1
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Johansen NT, Bonaccorsi M, Bengtsen T, Larsen AH, Tidemand FG, Pedersen MC, Huda P, Berndtsson J, Darwish T, Yepuri NR, Martel A, Pomorski TG, Bertarello A, Sansom MS, Rapp M, Crehuet R, Schubeis T, Lindorff-Larsen K, Pintacuda G, Arleth L. Mg 2+-dependent conformational equilibria in CorA and an integrated view on transport regulation. eLife 2022; 11:71887. [PMID: 35129435 PMCID: PMC8865849 DOI: 10.7554/elife.71887] [Citation(s) in RCA: 12] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2021] [Accepted: 02/04/2022] [Indexed: 11/13/2022] Open
Abstract
The CorA family of proteins regulates the homeostasis of divalent metal ions in many bacteria, archaea, and eukaryotic mitochondria, making it an important target in the investigation of the mechanisms of transport and its functional regulation. Although numerous structures of open and closed channels are now available for the CorA family, the mechanism of the transport regulation remains elusive. Here, we investigated the conformational distribution and associated dynamic behaviour of the pentameric Mg2+ channel CorA at room temperature using small-angle neutron scattering (SANS) in combination with molecular dynamics (MD) simulations and solid-state nuclear magnetic resonance spectroscopy (NMR). We find that neither the Mg2+-bound closed structure nor the Mg2+-free open forms are sufficient to explain the average conformation of CorA. Our data support the presence of conformational equilibria between multiple states, and we further find a variation in the behaviour of the backbone dynamics with and without Mg2+. We propose that CorA must be in a dynamic equilibrium between different non-conducting states, both symmetric and asymmetric, regardless of bound Mg2+ but that conducting states become more populated in Mg2+-free conditions. These properties are regulated by backbone dynamics and are key to understanding the functional regulation of CorA.
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Affiliation(s)
| | - Marta Bonaccorsi
- Centre de RMN à Très hauts Champs de Lyon, UMR 5280, CNRS, University of Lyon, Villeurbanne, France
| | - Tone Bengtsen
- Department of Biology, University of Copenhagen, Copenhagen N, Denmark
| | - Andreas Haahr Larsen
- Condensed Matter Physics, Niels Bohr Institute, University of Copenhagen, Copenhagen E, Denmark
| | | | - Martin Cramer Pedersen
- Condensed Matter Physics, Niels Bohr Institute, University of Copenhagen, Copenhagen E, Denmark
| | - Pie Huda
- Australian Institute for Bioengineering and Nanotechnology, University of Queensland, Brisbane, Australia
| | - Jens Berndtsson
- Department of Biochemistry and Biophysics, Stockholm University, Stockholm, Sweden
| | - Tamim Darwish
- National Deuteration Facility, Australian Nuclear Science and Technology Organization, Lucas Heights, Australia
| | - Nageshewar Rao Yepuri
- National Deuteration Facility, Australian Nuclear Science and Technology Organization, Lucas Heights, Australia
| | | | - Thomas Günther Pomorski
- Department of Plant and Environmental Sciences, University of Copenhagen, Frederiksberg, Denmark
| | - Andrea Bertarello
- Centre de RMN à Très hauts Champs de Lyon, UMR 5280, CNRS, University of Lyon, Villeurbanne, France
| | - Mark Sp Sansom
- Department of Biochemistry, University of Oxford, Oxford, United Kingdom
| | - Mikaela Rapp
- Department of Biochemistry and Biophysics, Stockholm University, Stockholm, Sweden
| | - Ramon Crehuet
- Department of Biology, University of Copenhagen, Copenhagen N, Denmark
| | - Tobias Schubeis
- Centre de RMN à Très hauts Champs de Lyon, UMR 5280, CNRS, University of Lyon, Villeurbanne, France
| | | | - Guido Pintacuda
- Centre de RMN à Très hauts Champs de Lyon, UMR 5280, CNRS, University of Lyon, Villeurbanne, France
| | - Lise Arleth
- Condensed Matter Physics, Niels Bohr Institute, University of Copenhagen, Copenhagen, Denmark
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2
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Goyal A, Bittleston LS, Leventhal GE, Lu L, Cordero O. Interactions between strains govern the eco-evolutionary dynamics of microbial communities. eLife 2022; 11:74987. [PMID: 35119363 PMCID: PMC8884728 DOI: 10.7554/elife.74987] [Citation(s) in RCA: 29] [Impact Index Per Article: 14.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2021] [Accepted: 02/03/2022] [Indexed: 11/13/2022] Open
Abstract
Genomic data has revealed that genotypic variants of the same species, that is, strains, coexist and are abundant in natural microbial communities. However, it is not clear if strains are ecologically equivalent, and at what characteristic genetic distance they might exhibit distinct interactions and dynamics. Here, we address this problem by tracking 10 taxonomically diverse microbial communities from the pitcher plant Sarracenia purpurea in the laboratory for more than 300 generations. Using metagenomic sequencing, we reconstruct their dynamics over time and across scales, from distant phyla to closely related genotypes. We find that most strains are not ecologically equivalent and exhibit distinct dynamical patterns, often being significantly more correlated with strains from another species than their own. Although even a single mutation can affect laboratory strains, on average, natural strains typically decouple in their dynamics beyond a genetic distance of 100 base pairs. Using mathematical consumer-resource models, we show that these taxonomic patterns emerge naturally from ecological interactions between community members, but only if the interactions are coarse-grained at the level of strains, not species. Finally, by analyzing genomic differences between strains, we identify major functional hubs such as transporters, regulators, and carbohydrate-catabolizing enzymes, which might be the basis for strain-specific interactions. Our work suggests that fine-scale genetic differences in natural communities could be created and stabilized via the rapid diversification of ecological interactions between strains.
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Affiliation(s)
- Akshit Goyal
- Department of Physics, Massachusetts Institute of Technology, Cambridge, United States
| | - Leonora S Bittleston
- Department of Civil and Environmental Engineering, Massachusetts Institute of Technology, Cambridge, United States
| | - Gabriel E Leventhal
- Department of Civil and Environmental Engineering, Massachusetts Institute of Technology, Cambridge, United States
| | - Lu Lu
- Department of Civil and Environmental Engineering, Massachusetts Institute of Technology, Cambridge, United States
| | - Otto Cordero
- Department of Civil and Environmental Engineering, Massachusetts Institute of Technology, Cambridge, United States
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3
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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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4
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Abstract
Metals and metalloids have been used alongside antibiotics in livestock production for a long time. The potential and acute negative impact on the environment and human health of these livestock feed supplements has prompted lawmakers to ban or discourage the use of some or all of these supplements. This article provides an overview of current use in the European Union and the United States, detected metal resistance determinants, and the proteins and mechanisms responsible for conferring copper and zinc resistance in bacteria. A detailed description of the most common copper and zinc metal resistance determinants is given to illustrate not only the potential danger of coselecting antibiotic resistance genes but also the potential to generate bacterial strains with an increased potential to be pathogenic to humans. For example, the presence of a 20-gene copper pathogenicity island is highlighted since bacteria containing this gene cluster could be readily isolated from copper-fed pigs, and many pathogenic strains, including Escherichia coli O104:H4, contain this potential virulence factor, suggesting a potential link between copper supplements in livestock and the evolution of pathogens.
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5
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Kowatz T, Maguire ME. Loss of cytosolic Mg 2+ binding sites in the Thermotoga maritima CorA Mg 2+ channel is not sufficient for channel opening. Biochim Biophys Acta Gen Subj 2018; 1863:25-30. [PMID: 30293964 DOI: 10.1016/j.bbagen.2018.09.001] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2018] [Revised: 08/29/2018] [Accepted: 09/03/2018] [Indexed: 10/28/2022]
Abstract
The CorA Mg2+ channel is a homopentamer with five-fold symmetry. Each monomer consists of a large cytoplasmic domain and two transmembrane helices connected via a short periplasmic loop. In the Thermotoga maritima CorA crystal structure, a Mg2+ is bound between D89 of one monomer and D253 of the adjacent monomer (M1 binding site). Release of Mg2+ from these sites has been hypothesized to cause opening of the channel. We generated mutants to disrupt Mg2+ interaction with the M1 site. Crystal structures of the D89K/D253K and D89R/D253R mutants, determined to 3.05 and 3.3 Å, respectively, showed no significant structural differences with the wild type structure despite absence of Mg2+ at the M1 sites. Both mutants still appear to be in the closed state. All three mutant CorA proteins exhibited transport of 63Ni2+, indicating functionality. Thus, absence of Mg2+ from the M1 sites neither causes channel opening nor prevents function. We also provide evidence that the T. maritima CorA is a Mg2+ channel and not a Co2+ channel.
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Affiliation(s)
- Thomas Kowatz
- Department of Pharmacology, School of Medicine, Case Western Reserve University, Cleveland, OH 44106-4965, USA
| | - Michael E Maguire
- Department of Pharmacology, School of Medicine, Case Western Reserve University, Cleveland, OH 44106-4965, USA.
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6
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Schmitz J, Tierbach A, Lenz H, Meschenmoser K, Knoop V. Membrane protein interactions between different Arabidopsis thaliana MRS2-type magnesium transporters are highly permissive. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2013; 1828:2032-40. [DOI: 10.1016/j.bbamem.2013.05.019] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/29/2012] [Revised: 05/06/2013] [Accepted: 05/22/2013] [Indexed: 12/25/2022]
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7
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Palombo I, Daley DO, Rapp M. Why Is the GMN Motif Conserved in the CorA/Mrs2/Alr1 Superfamily of Magnesium Transport Proteins? Biochemistry 2013; 52:4842-7. [DOI: 10.1021/bi4007397] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Isolde Palombo
- Center for Biomembrane
Research,
Department of Biochemistry and Biophysics, Stockholm University, SE-106 91 Stockholm, Sweden
| | - Daniel O. Daley
- Center for Biomembrane
Research,
Department of Biochemistry and Biophysics, Stockholm University, SE-106 91 Stockholm, Sweden
| | - Mikaela Rapp
- Division of Biophysics, Department
of Medical Biochemistry and Biophysics, Karolinska Institutet, SE-171 77 Stockholm, Sweden
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8
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Lenz H, Dombinov V, Dreistein J, Reinhard MR, Gebert M, Knoop V. Magnesium deficiency phenotypes upon multiple knockout of Arabidopsis thaliana MRS2 clade B genes can be ameliorated by concomitantly reduced calcium supply. PLANT & CELL PHYSIOLOGY 2013; 54:1118-31. [PMID: 23628997 DOI: 10.1093/pcp/pct062] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/13/2023]
Abstract
Plant MRS2 membrane protein family members have been shown to play important roles in magnesium uptake and homeostasis. Single and double knockouts for two Arabidopsis thaliana genes, AtMRS2-1 and AtMRS2-5, have previously not shown significant phenotypes even under limiting Mg(2+) supply although both are strongly expressed already in early seedlings. Together with AtMRS2-10, these genes form clade B of the AtMRS2 gene family. We now succeeded in obtaining homozygous AtMRS2-1/10 double and AtMRS2-1/5/10 triple knockout lines after selection under increased magnesium supply. Although wilting early, both new mutant lines develop fully and are also fertile under standard magnesium supply, but show severe developmental retardation under limiting Mg(2+) concentrations. To investigate nutrient dependency of germination and seedling development under various conditions, including variable supplies of Mg(2+), Ca(2+), Zn(2+), Mn(2+), Co(2+), Cd(2+) and Cu(2+), in a reproducible and economical way, we employed a small-scale liquid culturing system in 24-well plate set-ups. This allowed the growth and monitoring of individual plantlets of different mutant lines under several nutritional conditions in parallel, and the scoring and statistical evaluation of developmental stages and biomass accumulation. Detrimental effects of higher concentrations of these elements were similar in mutants and the wild type. However, growth retardation phenotypes seen upon hydroponic cultivation under low Mg(2+) could be ameliorated when Ca(2+) concentrations were concomitantly lowered, supporting indications for an important interplay of these two most abundant divalent cations in the nutrient homeostasis of plants.
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Affiliation(s)
- Henning Lenz
- Abteilung Molekulare Evolution, IZMB-Institut für Zelluläre und Molekulare Botanik, Universität Bonn, Kirschallee 1, D-53115 Bonn, Germany
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9
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Exploring the structure and function of Thermotoga maritima CorA reveals the mechanism of gating and ion selectivity in Co2+/Mg2+ transport. Biochem J 2013; 451:365-74. [PMID: 23425532 PMCID: PMC3629940 DOI: 10.1042/bj20121745] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
The CorA family of divalent cation transporters utilizes Mg2+ and Co2+ as
primary substrates. The molecular mechanism of its function, including ion selectivity and gating,
has not been fully characterized. Recently we reported a new structure of a CorA homologue from
Methanocaldococcus jannaschii, which provided novel structural details that offered
the conception of a unique gating mechanism involving conversion of an open hydrophilic gate into a
closed hydrophobic one. In the present study we report functional evidence for this novel gating
mechanism in the Thermotoga maritima CorA together with an improved crystal
structure of this CorA to 2.7 Å (1 Å=0.1 nm) resolution. The latter reveals the
organization of the selectivity filter to be similar to that of M. jannaschii CorA
and also the previously unknown organization of the second signature motif of the CorA family. The
proposed gating is achieved by a helical rotation upon the binding of a metal ion substrate to the
regulatory binding sites. Additionally, our data suggest that the preference of this CorA for
Co2+ over Mg2+ is controlled by the presence of threonine side chains in the
channel. Finally, the roles of the intracellular metal-binding sites have been assigned to increased
thermostability and regulation of the gating. These mechanisms most likely apply to the entire CorA
family as they are regulated by the highly conserved amino acids.
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10
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Structural insights into the mechanisms of Mg2+ uptake, transport, and gating by CorA. Proc Natl Acad Sci U S A 2012; 109:18459-64. [PMID: 23091000 DOI: 10.1073/pnas.1210076109] [Citation(s) in RCA: 53] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
Despite the importance of Mg(2+) for numerous cellular activities, the mechanisms underlying its import and homeostasis are poorly understood. The CorA family is ubiquitous and is primarily responsible for Mg(2+) transport. However, the key questions-such as, the ion selectivity, the transport pathway, and the gating mechanism-have remained unanswered for this protein family. We present a 3.2 Å resolution structure of the archaeal CorA from Methanocaldococcus jannaschii, which is a unique complete structure of a CorA protein and reveals the organization of the selectivity filter, which is composed of the signature motif of this family. The structure reveals that polar residues facing the channel coordinate a partially hydrated Mg(2+) during the transport. Based on these findings, we propose a unique gating mechanism involving a helical turn upon the binding of Mg(2+) to the regulatory intracellular binding sites, and thus converting a polar ion passage into a narrow hydrophobic pore. Because the amino acids involved in the uptake, transport, and gating are all conserved within the entire CorA family, we believe this mechanism is general for the whole family including the eukaryotic homologs.
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11
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Guskov A, Eshaghi S. The mechanisms of Mg2+ and Co2+ transport by the CorA family of divalent cation transporters. CURRENT TOPICS IN MEMBRANES 2012; 69:393-414. [PMID: 23046658 DOI: 10.1016/b978-0-12-394390-3.00014-8] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
The metal ions Mg(2+) and Co(2+) are essential for life, although to different degree. They have similar chemical and physical properties, but their slight differences result in Mg(2+) to be the most abundant metal ion in living cells and the trace element Co(2+) being toxic at relatively low concentrations. Specialized transporters have evolved in living cells to supply and balance the Mg(2+) and Co(2+) need of the cells. The current knowledge of the molecular mechanisms of Mg(2+) and Co(2+) -specific transporters is very limited at this point. Recently, there has been remarkable advances to understand the CorA family, a family of transporters that are able to transport both ions. These new data have increased our insights in how Mg(2+) and Co(2+) are translocated across membranes. Presently, CorA is probably the best system to study the mechanisms of Mg(2+) and Co(2+) transport. This chapter discusses the mechanisms through which CorA selects, transports, and regulates the translocation of its substrate. In addition, we highlight the physical and chemical properties of the substrates, which are important parameters required for better understanding of the transporter action.
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Affiliation(s)
- Albert Guskov
- School of Biological Sciences, Nanyang Technological University, Singapore, Republic of Singapore
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12
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Lim PH, Pisat NP, Gadhia N, Pandey A, Donovan FX, Stein L, Salt DE, Eide DJ, MacDiarmid CW. Regulation of Alr1 Mg transporter activity by intracellular magnesium. PLoS One 2011; 6:e20896. [PMID: 21738593 PMCID: PMC3125163 DOI: 10.1371/journal.pone.0020896] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2011] [Accepted: 05/12/2011] [Indexed: 12/15/2022] Open
Abstract
Mg homeostasis is critical to eukaryotic cells, but the contribution of Mg transporter activity to homeostasis is not fully understood. In yeast, Mg uptake is primarily mediated by the Alr1 transporter, which also allows low affinity uptake of other divalent cations such as Ni(2+), Mn(2+), Zn(2+) and Co(2+). Using Ni(2+) uptake to assay Alr1 activity, we observed approximately nine-fold more activity under Mg-deficient conditions. The mnr2 mutation, which is thought to block release of vacuolar Mg stores, was associated with increased Alr1 activity, suggesting Alr1 was regulated by intracellular Mg supply. Consistent with a previous report of the regulation of Alr1 expression by Mg supply, Mg deficiency and the mnr2 mutation both increased the accumulation of a carboxy-terminal epitope-tagged version of the Alr1 protein (Alr1-HA). However, Mg supply had little effect on ALR1 promoter activity or mRNA levels. In addition, while Mg deficiency caused a seven-fold increase in Alr1-HA accumulation, the N-terminally tagged and untagged Alr1 proteins increased less than two-fold. These observations argue that the Mg-dependent accumulation of the C-terminal epitope-tagged protein was primarily an artifact of its modification. Plasma membrane localization of YFP-tagged Alr1 was also unaffected by Mg supply, indicating that a change in Alr1 location did not explain the increased activity we observed. We conclude that variation in Alr1 protein accumulation or location does not make a substantial contribution to its regulation by Mg supply, suggesting Alr1 activity is directly regulated via as yet unknown mechanisms.
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Affiliation(s)
- Phaik Har Lim
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, Texas, United States of America
| | - Nilambari P. Pisat
- Department of Genetics, Washington University School of Medicine, St. Louis, Missouri, United States of America
| | - Nidhi Gadhia
- Department of Pharmacology and Pharmacokinetics, Regeneron Pharmaceuticals, Inc., Tarrytown, New York, United States of America
| | - Abhinav Pandey
- Bijvoet Center for Biomolecular Research, Faculty of Science, Utrecht University, Utrecht, The Netherlands
| | - Frank X. Donovan
- Cancer Genetics Branch, National Human Genome Research Institute, National Institutes of Health, Bethesda, Maryland, United States of America
| | - Lauren Stein
- Department of Pharmacology and Toxicology, Medical College of Wisconsin, Wauwatosa, Wisconsin, United States of America
| | - David E. Salt
- School of Biological Sciences, University of Aberdeen, Aberdeen, Scotland, United Kingdom
| | - David J. Eide
- Department of Nutritional Sciences, University of Wisconsin-Madison, Madison, Wisconsin, United States of America
| | - Colin W. MacDiarmid
- Department of Nutritional Sciences, University of Wisconsin-Madison, Madison, Wisconsin, United States of America
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13
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Wan Q, Ahmad MF, Fairman J, Gorzelle B, de la Fuente M, Dealwis C, Maguire ME. X-ray crystallography and isothermal titration calorimetry studies of the Salmonella zinc transporter ZntB. Structure 2011; 19:700-10. [PMID: 21565704 PMCID: PMC3094545 DOI: 10.1016/j.str.2011.02.011] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2010] [Revised: 02/11/2011] [Accepted: 02/21/2011] [Indexed: 11/17/2022]
Abstract
The ZntB Zn(2+) efflux system is important for maintenance of Zn(2+) homeostasis in Enterobacteria. We report crystal structures of ZntB cytoplasmic domains from Salmonella enterica serovar Typhimurium (StZntB) in dimeric and physiologically relevant homopentameric forms at 2.3 Å and 3.1 Å resolutions, respectively. The funnel-like structure is similar to that of the homologous Thermotoga maritima CorA Mg(2+) channel and a Vibrio parahaemolyticus ZntB (VpZntB) soluble domain structure. However, the central α7 helix forming the inner wall of the StZntB funnel is oriented perpendicular to the membrane instead of the marked angle seen in CorA or VpZntB. Consequently, the StZntB funnel pore is cylindrical, not tapered, which may represent an "open" form of the ZntB soluble domain. Our crystal structures and isothermal titration calorimetry data indicate that there are three Zn(2+) binding sites in the full-length ZntB, two of which could be involved in Zn(2+) transport.
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Affiliation(s)
- Qun Wan
- Department of Pharmacology, School of Medicine, Case Western Reserve University, Cleveland, OH 44106-4965, USA
| | - Md Faiz Ahmad
- Department of Pharmacology, School of Medicine, Case Western Reserve University, Cleveland, OH 44106-4965, USA
| | - James Fairman
- Department of Biochemistry and Cellular and Molecular Biology, University of Tennessee, Knoxville, TN 37996, USA
| | - Bonnie Gorzelle
- Department of Pharmacology, School of Medicine, Case Western Reserve University, Cleveland, OH 44106-4965, USA
| | - María de la Fuente
- Department of Pharmacology, School of Medicine, Case Western Reserve University, Cleveland, OH 44106-4965, USA
| | - Chris Dealwis
- Department of Pharmacology, School of Medicine, Case Western Reserve University, Cleveland, OH 44106-4965, USA
| | - Michael E. Maguire
- Department of Pharmacology, School of Medicine, Case Western Reserve University, Cleveland, OH 44106-4965, USA
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14
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Van Pham ST, Engman H, Dahlgren LG, Cornvik T, Eshaghi S. A systematic approach to isolate mono-disperse membrane proteins - purification of zinc transporter ZntB. Protein Expr Purif 2010; 72:48-54. [PMID: 20159043 DOI: 10.1016/j.pep.2010.02.006] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2009] [Revised: 02/11/2010] [Accepted: 02/11/2010] [Indexed: 10/19/2022]
Abstract
Obtaining mono-disperse and stable protein is a requirement for successful structural and biochemical investigation of proteins. For membrane proteins, such preparation is one of the major hurdles, which consequently has contributed to the slow progress in studying them. During the past few years, many screening methods have been developed to make studies of membrane proteins more efficient. Despite these advances, many membrane proteins remain challenging to even isolate in a stable and homogeneous form. The bacterial zinc transporter ZntB is such a protein, for which no isolation procedure has been reported. Here, we present a systematic approach to obtain homogeneous and mono-disperse zinc transporter ZntB in quantities sufficient for structural and biochemical studies. Important aspects of this study that can be applied to other membrane proteins are also discussed.
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Affiliation(s)
- Sally Thanh Van Pham
- Centre for Biomedical Structural Biology, School of Biological Sciences, Nanyang Technological University, Singapore
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15
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Hu J, Sharma M, Qin H, Gao FP, Cross TA. Ligand binding in the conserved interhelical loop of CorA, a magnesium transporter from Mycobacterium tuberculosis. J Biol Chem 2009; 284:15619-28. [PMID: 19346249 DOI: 10.1074/jbc.m901581200] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
CorA is a constitutively expressed magnesium transporter in many bacteria. The crystal structures of Thermotoga maritima CorA provide an excellent structural framework for continuing studies. Here, the ligand binding properties of the conserved interhelical loop, the only portion of the protein exposed to the periplasmic space, are characterized by solution nuclear magnetic resonance spectroscopy. Through titration experiments performed on the isolated transmembrane domain of Mycobacterium tuberculosis CorA, it was found that two CorA substrates (Mg2+ and Co2+) and the CorA-specific inhibitor (Co(III) hexamine chloride) bind in the loop at the same binding site. This site includes the glutamic acid residue from the conserved "MPEL" motif. The relatively large dissociation constants indicate that such interactions are weak but not atypical for channels. The present data support the hypothesis that the negatively charged loop could act as an electrostatic ring, increasing local substrate concentrations before transport across the membrane.
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Affiliation(s)
- Jian Hu
- Department of Chemistry and Biochemistry, Florida State University, Tallahassee, Florida 32306, USA
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16
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Zhu Y, Davis A, Smith BJ, Curtis J, Handman E. Leishmania major CorA-like magnesium transporters play a critical role in parasite development and virulence. Int J Parasitol 2008; 39:713-23. [PMID: 19136005 DOI: 10.1016/j.ijpara.2008.11.010] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2008] [Revised: 11/13/2008] [Accepted: 11/14/2008] [Indexed: 11/15/2022]
Abstract
Establishment of infection by Leishmania depends on the transformation of the invading metacyclic promastigotes into the obligatory intracellular amastigotes, and their subsequent survival in the macrophage phagolysosome, which is low in magnesium. We show that two Leishmania major proteins designated MGT1 and MGT2, which play a critical role in these processes, belong to the two-transmembrane domain (2-TM-GxN) cation transporter family and share homology with the major bacterial magnesium transporter CorA. Although both are present in the endoplasmic reticulum throughout the life cycle of the parasite, MGT1 is more highly expressed in the infectious metacyclic parasites, while MGT2 is enriched in the immature procyclic stages. The two proteins, although predicted to be structurally similar, have features that suggest different regulatory or gating mechanisms. The two proteins may also be functionally distinct, since only MGT1 complements an Escherichia coli DeltaCorA mutant. In addition, deletion of one mgt1 allele from L. major led to increased virulence, while deletion of one allele of mgt2 resulted in slower growth and total loss of virulence in vitro and in vivo. This loss of virulence may be due to an impaired transformation of the parasites into amastigotes. Deletion of both mgt1 alleles in the hemizygous MGT2 knockdown parasites reversed the growth defect and partially restored virulence. Our data indicate that the MGTs play a critical role in parasite growth, development and virulence.
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Affiliation(s)
- Ying Zhu
- The Walter and Eliza Hall Institute of Medical Research, Melbourne, Vic., Australia.
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17
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Regulation of CorA Mg2+ channel function affects the virulence of Salmonella enterica serovar typhimurium. J Bacteriol 2008; 190:6509-16. [PMID: 18676666 DOI: 10.1128/jb.00144-08] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The CorA Mg(2+) channel is the primary source of intracellular Mg(2+) in Salmonella enterica serovar Typhimurium. In another study, we found that a strain lacking corA was attenuated in mice and also defective for invasion and replication within Caco-2 epithelial cells (K. M. Papp-Wallace, M. Nartea, D. G. Kehres, S. Porwollik, M. McClelland, S. J. Libby, F. C. Fang, and M. E. Maguire, J. Bacteriol. 190:6517-6523, 2008). Therefore, we further examined Salmonella interaction with Caco-2 epithelial cells. Inhibiting CorA acutely or chronically with a high concentration of a selective inhibitor, Co(III) hexaammine, had no effect on S. enterica serovar Typhimurium invasion of Caco-2 epithelial cells. Complementing the corA mutation with corA from various species rescued the invasion defect only if the complementing allele was functional and if it was evolutionarily similar to S. enterica serovar Typhimurium CorA. One explanation for these results could be that regulation of CorA function is needed for optimal virulence. Further experiments examining corA transcription, CorA protein content, CorA transport, and cell Mg(2+) content indicated that both CorA expression and CorA function are differentially regulated. Moreover, the rates of Mg(2+) influx via CorA are not closely correlated with either protein levels or Mg(2+) content. We conclude that loss of the CorA protein disrupts a regulatory network(s) with the ultimate phenotype of decreased virulence. This conclusion is compatible with the microarray results in our other study, which showed that loss of corA resulted in changes in transcription (and protein expression) in multiple metabolic pathways (Papp-Wallace et al., J. Bacteriol. 190:6517-6523, 2008). Further study of the regulation of CorA expression and function provides an opportunity to dissect the complexity of Mg(2+) homeostasis and its ties to virulence within the bacterium.
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Payandeh J, Li C, Ramjeesingh M, Poduch E, Bear CE, Pai EF. Probing structure-function relationships and gating mechanisms in the CorA Mg2+ transport system. J Biol Chem 2008; 283:11721-33. [PMID: 18276588 DOI: 10.1074/jbc.m707889200] [Citation(s) in RCA: 55] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023] Open
Abstract
Recent crystal structures of the CorA Mg(2+) transport protein from Thermotoga maritima (TmCorA) revealed an unusually long ion pore putatively gated by hydrophobic residues near the intracellular end and by universally conserved asparagine residues at the periplasmic entrance. A conformational change observed in an isolated funnel domain structure also led to a proposal for the structural basis of gating. Because understanding the molecular mechanisms underlying ion channel and transporter gating remains an important challenge, we have undertaken a structure-guided engineering approach to probe structure-function relationships in TmCorA. The intracellular funnel domain is shown to constitute an allosteric regulatory module that can be engineered to promote an activated or closed state. A periplasmic gate centered about a proline-induced kink of the pore-lining helix is described where "helix-straightening" mutations produce a dramatic gain-of-function. Mutation to the narrowest constriction along the pore demonstrates that a hydrophobic gate is operational within this Mg(2+)-selective transport protein and likely forms an energetic barrier to ion flux. We also provide evidence that highly conserved acidic residues found in the short periplasmic loop are not essential for TmCorA function or Mg(2+) selectivity but may be required for proper protein folding and stability. This work extends our gating model for the CorA-Alr1-Mrs2 superfamily and reveals features that are characteristic of an ion channel. Aspects of these results that have broader implications for a range of channel and transporter families are highlighted.
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Affiliation(s)
- Jian Payandeh
- Department of Medical Biophysics, University of Toronto, Toronto, Ontario M5G 1L7, Canada.
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