex process involving a specific set of genes that are conserved across MTB. Two of the most conserved genes are mamB and mamM, that encode for the magnetosome-associated proteins and are homologous to the cation diffusion facilitator (CDF) protein family. In magnetotactic Alphaproteobacteria MTB species, MamB and MamM proteins have been well characterized and play a central role in iron-transport required for biomineralization. However, their structural conservation and their role in more ancestral groups of MTB like the Deltaproteobacteria have not been established. Here we studied magnetite cluster MamB and MamM cytosolic C-terminal domain (CTD) structures from a phylogenetically distant magnetotactic Deltaproteobacteria species represented by BW-1 strain, which has the unique ability to biomineralize magnetite and greigite. We characterized them in solution, analyzed their crystal structures and compared them to those characterized in Alphaproteobacteria MTB species. We showed that despite the high phylogenetic distance, MamBBW-1 and MamMBW-1 CTDs share high structural similarity with known CDF-CTDs and will probably share a common function with the Alphaproteobacteria MamB and MamM.
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Affiliation(s)
- Noa Keren-Khadmy
- Department of Life Sciences, Ben-Gurion University of the Negev, Beer-Sheva, Israel
- The National Institute for Biotechnology in the Negev, Ben-Gurion University of the Negev, Beer-Sheva, Israel
- Ilse Katz Institute for Nanoscale Science & Technology, Ben-Gurion University of the Negev, Beer-Sheva, Israel
| | - Natalie Zeytuni
- Department of Life Sciences, Ben-Gurion University of the Negev, Beer-Sheva, Israel
- The National Institute for Biotechnology in the Negev, Ben-Gurion University of the Negev, Beer-Sheva, Israel
- Ilse Katz Institute for Nanoscale Science & Technology, Ben-Gurion University of the Negev, Beer-Sheva, Israel
| | - Nitzan Kutnowski
- Department of Life Sciences, Ben-Gurion University of the Negev, Beer-Sheva, Israel
| | - Guy Perriere
- Laboratoire de Biométrie et Biologie Evolutive, UMR CNRS 5558, Université de Lyon, Villeurbanne Cedex, France
| | - Caroline Monteil
- Laboratoire de Biométrie et Biologie Evolutive, UMR CNRS 5558, Université de Lyon, Villeurbanne Cedex, France
- CNRS, CEA, Aix-Marseille Université, UMR7265 Biosciences and Biotechnologies Institute of Aix-Marseille, Saint Paul lez Durance, France
| | - Raz Zarivach
- Department of Life Sciences, Ben-Gurion University of the Negev, Beer-Sheva, Israel
- The National Institute for Biotechnology in the Negev, Ben-Gurion University of the Negev, Beer-Sheva, Israel
- Ilse Katz Institute for Nanoscale Science & Technology, Ben-Gurion University of the Negev, Beer-Sheva, Israel
- * E-mail:
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Eide DJ. Transcription factors and transporters in zinc homeostasis: lessons learned from fungi. Crit Rev Biochem Mol Biol 2020; 55:88-110. [PMID: 32192376 DOI: 10.1080/10409238.2020.1742092] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
Abstract
Zinc is an essential nutrient for all organisms because this metal serves as a critical structural or catalytic cofactor for many proteins. These zinc-dependent proteins are abundant in the cytosol as well as within organelles of eukaryotic cells such as the nucleus, mitochondria, endoplasmic reticulum, Golgi, and storage compartments such as the fungal vacuole. Therefore, cells need zinc transporters so that they can efficiently take up the metal and move it around within cells. In addition, because zinc levels in the environment can vary drastically, the activity of many of these transporters and other components of zinc homeostasis is regulated at the level of transcription by zinc-responsive transcription factors. Mechanisms of post-transcriptional control are also important for zinc homeostasis. In this review, the focus will be on our current knowledge of zinc transporters and their regulation by zinc-responsive transcription factors and other mechanisms in fungi because these organisms have served as useful paradigms of zinc homeostasis in all organisms. With this foundation, extension to other organisms will be made where warranted.
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Affiliation(s)
- David J Eide
- Department of Nutritional Sciences, University of Wisconsin-Madison, Madison, WI, USA
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Anderl A, Kolmar H, Fuchsbauer HL. The metal-binding properties of the long chaplin from Streptomyces mobaraensis: A bioinformatic and biochemical approach. J Inorg Biochem 2019; 202:110878. [PMID: 31698184 DOI: 10.1016/j.jinorgbio.2019.110878] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2019] [Revised: 09/05/2019] [Accepted: 10/02/2019] [Indexed: 02/07/2023]
Abstract
Chaplins are amphiphilic proteins coating the surface of aerial hyphae under formation of amyloid-like rodlet layers in streptomycetes. The long chaplin from Streptomyces mobaraensis, Sm-Chp1, harbors extended histidine-rich stretches allowing protein attachment to metal affinity resins. A comprehensive BLASTP search revealed similarity with many putative metal-binding proteins but the deduced sequence motifs were not shared by histidine-rich domains of well-studied proteins. Biochemical analyses showed affinity of Sm-Chp1 for Ni2+, Cu2+ and Zn2+, a binding capacity of 7-8 metal ions, and dissociation constants in a double digit micromolar range. The occurrence of genes for membrane-bound metal transporters and several intra- and extracellular metalloenzymes in the genome of S. mobaraensis suggests that Sm-Chp1 may be a novel type of translocase shifting metals across the rodlet layer from the environment into the cell wall.
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Affiliation(s)
- Anita Anderl
- Department of Chemical Engineering and Biotechnology, University of Applied Sciences of Darmstadt, Stephanstraße 7, 64295 Darmstadt, Germany; Department of Chemistry, Technische Universität Darmstadt, Alarich-Weiß-Straße 12, 64287 Darmstadt, Germany
| | - Harald Kolmar
- Department of Chemistry, Technische Universität Darmstadt, Alarich-Weiß-Straße 12, 64287 Darmstadt, Germany
| | - Hans-Lothar Fuchsbauer
- Department of Chemical Engineering and Biotechnology, University of Applied Sciences of Darmstadt, Stephanstraße 7, 64295 Darmstadt, Germany.
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Sala D, Giachetti A, Rosato A. An atomistic view of the YiiP structural changes upon zinc(II) binding. Biochim Biophys Acta Gen Subj 2019; 1863:1560-1567. [PMID: 31176764 DOI: 10.1016/j.bbagen.2019.06.001] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2019] [Revised: 05/28/2019] [Accepted: 06/03/2019] [Indexed: 10/26/2022]
Abstract
BACKGROUND YiiP is a bacterial zinc-for-proton antiporter belonging to the cation diffusion facilitator family. The zinc(II) ions are transported across the cell membrane, from the cytosol to the extracellular space. METHODS We performed atomistic molecular dynamics simulations of the YiiP dimer with zinc(II) ions in solution to elucidate how the metal ions interact with the protein while moving from the cytosol to the transport site. RESULTS We observed that of the two cavities of the dimer, only one was accessible from the cytosol during transport. Zinc(II) binding to D49 of the transport site triggered a rearrangement of the transmembrane domain that closed the accessible cavity. Finally, we analyzed the free-energy profiles of metal transit in the channel and observed the existence of a high barrier preventing release from the transport site. CONCLUSIONS The observed dynamics is consistent with the dimer-dimer interface forming a stable scaffold against which the rest of the trans-membrane rearranges. GENERAL SIGNIFICANCE Zinc(II) transporters are present in all kingdoms of life. The present study highlights structural features that might be of general relevance.
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Affiliation(s)
- Davide Sala
- Magnetic Resonance Center (CERM), University of Florence, Tuscany, Sesto Fiorentino, Italy
| | - Andrea Giachetti
- Consorzio Interuniversitario di Risonanze Magnetiche di Metallo Proteine, Tuscany, Sesto Fiorentino, Italy
| | - Antonio Rosato
- Magnetic Resonance Center (CERM), University of Florence, Tuscany, Sesto Fiorentino, Italy; Consorzio Interuniversitario di Risonanze Magnetiche di Metallo Proteine, Tuscany, Sesto Fiorentino, Italy; Department of Chemistry, University of Florence, Tuscany, Sesto Fiorentino, Italy.
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Cotrim CA, Jarrott RJ, Martin JL, Drew D. A structural overview of the zinc transporters in the cation diffusion facilitator family. Acta Crystallogr D Struct Biol 2019; 75:357-367. [PMID: 30988253 PMCID: PMC6465983 DOI: 10.1107/s2059798319003814] [Citation(s) in RCA: 30] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2018] [Accepted: 03/19/2019] [Indexed: 01/07/2023] Open
Abstract
The cation diffusion facilitators (CDFs) are a family of membrane-bound proteins that maintain cellular homeostasis of essential metal ions. In humans, the zinc-transporter CDF family members (ZnTs) play important roles in zinc homeostasis. They do this by facilitating zinc efflux from the cytoplasm to the extracellular space across the plasma membrane or into intracellular organelles. Several ZnTs have been implicated in human health owing to their association with type 2 diabetes and neurodegenerative diseases. Although the structure determination of CDF family members is not trivial, recent advances in membrane-protein structural biology have resulted in two structures of bacterial YiiPs and several structures of their soluble C-terminal domains. These data reveal new insights into the molecular mechanism of ZnT proteins, suggesting a unique rocking-bundle mechanism that provides alternating access to the metal-binding site.
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Affiliation(s)
- Camila A. Cotrim
- Griffith Institute for Drug Discovery, Griffith University, Nathan, QLD 4111, Australia
| | - Russell J. Jarrott
- Griffith Institute for Drug Discovery, Griffith University, Nathan, QLD 4111, Australia
| | - Jennifer L. Martin
- Griffith Institute for Drug Discovery, Griffith University, Nathan, QLD 4111, Australia
| | - David Drew
- Department of Biochemistry and Biophysics, Stockholm University, SE-106 91 Stockholm, Sweden
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Golan Y, Alhadeff R, Warshel A, Assaraf YG. ZnT2 is an electroneutral proton-coupled vesicular antiporter displaying an apparent stoichiometry of two protons per zinc ion. PLoS Comput Biol 2019; 15:e1006882. [PMID: 30893306 PMCID: PMC6443192 DOI: 10.1371/journal.pcbi.1006882] [Citation(s) in RCA: 28] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2018] [Revised: 04/01/2019] [Accepted: 02/18/2019] [Indexed: 01/29/2023] Open
Abstract
Zinc is a vital trace element crucial for the proper function of some 3,000 cellular proteins. Specifically, zinc is essential for key physiological processes including nucleic acid metabolism, regulation of gene expression, signal transduction, cell division, immune- and nervous system functions, wound healing, and apoptosis. Consequently, impairment of zinc homeostasis disrupts key cellular functions resulting in various human pathologies. Mammalian zinc transport proceeds via two transporter families ZnT and ZIP. However, the detailed mechanism of action of ZnT2, which is responsible for vesicular zinc accumulation and zinc secretion into breast milk during lactation, is currently unknown. Moreover, although the putative coupling of zinc transport to the proton gradient in acidic vesicles has been suggested, it has not been conclusively established. Herein we modeled the mechanism of action of ZnT2 and demonstrated both computationally and experimentally, using functional zinc transport assays, that ZnT2 is indeed a proton-coupled zinc antiporter. Bafilomycin A1, a specific inhibitor of vacuolar-type proton ATPase (V-ATPase) which alkalizes acidic vesicles, abolished ZnT2-dependent zinc transport into intracellular vesicles. Moreover, using LysoTracker Red and Lyso-pHluorin, we further showed that upon transient ZnT2 overexpression in intracellular vesicles and addition of exogenous zinc, the vesicular pH underwent alkalization, presumably due to a proton-zinc antiport; this phenomenon was reversed in the presence of TPEN, a specific zinc chelator. Finally, based on computational energy calculations, we propose that ZnT2 functions as an antiporter with a stoichiometry of 2H+/Zn2+ ion. Hence, ZnT2 is a proton motive force-driven, electroneutral vesicular zinc exchanger, concentrating zinc in acidic vesicles on the expense of proton extrusion to the cytoplasm. Herein we explored the mechanism of action of the human ZnT2 zinc transporter. ZnT2 is essential for zinc accumulation in breast milk and is therefore of paramount medical significance. Expanding on our previous study, we herein present energy calculations suggesting that ZnT2 functions as a proton/zinc antiporter. Our calculations consist of electrostatic and pKa calculations as well as zinc binding free-energy curves. Upon integration of our calculation results, we conclude that ZnT2 functions as an antiporter with a 2H+/Zn2+ stoichiometry, construct a Monte Carlo model to test this mode of ZnT2 transport activity, and validate our computational results experimentally using live human breast epithelial cells. These functional experiments reveal that ZnT2 cannot function in the absence of protons suggesting that it operates as a substrate-induced alternating-access transporter, displaying an apparent 2H+/Zn2+ stoichiometry.
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Affiliation(s)
- Yarden Golan
- The Fred Wyszkowski Cancer Research Laboratory, Department of Biology, Technion-Israel Institute of Technology, Haifa, Israel
| | - Raphael Alhadeff
- Department of Chemistry, University of Southern California, Los Angeles, California
| | - Arieh Warshel
- Department of Chemistry, University of Southern California, Los Angeles, California
| | - Yehuda G. Assaraf
- The Fred Wyszkowski Cancer Research Laboratory, Department of Biology, Technion-Israel Institute of Technology, Haifa, Israel
- * E-mail:
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Barber‐Zucker S, Hall J, Mangapuram SV, Kass I, Kolusheva S, MacMillan F, Zarivach R, Henn A. Metal binding to the dynamic cytoplasmic domain of the cation diffusion facilitator (CDF) protein MamM induces a ‘locked‐in’ configuration. FEBS J 2019; 286:2193-2215. [DOI: 10.1111/febs.14795] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2018] [Revised: 02/02/2019] [Accepted: 02/25/2019] [Indexed: 01/03/2023]
Affiliation(s)
- Shiran Barber‐Zucker
- Department of Life Sciences Ben‐Gurion University of the Negev Beer Sheva Israel
- The National Institute for Biotechnology in the Negev Ben‐Gurion University of the Negev Beer Sheva Israel
- Ilse Katz Institute for Nanoscale Science and Technology Ben‐Gurion University of the Negev Beer Sheva Israel
| | - Jenny Hall
- School of Chemistry University of East Anglia Norwich Research Park UK
| | | | - Itamar Kass
- The National Institute for Biotechnology in the Negev Ben‐Gurion University of the Negev Beer Sheva Israel
| | - Sofiya Kolusheva
- Ilse Katz Institute for Nanoscale Science and Technology Ben‐Gurion University of the Negev Beer Sheva Israel
| | - Fraser MacMillan
- School of Chemistry University of East Anglia Norwich Research Park UK
| | - Raz Zarivach
- Department of Life Sciences Ben‐Gurion University of the Negev Beer Sheva Israel
- The National Institute for Biotechnology in the Negev Ben‐Gurion University of the Negev Beer Sheva Israel
- Ilse Katz Institute for Nanoscale Science and Technology Ben‐Gurion University of the Negev Beer Sheva Israel
| | - Arnon Henn
- Faculty of Biology Technion‐ Israel Institute of Technology Haifa Israel
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Golan Y, Alhadeff R, Glaser F, Ganoth A, Warshel A, Assaraf YG. Demonstrating aspects of multiscale modeling by studying the permeation pathway of the human ZnT2 zinc transporter. PLoS Comput Biol 2018; 14:e1006503. [PMID: 30388104 PMCID: PMC6241132 DOI: 10.1371/journal.pcbi.1006503] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2018] [Revised: 11/14/2018] [Accepted: 09/11/2018] [Indexed: 11/18/2022] Open
Abstract
Multiscale modeling provides a very powerful means of studying complex biological systems. An important component of this strategy involves coarse-grained (CG) simplifications of regions of the system, which allow effective exploration of complex systems. Here we studied aspects of CG modeling of the human zinc transporter ZnT2. Zinc is an essential trace element with 10% of the proteins in the human proteome capable of zinc binding. Thus, zinc deficiency or impairment of zinc homeostasis disrupt key cellular functions. Mammalian zinc transport proceeds via two transporter families: ZnT and ZIP; however, little is known about the zinc permeation pathway through these transporters. As a step towards this end, we herein undertook comprehensive computational analyses employing multiscale techniques, focusing on the human zinc transporter ZnT2 and its bacterial homologue, YiiP. Energy calculations revealed a favorable pathway for zinc translocation via alternating access. We then identified key residues presumably involved in the passage of zinc ions through ZnT2 and YiiP, and functionally validated their role in zinc transport using site-directed mutagenesis of ZnT2 residues. Finally, we use a CG Monte Carlo simulation approach to sample the transition between the inward-facing and the outward-facing states. We present our structural models of the inward- and outward-facing conformations of ZnT2 as a blueprint prototype of the transporter conformations, including the putative permeation pathway and participating residues. The insights gained from this study may facilitate the delineation of the pathways of other zinc transporters, laying the foundations for the molecular basis underlying ion permeation. This may possibly facilitate the development of therapeutic interventions in pathological states associated with zinc deficiency and other disorders based on loss-of-function mutations in solute carriers.
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Affiliation(s)
- Yarden Golan
- The Fred Wyszkowski Cancer Research Laboratory, Dept. of Biology, Technion-Israel Institute of Technology, Haifa, Israel
| | - Raphael Alhadeff
- Department of Chemistry, University of Southern California, Los Angeles, CA, United States of America
| | - Fabian Glaser
- Lorry I. Lokey Interdisciplinary Center for Life Sciences and Engineering, Technion-Israel Institute of Technology, Haifa, Israel
| | - Assaf Ganoth
- The Interdisciplinary Center (IDC), Herzliya, Israel
| | - Arieh Warshel
- Department of Chemistry, University of Southern California, Los Angeles, CA, United States of America
- * E-mail: (AW); (YGA)
| | - Yehuda G. Assaraf
- The Fred Wyszkowski Cancer Research Laboratory, Dept. of Biology, Technion-Israel Institute of Technology, Haifa, Israel
- * E-mail: (AW); (YGA)
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Evaluation of the roles of the cytosolic N-terminus and His-rich loop of ZNT proteins using ZNT2 and ZNT3 chimeric mutants. Sci Rep 2018; 8:14084. [PMID: 30237557 PMCID: PMC6147782 DOI: 10.1038/s41598-018-32372-8] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2018] [Accepted: 09/07/2018] [Indexed: 12/01/2022] Open
Abstract
The physiological roles of Zn transporter (ZNT) proteins are being increasingly recognized, and three dimensional structures of ZNT bacterial homologs have facilitated our understanding of their biochemical characteristics at the molecular level. However, the biological role of the unique structural features of vertebrate ZNTs, which are absent in their bacterial homologues, is not completely understood. These ZNT sequences include a cytosolic His-rich loop between transmembrane helices IV and V and the cytosolic N-terminus. This study investigated the contribution of these features to zinc transport by ZNT proteins. The importance of the His residues in the cytosolic His-rich loop was investigated using ZNT2 Ala substitution and deletion mutants. The presence of His residues was not essential for zinc transport, even though they possibly participate in modulation of zinc transport activity. Furthermore, we determined the role of the N-terminus by characterizing ZNT2 and ZNT3 domain-swapped and deletion mutants. Unexpectedly, the N-terminus was also not essential for zinc transport by ZNT2 and the domain-swapped ZNT2 mutant, in which the cytosolic His-rich loop was substituted with that of ZNT3. These results provide molecular insights into understanding the roles of the cytosolic parts of ZNT2, ZNT3, and probably other members of their subgroup.
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