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Vogel K, Greinert T, Reichard M, Held C, Harms H, Maskow T. Thermodynamics and Kinetics of Glycolytic Reactions. Part II: Influence of Cytosolic Conditions on Thermodynamic State Variables and Kinetic Parameters. Int J Mol Sci 2020; 21:ijms21217921. [PMID: 33113841 PMCID: PMC7663428 DOI: 10.3390/ijms21217921] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2020] [Revised: 10/18/2020] [Accepted: 10/20/2020] [Indexed: 01/22/2023] Open
Abstract
For systems biology, it is important to describe the kinetic and thermodynamic properties of enzyme-catalyzed reactions and reaction cascades quantitatively under conditions prevailing in the cytoplasm. While in part I kinetic models based on irreversible thermodynamics were tested, here in part II, the influence of the presumably most important cytosolic factors was investigated using two glycolytic reactions (i.e., the phosphoglucose isomerase reaction (PGI) with a uni-uni-mechanism and the enolase reaction with an uni-bi-mechanism) as examples. Crowding by macromolecules was simulated using polyethylene glycol (PEG) and bovine serum albumin (BSA). The reactions were monitored calorimetrically and the equilibrium concentrations were evaluated using the equation of state ePC-SAFT. The pH and the crowding agents had the greatest influence on the reaction enthalpy change. Two kinetic models based on irreversible thermodynamics (i.e., single parameter flux-force and two-parameter Noor model) were applied to investigate the influence of cytosolic conditions. The flux-force model describes the influence of cytosolic conditions on reaction kinetics best. Concentrations of magnesium ions and crowding agents had the greatest influence, while temperature and pH-value had a medium influence on the kinetic parameters. With this contribution, we show that the interplay of thermodynamic modeling and calorimetric process monitoring allows a fast and reliable quantification of the influence of cytosolic conditions on kinetic and thermodynamic parameters.
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Affiliation(s)
- Kristina Vogel
- UFZ - Helmholtz Centre for Environmental Research, Department Environmental Microbiology, Leipzig, Permoserstr. 15, D-04318 Leipzig, Germany; (K.V.); (M.R.); (H.H.)
- Institute for Drug Development, Leipzig University Medical School, Leipzig University, Bruederstr. 34, 04103 Leipzig, Germany
| | - Thorsten Greinert
- Laboratory of Thermodynamics, Department of Biochemical and Chemical Engineering, Technische Universitaet Dortmund, Emil-Figge-Str. 70, 44227 Dortmund, Germany;
| | - Monique Reichard
- UFZ - Helmholtz Centre for Environmental Research, Department Environmental Microbiology, Leipzig, Permoserstr. 15, D-04318 Leipzig, Germany; (K.V.); (M.R.); (H.H.)
| | - Christoph Held
- Laboratory of Thermodynamics, Department of Biochemical and Chemical Engineering, Technische Universitaet Dortmund, Emil-Figge-Str. 70, 44227 Dortmund, Germany;
- Correspondence: (C.H.); (T.M.)
| | - Hauke Harms
- UFZ - Helmholtz Centre for Environmental Research, Department Environmental Microbiology, Leipzig, Permoserstr. 15, D-04318 Leipzig, Germany; (K.V.); (M.R.); (H.H.)
| | - Thomas Maskow
- UFZ - Helmholtz Centre for Environmental Research, Department Environmental Microbiology, Leipzig, Permoserstr. 15, D-04318 Leipzig, Germany; (K.V.); (M.R.); (H.H.)
- Correspondence: (C.H.); (T.M.)
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Pokharel R, Gerrits R, Schuessler JA, Frings PJ, Sobotka R, Gorbushina AA, von Blanckenburg F. Magnesium Stable Isotope Fractionation on a Cellular Level Explored by Cyanobacteria and Black Fungi with Implications for Higher Plants. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2018; 52:12216-12224. [PMID: 30351034 DOI: 10.1021/acs.est.8b02238] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/25/2023]
Abstract
In a controlled growth experiment we found that the cyanobacterium Nostoc punctiforme has a bulk cell 26Mg/24Mg ratio (expressed as δ26Mg) that is -0.27‰ lower than the growth solution at a pH of ca. 5.9. This contrasts with a recently published δ26Mg value that was 0.65‰ higher than growth solution for the black fungus Knufia petricola at similar laboratory conditions, interpreted to reflect loss of 24Mg during cell growth. By a mass balance model constrained by δ26Mg in chlorophyll extract we inferred the δ26 Mg value of the main Mg compartments in a cyanobacteria cell: free cytosolic Mg (-2.64‰), chlorophyll (1.85‰), and the nonchlorophyll-bonded Mg compartments like ATP and ribosomes (-0.64‰). The lower δ26Mg found in Nostoc punctiforme would thus result from the absence of significant Mg efflux during cell growth in combination with either (a) discrimination against 26Mg during uptake by desolvation of Mg or transport across protein channels or (b) discrimination against 24Mg in the membrane transporter during efflux. The model predicts the preferential incorporation of 26Mg in cells and plant organs low in Mg and the absence of isotope fractionation in those high in Mg, corroborated by a compilation of Mg isotope ratios from fungi, bacteria, and higher plants.
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Affiliation(s)
- Rasesh Pokharel
- GFZ German Research Centre for Geosciences , Section 3.3, Earth Surface Geochemistry, Telegrafenberg, 14473 Potsdam , Germany
- Institute of Geological Sciences , Freie Universität Berlin , 12249 Berlin , Germany
| | - Ruben Gerrits
- Department 4, Materials & Environment , BAM Federal Institute for Materials Research & Testing , 12205 Berlin , Germany
- Department of Biology, Chemistry and Pharmacy , Freie Universität Berlin , 14195 Berlin , Germany
| | - Jan A Schuessler
- GFZ German Research Centre for Geosciences , Section 3.3, Earth Surface Geochemistry, Telegrafenberg, 14473 Potsdam , Germany
| | - Patrick J Frings
- GFZ German Research Centre for Geosciences , Section 3.3, Earth Surface Geochemistry, Telegrafenberg, 14473 Potsdam , Germany
| | - Roman Sobotka
- Institute of Microbiology , Centre Algatech , 379 81 Třebon , Czech Republic
| | - Anna A Gorbushina
- Institute of Geological Sciences , Freie Universität Berlin , 12249 Berlin , Germany
- Department 4, Materials & Environment , BAM Federal Institute for Materials Research & Testing , 12205 Berlin , Germany
- Department of Biology, Chemistry and Pharmacy , Freie Universität Berlin , 14195 Berlin , Germany
| | - Friedhelm von Blanckenburg
- GFZ German Research Centre for Geosciences , Section 3.3, Earth Surface Geochemistry, Telegrafenberg, 14473 Potsdam , Germany
- Institute of Geological Sciences , Freie Universität Berlin , 12249 Berlin , Germany
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Wilson ZN, Scott AL, Dowell RD, Odorizzi G. PI(3,5)P 2 controls vacuole potassium transport to support cellular osmoregulation. Mol Biol Cell 2018; 29:1718-1731. [PMID: 29791245 PMCID: PMC6080712 DOI: 10.1091/mbc.e18-01-0015] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023] Open
Abstract
Lysosomes are dynamic organelles with critical roles in cellular physiology. The lysosomal signaling lipid phosphatidylinositol 3,5-bisphosphate (PI(3,5)P2) is a key regulator that has been implicated to control lysosome ion homeostasis, but the scope of ion transporters targeted by PI(3,5)P2 and the purpose of this regulation is not well understood. Through an unbiased screen in Saccharomyces cerevisiae, we identified loss-of-function mutations in the vacuolar H+-ATPase (V-ATPase) and in Vnx1, a vacuolar monovalent cation/proton antiporter, as suppressor mutations that relieve the growth defects and osmotic swelling of vacuoles (lysosomes) in yeast lacking PI(3,5)P2. We observed that depletion of PI(3,5)P2 synthesis in yeast causes a robust accumulation of multiple cations, most notably an ∼85 mM increase in the cellular concentration of potassium, a critical ion used by cells to regulate osmolarity. The accumulation of potassium and other cations in PI(3,5)P2-deficient yeast is relieved by mutations that inactivate Vnx1 or inactivate the V-ATPase and by mutations that increase the activity of a vacuolar cation export channel, Yvc1. Collectively, our data demonstrate that PI(3,5)P2 signaling orchestrates vacuole/lysosome cation transport to aid cellular osmoregulation.
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Affiliation(s)
- Zachary N Wilson
- Department of Molecular, Cellular, and Developmental Biology, University of Colorado, Boulder, CO 80309-0347
| | - Amber L Scott
- Department of Molecular, Cellular, and Developmental Biology, University of Colorado, Boulder, CO 80309-0347
| | - Robin D Dowell
- Department of Molecular, Cellular, and Developmental Biology, University of Colorado, Boulder, CO 80309-0347
| | - Greg Odorizzi
- Department of Molecular, Cellular, and Developmental Biology, University of Colorado, Boulder, CO 80309-0347
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Cabrera-Orefice A, Ibarra-García-Padilla R, Maldonado-Guzmán R, Guerrero-Castillo S, Luévano-Martínez LA, Pérez-Vázquez V, Gutiérrez-Aguilar M, Uribe-Carvajal S. The Saccharomyces cerevisiae mitochondrial unselective channel behaves as a physiological uncoupling system regulated by Ca2+, Mg2+, phosphate and ATP. J Bioenerg Biomembr 2015; 47:477-91. [PMID: 26530988 DOI: 10.1007/s10863-015-9632-x] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2015] [Accepted: 10/23/2015] [Indexed: 02/07/2023]
Abstract
It is proposed that the Saccharomyces cerevisiae the Mitochondrial Unselective Channel ((Sc)MUC) is tightly regulated constituting a physiological uncoupling system that prevents overproduction of reactive oxygen species (ROS). Mg(2+), Ca(2+) or phosphate (Pi) close (Sc)MUC, while ATP or a high rate of oxygen consumption open it. We assessed (Sc)MUC activity by measuring in isolated mitochondria the respiratory control, transmembrane potential (ΔΨ), swelling and production of ROS. At increasing [Pi], less [Ca(2+)] and/or [Mg(2+)] were needed to close (Sc)MUC or increase ATP synthesis. The Ca(2+)-mediated closure of (Sc)MUC was prevented by high [ATP] while the Mg(2+) or Pi effect was not. When Ca(2+) and Mg(2+) were alternatively added or chelated, (Sc)MUC opened and closed reversibly. Different effects of Ca(2+) vs Mg(2+) effects were probably due to mitochondrial Mg(2+) uptake. Our results suggest that (Sc)MUC activity is dynamically controlled by both the ATP/Pi ratio and divalent cation fluctuations. It is proposed that the reversible opening/closing of (Sc)MUC leads to physiological uncoupling and a consequent decrease in ROS production.
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Affiliation(s)
- Alfredo Cabrera-Orefice
- Departamento de Genética Molecular, Instituto de Fisiología Celular, Universidad Nacional Autónoma de México, Mexico City, Mexico
| | - Rodrigo Ibarra-García-Padilla
- Departamento de Genética Molecular, Instituto de Fisiología Celular, Universidad Nacional Autónoma de México, Mexico City, Mexico
| | - Rocío Maldonado-Guzmán
- Departamento de Genética Molecular, Instituto de Fisiología Celular, Universidad Nacional Autónoma de México, Mexico City, Mexico
| | | | - Luis A Luévano-Martínez
- Departamento de Bioquímica, Instituto de Química, Universidade de São Paulo, São Paulo, SP, Brazil
| | | | | | - Salvador Uribe-Carvajal
- Departamento de Genética Molecular, Instituto de Fisiología Celular, Universidad Nacional Autónoma de México, Mexico City, Mexico. .,Salvador Uribe-Carvajal, Department of Molecular Genetics, Instituto de Fisiología Celular, UNAM, Apdo. postal 70-242, 04510, Mexico City, Mexico.
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Bradshaw PC, Pfeiffer DR. Characterization of the respiration-induced yeast mitochondrial permeability transition pore. Yeast 2014; 30:471-83. [PMID: 24166770 DOI: 10.1002/yea.2984] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2013] [Revised: 09/29/2013] [Accepted: 10/17/2013] [Indexed: 11/11/2022] Open
Abstract
When isolated mitochondria from the yeast Saccharomyces cerevisiae oxidize respiratory substrates in the absence of phosphate and ADP, the yeast mitochondrial unselective channel, also called the yeast permeability transition pore (yPTP), opens in the inner membrane, dissipating the electrochemical gradient. ATP also induces yPTP opening. yPTP opening allows mannitol transport into isolated mitochondria of laboratory yeast strains, but mannitol is not readily permeable through the yPTP in an industrial yeast strain, Yeast Foam. The presence of oligomycin, an inhibitor of ATP synthase, allowed for respiration-induced mannitol permeability in mitochondria from this strain. Potassium (K+) had varied effects on the respiration-induced yPTP, depending on the concentration of the respiratory substrate added. At low respiratory substrate concentrations K+ inhibited respiration-induced yPTP opening, while at high substrate concentrations this effect diminished. However, at the high respiratory substrate concentrations, the presence of K+ partially prevented phosphate inhibition of yPTP opening. Phosphate was found to inhibit respiration-induced yPTP opening by binding a site on the matrix space side of the inner membrane in addition to its known inhibitory effect of donating protons to the matrix space to prevent the pH change necessary for yPTP opening. The respiration-induced yPTP was also inhibited by NAD, Mg2+, NH4 + or the oxyanion vanadate polymerized to decavanadate. The results demonstrate similar effectors of the respiration-induced yPTP as those previously described for the ATP-induced yPTP and reconcile previous strain-dependent differences in yPTP solute selectivity.
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Abstract
All living organisms require nutrient minerals for growth and have developed mechanisms to acquire, utilize, and store nutrient minerals effectively. In the aqueous cellular environment, these elements exist as charged ions that, together with protons and hydroxide ions, facilitate biochemical reactions and establish the electrochemical gradients across membranes that drive cellular processes such as transport and ATP synthesis. Metal ions serve as essential enzyme cofactors and perform both structural and signaling roles within cells. However, because these ions can also be toxic, cells have developed sophisticated homeostatic mechanisms to regulate their levels and avoid toxicity. Studies in Saccharomyces cerevisiae have characterized many of the gene products and processes responsible for acquiring, utilizing, storing, and regulating levels of these ions. Findings in this model organism have often allowed the corresponding machinery in humans to be identified and have provided insights into diseases that result from defects in ion homeostasis. This review summarizes our current understanding of how cation balance is achieved and modulated in baker's yeast. Control of intracellular pH is discussed, as well as uptake, storage, and efflux mechanisms for the alkali metal cations, Na(+) and K(+), the divalent cations, Ca(2+) and Mg(2+), and the trace metal ions, Fe(2+), Zn(2+), Cu(2+), and Mn(2+). Signal transduction pathways that are regulated by pH and Ca(2+) are reviewed, as well as the mechanisms that allow cells to maintain appropriate intracellular cation concentrations when challenged by extreme conditions, i.e., either limited availability or toxic levels in the environment.
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Morales Quinones M, Winston JT, Stromhaug PE. Propeptide of aminopeptidase 1 protein mediates aggregation and vesicle formation in cytoplasm-to-vacuole targeting pathway. J Biol Chem 2011; 287:10121-10133. [PMID: 22123825 DOI: 10.1074/jbc.m111.311696] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023] Open
Abstract
Misfolded protein aggregation causes disease and aging; autophagy counteracts this by eliminating damaged components, enabling cells to survive starvation. The cytoplasm-to-vacuole targeting pathway in yeast encompasses the aggregation of the premature form of aminopeptidase 1 (prApe1) in cytosol and its sequestration by autophagic proteins into a vesicle for vacuolar transport. We show that the propeptide of Ape1 is important for aggregation and vesicle formation and that it is sufficient for binding to prApe1 and Atg19. Defective aggregation disrupts vacuolar transport, suggesting that aggregate shape is important in vesicle formation, whereas Atg19 binding is not sufficient for vacuolar transport. Aggregation involves hydrophobicity, whereas Atg19 binding requires additional electrostatic interactions. Ape1 dodecamerization may cluster propeptides into trimeric structures, with sufficient affinity to form propeptide hexamers by binding to other dodecamers, causing aggregation. We show that Ape1 aggregates bind Atg19 and Atg8 in vitro; this could be used as a scaffold for an in vitro assay of autophagosome formation to elucidate the mechanisms of autophagy.
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Affiliation(s)
| | - Jared T Winston
- Department of Biological Sciences, University of Missouri, Columbia, Missouri 65211
| | - Per E Stromhaug
- Department of Biological Sciences, University of Missouri, Columbia, Missouri 65211.
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Standardized assay medium to measure Lactococcus lactis enzyme activities while mimicking intracellular conditions. Appl Environ Microbiol 2011; 78:134-43. [PMID: 22020503 DOI: 10.1128/aem.05276-11] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Knowledge of how the activity of enzymes is affected under in vivo conditions is essential for analyzing their regulation and constructing models that yield an integrated understanding of cell behavior. Current kinetic parameters for Lactococcus lactis are scattered through different studies and performed under different assay conditions. Furthermore, assay conditions often diverge from conditions prevailing in the intracellular environment. To establish uniform assay conditions that resemble intracellular conditions, we analyzed the intracellular composition of anaerobic glucose-limited chemostat cultures of L. lactis subsp. cremoris MG 1363. Based on this, we designed a new assay medium for enzyme activity measurements of growing cells of L. lactis, mimicking as closely as practically possible its intracellular environment. Procedures were optimized to be carried out in 96-well plates, and the reproducibility and dynamic range were checked for all enzyme activity measurements. The effects of freezing and the carryover of ammonium sulfate from the addition of coupling enzymes were also established. Activities of all 10 glycolytic and 4 fermentative enzymes were measured. Remarkably, most in vivo-like activities were lower than previously published data. Yet, the ratios of V(max) over measured in vivo fluxes were above 1. With this work, we have developed and extensively validated standard protocols for enzyme activity measurements for L. lactis.
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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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Cunningham KW. Acidic calcium stores of Saccharomyces cerevisiae. Cell Calcium 2011; 50:129-38. [PMID: 21377728 DOI: 10.1016/j.ceca.2011.01.010] [Citation(s) in RCA: 95] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/29/2010] [Revised: 01/25/2011] [Accepted: 01/31/2011] [Indexed: 02/06/2023]
Abstract
Fungi and animals constitute sister kingdoms in the eukaryotic domain of life. The major classes of transporters, channels, sensors, and effectors that move and respond to calcium ions were already highly networked in the common ancestor of fungi and animals. Since that time, some key components of the network have been moved, altered, relocalized, lost, or duplicated in the fungal and animal lineages and at the same time some of the regulatory circuitry has been dramatically rewired. Today the calcium transport and signaling networks in fungi provide a fresh perspective on the scene that has emerged from studies of the network in animal cells. This review provides an overview of calcium signaling networks in fungi, particularly the model yeast Saccharomyces cerevisiae, with special attention to the dominant roles of acidic calcium stores in fungal cell physiology.
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Affiliation(s)
- Kyle W Cunningham
- Department of Biology, Johns Hopkins University, 3400 N. Charles Street, Baltimore, MD 21218, USA.
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11
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van Eunen K, Bouwman J, Daran-Lapujade P, Postmus J, Canelas AB, Mensonides FIC, Orij R, Tuzun I, van den Brink J, Smits GJ, van Gulik WM, Brul S, Heijnen JJ, de Winde JH, Teixeira de Mattos MJ, Kettner C, Nielsen J, Westerhoff HV, Bakker BM. Measuring enzyme activities under standardized in vivo-like conditions for systems biology. FEBS J 2010; 277:749-60. [DOI: 10.1111/j.1742-4658.2009.07524.x] [Citation(s) in RCA: 126] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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12
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Maheshwari V, Fomenko DE, Singh G, Saraf RF. Ion mediated monolayer deposition of gold nanoparticles on microorganisms: discrimination by age. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2010; 26:371-7. [PMID: 19728732 DOI: 10.1021/la9021195] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
A general strategy to target cells by nanoparticles for drug delivery, imaging, or diagnostics involves immunospecific binding between the probes and target molecules on the particles and on the cell surface, respectively. Usually, the macromolecular nature of the molecules requires a specific conformation to achieve the desired immunospecificity, and the extent of deposition of particles is limited by the number of receptor molecules present on the cell. In this report, we successfully obtain targeted binding by decorating the nanoparticle with simple ions, such as Ca(2+), without affecting the cell's vitality. The yeast cells for study, Saccharomyces cerevisiae, have no specific electrostatic affinity toward positive charge as confirmed by lysine-coated Au nanoparticles. The specificity of nanoparticle binding is found to be directly related to the metabolic vitality of the yeast cell (i.e., a significantly larger deposition occurs on a younger generation with higher metabolism than on older cells). The ion-mediated targeted deposition seems to be a general phenomenon for biologically important ions, as demonstrated by the contrast between Mg(2+) and (toxic) Cd(2+). The high density of (percolating) nanoparticle deposition as a monolayer on the cells, as a result of the large number of ion receptors on the cell surface, is shown to be a potential method for building bioelectronic devices. The use of ions as an interface to target cells can have possible applications in diagnosing diseases and making biosensors using live cells.
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Affiliation(s)
- Vivek Maheshwari
- Department of Chemical and Biomolecular Engineering, Universityof Nebraska, Lincoln, Nebraska 68588, USA.
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Meyer AE, Hoover LA, Craig EA. The cytosolic J-protein, Jjj1, and Rei1 function in the removal of the pre-60 S subunit factor Arx1. J Biol Chem 2009; 285:961-8. [PMID: 19901025 DOI: 10.1074/jbc.m109.038349] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Although the biogenesis of ribosomal subunits occurs predominantly in the nucleus, final remodeling steps take place in the cytosol. One cytosolic step has two components: 1) the removal of the maturation factor Arx1, which transits from the nucleus to the cytosol with the pre-60 S subunit, and 2) its subsequent transport back into the nucleus. Two cytosolic proteins, Rei1 and Jjj1, are required, but their individual contributions to this step are not understood. Here we report that Rei1 and Jjj1 directly interact. This interaction is mediated by a C-terminal segment of Jjj1 encompassing a region rich in charged residues, flanked by C(2)H(2)-type zinc fingers. Deletion of the charged region results in defects in 60 S subunit biogenesis in vivo. In addition, we report resolution of an apparent contradiction in the literature regarding the association of Arx1 with the pre-60 S subunit in the absence of Rei1. The association of Arx1 with ribosomes is sensitive to the concentration of magnesium ions when Rei1 is absent. At near physiological concentrations, Arx1 remains associated with the pre-60 S particle, as it does in the absence of Jjj1; at higher concentrations, Arx1 dissociates in the absence of Rei1 but not in the absence of Jjj1. As both Rei1 and Jjj1 are required for dissociation of Arx1 from the pre-60 S subunit, and the region of Jjj1 that mediates interaction with Rei1 is required in vivo for 60 S subunit biogenesis, our data support the idea that the primary role of both Rei1 and Jjj1 is the first step of the Arx1 removal/recycling process.
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Affiliation(s)
- Alison E Meyer
- Department of Biochemistry, University of Wisconsin, Madison, Wisconsin 53706, USA
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Abstract
Magnesium (Mg) is an essential enzyme cofactor and a key structural component of biological molecules, but relatively little is known about the molecular components required for Mg homeostasis in eukaryotic cells. The yeast genome encodes four characterized members of the CorA Mg transporter superfamily located in the plasma membrane (Alr1 and Alr2) or the mitochondrial inner membrane (Mrs2 and Lpe10). We describe a fifth yeast CorA homolog (Mnr2) required for Mg homeostasis. MNR2 gene inactivation was associated with an increase in both the Mg requirement and the Mg content of yeast cells. In Mg-replete conditions, wild-type cells accumulated an intracellular store of Mg that supported growth under deficient conditions. An mnr2 mutant was unable to access this store, suggesting that Mg was trapped in an intracellular compartment. Mnr2 was localized to the vacuole membrane, implicating this organelle in Mg storage. The mnr2 mutant growth and Mg-content phenotypes were dependent on vacuolar proton-ATPase activity, but were unaffected by the loss of mitochondrial Mg uptake, indicating a specific dependence on vacuole function. Overexpression of Mnr2 suppressed the growth defect of an alr1 alr2 mutant, indicating that Mnr2 could function independently of the ALR genes. Together, our results implicate a novel eukaryotic CorA homolog in the regulation of intracellular Mg storage.
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Simm C, Lahner B, Salt D, LeFurgey A, Ingram P, Yandell B, Eide DJ. Saccharomyces cerevisiae vacuole in zinc storage and intracellular zinc distribution. EUKARYOTIC CELL 2007; 6:1166-77. [PMID: 17526722 PMCID: PMC1951117 DOI: 10.1128/ec.00077-07] [Citation(s) in RCA: 82] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Previous studies of the yeast Saccharomyces cerevisiae indicated that the vacuole is a major site of zinc storage in the cell. However, these studies did not address the absolute level of zinc that was stored in the vacuole nor did they examine the abundances of stored zinc in other compartments of the cell. In this report, we describe an analysis of the cellular distribution of zinc by use of both an organellar fractionation method and an electron probe X-ray microanalysis. With these methods, we determined that zinc levels in the vacuole vary with zinc status and can rise to almost 100 mM zinc (i.e., 7 x 10(8) atoms of vacuolar zinc per cell). Moreover, this zinc can be mobilized effectively to supply the needs of as many as eight generations of progeny cells under zinc starvation conditions. While the Zrc1 and Cot1 zinc transporters are essential for zinc uptake into the vacuole under steady-state growth conditions, additional transporters help mediate zinc uptake into the vacuole during "zinc shock," when zinc-limited cells are resupplied with zinc. In addition, we found that other compartments of the cell do not provide significant stores of zinc. In particular, zinc accumulation in mitochondria is low and is homeostatically regulated independently of vacuolar zinc storage. Finally, we observed a strong correlation between zinc status and the levels of magnesium and phosphorus accumulated in cells. Our results implicate zinc as a major determinant of the ability of the cell to store these other important nutrients.
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Affiliation(s)
- Claudia Simm
- Department of Nutritional Sciences, 1415 Linden Drive, University of Wisconsin-Madison, Madison, WI 53706, USA
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16
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Wiesenberger G, Steinleitner K, Malli R, Graier WF, Vormann J, Schweyen RJ, Stadler JA. Mg2+ deprivation elicits rapid Ca2+ uptake and activates Ca2+/calcineurin signaling in Saccharomyces cerevisiae. EUKARYOTIC CELL 2007; 6:592-9. [PMID: 17337637 PMCID: PMC1865649 DOI: 10.1128/ec.00382-06] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
To learn about the cellular processes involved in Mg(2+) homeostasis and the mechanisms allowing cells to cope with low Mg(2+) availability, we performed RNA expression-profiling experiments and followed changes in gene activity upon Mg(2+) depletion on a genome-wide scale. A striking portion of genes up-regulated under Mg(2+) depletion are also induced by high Ca(2+) and/or alkalinization. Among the genes significantly up-regulated by Mg(2+) starvation, Ca(2+) stress, and alkalinization are ENA1 (encoding a P-type ATPase sodium pump) and PHO89 (encoding a sodium/phosphate cotransporter). We show that up-regulation of these genes is dependent on the calcineurin/Crz1p (calcineurin-responsive zinc finger protein) signaling pathway. Similarly to Ca(2+) stress, Mg(2+) starvation induces translocation of the transcription factor Crz1p from the cytoplasm into the nucleus. The up-regulation of ENA1 and PHO89 upon Mg(2+) starvation depends on extracellular Ca(2+). Using fluorescence resonance energy transfer microscopy, we demonstrate that removal of Mg(2+) results in an immediate increase in free cytoplasmic Ca(2+). This effect is dependent on external Ca(2+). The results presented indicate that Mg(2+) depletion in yeast cells leads to enhanced cellular Ca(2+) concentrations, which activate the Crz1p/calcineurin pathway. We provide evidence that calcineurin/Crz1p signaling is crucial for yeast cells to cope with Mg(2+) depletion stress.
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Affiliation(s)
- Gerlinde Wiesenberger
- Max F. Perutz Laboratories, Department of Genetics, University of Vienna, Vienna, Austria
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17
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Pyle AM, Fedorova O, Waldsich C. Folding of group II introns: a model system for large, multidomain RNAs? Trends Biochem Sci 2007; 32:138-45. [PMID: 17289393 DOI: 10.1016/j.tibs.2007.01.005] [Citation(s) in RCA: 83] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2006] [Revised: 01/09/2007] [Accepted: 01/30/2007] [Indexed: 01/21/2023]
Abstract
Group II introns are among the largest ribozymes in nature. They have a highly complex tertiary architecture that enables them to catalyze numerous processes, including self-splicing and transposition reactions that have probably contributed to the evolution of eukaryotic genomes. Biophysical analyses show that, despite their large size, these RNAs can fold to their native state through direct pathways that are populated by structurally defined intermediates. In addition, proteins have specific and important roles in this folding process. As a consequence, the study of the group II introns provides a valuable system for both exploring the driving forces behind the folding of multidomain RNA molecules and investigating ribonucleoprotein assembly.
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Affiliation(s)
- Anna Marie Pyle
- Howard Hughes Medical Institute, Yale University, 266 Whitney Avenue, New Haven, CT 06520, USA.
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18
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Burgstaller W. Thermodynamic boundary conditions suggest that a passive transport step suffices for citrate excretion in Aspergillus and Penicillium. MICROBIOLOGY-SGM 2006; 152:887-893. [PMID: 16514167 DOI: 10.1099/mic.0.28454-0] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Excretion of organic acids, e.g. citrate, by anamorphic fungi is a frequent phenomenon in natural habitats and in laboratory cultures. In biotechnological processes for citrate production with Aspergillus niger extracellular citrate concentrations up to 1 mol l(-1) are achieved. Intracellular citrate concentrations are in the millimolar range. Therefore the question arises whether citrate excretion depends on active transport. In this article thermodynamic calculations are presented for citrate excretion by A. niger at an extracellular pH of 3 and by Penicillium simplicissimum at an extracellular pH of 7. From the results of these calculations it is concluded that in both cases a passive transport step suffices for citrate excretion.
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19
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Bradshaw PC, Pfeiffer DR. Release of Ca2+ and Mg2+ from yeast mitochondria is stimulated by increased ionic strength. BMC BIOCHEMISTRY 2006; 7:4. [PMID: 16460565 PMCID: PMC1386685 DOI: 10.1186/1471-2091-7-4] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 11/03/2005] [Accepted: 02/06/2006] [Indexed: 11/10/2022]
Abstract
Background Divalent cations are required for many essential functions of mitochondrial metabolism. Yet the transporters that mediate the flux of these molecules into and out of the mitochondrion remain largely unknown. Previous studies in yeast have led to the molecular identification of a component of the major mitochondrial electrophoretic Mg2+ uptake system in this organism as well as a functional mammalian homolog. Other yeast mitochondrial studies have led to the characterization of an equilibrative fatty acid-stimulated Ca2+ transport activity. To gain a deeper understanding of the regulation of mitochondrial divalent cation levels we further characterized the efflux of Ca2+ and Mg2+ from yeast mitochondria. Results When isolated mitochondria from the yeast Saccharomyces cerevisiae were suspended in a salt-based suspension medium, Ca2+ and Mg2+ were released from the matrix space. Release did not spontaneously occur in a non-ionic mannitol media. When energized mitochondria were suspended in a mannitol medium in the presence of Ca2+ they were able to accumulate Ca2+ by the addition of the electrogenic Ca2+ ionophore ETH-129. However, in a KCl or choline Cl medium under the same conditions, they were unable to retain the Ca2+ that was taken up due to the activation of the Ca2+ efflux pathway, although a substantial membrane potential driving Ca2+ uptake was maintained. This Ca2+ efflux was independent of fatty acids, which have previously been shown to activate Ca2+ transport. Endogenous mitochondrial Mg2+ was also released when mitochondria were suspended in an ionic medium, but was retained in mitochondria upon fatty acid addition. When suspended in a mannitol medium, metal chelators released mitochondrial Mg2+, supporting the existence of an external divalent cation-binding site regulating release. Matrix space Mg2+ was also slowly released from mitochondria by the addition of Ca2+, respiratory substrates, increasing pH, or the nucleotides ATP, ADP, GTP, and ATP-gamma-S. Conclusion In isolated yeast mitochondria Ca2+ and Mg2+ release was activated by increased ionic strength. Free nucleotides, metal ion chelators, and increased pH also stimulated release. In yeast cells this release is likely an important mechanism in the regulation of mitochondrial matrix space divalent cation concentrations.
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Affiliation(s)
| | - Douglas R Pfeiffer
- Department of Molecular and Cellular Biochemistry, Department of Internal Medicine, Institute for Mitochondrial Biology, The Ohio State University, Columbus, OH, USA
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20
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Grajcar L, El Amri C, Ghomi M, Fermandjian S, Huteau V, Mandel R, Lecomte S, Baron MH. Assessment of adenyl residue reactivity within model nucleic acids by surface enhanced Raman spectroscopy. Biopolymers 2006; 82:6-28. [PMID: 16425174 DOI: 10.1002/bip.20455] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
We rank the reactivity of the adenyl residues (A) of model DNA and RNA molecules with electropositive subnano size [Ag]n+ sites as a function of nucleic acid primary sequences and secondary structures and in the presence of biological amounts of Cl- and Na+ or Mg2+ ions. In these conditions A is markedly more reactive than any other nucleic acid bases. A reactivity is higher in ribo (r) than in deoxyribo (d) species [pA>pdA and (pA)n>>(pdA)n]. Base pairing decreases A reactivity in corresponding duplexes but much less in r than in d. In linear single and paired dCAG or dGAC loci, base stacking inhibits A reactivity even if A is bulged or mispaired (A.A). dA tracts are highly reactive only when dilution prevents self-association and duplex structures. In d hairpins the solvent-exposed A residues are reactive in CAG and GAC triloops and even more in ATC loops. Among the eight rG1N2R3A4 loops, those bearing a single A (A4) are the least reactive. The solvent-exposed A2 is reactive, but synergistic structural transitions make the initially stacked A residues of any rGNAA loop much more reactive. Mg2+ cross-bridging single strands via phosphates may screen A reactivity. In contrast d duplexes cross-bridging enables "A flipping" much more in rA.U pairs than in dA.T. Mg2+ promotes A reactivity in unpaired strands. For hairpins Mg2+ binding stabilizes the stems, but according to A position in the loops, A reactivity may be abolished, reduced, or enhanced. It is emphasized that not only accessibility but also local flexibility, concerted docking, and cation and anion binding control A reactivity.
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Affiliation(s)
- Lydie Grajcar
- Laboratoire de Dynamique Interactions et Réactivité, UMR 7075, Université Paris 6 CNRS, 2 rue Henri Dunant, 94320, Thiais, France
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21
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Lee MH, Chang YC, Hong EL, Grubb J, Chang CS, Bishop DK, Wang TF. Calcium ion promotes yeast Dmc1 activity via formation of long and fine helical filaments with single-stranded DNA. J Biol Chem 2005; 280:40980-4. [PMID: 16204247 DOI: 10.1074/jbc.m505896200] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Dmc1 is specifically required for homologous recombination during meiosis. Here we report that the calcium ion enabled Dmc1 from budding yeast to form regular helical filaments on single-stranded DNA (ssDNA) and activate its strand assimilation activity. Relative to magnesium, calcium increased the affinity of Dmc1 for ATP and but reduces its DNA-dependent ATPase activity. These effects, together with previous studies of other RecA-like recombinases, support the view that ATP binding to Dmc1 protomers is required for functional filament structure. The helical pitch of the Saccharomyces cerevisiae Dmc1-ssDNA helical filament was estimated to be 13.4 +/- 2.5 nm. Analysis of apparently "complete" Dmc1-ssDNA filaments indicated a stoichiometry of 24 +/- 2 nucleotides per turn of the Dmc1 helix. This finding suggests that the number or protomers per helical turn and/or the number of nucleotides bound per Dmc1 protomer differs from that reported previously for Rad51 and RecA filaments. Our data support the view that the active form of Dmc1 protein is a helical filament rather than a ring. We speculate that Ca(2+) plays a significant role in regulating meiotic recombination.
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Affiliation(s)
- Ming-Hui Lee
- Institute of Biological Chemistry, Academia Sinica, Taipei 11529, Taiwan
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22
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Eide DJ, Clark S, Nair TM, Gehl M, Gribskov M, Guerinot ML, Harper JF. Characterization of the yeast ionome: a genome-wide analysis of nutrient mineral and trace element homeostasis in Saccharomyces cerevisiae. Genome Biol 2005; 6:R77. [PMID: 16168084 PMCID: PMC1242212 DOI: 10.1186/gb-2005-6-9-r77] [Citation(s) in RCA: 173] [Impact Index Per Article: 9.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2005] [Revised: 06/21/2005] [Accepted: 07/18/2005] [Indexed: 11/24/2022] Open
Abstract
BACKGROUND Nutrient minerals are essential yet potentially toxic, and homeostatic mechanisms are required to regulate their intracellular levels. We describe here a genome-wide screen for genes involved in the homeostasis of minerals in Saccharomyces cerevisiae. Using inductively coupled plasma-atomic emission spectroscopy (ICP-AES), we assayed 4,385 mutant strains for the accumulation of 13 elements (calcium, cobalt, copper, iron, potassium, magnesium, manganese, nickel, phosphorus, selenium, sodium, sulfur, and zinc). We refer to the resulting accumulation profile as the yeast 'ionome'. RESULTS We identified 212 strains that showed altered ionome profiles when grown on a rich growth medium. Surprisingly few of these mutants (four strains) were affected for only one element. Rather, levels of multiple elements were altered in most mutants. It was also remarkable that only six genes previously shown to be involved in the uptake and utilization of minerals were identified here, indicating that homeostasis is robust under these replete conditions. Many mutants identified affected either mitochondrial or vacuolar function and these groups showed similar effects on the accumulation of many different elements. In addition, intriguing positive and negative correlations among different elements were observed. Finally, ionome profile data allowed us to correctly predict a function for a previously uncharacterized gene, YDR065W. We show that this gene is required for vacuolar acidification. CONCLUSION Our results indicate the power of ionomics to identify new aspects of mineral homeostasis and how these data can be used to develop hypotheses regarding the functions of previously uncharacterized genes.
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Affiliation(s)
- David J Eide
- Department of Nutritional Sciences, University of Wisconsin-Madison, Madison, WI 53706, USA.
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23
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Affiliation(s)
- Graeme M Walker
- Division of Biotechnology and Forensic Science, School of Contemporary Sciences, University of Abertay Dundee, Bell Street, Dundee DD1 1HG, United Kingdom
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24
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Rudge SA, Anderson DM, Emr SD. Vacuole size control: regulation of PtdIns(3,5)P2 levels by the vacuole-associated Vac14-Fig4 complex, a PtdIns(3,5)P2-specific phosphatase. Mol Biol Cell 2003; 15:24-36. [PMID: 14528018 PMCID: PMC307524 DOI: 10.1091/mbc.e03-05-0297] [Citation(s) in RCA: 163] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
In the budding yeast Saccharomyces cerevisiae, phosphatidylinositol 3,5-bisphosphate (PtdIns(3,5)P2) is synthesized by a single phosphatidylinositol 3-phosphate 5-kinase, Fab1. Cells deficient in PtdIns(3,5)P2 synthesis exhibit a grossly enlarged vacuole morphology, whereas increased levels of PtdIns(3,5)P2 provokes the formation of multiple small vacuoles, suggesting a specific role for PtdIns(3,5)P2 in vacuole size control. Genetic studies have indicated that Fab1 kinase is positively regulated by Vac7 and Vac14; deletion of either gene results in ablation of PtdIns(3,5)P2 synthesis and the formation of a grossly enlarged vacuole. More recently, a suppressor of vac7Delta mutants was identified and shown to encode a putative phosphoinositide phosphatase, Fig4. We demonstrate that Fig4 is a magnesium-activated PtdIns(3,5)P2-selective phosphoinositide phosphatase in vitro. Analysis of a Fig4-GFP fusion protein revealed that the Fig4 phosphatase is localized to the limiting membrane of the vacuole. Surprisingly, in the absence of Vac14, Fig4-GFP no longer localizes to the vacuole. However, Fig4-GFP remains localized to the grossly enlarged vacuoles of vac7 deletion mutants. Consistent with these observations, we found that Fig4 physically associates with Vac14 in a common membrane-associated complex. Our studies indicate that Vac14 both positively regulates Fab1 kinase activity and directs the localization/activation of the Fig4 PtdIns(3,5)P2 phosphatase.
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Affiliation(s)
- Simon A Rudge
- Department of Cellular and Molecular Medicine, and the Howard Hughes Medical Institute, University of California at San Diego, School of Medicine, La Jolla, California 92093-0668, USA
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25
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Abstract
We know very little about the regulation of magnesium uptake and the control of magnesium homeostasis. After years of relative neglect, however, rapid progress is now being made in understanding the molecular biology of magnesium transport in eukaryotes. Several new gene families have been implicated, and tools are in place for the dissection of the biochemical and biological roles played by the encoded proteins.
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Affiliation(s)
- Richard C Gardner
- School of Biological Sciences, University of Auckland, Private Bag 92019, Auckland, New Zealand.
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26
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Abstract
The internal environment of the ER is regulated to accommodate essential cellular processes, yet our understanding of this regulation remains incomplete. Cod1p/Spf1p belongs to the widely conserved, uncharacterized type V branch of P-type ATPases, a large family of ion pumps. Our previous work suggested Cod1p may function in the ER. Consistent with this hypothesis, we localized Cod1p to the ER membrane. The cod1Delta mutant disrupted cellular calcium homeostasis, causing increased transcription of calcium-regulated genes and a synergistic increase in cellular calcium when paired with disruption of the Golgi apparatus-localized Ca2+ pump Pmr1p. Deletion of COD1 also impaired ER function, causing constitutive activation of the unfolded protein response, hypersensitivity to the glycosylation inhibitor tunicamycin, and synthetic lethality with deletion of the unfolded protein response regulator HAC1. Expression of the Drosophila melanogaster homologue of Cod1p complemented the cod1Delta mutant. Finally, we demonstrated the ATPase activity of the purified protein. This study provides the first biochemical characterization of a type V P-type ATPase, implicates Cod1p in ER function and ion homeostasis, and indicates that these functions are conserved among Cod1p's metazoan homologues.
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Affiliation(s)
- Stephen R Cronin
- Division of Biology, University of California San Diego, La Jolla, CA 92093-0347, USA
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27
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Bolton EC, Mildvan AS, Boeke JD. Inhibition of reverse transcription in vivo by elevated manganese ion concentration. Mol Cell 2002; 9:879-89. [PMID: 11983178 DOI: 10.1016/s1097-2765(02)00495-1] [Citation(s) in RCA: 62] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
Mutations in PMR1, a yeast gene encoding a calcium/manganese exporter, dramatically decrease Ty1 retrotransposition. Ty1 cDNA is reduced in pmr1 mutant cells, despite normal levels of Ty1 RNA and proteins. The transposition defect results from Mn(2+) accumulation that inhibits reverse transcription. Cytoplasmic accumulation of Mn(2+) in pmr1 cells may directly affect reverse transcriptase (RT) activity. Trace amounts of Mn(2+) potently inhibit Ty1 RT and HIV-1 RT in vitro when the preferred cation, Mg(2+), is present. Both Mn(2+) and Mg(2+) alone activate Ty1 RT cooperatively with Hill coefficients of 2, providing kinetic evidence for a dual divalent cation requirement at the RT active site. We propose that occupancy of the B site is the major determinant of catalytic activity and that Mn(2+) at this site greatly reduces catalytic activity.
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Affiliation(s)
- Eric C Bolton
- Department of Molecular Biology and Genetics, The Johns Hopkins University School of Medicine, 725 North Wolfe Street, Baltimore, MD 21205, USA
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28
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Borrelly G, Boyer JC, Touraine B, Szponarski W, Rambier M, Gibrat R. The yeast mutant vps5Delta affected in the recycling of Golgi membrane proteins displays an enhanced vacuolar Mg2+/H+ exchange activity. Proc Natl Acad Sci U S A 2001; 98:9660-5. [PMID: 11493679 PMCID: PMC55508 DOI: 10.1073/pnas.161215198] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Growth of the yeast vacuolar protein-sorting mutant vps5Delta affected in the endosome-to-Golgi retromer complex was more sensitive to Mg2+-limiting conditions than was the growth of the wild-type (WT) strain. This sensitivity was enhanced at acidic pH. The vps5Delta strain was also sensitive to Al3+, known to inhibit Mg2+ uptake in yeast cells. In contrast, it was found to be resistant to Ni2+ and Co2+, two cytotoxic analogs of Mg2+. Resistance to Ni2+ did not seem to result from the alteration of plasma-membrane transport properties because mutant and WT cells displayed similar Ni2+ uptake. After plasma-membrane permeabilization, intracellular Ni2+ uptake in vps5Delta cells was 3-fold higher than in WT cells, which is consistent with the implication of the vacuole in the observed phenotypes. In reconstituted vacuolar vesicles prepared from vps5Delta, the rates of H+ exchange with Ni2+, Co2+, and Mg2+ were increased (relative to WT) by 170%, 130%, and 50%, respectively. The rates of H+ exchange with Ca2+, Cd2+, and K+ were similar in both strains, as were alpha-mannosidase and H+-ATPase activities, and SDS/PAGE patterns of vacuolar proteins. Among 14 other vacuolar protein-sorting mutants tested, only the 8 mutants affected in the recycling of trans-Golgi network membrane proteins shared the same Ni2+ resistance phenotype as vps5Delta. It is proposed that a trans-Golgi network Mg2+/H+ exchanger, mislocalized to vps5Delta vacuole, could be responsible for the phenotypes observed in vivo and in vitro.
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Affiliation(s)
- G Borrelly
- Biochimie et Physiologie Moléculaire des Plantes, Ecole Nationale Supérieure d'Agronomie de Montpellier (Agro-M)/Institut National de la Recherche Agronomique, France
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29
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Graschopf A, Stadler JA, Hoellerer MK, Eder S, Sieghardt M, Kohlwein SD, Schweyen RJ. The yeast plasma membrane protein Alr1 controls Mg2+ homeostasis and is subject to Mg2+-dependent control of its synthesis and degradation. J Biol Chem 2001; 276:16216-22. [PMID: 11279208 DOI: 10.1074/jbc.m101504200] [Citation(s) in RCA: 103] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The Saccharomyces cerevisiae ALR1 (YOL130w) gene product Alr1p is the first known candidate for a Mg(2+) transport system in eukaryotic cells and is distantly related to the bacterial CorA Mg(2+) transporter family. Here we provide the first experimental evidence for the location of Alr1p in the yeast plasma membrane and for the tight control of its expression and turnover by Mg(2+). Using well characterized npi1 and end3 mutants deficient in the endocytic pathway, we demonstrate that Alr1 protein turnover is dependent on ubiquitination and endocytosis. Furthermore, cells lacking the vacuolar protease Pep4p accumulated Alr1p in the vacuole. Mutants lacking Alr1p (Deltaalr1) showed a 60% reduction of total intracellular Mg(2+) compared with the wild type and failed to grow in standard media. When starved of Mg(2+), mutant and wild-type cells had similar low levels of intracellular Mg(2+); but upon addition of Mg(2+), wild-type cells replenished the intracellular Mg(2+) pool within a few hours, whereas Deltaalr1 mutant cells did not. Expression of the bacterial Mg(2+) transporter CorA in the yeast Deltaalr1 mutant partially restored growth in standard media. The results are discussed in terms of Alr1p being a plasma membrane transporter with high selectivity for Mg(2+).
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Affiliation(s)
- A Graschopf
- Vienna Biocenter, Institute of Microbiology and Genetics, University of Vienna, A-1030 Vienna, Austria
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30
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Ivanov KI, Puustinen P, Merits A, Saarma M, Mäkinen K. Phosphorylation down-regulates the RNA binding function of the coat protein of potato virus A. J Biol Chem 2001; 276:13530-40. [PMID: 11152464 DOI: 10.1074/jbc.m009551200] [Citation(s) in RCA: 74] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Plant viruses encode movement proteins (MPs) to facilitate transport of their genomes from infected into neighboring healthy cells through plasmodesmata. Growing evidence suggests that specific phosphorylation events can regulate MP functions. The coat protein (CP) of potato virus A (PVA; genus Potyvirus) is a multifunctional protein involved both in virion assembly and virus movement. Labeling of PVA-infected tobacco leaves with [(33)P]orthophosphate demonstrated that PVA CP is phosphorylated in vivo. Competition assays established that PVA CP and the well characterized 30-kDa MP of tobacco mosaic virus (genus Tobamovirus) are phosphorylated in vitro by the same Ser/Thr kinase activity from tobacco leaves. This activity exhibits a strong preference for Mn(2+) over Mg(2+), can be inhibited by micromolar concentrations of Zn(2+) and Cd(2+), and is not Ca(2+)-dependent. Tryptic phosphopeptide mapping revealed that PVA CP was phosphorylated by this protein kinase activity on multiple sites. In contrast, PVA CP was not phosphorylated when packaged into virions, suggesting that the phosphorylation sites are located within the RNA binding domain and not exposed on the surface of the virion. Furthermore, two independent experimental approaches demonstrated that the RNA binding function of PVA CP is strongly inhibited by phosphorylation. From these findings, we suggest that protein phosphorylation represents a possible mechanism regulating formation and/or stability of viral ribonucleoproteins in planta.
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Affiliation(s)
- K I Ivanov
- Institute of Biotechnology, Viikki Biocenter, P.O. Box 56, FIN-00014 University of Helsinki, Finland
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31
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Affiliation(s)
- Todor Dudev
- Institute of Biomedical Sciences, Academia Sinica, Taipei 11529, Taiwan, R.O.C., and Department of Chemistry, National Tsing Hua University, Hsinchu 300, Taiwan, R.O.C
| | - Carmay Lim
- Institute of Biomedical Sciences, Academia Sinica, Taipei 11529, Taiwan, R.O.C., and Department of Chemistry, National Tsing Hua University, Hsinchu 300, Taiwan, R.O.C
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32
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Nishimura K, Yasumura K, Igarashi K, Harashima S, Kakinuma Y. Transcription of some PHO genes in Saccharomyces cerevisiae is regulated by spt7p. Yeast 1999; 15:1711-7. [PMID: 10590460 DOI: 10.1002/(sici)1097-0061(199912)15:16<1711::aid-yea497>3.0.co;2-8] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/28/2022] Open
Abstract
Spt7p is a new global transcription factor in Saccharomyces cerevisiae(Gansheroff et al., 1995). We report here that the activities of high affinity phosphate transport and acid phosphatase in particular were decreased in a spt7 null mutant. Northern blot experiments revealed that transcription of the PHO84 and PHO5 genes was impaired in this mutant; expression of the PHO regulatory genes, PHO4 and PHO2, was normal. Spt7p is thus linked with expression of several structural genes of the PHO regulon in yeast.
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Affiliation(s)
- K Nishimura
- Faculty of Pharmaceutical Sciences, Chiba University, Japan
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33
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Bui DM, Gregan J, Jarosch E, Ragnini A, Schweyen RJ. The bacterial magnesium transporter CorA can functionally substitute for its putative homologue Mrs2p in the yeast inner mitochondrial membrane. J Biol Chem 1999; 274:20438-43. [PMID: 10400670 DOI: 10.1074/jbc.274.29.20438] [Citation(s) in RCA: 128] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The yeast nuclear gene MRS2 encodes a protein of 54 kDa, the presence of which has been shown to be essential for the splicing of group II intron RNA in mitochondria and, independently, for the maintenance of a functional respiratory system. Here we show that the MRS2 gene product (Mrs2p) is an integral protein of the inner mitochondrial membrane. It appears to be inserted into this membrane by virtue of two neighboring membrane spanning domains in its carboxyl-terminal half. A large amino-terminal and a shorter carboxyl-terminal part are likely to be exposed to the matrix space. Structural features and a short sequence motif indicate that Mrs2p may be related to the bacterial CorA Mg2+ transporter. In fact, overexpression of the CorA gene in yeast partially suppresses the pet- phenotype of an mrs2 disrupted yeast strain. Disruption of the MRS2 gene leads to a significant decrease in total magnesium content of mitochondria which is compensated for by the overexpression of the CorA gene. Mutants lacking or overproducing Mrs2p exhibit phenotypes consistent with the involvement of Mrs2p in mitochondrial Mg2+ homeostasis.
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Affiliation(s)
- D M Bui
- Vienna Biocenter, Department of Microbiology and Genetics, University of Vienna, Dr. Bohrgasse 9, A-1030 Vienna, Austria
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