1
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He Z, Tu YC, Tsai CW, Mount J, Zhang J, Tsai MF, Yuan P. Structure and function of the human mitochondrial MRS2 channel. Nat Struct Mol Biol 2025; 32:459-468. [PMID: 39609651 PMCID: PMC11922672 DOI: 10.1038/s41594-024-01420-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2023] [Accepted: 10/04/2024] [Indexed: 11/30/2024]
Abstract
The human mitochondrial RNA splicing 2 protein (MRS2) has been implicated in Mg2+ transport across mitochondrial inner membranes, thus having an important role in Mg2+ homeostasis critical for mitochondrial integrity and function. However, the molecular mechanisms underlying its fundamental channel properties such as ion selectivity and regulation remain unclear. Here we present a structural and functional investigation of MRS2. Cryo-electron microscopy structures in various ionic conditions reveal a pentameric channel architecture and the molecular basis of ion permeation and potential regulation mechanisms. Electrophysiological analyses demonstrate that MRS2 is a Ca2+-regulated, nonselective channel permeable to Mg2+, Ca2+, Na+ and K+, which contrasts with its prokaryotic ortholog, CorA, operating as a Mg2+-gated Mg2+ channel. Moreover, a conserved arginine ring within the pore of MRS2 functions to restrict cation movements, thus preventing the channel from collapsing the proton motive force that drives mitochondrial adenosine triphosphate synthesis. Together, our results provide a molecular framework for further understanding MRS2 in mitochondrial function and disease.
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Affiliation(s)
- Zhihui He
- Department of Cell Biology and Physiology, Washington University School of Medicine, Saint Louis, MO, USA
| | - Yung-Chi Tu
- Department of Physiology and Biophysics, University of Colorado Anschutz Medical Campus, Aurora, CO, USA
- Department of Molecular Physiology and Biological Physics, University of Virginia, Charlottesville, VA, USA
| | - Chen-Wei Tsai
- Department of Physiology and Biophysics, University of Colorado Anschutz Medical Campus, Aurora, CO, USA
- Department of Molecular Physiology and Biological Physics, University of Virginia, Charlottesville, VA, USA
| | - Jonathan Mount
- Department of Cell Biology and Physiology, Washington University School of Medicine, Saint Louis, MO, USA
- Department of Pharmacological Sciences, Icahn School of Medicine at Mount Sinai, New York, NY, USA
| | - Jingying Zhang
- Department of Cell Biology and Physiology, Washington University School of Medicine, Saint Louis, MO, USA
- Department of Pharmacological Sciences, Icahn School of Medicine at Mount Sinai, New York, NY, USA
| | - Ming-Feng Tsai
- Department of Physiology and Biophysics, University of Colorado Anschutz Medical Campus, Aurora, CO, USA.
- Department of Molecular Physiology and Biological Physics, University of Virginia, Charlottesville, VA, USA.
| | - Peng Yuan
- Department of Cell Biology and Physiology, Washington University School of Medicine, Saint Louis, MO, USA.
- Department of Pharmacological Sciences, Icahn School of Medicine at Mount Sinai, New York, NY, USA.
- Department of Neuroscience, Icahn School of Medicine at Mount Sinai, New York, NY, USA.
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2
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Tu MM, Carfrae LA, Rachwalski K, French S, Catacutan D, Gordzevich R, MacNair CR, Speagle ME, Werah F, Stokes JM, Brown ED. Exploiting the fitness cost of metallo-β-lactamase expression can overcome antibiotic resistance in bacterial pathogens. Nat Microbiol 2025; 10:53-65. [PMID: 39747690 DOI: 10.1038/s41564-024-01883-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2023] [Accepted: 11/13/2024] [Indexed: 01/04/2025]
Abstract
Carbapenems are last-resort antibiotics for treating bacterial infections. The widespread acquisition of metallo-β-lactamases, such as VIM-2, contributes to the emergence of carbapenem-resistant pathogens, and currently, no metallo-β-lactamase inhibitors are available in the clinic. Here we show that bacteria expressing VIM-2 have impaired growth in zinc-deprived environments, including human serum and murine infection models. Using transcriptomic, genomic and chemical probes, we identified molecular pathways critical for VIM-2 expression under zinc limitation. In particular, disruption of envelope stress response pathways reduced the growth of VIM-2-expressing bacteria in vitro and in vivo. Furthermore, we showed that VIM-2 expression disrupts the integrity of the outer membrane, rendering VIM-2-expressing bacteria more susceptible to azithromycin. Using a systemic murine infection model, we showed azithromycin's therapeutic potential against VIM-2-expressing pathogens. In all, our findings provide a framework to exploit the fitness trade-offs of resistance, potentially accelerating the discovery of additional treatments for infections caused by multidrug-resistant bacteria.
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Affiliation(s)
- Megan M Tu
- Institute of Infectious Disease Research, McMaster University, Hamilton, Ontario, Canada
- Biochemistry and Biomedical Sciences, McMaster University, Hamilton, Ontario, Canada
- David Braley Centre for Antibiotic Discovery, McMaster University, Hamilton, Ontario, Canada
| | - Lindsey A Carfrae
- Institute of Infectious Disease Research, McMaster University, Hamilton, Ontario, Canada
- Biochemistry and Biomedical Sciences, McMaster University, Hamilton, Ontario, Canada
- David Braley Centre for Antibiotic Discovery, McMaster University, Hamilton, Ontario, Canada
| | - Kenneth Rachwalski
- Institute of Infectious Disease Research, McMaster University, Hamilton, Ontario, Canada
- Biochemistry and Biomedical Sciences, McMaster University, Hamilton, Ontario, Canada
- David Braley Centre for Antibiotic Discovery, McMaster University, Hamilton, Ontario, Canada
| | - Shawn French
- Institute of Infectious Disease Research, McMaster University, Hamilton, Ontario, Canada
- Biochemistry and Biomedical Sciences, McMaster University, Hamilton, Ontario, Canada
- David Braley Centre for Antibiotic Discovery, McMaster University, Hamilton, Ontario, Canada
| | - Denise Catacutan
- Institute of Infectious Disease Research, McMaster University, Hamilton, Ontario, Canada
- Biochemistry and Biomedical Sciences, McMaster University, Hamilton, Ontario, Canada
- David Braley Centre for Antibiotic Discovery, McMaster University, Hamilton, Ontario, Canada
| | - Rodion Gordzevich
- Institute of Infectious Disease Research, McMaster University, Hamilton, Ontario, Canada
- Biochemistry and Biomedical Sciences, McMaster University, Hamilton, Ontario, Canada
- David Braley Centre for Antibiotic Discovery, McMaster University, Hamilton, Ontario, Canada
| | - Craig R MacNair
- Institute of Infectious Disease Research, McMaster University, Hamilton, Ontario, Canada
- Biochemistry and Biomedical Sciences, McMaster University, Hamilton, Ontario, Canada
- David Braley Centre for Antibiotic Discovery, McMaster University, Hamilton, Ontario, Canada
| | - Melissa E Speagle
- Institute of Infectious Disease Research, McMaster University, Hamilton, Ontario, Canada
- Biochemistry and Biomedical Sciences, McMaster University, Hamilton, Ontario, Canada
- David Braley Centre for Antibiotic Discovery, McMaster University, Hamilton, Ontario, Canada
| | - Firas Werah
- Institute of Infectious Disease Research, McMaster University, Hamilton, Ontario, Canada
- Biochemistry and Biomedical Sciences, McMaster University, Hamilton, Ontario, Canada
- David Braley Centre for Antibiotic Discovery, McMaster University, Hamilton, Ontario, Canada
| | - Jonathan M Stokes
- Institute of Infectious Disease Research, McMaster University, Hamilton, Ontario, Canada
- Biochemistry and Biomedical Sciences, McMaster University, Hamilton, Ontario, Canada
- David Braley Centre for Antibiotic Discovery, McMaster University, Hamilton, Ontario, Canada
| | - Eric D Brown
- Institute of Infectious Disease Research, McMaster University, Hamilton, Ontario, Canada.
- Biochemistry and Biomedical Sciences, McMaster University, Hamilton, Ontario, Canada.
- David Braley Centre for Antibiotic Discovery, McMaster University, Hamilton, Ontario, Canada.
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3
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Molina-Sánchez MD, Martínez-Abarca F, Millán V, Mestre MR, Stehantsev P, Stetsenko A, Guskov A, Toro N. Adaptive immunity of type VI CRISPR-Cas systems associated with reverse transcriptase-Cas1 fusion proteins. Nucleic Acids Res 2024; 52:14229-14243. [PMID: 39673266 DOI: 10.1093/nar/gkae1154] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2024] [Revised: 10/29/2024] [Accepted: 11/05/2024] [Indexed: 12/16/2024] Open
Abstract
Cas13-containing type VI CRISPR-Cas systems specifically target RNA; however, the mechanism of spacer acquisition remains unclear. We have previously reported the association of reverse transcriptase-Cas1 (RT-Cas1) fusion proteins with certain types of VI-A systems. Here, we show that RT-Cas1 fusion proteins are also recruited by type VI-B systems in bacteria from gut microbiomes, constituting a VI-B1 variant system that includes a CorA-encoding locus in addition to the CRISPR array and the RT-Cas1/Cas2 adaptation module. We found that type VI RT-CRISPR systems were functional for spacer acquisition, CRISPR array processing and interference activity, demonstrating that adaptive immunity mediated by these systems can function independently of other in trans systems. We provide evidence that the RT associated with these systems enables spacer acquisition from RNA molecules. We also found that CorA encoded by type VI-B1 RT-associated systems can transport divalent metal ions and downregulate Cas13b-mediated RNA interference. These findings highlight the importance of RTs in RNA-targeting CRISPR-Cas systems, potentially enabling the integration of RNA-derived spacers into CRISPR arrays as a mechanism against RNA-based invaders in specific environments.
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Affiliation(s)
- María Dolores Molina-Sánchez
- Department of Soil and Plant Microbiology, Estación Experimental del Zaidín, Consejo Superior de Investigaciones Científicas, Structure, Dynamics and Function of Bacterial Genomes, Grupo de Ecología Genética de la Rizosfera, C/Profesor Albareda 1, 18008 Granada, Spain
| | - Francisco Martínez-Abarca
- Department of Soil and Plant Microbiology, Estación Experimental del Zaidín, Consejo Superior de Investigaciones Científicas, Structure, Dynamics and Function of Bacterial Genomes, Grupo de Ecología Genética de la Rizosfera, C/Profesor Albareda 1, 18008 Granada, Spain
| | - Vicenta Millán
- Department of Soil and Plant Microbiology, Estación Experimental del Zaidín, Consejo Superior de Investigaciones Científicas, Structure, Dynamics and Function of Bacterial Genomes, Grupo de Ecología Genética de la Rizosfera, C/Profesor Albareda 1, 18008 Granada, Spain
| | - Mario Rodríguez Mestre
- Department of Soil and Plant Microbiology, Estación Experimental del Zaidín, Consejo Superior de Investigaciones Científicas, Structure, Dynamics and Function of Bacterial Genomes, Grupo de Ecología Genética de la Rizosfera, C/Profesor Albareda 1, 18008 Granada, Spain
- Section of Microbiology, Department of Biology, University of Copenhagen, Universitetsparken 15, 2100 Copenhagen, Denmark
| | - Pavlo Stehantsev
- Groningen Biomolecular & Biotechnology Institute, University of Groningen, Nijenborgh 7, 9747 AG Groningen, The Netherlands
| | - Artem Stetsenko
- Groningen Biomolecular & Biotechnology Institute, University of Groningen, Nijenborgh 7, 9747 AG Groningen, The Netherlands
| | - Albert Guskov
- Groningen Biomolecular & Biotechnology Institute, University of Groningen, Nijenborgh 7, 9747 AG Groningen, The Netherlands
| | - Nicolás Toro
- Department of Soil and Plant Microbiology, Estación Experimental del Zaidín, Consejo Superior de Investigaciones Científicas, Structure, Dynamics and Function of Bacterial Genomes, Grupo de Ecología Genética de la Rizosfera, C/Profesor Albareda 1, 18008 Granada, Spain
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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 PMCID: PMC10932157 DOI: 10.3390/ijms25053045] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 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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Lai LTF, Balaraman J, Zhou F, Matthies D. Cryo-EM structures of human magnesium channel MRS2 reveal gating and regulatory mechanisms. Nat Commun 2023; 14:7207. [PMID: 37938562 PMCID: PMC10632456 DOI: 10.1038/s41467-023-42599-3] [Citation(s) in RCA: 10] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2023] [Accepted: 10/16/2023] [Indexed: 11/09/2023] Open
Abstract
Magnesium ions (Mg2+) play an essential role in cellular physiology. In mitochondria, protein and ATP synthesis and various metabolic pathways are directly regulated by Mg2+. MRS2, a magnesium channel located in the inner mitochondrial membrane, mediates the influx of Mg2+ into the mitochondrial matrix and regulates Mg2+ homeostasis. Knockdown of MRS2 in human cells leads to reduced uptake of Mg2+ into mitochondria and disruption of the mitochondrial metabolism. Despite the importance of MRS2, the Mg2+ translocation and regulation mechanisms of MRS2 are still unclear. Here, using cryo-EM we report the structures of human MRS2 in the presence and absence of Mg2+ at 2.8 Å and 3.3 Å, respectively. From the homo-pentameric structures, we identify R332 and M336 as major gating residues, which are then tested using mutagenesis and two cellular divalent ion uptake assays. A network of hydrogen bonds is found connecting the gating residue R332 to the soluble domain, potentially regulating the gate. Two Mg2+-binding sites are identified in the MRS2 soluble domain, distinct from the two sites previously reported in CorA, a homolog of MRS2 in prokaryotes. Altogether, this study provides the molecular basis for understanding the Mg2+ translocation and regulatory mechanisms of MRS2.
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Affiliation(s)
- Louis Tung Faat Lai
- Unit on Structural Biology, Division of Basic and Translational Biophysics, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD, 20892, USA
| | - Jayashree Balaraman
- Unit on Structural Biology, Division of Basic and Translational Biophysics, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD, 20892, USA
| | - Fei Zhou
- Unit on Structural Biology, Division of Basic and Translational Biophysics, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD, 20892, USA
| | - Doreen Matthies
- Unit on Structural Biology, Division of Basic and Translational Biophysics, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD, 20892, USA.
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6
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Raghavan D, Patinharekkara SC, Elampilay ST, Payatatti VKI, Charles S, Veeraraghavan S, Kadiyalath J, Vandana S, Purayil SK, Prasadam H, Anitha SJ. New insights into bacterial Zn homeostasis and molecular architecture of the metal resistome in soil polluted with nano zinc oxide. ECOTOXICOLOGY AND ENVIRONMENTAL SAFETY 2023; 263:115222. [PMID: 37418939 DOI: 10.1016/j.ecoenv.2023.115222] [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: 03/27/2023] [Revised: 06/19/2023] [Accepted: 06/29/2023] [Indexed: 07/09/2023]
Abstract
Accumulation of nano ZnO (nZnO) in soils could be toxic to bacterial communities through disruption of Zn homeostasis. Under such conditions, bacterial communities strive to maintain cellular Zn levels by accentuation of appropriate cellular machinery. In this study, soil was exposed to a gradient (50-1000 mg Zn kg-1) of nZnO for evaluating their effects on genes involved in Zn homeostasis (ZHG). The responses were compared with similar levels of its bulk counterpart (bZnO). It was observed that ZnO (as nZnO or bZnO) induced a plethora of influx and efflux transporters as well as metallothioneins (MTs) and metallochaperones mediated by an array of Zn sensitive regulatory proteins. Major influx system identified was the ZnuABC transporter, while important efflux transporters identified were CzcCBA, ZntA, YiiP and the major regulator was Zur. The response of communities was dose- dependent at lower concentrations (<500 mg Zn kg-1 as nZnO or bZnO). However, at 1000 mg Zn kg-1, a size-dependent threshold of gene/gene family abundances was evident. Under nZnO, a poor adaptation to toxicity induced anaerobic conditions due to deployment of major influx and secondary detoxifying systems as well as poor chelation of free Zn ions was evident. Moreover, Zn homeostasis related link with biofilm formation and virulence were accentuated under nZnO than bZnO. While these findings were verified by PCoA and Procrustes analysis, Network analysis and taxa vs ZHG associations also substantiated that a stronger Zn shunting mechanism was induced under nZnO due to higher toxicity. Molecular crosstalks with systems governing Cu and Fe homeostasis were also evident. Expression analysis of important resistance genes by qRT-PCR showed good alignment with the predictive metagenome data, thereby validating our findings. From the study it was evident that the induction of detoxifying and resistant genes was greatly lowered under nZnO, which markedly hampered Zn homeostasis among the soil bacterial communities.
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Affiliation(s)
- Dinesh Raghavan
- ICAR-Indian Institute of Spices Research, Marikunnu PO, Kozhikode, Kerala, India
| | | | | | | | - Sona Charles
- ICAR-Indian Institute of Spices Research, Marikunnu PO, Kozhikode, Kerala, India
| | | | - Jayarajan Kadiyalath
- ICAR-Indian Institute of Spices Research, Marikunnu PO, Kozhikode, Kerala, India
| | - Sajith Vandana
- National Institute of Technology, NIT Campus PO, Kozhikode, Kerala, India
| | | | - Haritha Prasadam
- ICAR-Indian Institute of Spices Research, Marikunnu PO, Kozhikode, Kerala, India
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Dey S, Patel A, Haloi N, Srimayee S, Paul S, Barik GK, Akhtar N, Shaw D, Hazarika G, Prusty BM, Kumar M, Santra MK, Tajkhorshid E, Bhattacharjee S, Manna D. Quinoline Thiourea-Based Zinc Ionophores with Antibacterial Activity. J Med Chem 2023; 66:11078-11093. [PMID: 37466499 DOI: 10.1021/acs.jmedchem.3c00368] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 07/20/2023]
Abstract
The increasing resistance of bacteria to commercially available antibiotics threatens patient safety in healthcare settings. Perturbation of ion homeostasis has emerged as a potential therapeutic strategy to fight against antibacterial resistance and other channelopathies. This study reports the development of 8-aminoquinoline (QN) derivatives and their transmembrane Zn2+ transport activities. Our findings showed that a potent QN-based Zn2+ transporter exhibits promising antibacterial properties against Gram-positive bacteria with reduced hemolytic activity and cytotoxicity to mammalian cells. Furthermore, this combination showed excellent in vivo efficacy against Staphylococcus aureus. Interestingly, this combination prevented bacterial resistance and restored susceptibility of gentamicin and methicillin-resistant S. aureus to commercially available β-lactam and other antibiotics that had lost their activity against the drug-resistant bacterial strain. Our findings suggest that the transmembrane transport of Zn2+ by QN derivatives could be a promising strategy to combat bacterial infections and restore the activity of other antibiotics.
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Affiliation(s)
- Subhasis Dey
- Department of Chemistry, Indian Institute of Technology Guwahati, Guwahati, Assam 781039, India
| | - Anjali Patel
- Centre for Environment, Indian Institute of Technology Guwahati, Guwahati, Assam 781039, India
| | - Nandan Haloi
- Theoretical and Computational Biophysics Group, NIH Center for Macromolecular Modeling and Bioinformatics, Beckman Institute for Advanced Science and Technology, Department of Biochemistry, and Center for Biophysics and Quantitative Biology, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, United States
| | - Soumya Srimayee
- Department of Chemistry, Indian Institute of Technology Guwahati, Guwahati, Assam 781039, India
| | - Suman Paul
- Department of Molecular Biology and Bioinformatics, Tripura University (A Central University), Suryamaninagar, Tripura 799022, India
| | | | - Nasim Akhtar
- Department of Chemistry, Indian Institute of Technology Guwahati, Guwahati, Assam 781039, India
| | - Dipanjan Shaw
- Department of Chemistry, Indian Institute of Technology Guwahati, Guwahati, Assam 781039, India
| | - Gunanka Hazarika
- Centre for Environment, Indian Institute of Technology Guwahati, Guwahati, Assam 781039, India
| | - Biswa Mohan Prusty
- Department of Chemistry, Indian Institute of Technology Guwahati, Guwahati, Assam 781039, India
| | - Mohit Kumar
- Department of Chemistry, Indian Institute of Technology Guwahati, Guwahati, Assam 781039, India
| | | | - Emad Tajkhorshid
- Theoretical and Computational Biophysics Group, NIH Center for Macromolecular Modeling and Bioinformatics, Beckman Institute for Advanced Science and Technology, Department of Biochemistry, and Center for Biophysics and Quantitative Biology, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, United States
| | - Surajit Bhattacharjee
- Department of Molecular Biology and Bioinformatics, Tripura University (A Central University), Suryamaninagar, Tripura 799022, India
| | - Debasis Manna
- Department of Chemistry, Indian Institute of Technology Guwahati, Guwahati, Assam 781039, India
- Centre for Environment, Indian Institute of Technology Guwahati, Guwahati, Assam 781039, India
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8
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Lai LTF, Balaraman J, Zhou F, Matthies D. Cryo-EM structures of human magnesium channel MRS2 reveal gating and regulatory mechanisms. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.08.22.553867. [PMID: 37662257 PMCID: PMC10473633 DOI: 10.1101/2023.08.22.553867] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 09/05/2023]
Abstract
Magnesium ions (Mg2+) play an essential role in cellular physiology. In mitochondria, protein and ATP synthesis and various metabolic pathways are directly regulated by Mg2+. MRS2, a magnesium channel located in the inner mitochondrial membrane, mediates the influx of Mg2+ into the mitochondrial matrix and regulates Mg2+ homeostasis. Knockdown of MRS2 in human cells leads to reduced uptake of Mg2+ into mitochondria and disruption of the mitochondrial metabolism. Despite the importance of MRS2, the Mg2+ translocation and regulation mechanisms of MRS2 are still unclear. Here, using cryo-EM we determined the structure of human MRS2 in the presence and absence of Mg2+ at 2.8 Å and 3.3 Å, respectively. From the homo-pentameric structures, we identified R332 and M336 as major gating residues, which were then tested using mutagenesis and two cellular divalent ion uptake assays. A network of hydrogen bonds was found connecting the gating residue R332 to the soluble domain, potentially regulating the gate. Two Mg2+-binding sites were identified in the MRS2 soluble domain, distinct from the two sites previously reported in CorA, a homolog of MRS2 in prokaryotes. Altogether, this study provides the molecular basis for understanding the Mg2+ translocation and regulatory mechanisms of MRS2.
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Affiliation(s)
- Louis Tung Faat Lai
- Unit on Structural Biology, Division of Basic and Translational Biophysics, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda MD 20892, USA
| | - Jayashree Balaraman
- Unit on Structural Biology, Division of Basic and Translational Biophysics, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda MD 20892, USA
| | - Fei Zhou
- Unit on Structural Biology, Division of Basic and Translational Biophysics, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda MD 20892, USA
| | - Doreen Matthies
- Unit on Structural Biology, Division of Basic and Translational Biophysics, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda MD 20892, USA
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9
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He Z, Tu YC, Tsai CW, Mount J, Zhang J, Tsai MF, Yuan P. Structure and function of the human mitochondrial MRS2 channel. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.08.12.553106. [PMID: 37645897 PMCID: PMC10462007 DOI: 10.1101/2023.08.12.553106] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 08/31/2023]
Abstract
The human Mitochondrial RNA Splicing 2 protein (MRS2) has been implicated in Mg2+ transport across mitochondrial inner membranes, thus playing an important role in Mg2+ homeostasis critical for mitochondrial integrity and function. However, the molecular mechanisms underlying its fundamental channel properties such as ion selectivity and regulation remain unclear. Here, we present structural and functional investigation of MRS2. Cryo-electron microscopy structures in various ionic conditions reveal a pentameric channel architecture and the molecular basis of ion permeation and potential regulation mechanisms. Electrophysiological analyses demonstrate that MRS2 is a Ca2+-regulated, non-selective channel permeable to Mg2+, Ca2+, Na+ and K+, which contrasts with its prokaryotic ortholog, CorA, operating as a Mg2+-gated Mg2+ channel. Moreover, a conserved arginine ring within the pore of MRS2 functions to restrict cation movements, likely preventing the channel from collapsing the proton motive force that drives mitochondrial ATP synthesis. Together, our results provide a molecular framework for further understanding MRS2 in mitochondrial function and disease.
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Affiliation(s)
- Zhihui He
- Department of Cell Biology and Physiology, Washington University School of Medicine, Saint Louis, MO, USA
- These authors contributed equally to this work
| | - Yung-Chi Tu
- Department of Physiology and Biophysics, University of Colorado Anschutz Medical Campus, Aurora, CO, USA
- These authors contributed equally to this work
| | - Chen-Wei Tsai
- Department of Physiology and Biophysics, University of Colorado Anschutz Medical Campus, Aurora, CO, USA
| | - Jonathan Mount
- Department of Cell Biology and Physiology, Washington University School of Medicine, Saint Louis, MO, USA
- Department of Pharmacological Sciences, Icahn School of Medicine at Mount Sinai, New York, NY, USA
| | - Jingying Zhang
- Department of Cell Biology and Physiology, Washington University School of Medicine, Saint Louis, MO, USA
- Department of Pharmacological Sciences, Icahn School of Medicine at Mount Sinai, New York, NY, USA
| | - Ming-Feng Tsai
- Department of Physiology and Biophysics, University of Colorado Anschutz Medical Campus, Aurora, CO, USA
| | - Peng Yuan
- Department of Cell Biology and Physiology, Washington University School of Medicine, Saint Louis, MO, USA
- Department of Pharmacological Sciences, Icahn School of Medicine at Mount Sinai, New York, NY, USA
- Department of Neuroscience, Icahn School of Medicine at Mount Sinai, New York, NY, USA
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10
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Li M, Li Y, Lu Y, Li J, Lu X, Ren Y, Wen T, Wang Y, Chang S, Zhang X, Yang X, Shen Y. Molecular basis of Mg 2+ permeation through the human mitochondrial Mrs2 channel. Nat Commun 2023; 14:4713. [PMID: 37543649 PMCID: PMC10404273 DOI: 10.1038/s41467-023-40516-2] [Citation(s) in RCA: 14] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2023] [Accepted: 07/25/2023] [Indexed: 08/07/2023] Open
Abstract
Mitochondrial RNA splicing 2 (Mrs2), a eukaryotic CorA ortholog, enables Mg2+ to permeate the inner mitochondrial membrane and plays an important role in mitochondrial metabolic function. However, the mechanism by which Mrs2 permeates Mg2+ remains unclear. Here, we report four cryo-electron microscopy (cryo-EM) reconstructions of Homo sapiens Mrs2 (hMrs2) under various conditions. All of these hMrs2 structures form symmetrical pentamers with very similar pentamer and protomer conformations. A special structural feature of Cl--bound R-ring, which consists of five Arg332 residues, was found in the hMrs2 structure. Molecular dynamics simulations and mitochondrial Mg2+ uptake assays show that the R-ring may function as a charge repulsion barrier, and Cl- may function as a ferry to jointly gate Mg2+ permeation in hMrs2. In addition, the membrane potential is likely to be the driving force for Mg2+ permeation. Our results provide insights into the channel assembly and Mg2+ permeation of hMrs2.
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Affiliation(s)
- Ming Li
- State Key Laboratory of Medicinal Chemical Biology and Frontiers Science Center for Cell Responses, College of Life Sciences, Nankai University, Tianjin, 300350, China
| | - Yang Li
- State Key Laboratory of Medicinal Chemical Biology and Frontiers Science Center for Cell Responses, College of Life Sciences, Nankai University, Tianjin, 300350, China
| | - Yue Lu
- State Key Laboratory of Medicinal Chemical Biology and Frontiers Science Center for Cell Responses, College of Life Sciences, Nankai University, Tianjin, 300350, China
| | - Jianhui Li
- State Key Laboratory of Medicinal Chemical Biology and Frontiers Science Center for Cell Responses, College of Life Sciences, Nankai University, Tianjin, 300350, China
| | - Xuhang Lu
- State Key Laboratory of Medicinal Chemical Biology and Frontiers Science Center for Cell Responses, College of Life Sciences, Nankai University, Tianjin, 300350, China
| | - Yue Ren
- State Key Laboratory of Medicinal Chemical Biology and Frontiers Science Center for Cell Responses, College of Life Sciences, Nankai University, Tianjin, 300350, China
| | - Tianlei Wen
- State Key Laboratory of Medicinal Chemical Biology and Frontiers Science Center for Cell Responses, College of Life Sciences, Nankai University, Tianjin, 300350, China
| | - Yaojie Wang
- State Key Laboratory of Medicinal Chemical Biology and Frontiers Science Center for Cell Responses, College of Life Sciences, Nankai University, Tianjin, 300350, China
| | - Shenghai Chang
- Department of Biophysics and Department of Pathology of Sir Run Run Shaw Hospital, School of Medicine, Zhejiang University, Hangzhou, 310058, China
- Center of Cryo Electron Microscopy, Zhejiang University, Hangzhou, 310058, China
| | - Xing Zhang
- Department of Biophysics and Department of Pathology of Sir Run Run Shaw Hospital, School of Medicine, Zhejiang University, Hangzhou, 310058, China
- Center of Cryo Electron Microscopy, Zhejiang University, Hangzhou, 310058, China
| | - Xue Yang
- State Key Laboratory of Medicinal Chemical Biology and Frontiers Science Center for Cell Responses, College of Life Sciences, Nankai University, Tianjin, 300350, China.
| | - Yuequan Shen
- State Key Laboratory of Medicinal Chemical Biology and Frontiers Science Center for Cell Responses, College of Life Sciences, Nankai University, Tianjin, 300350, China.
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11
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Huynh U, Nguyen HN, Trinh BK, Elhaj J, Zastrow ML. A bioinformatic analysis of zinc transporters in intestinal Lactobacillaceae. Metallomics 2023; 15:mfad044. [PMID: 37463796 PMCID: PMC10391621 DOI: 10.1093/mtomcs/mfad044] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2023] [Accepted: 07/17/2023] [Indexed: 07/20/2023]
Abstract
As the second most abundant transition element and a crucial cofactor for many proteins, zinc is essential for the survival of all living organisms. To maintain required zinc levels and prevent toxic overload, cells and organisms have a collection of metal transport proteins for uptake and efflux of zinc. In bacteria, metal transport proteins are well defined for model organisms and many pathogens, but fewer studies have explored metal transport proteins, including those for zinc, in commensal bacteria from the gut microbiota. The healthy human gut microbiota comprises hundreds of species and among these, bacteria from the Lactobacillaceae family are well documented to have various beneficial effects on health. Furthermore, changes in dietary metal intake, such as for zinc and iron, are frequently correlated with changes in abundance of Lactobacillaceae. Few studies have explored zinc requirements and zinc homeostasis mechanisms in Lactobacillaceae, however. Here we applied a bioinformatics approach to identify and compare predicted zinc uptake and efflux proteins in several Lactobacillaceae genera of intestinal relevance. Few Lactobacillaceae had zinc transporters currently annotated in proteomes retrieved from the UniProt database, but protein sequence-based homology searches revealed that high-affinity ABC transporter genes are likely common, albeit with genus-specific domain features. P-type ATPase transporters are probably also common and some Lactobacillaceae genera code for predicted zinc efflux cation diffusion facilitators. This analysis confirms that Lactobacillaceae harbor genes for various zinc transporter homologs, and provides a foundation for systematic experimental studies to elucidate zinc homeostasis mechanisms in these bacteria.
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Affiliation(s)
- Uyen Huynh
- Department of Chemistry, University of Houston, Houston, TX 77204, USA
| | - Hazel N Nguyen
- Department of Chemistry, University of Houston, Houston, TX 77204, USA
| | - Brittany K Trinh
- Department of Chemistry, University of Houston, Houston, TX 77204, USA
| | - Joanna Elhaj
- Department of Chemistry, University of Houston, Houston, TX 77204, USA
| | - Melissa L Zastrow
- Department of Chemistry, University of Houston, Houston, TX 77204, USA
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12
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Guardia AE, Wagner A, Busalmen JP, Di Capua C, Cortéz N, Beligni MV. The draft genome of Andean Rhodopseudomonas sp. strain AZUL predicts genome plasticity and adaptation to chemical homeostasis. BMC Microbiol 2022; 22:297. [PMID: 36494611 PMCID: PMC9733117 DOI: 10.1186/s12866-022-02685-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2021] [Accepted: 10/29/2022] [Indexed: 12/13/2022] Open
Abstract
The genus Rhodopseudomonas comprises purple non-sulfur bacteria with extremely versatile metabolisms. Characterization of several strains revealed that each is a distinct ecotype highly adapted to its specific micro-habitat. Here we present the sequencing, genomic comparison and functional annotation of AZUL, a Rhodopseudomonas strain isolated from a high altitude Andean lagoon dominated by extreme conditions and fluctuating levels of chemicals. Average nucleotide identity (ANI) analysis of 39 strains of this genus showed that the genome of AZUL is 96.2% identical to that of strain AAP120, which suggests that they belong to the same species. ANI values also show clear separation at the species level with the rest of the strains, being more closely related to R. palustris. Pangenomic analyses revealed that the genus Rhodopseudomonas has an open pangenome and that its core genome represents roughly 5 to 12% of the total gene repertoire of the genus. Functional annotation showed that AZUL has genes that participate in conferring genome plasticity and that, in addition to sharing the basal metabolic complexity of the genus, it is also specialized in metal and multidrug resistance and in responding to nutrient limitation. Our results also indicate that AZUL might have evolved to use some of the mechanisms involved in resistance as redox reactions for bioenergetic purposes. Most of those features are shared with strain AAP120, and mainly involve the presence of additional orthologs responsible for the mentioned processes. Altogether, our results suggest that AZUL, one of the few bacteria from its habitat with a sequenced genome, is highly adapted to the extreme and changing conditions that constitute its niche.
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Affiliation(s)
- Aisha E. Guardia
- grid.473319.b0000 0004 0461 9871Ingeniería de Interfases y Bioprocesos, Instituto de Tecnología de Materiales (INTEMA-CONICET-UNMdP), Mar del Plata, Argentina
| | - Agustín Wagner
- grid.10814.3c0000 0001 2097 3211Facultad de Ciencias Agrarias, Universidad Nacional de Rosario, Zavalla, Argentina
| | - Juan P. Busalmen
- grid.473319.b0000 0004 0461 9871Ingeniería de Interfases y Bioprocesos, Instituto de Tecnología de Materiales (INTEMA-CONICET-UNMdP), Mar del Plata, Argentina
| | - Cecilia Di Capua
- grid.501777.30000 0004 0638 1836Facultad de Ciencias Bioquímicas y Farmacéuticas, Instituto de Biología Molecular y Celular de Rosario (IBR-CONICET-UNR), Universidad Nacional de Rosario, Rosario, Argentina
| | - Néstor Cortéz
- grid.501777.30000 0004 0638 1836Facultad de Ciencias Bioquímicas y Farmacéuticas, Instituto de Biología Molecular y Celular de Rosario (IBR-CONICET-UNR), Universidad Nacional de Rosario, Rosario, Argentina
| | - María V. Beligni
- grid.412221.60000 0000 9969 0902Instituto de Investigaciones Biológicas (IIB-CONICET-UNMdP), Facultad de Ciencias Exactas y Naturales, Universidad Nacional de Mar del Plata, Mar del Plata, Argentina
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13
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Zhu Y, Wang Y, Zhang Y, Pu M, Miao W, Bai M, Bao R, Geng J. Ion selectivity and gating behavior of the CorA-type channel Bpss1228. Front Chem 2022; 10:998075. [PMID: 36171999 PMCID: PMC9511408 DOI: 10.3389/fchem.2022.998075] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2022] [Accepted: 08/25/2022] [Indexed: 11/24/2022] Open
Abstract
Magnesium is an essential element to sustain all forms of life. Total intracellular magnesium content is determined by the balance of magnesium influx and efflux. CorA is a divalent selective channel in the metal ion transport superfamily and is the major Mg2+ uptake pathway in prokaryotes and eukaryotic mitochondria. Previous studies have demonstrated that CorA showed distinct magnesium bound closed conformation and Mg2+-free states. In addition, CorA is regulated by cytoplasmic magnesium ions and its gating mechanism has been investigated by electron paramagnetic resonance technique and molecular dynamic simulations. Here, we report a study of the putative CorA-type channel Bpss1228 from Burkholderia pseudomallei, which has been shown to be significantly associated with pseudomallei infection. We expressed and purified the Bpss1228 in full-length. Subsequently, electrophysiological experiments further investigated the electrical characteristics of Bpss1228 and revealed that it was a strictly cation-selective channel. We also proved that Bpss1228 not only possessed magnesium-mediated regulatory property a remarkable ability to be modulated by magnesium ions. Finally, we observed the three-step gating behavior of Bpss1228 on planar lipid bilayer, and further proposed a synergistic gating mechanism by which CorA family channels control intracellular magnesium homeostasis.
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Affiliation(s)
| | | | | | | | | | | | - Rui Bao
- *Correspondence: Rui Bao, ; Jia Geng,
| | - Jia Geng
- *Correspondence: Rui Bao, ; Jia Geng,
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14
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Jin F, Huang Y, Hattori M. Recent Advances in the Structural Biology of Mg 2+ Channels and Transporters. J Mol Biol 2022; 434:167729. [PMID: 35841930 DOI: 10.1016/j.jmb.2022.167729] [Citation(s) in RCA: 16] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/29/2021] [Revised: 07/06/2022] [Accepted: 07/07/2022] [Indexed: 10/17/2022]
Abstract
Magnesium ions (Mg2+) are the most abundant divalent cations in living organisms and are essential for various physiological processes, including ATP utilization and the catalytic activity of numerous enzymes. Therefore, the homeostatic mechanisms associated with cellular Mg2+ are crucial for both eukaryotic and prokaryotic organisms and are thus strictly controlled by Mg2+ channels and transporters. Technological advances in structural biology, such as the expression screening of membrane proteins, in meso phase crystallization, and recent cryo-EM techniques, have enabled the structure determination of numerous Mg2+ channels and transporters. In this review article, we provide an overview of the families of Mg2+ channels and transporters (MgtE/SLC41, TRPM6/7, CorA/Mrs2, CorC/CNNM), and discuss the structural biology prospects based on the known structures of MgtE, TRPM7, CorA and CorC.
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Affiliation(s)
- Fei Jin
- State Key Laboratory of Genetic Engineering, Shanghai Key Laboratory of Bioactive Small Molecules, Collaborative Innovation Center of Genetics and Development, Department of Physiology and Neurobiology, School of Life Sciences, Fudan University, Shanghai 200438, China
| | - Yichen Huang
- State Key Laboratory of Genetic Engineering, Shanghai Key Laboratory of Bioactive Small Molecules, Collaborative Innovation Center of Genetics and Development, Department of Physiology and Neurobiology, School of Life Sciences, Fudan University, Shanghai 200438, China
| | - Motoyuki Hattori
- State Key Laboratory of Genetic Engineering, Shanghai Key Laboratory of Bioactive Small Molecules, Collaborative Innovation Center of Genetics and Development, Department of Physiology and Neurobiology, School of Life Sciences, Fudan University, Shanghai 200438, China.
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15
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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: 3.7] [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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16
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Abstract
Klebsiella pneumoniae is an opportunistic Gram-negative pathogen that is a leading cause of healthcare-associated infections, including pneumonia, urinary tract infections, and sepsis. Essential to the colonization and infection by K. pneumoniae is the acquisition of nutrients, such as the transition metal ion zinc. Zinc has crucial structural and catalytic roles in the proteome of all organisms. Nevertheless, in excess, it has the potential to mediate significant toxicity by dysregulating the homeostasis of other transition elements, disrupting enzymatic processes, and perturbing metalloprotein cofactor acquisition. Here, we sought to elucidate the zinc detoxification mechanisms of K. pneumoniae, which remain poorly defined. Using the representative K. pneumoniae AJ218 strain, we showed that the P-type ATPase, ZntA, which is upregulated in response to cellular zinc stress, was the primary zinc efflux pathway. Deletion of zntA rendered K. pneumoniae AJ218 highly susceptible to exogenous zinc stress and manifested as an impaired growth phenotype and increased cellular accumulation of the metal. Loss of zntA also increased sensitivity to cadmium stress, indicating a role for this efflux pathway in cadmium resistance. Disruption of zinc homeostasis in the K. pneumoniae AJ218 ΔzntA strain also impacted manganese and iron homeostasis and was associated with increased production of biofilm. Collectively, this work showed the critical role of ZntA in K. pneumoniae zinc tolerance and provided a foundation for further studies on zinc homeostasis and the future development of novel antimicrobials to target this pathway. IMPORTANCE Klebsiella pneumoniae is a leading cause of healthcare-associated infections, including pneumonia, urinary tract infections, and sepsis. Treatment of K. pneumoniae infections is becoming increasingly challenging due to high levels of antibiotic resistance and the rising prevalence of carbapenem-resistant, extended-spectrum β-lactamases producing strains. Zinc is essential to the colonization and infection by many bacterial pathogens but toxic in excess. This work described the first dissection of the pathways associated with resisting extracellular zinc stress in K. pneumoniae. This study revealed that the P-type ATPase ZntA was highly upregulated in response to exogenous zinc stress and played a major role in maintaining bacterial metal homeostasis. Knowledge of how this major bacterial pathogen resists zinc stress provided a foundation for antimicrobial development studies to target and abrogate their essential function.
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17
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Keseler IM, Gama-Castro S, Mackie A, Billington R, Bonavides-Martínez C, Caspi R, Kothari A, Krummenacker M, Midford PE, Muñiz-Rascado L, Ong WK, Paley S, Santos-Zavaleta A, Subhraveti P, Tierrafría VH, Wolfe AJ, Collado-Vides J, Paulsen IT, Karp PD. The EcoCyc Database in 2021. Front Microbiol 2021; 12:711077. [PMID: 34394059 PMCID: PMC8357350 DOI: 10.3389/fmicb.2021.711077] [Citation(s) in RCA: 149] [Impact Index Per Article: 37.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2021] [Accepted: 07/02/2021] [Indexed: 11/13/2022] Open
Abstract
The EcoCyc model-organism database collects and summarizes experimental data for Escherichia coli K-12. EcoCyc is regularly updated by the manual curation of individual database entries, such as genes, proteins, and metabolic pathways, and by the programmatic addition of results from select high-throughput analyses. Updates to the Pathway Tools software that supports EcoCyc and to the web interface that enables user access have continuously improved its usability and expanded its functionality. This article highlights recent improvements to the curated data in the areas of metabolism, transport, DNA repair, and regulation of gene expression. New and revised data analysis and visualization tools include an interactive metabolic network explorer, a circular genome viewer, and various improvements to the speed and usability of existing tools.
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Affiliation(s)
- Ingrid M. Keseler
- Bioinformatics Research Group, Artificial Intelligence Center, SRI International, Menlo Park, CA, United States
| | - Socorro Gama-Castro
- Centro de Ciencias Genómicas, Universidad Nacional Autónoma de México, Cuernavaca, México
| | - Amanda Mackie
- Department of Molecular Sciences, Macquarie University, Sydney, NSW, Australia
| | - Richard Billington
- Bioinformatics Research Group, Artificial Intelligence Center, SRI International, Menlo Park, CA, United States
| | | | - Ron Caspi
- Bioinformatics Research Group, Artificial Intelligence Center, SRI International, Menlo Park, CA, United States
| | - Anamika Kothari
- Bioinformatics Research Group, Artificial Intelligence Center, SRI International, Menlo Park, CA, United States
| | - Markus Krummenacker
- Bioinformatics Research Group, Artificial Intelligence Center, SRI International, Menlo Park, CA, United States
| | - Peter E. Midford
- Bioinformatics Research Group, Artificial Intelligence Center, SRI International, Menlo Park, CA, United States
| | - Luis Muñiz-Rascado
- Centro de Ciencias Genómicas, Universidad Nacional Autónoma de México, Cuernavaca, México
| | - Wai Kit Ong
- Bioinformatics Research Group, Artificial Intelligence Center, SRI International, Menlo Park, CA, United States
| | - Suzanne Paley
- Bioinformatics Research Group, Artificial Intelligence Center, SRI International, Menlo Park, CA, United States
| | - Alberto Santos-Zavaleta
- Centro de Ciencias Genómicas, Universidad Nacional Autónoma de México, Cuernavaca, México
- Instituto de Energías Renovables, Universidad Nacional Autónoma de México, Temixco, México
| | - Pallavi Subhraveti
- Bioinformatics Research Group, Artificial Intelligence Center, SRI International, Menlo Park, CA, United States
| | - Víctor H. Tierrafría
- Centro de Ciencias Genómicas, Universidad Nacional Autónoma de México, Cuernavaca, México
| | - Alan J. Wolfe
- Department of Microbiology and Immunology, Stritch School of Medicine, Loyola University Chicago, Maywood, IL, United States
| | - Julio Collado-Vides
- Centro de Ciencias Genómicas, Universidad Nacional Autónoma de México, Cuernavaca, México
- Department of Biomedical Engineering, Boston University, Boston, MA, United States
| | - Ian T. Paulsen
- Department of Molecular Sciences, Macquarie University, Sydney, NSW, Australia
| | - Peter D. Karp
- Bioinformatics Research Group, Artificial Intelligence Center, SRI International, Menlo Park, CA, United States
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18
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Stetsenko A, Stehantsev P, Dranenko NO, Gelfand MS, Guskov A. Structural and biochemical characterization of a novel ZntB (CmaX) transporter protein from Pseudomonas aeruginosa. Int J Biol Macromol 2021; 184:760-767. [PMID: 34175341 DOI: 10.1016/j.ijbiomac.2021.06.130] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2021] [Revised: 06/16/2021] [Accepted: 06/18/2021] [Indexed: 11/19/2022]
Abstract
The 2-TM-GxN family of membrane proteins is widespread in prokaryotes and plays an important role in transport of divalent cations. The canonical signature motif, which is also a selectivity filter, has a composition of Gly-Met-Asn. Some members though deviate from this composition, however no data are available as to whether this has any functional implications. Here we report the functional and structural analysis of CmaX protein from a pathogenic Pseudomonas aeruginosa bacterium, which has a Gly-Ile-Asn signature motif. CmaX readily transports Zn2+, Mg2+, Cd2+, Ni2+ and Co2+ ions, but it does not utilize proton-symport as does ZntB from Escherichia coli. Together with the bioinformatics analysis, our data suggest that deviations from the canonical signature motif do not reveal any changes in substrate selectivity or transport and easily alter in course of evolution.
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Affiliation(s)
- Artem Stetsenko
- Groningen Biomolecular Sciences and Biotechnology Institute, University of Groningen, the Netherlands
| | - Pavlo Stehantsev
- Groningen Biomolecular Sciences and Biotechnology Institute, University of Groningen, the Netherlands
| | - Natalia O Dranenko
- Institute for Information Transmission Problems (Kharkevich Institute) RAS, Moscow, Russia
| | - Mikhail S Gelfand
- Institute for Information Transmission Problems (Kharkevich Institute) RAS, Moscow, Russia; Skolkovo Institute of Science and Technology, Moscow, Russia
| | - Albert Guskov
- Groningen Biomolecular Sciences and Biotechnology Institute, University of Groningen, the Netherlands; Moscow Institute of Physics and Technology, Dolgoprudny, Russia.
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19
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Cation Transporters of Candida albicans-New Targets to Fight Candidiasis? Biomolecules 2021; 11:biom11040584. [PMID: 33923411 PMCID: PMC8073359 DOI: 10.3390/biom11040584] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2021] [Accepted: 04/14/2021] [Indexed: 02/07/2023] Open
Abstract
Candidiasis is the wide-spread fungal infection caused by numerous strains of yeast, with the prevalence of Candida albicans. The current treatment of candidiasis is becoming rather ineffective and costly owing to the emergence of resistant strains; hence, the exploration of new possible drug targets is necessary. The most promising route is the development of novel antibiotics targeting this pathogen. In this review, we summarize such candidates found in C. albicans and those involved in the transport of (metal) cations, as the latter are essential for numerous processes within the cell; hence, disruption of their fluxes can be fatal for C. albicans.
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20
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Cunrath O, Palmer JD. An overview of Salmonella enterica metal homeostasis pathways during infection. ACTA ACUST UNITED AC 2021; 2:uqab001. [PMID: 34250489 PMCID: PMC8264917 DOI: 10.1093/femsml/uqab001] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2020] [Accepted: 03/19/2021] [Indexed: 12/14/2022]
Abstract
Nutritional immunity is a powerful strategy at the core of the battlefield between host survival and pathogen proliferation. A host can prevent pathogens from accessing biological metals such as Mg, Fe, Zn, Mn, Cu, Co or Ni, or actively intoxicate them with metal overload. While the importance of metal homeostasis for the enteric pathogen Salmonella enterica Typhimurium was demonstrated many decades ago, inconsistent results across various mouse models, diverse Salmonella genotypes, and differing infection routes challenge aspects of our understanding of this phenomenon. With expanding access to CRISPR-Cas9 for host genome manipulation, it is now pertinent to re-visit past results in the context of specific mouse models, identify gaps and incongruities in current knowledge landscape of Salmonella homeostasis, and recommend a straight path forward towards a more universal understanding of this historic host-microbe relationship.
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Affiliation(s)
- Olivier Cunrath
- Department of Zoology, University of Oxford, Zoology Research and Administration Building, 11a Mansfield Rd, Oxford, UK OX1 3SZ
| | - Jacob D Palmer
- Department of Zoology, University of Oxford, Zoology Research and Administration Building, 11a Mansfield Rd, Oxford, UK OX1 3SZ
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21
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Fu T, Cai Z, Yue Z, Yang H, Fang B, Zhang X, Fan Z, Pan X, Yang F, Jin Y, Cheng Z, Wu W, Sun B, Huigens RW, Yang L, Bai F. Evolution of Resistance to Phenazine Antibiotics in Staphylococcus aureus and Its Role During Coinfection with Pseudomonas aeruginosa. ACS Infect Dis 2021; 7:636-649. [PMID: 33650853 DOI: 10.1021/acsinfecdis.0c00837] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
In the niches that Staphylococcus aureus and Pseudomonas aeruginosa coinhabit, the later pathogen produces phenazine antibiotics to inhibit the growth of S. aureus. Recently, a group of halogenated phenazines (HPs) has been shown to have potent antimicrobial activities against Staphylococci; however, no HP-resistant mutant has been reported. Here, we demonstrate that S. aureus develops HP-resistance via single amino acid change (Arg116Cys) in a transcriptional repressor TetR21. RNA-seq analysis showed that the TetR21R116C variation caused drastic up-regulation of an adjacent gene hprS (halogenated phenazine resistance protein of S. aureus). Deletion of the hprS in the TetR21R116C background restored bacterial susceptibility to HP, while hprS overexpression in S. aureus conferred HP-resistance. The expression of HprS is under tight transcriptional control of the TetR21 via direct binding to the promoter region of hprS. The R116C mutation in TetR21 significantly reduced its DNA binding affinity. Moreover, natural phenazine antibiotics (phenazine-1-carboxylic acid and pyocyanin) and a HP analog (HP-22) are ligands for the TetR21, regulating its repressor activity. Combining homology analysis and LC-MS/MS assay we demonstrated that HprS is a phenazine efflux pump. To the best of our knowledge, we provide the first report of phenazine efflux pump in S. aureus. Interestingly, the TetR21R116C variation has been found in some clinical S. aureus isolates, and a laboratory strain of S. aureus with TetR21R116C variation showed enhanced growth competitiveness toward P. aeruginosa and promoted coinfection with P. aeruginosa in the host environment, demonstrating significance of the mutation in host infections.
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Affiliation(s)
- Tongtong Fu
- State Key Laboratory of Medicinal Chemical Biology, Key Laboratory of Molecular Microbiology and Technology of the Ministry of Education, College of Life Sciences, Nankai University, Tianjin, 300071, China
| | - Zhao Cai
- School of Medicine, Southern University of Science and Technology (SUSTec), Shenzhen 518055, China
| | - Zhuo Yue
- State Key Laboratory of Medicinal Chemical Biology, Key Laboratory of Molecular Microbiology and Technology of the Ministry of Education, College of Life Sciences, Nankai University, Tianjin, 300071, China
| | - Hongfen Yang
- Department of Medicinal Chemistry & Center for Natural Products, Drug Discovery and Development (CNPD3), College of Pharmacy, University of Florida, Gainesville, Florida 32610, United States
| | - Bo Fang
- School of Life Sciences and Medical Center, University of Science and Technology of China, Hefei, Anhui 230027, China
| | - Xinwen Zhang
- State Key Laboratory of Medicinal Chemical Biology, Key Laboratory of Molecular Microbiology and Technology of the Ministry of Education, College of Life Sciences, Nankai University, Tianjin, 300071, China
| | - Zheng Fan
- State Key Laboratory of Medicinal Chemical Biology, Key Laboratory of Molecular Microbiology and Technology of the Ministry of Education, College of Life Sciences, Nankai University, Tianjin, 300071, China
| | - Xiaolei Pan
- State Key Laboratory of Medicinal Chemical Biology, Key Laboratory of Molecular Microbiology and Technology of the Ministry of Education, College of Life Sciences, Nankai University, Tianjin, 300071, China
| | - Fan Yang
- State Key Laboratory of Medicinal Chemical Biology, Key Laboratory of Molecular Microbiology and Technology of the Ministry of Education, College of Life Sciences, Nankai University, Tianjin, 300071, China
| | - Yongxin Jin
- State Key Laboratory of Medicinal Chemical Biology, Key Laboratory of Molecular Microbiology and Technology of the Ministry of Education, College of Life Sciences, Nankai University, Tianjin, 300071, China
| | - Zhihui Cheng
- State Key Laboratory of Medicinal Chemical Biology, Key Laboratory of Molecular Microbiology and Technology of the Ministry of Education, College of Life Sciences, Nankai University, Tianjin, 300071, China
| | - Wuihui Wu
- State Key Laboratory of Medicinal Chemical Biology, Key Laboratory of Molecular Microbiology and Technology of the Ministry of Education, College of Life Sciences, Nankai University, Tianjin, 300071, China
| | - Baolin Sun
- School of Life Sciences and Medical Center, University of Science and Technology of China, Hefei, Anhui 230027, China
| | - Robert W. Huigens
- Department of Medicinal Chemistry & Center for Natural Products, Drug Discovery and Development (CNPD3), College of Pharmacy, University of Florida, Gainesville, Florida 32610, United States
| | - Liang Yang
- School of Medicine, Southern University of Science and Technology (SUSTec), Shenzhen 518055, China
| | - Fang Bai
- State Key Laboratory of Medicinal Chemical Biology, Key Laboratory of Molecular Microbiology and Technology of the Ministry of Education, College of Life Sciences, Nankai University, Tianjin, 300071, China
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22
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Tempio T, Anelli T. The pivotal role of ERp44 in patrolling protein secretion. J Cell Sci 2020; 133:133/21/jcs240366. [PMID: 33173013 DOI: 10.1242/jcs.240366] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
Interactions between protein ligands and receptors are the main language of intercellular communication; hence, how cells select proteins to be secreted or presented on the plasma membrane is a central concern in cell biology. A series of checkpoints are located along the secretory pathway, which ensure the fidelity of such protein signals (quality control). Proteins that pass the checkpoints operated in the endoplasmic reticulum (ER) by the binding immunoglobulin protein (BiP; also known as HSPA5 and GRP78) and the calnexin-calreticulin systems, must still overcome additional scrutiny in the ER-Golgi intermediate compartment (ERGIC) and the Golgi. One of the main players of this process in all metazoans is the ER-resident protein 44 (ERp44); by cycling between the ER and the Golgi, ERp44 controls the localization of key enzymes designed to act in the ER but that are devoid of suitable localization motifs. ERp44 also patrols the secretion of correctly assembled disulfide-linked oligomeric proteins. Here, we discuss the mechanisms driving ERp44 substrate recognition, with important consequences on the definition of 'thiol-mediated quality control'. We also describe how pH and zinc gradients regulate the functional cycle of ERp44, coupling quality control and membrane trafficking along the early secretory compartment.
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Affiliation(s)
- Tiziana Tempio
- Division of Genetics and Cell Biology, Vita-Salute San Raffaele University, Milan 20132, Italy.,IRCCS San Raffaele Scientific Institute, Milan 20132, Italy
| | - Tiziana Anelli
- Division of Genetics and Cell Biology, Vita-Salute San Raffaele University, Milan 20132, Italy .,IRCCS San Raffaele Scientific Institute, Milan 20132, Italy
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23
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Morante S, La Penna G, Rossi G, Stellato F. SARS-CoV-2 Virion Stabilization by Zn Binding. Front Mol Biosci 2020; 7:222. [PMID: 33195401 PMCID: PMC7533540 DOI: 10.3389/fmolb.2020.00222] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2020] [Accepted: 08/07/2020] [Indexed: 12/18/2022] Open
Abstract
Zinc plays a crucial role in the process of virion maturation inside the host cell. The accessory Cys-rich proteins expressed in SARS-CoV-2 by genes ORF7a and ORF8 are likely involved in zinc binding and in interactions with cellular antigens activated by extensive disulfide bonds. In this report we provide a proof of concept for the feasibility of a structural study of orf7a and orf8 proteins. A conceivable hypothesis is that lack of cellular zinc, or substitution thereof, might lead to a significant slowing down of viral maturation.
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Affiliation(s)
- Silvia Morante
- Dipartimento di Fisica, Università di Roma "Tor Vergata", Rome, Italy.,INFN, Sezione di Roma Tor Vergata, Rome, Italy
| | - Giovanni La Penna
- INFN, Sezione di Roma Tor Vergata, Rome, Italy.,CNR, Insitute of Chemistry of Organometallic Compounds, Firenze, Italy
| | - Giancarlo Rossi
- Dipartimento di Fisica, Università di Roma "Tor Vergata", Rome, Italy.,INFN, Sezione di Roma Tor Vergata, Rome, Italy.,Centro Fermi - Museo Storico della Fisica e Centro Studi e Ricerche "Enrico Fermi", Rome, Italy
| | - Francesco Stellato
- Dipartimento di Fisica, Università di Roma "Tor Vergata", Rome, Italy.,INFN, Sezione di Roma Tor Vergata, Rome, Italy
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24
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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: 2.8] [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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25
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Hierarchical Transcriptional Control of the LuxR Quorum-Sensing Regulon of Vibrio harveyi. J Bacteriol 2020; 202:JB.00047-20. [PMID: 32366592 DOI: 10.1128/jb.00047-20] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2020] [Accepted: 04/30/2020] [Indexed: 11/20/2022] Open
Abstract
In vibrios, quorum sensing controls hundreds of genes that are required for cell density-specific behaviors including bioluminescence, biofilm formation, competence, secretion, and swarming motility. The central transcription factor in the quorum-sensing pathway is LuxR/HapR, which directly regulates ∼100 genes in the >400-gene regulon of Vibrio harveyi Among these directly controlled genes are 15 transcription factors, which we predicted would comprise the second tier in the hierarchy of the LuxR regulon. We confirmed that LuxR binds to the promoters of these genes in vitro and quantified the extent of LuxR activation or repression of transcript levels. Transcriptome sequencing (RNA-seq) indicates that most of these transcriptional regulators control only a few genes, with the exception of MetJ, which is a global regulator. The genes regulated by these transcription factors are predicted to be involved in methionine and thiamine biosynthesis, membrane stability, RNA processing, c-di-GMP degradation, sugar transport, and other cellular processes. These data support a hierarchical model in which LuxR directly regulates 15 transcription factors that drive the second level of the gene expression cascade to influence cell density-dependent metabolic states and behaviors in V. harveyi IMPORTANCE Quorum sensing is important for survival of bacteria in nature and influences the actions of bacterial groups. In the relatively few studied examples of quorum-sensing-controlled genes, these genes are associated with competition or cooperation in complex microbial communities and/or virulence in a host. However, quorum sensing in vibrios controls the expression of hundreds of genes, and their functions are mostly unknown or uncharacterized. In this study, we identify the regulators of the second tier of gene expression in the quorum-sensing system of the aquaculture pathogen Vibrio harveyi Our identification of regulatory networks and metabolic pathways controlled by quorum sensing can be extended and compared to other Vibrio species to understand the physiology, ecology, and pathogenesis of these organisms.
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26
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Abstract
CorA proteins belong to 2-TM-GxN family of membrane proteins, and play a major role in Mg2+ transport in prokaryotes and eukaryotic mitochondria. The selection of substrate is believed to occur via the signature motif GxN, however there is no consensus how strict this selection within the family. To answer this question, we employed fluorescence-based transport assays on three different family members, namely CorA from bacterium Thermotoga maritima, CorA from the archeon Methanocaldococcus jannaschii and ZntB from bacterium Escherichia coli, reconstituted into proteoliposomes. Our results show that all three proteins readily transport Mg2+, Co2+, Ni2+ and Zn2+, but not Al3+. Despite the similarity in cation specificity, ZntB differs from the CorA proteins, as in the former transport is stimulated by a proton gradient, but in the latter by the membrane potential, confirming the hypothesis that CorA and ZntB proteins diverged to different transport mechanisms within the same protein scaffold.
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27
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Bozzi AT, Bane LB, Zimanyi CM, Gaudet R. Unique structural features in an Nramp metal transporter impart substrate-specific proton cotransport and a kinetic bias to favor import. J Gen Physiol 2019; 151:1413-1429. [PMID: 31619456 PMCID: PMC6888756 DOI: 10.1085/jgp.201912428] [Citation(s) in RCA: 20] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2019] [Accepted: 09/26/2019] [Indexed: 01/01/2023] Open
Abstract
Natural resistance-associated macrophage protein (Nramp) transporters enable uptake of essential transition metal micronutrients in numerous biological contexts. These proteins are believed to function as secondary transporters that harness the electrochemical energy of proton gradients by "coupling" proton and metal transport. Here we use the Deinococcus radiodurans (Dra) Nramp homologue, for which we have determined crystal structures in multiple conformations, to investigate mechanistic details of metal and proton transport. We untangle the proton-metal coupling behavior of DraNramp into two distinct phenomena: ΔpH stimulation of metal transport rates and metal stimulation of proton transport. Surprisingly, metal type influences substrate stoichiometry, leading to manganese-proton cotransport but cadmium uniport, while proton uniport also occurs. Additionally, a physiological negative membrane potential is required for high-affinity metal uptake. To begin to understand how Nramp's structure imparts these properties, we target a conserved salt-bridge network that forms a proton-transport pathway from the metal-binding site to the cytosol. Mutations to this network diminish voltage and ΔpH dependence of metal transport rates, alter substrate selectivity, perturb or eliminate metal-stimulated proton transport, and erode the directional bias favoring outward-to-inward metal transport under physiological-like conditions. Thus, this unique salt-bridge network may help Nramp-family transporters maximize metal uptake and reduce deleterious back-transport of acquired metals. We provide a new mechanistic model for Nramp proton-metal cotransport and propose that functional advantages may arise from deviations from the traditional model of symport.
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Affiliation(s)
- Aaron T Bozzi
- Department of Molecular and Cellular Biology, Harvard University, Cambridge, MA
| | - Lukas B Bane
- Department of Molecular and Cellular Biology, Harvard University, Cambridge, MA
| | - Christina M Zimanyi
- Department of Molecular and Cellular Biology, Harvard University, Cambridge, MA
| | - Rachelle Gaudet
- Department of Molecular and Cellular Biology, Harvard University, Cambridge, MA
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28
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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: 1.6] [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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