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Lindahl PA. Iron Homeostatic Regulation in Saccharomyces cerevisiae: Introduction to a Computational Modeling Method. Methods Mol Biol 2024; 2839:3-29. [PMID: 39008245 DOI: 10.1007/978-1-0716-4043-2_1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 07/16/2024]
Abstract
Over the past 30 years, much has been learned regarding iron homeostatic regulation in budding yeast, S. cerevisiae, including the identity of many of the proteins and molecular-level regulatory mechanisms involved. Most advances have involved inferring such mechanisms based on the analysis of iron-dysregulation phenotypes arising in various genetic mutant strains. Still lacking is a cellular- or system-level understanding of iron homeostasis. These experimental advances are summarized in this review, and a method for developing cellular-level regulatory mechanisms in yeast is presented. The method employs the results of Mössbauer spectroscopy of whole cells and organelles, iron quantification of the same, and ordinary differential equation-based mathematical models. Current models are simplistic when compared to the complexity of iron homeostasis in real cells, yet they hold promise as a useful, perhaps even required, complement to the popular genetics-based approach. The fundamental problem in comprehending cellular regulatory mechanisms is that, given the complexities involved, different molecular-level mechanisms can often give rise to virtually indistinguishable cellular phenotypes. Mathematical models cannot eliminate this problem, but they can minimize it.
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Affiliation(s)
- Paul A Lindahl
- Departments of Chemistry and of Biochemistry and Biophysics, Texas A&M University, College Station, TX, USA.
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Thorat S, Walton JR, Lindahl PA. A kinetic model of iron trafficking in growing Saccharomyces cerevisiae cells; applying mathematical methods to minimize the problem of sparse data and generate viable autoregulatory mechanisms. PLoS Comput Biol 2023; 19:e1011701. [PMID: 38113197 PMCID: PMC10729996 DOI: 10.1371/journal.pcbi.1011701] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2023] [Accepted: 11/20/2023] [Indexed: 12/21/2023] Open
Abstract
Iron is an essential transition metal for all eukaryotic cells, and its trafficking throughout the cell is highly regulated. However, the overall cellular mechanism of regulation is poorly understood despite knowing many of the molecular players involved. Here, an ordinary-differential-equations (ODE) based kinetic model of iron trafficking within a growing yeast cell was developed that included autoregulation. The 9-reaction 8-component in-silico cell model was solved under both steady-state and time-dependent dynamical conditions. The ODE for each component included a dilution term due to cell growth. Conserved rate relationships were obtained from the null space of the stoichiometric matrix, and the reduced-row-echelon-form was used to distinguish independent from dependent rates. Independent rates were determined from experimentally estimated component concentrations, cell growth rates, and the literature. Simple rate-law expressions were assumed, allowing rate-constants for each reaction to be estimated. Continuous Heaviside logistical functions were used to regulate rate-constants. These functions acted like valves, opening or closing depending on component "sensor" concentrations. Two cellular regulatory mechanisms were selected from 134,217,728 possibilities using a novel approach involving 6 mathematically-defined filters. Three cellular states were analyzed including healthy wild-type cells, iron-deficient wild-type cells, and a frataxin-deficient strain of cells characterizing the disease Friedreich's Ataxia. The model was stable toward limited perturbations, as determined by the eigenvalues of Jacobian matrices. Autoregulation allowed healthy cells to transition to the diseased state when triggered by a mutation in frataxin, and to the iron-deficient state when cells are placed in iron-deficient growth medium. The in-silico phenotypes observed during these transitions were similar to those observed experimentally. The model also predicted the observed effects of hypoxia on the diseased condition. A similar approach could be used to solve ODE-based kinetic models associated with other biochemical processes operating within growing cells.
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Affiliation(s)
- Shantanu Thorat
- Department of Computer Science and Engineering, Texas A&M University, College Station, Texas, United States of America
| | - Jay R. Walton
- Department of Mathematics, Texas A&M University, College Station Texas, Texas, United States of America
| | - Paul A. Lindahl
- Department of Chemistry, Texas A&M University, College Station Texas, Texas, United States of America
- Department of Biochemistry and Biophysics, Texas A&M University, College Station Texas, Texas, United States of America
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Kim JE, Jeon S, Lindahl PA. Discovery of an unusual copper homeostatic mechanism in yeast cells respiring on minimal medium and an unexpectedly diverse labile copper pool. J Biol Chem 2023; 299:105435. [PMID: 37944620 PMCID: PMC10704325 DOI: 10.1016/j.jbc.2023.105435] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2023] [Revised: 10/17/2023] [Accepted: 11/01/2023] [Indexed: 11/12/2023] Open
Abstract
Copper is essential for all eukaryotic cells but many details of how it is trafficked within the cell and how it is homeostatically regulated remain uncertain. Here, we characterized the copper content of cytosol and mitochondria using liquid chromatography with ICP-MS detection. Chromatograms of cytosol exhibited over two dozen peaks due to copper proteins and coordination complexes. Yeast cells respiring on minimal media did not regulate copper import as media copper concentration increased; rather, they imported copper at increasing rates while simultaneously increasing the expression of metallothionein CUP1 which then sequestered most of the excessive imported copper. Peak intensities due to superoxide dismutase SOD1, other copper proteins, and numerous coordination complexes also increased, but not as drastically. The labile copper pool was unexpectedly diverse and divided into two groups. One group approximately comigrated with copper-glutathione, -cysteine, and -histidine standards; the other developed only at high media copper concentrations and at greater elution volumes. Most cytosolic copper arose from copper-bound proteins, especially CUP1. Cytosol contained an unexpectedly high percentage of apo-copper proteins and apo-coordination complexes. Copper-bound forms of non-CUP1 proteins and complexes coexisted with apo-CUP1 and with the chelator BCS. Both experiments suggest unexpectedly stable-binding copper proteins and coordination complexes in cytosol. COX17Δ cytosol chromatograms were like those of WT cells. Chromatograms of soluble mitochondrial extracts were obtained, and mitoplasting helped distinguish copper species in the intermembrane space versus in the matrix/inner membrane. Issues involving the yeast copperome, copper homeostasis, labile copper pool, and copper trafficking are discussed.
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Affiliation(s)
- Joshua E Kim
- Department of Chemistry, Texas A&M University, College Station, Texas, USA
| | - Seoyoung Jeon
- Department of Chemistry, Texas A&M University, College Station, Texas, USA
| | - Paul A Lindahl
- Department of Chemistry, Texas A&M University, College Station, Texas, USA; Department of Biochemistry and Biophysics, Texas A&M University, College Station, Texas, USA.
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Lindahl PA, Vali SW. Mössbauer-based molecular-level decomposition of the Saccharomyces cerevisiae ironome, and preliminary characterization of isolated nuclei. Metallomics 2022; 14:mfac080. [PMID: 36214417 PMCID: PMC9624242 DOI: 10.1093/mtomcs/mfac080] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2022] [Accepted: 09/23/2022] [Indexed: 11/25/2022]
Abstract
One hundred proteins in Saccharomyces cerevisiae are known to contain iron. These proteins are found mainly in mitochondria, cytosol, nuclei, endoplasmic reticula, and vacuoles. Cells also contain non-proteinaceous low-molecular-mass labile iron pools (LFePs). How each molecular iron species interacts on the cellular or systems' level is underdeveloped as doing so would require considering the entire iron content of the cell-the ironome. In this paper, Mössbauer (MB) spectroscopy was used to probe the ironome of yeast. MB spectra of whole cells and isolated organelles were predicted by summing the spectral contribution of each iron-containing species in the cell. Simulations required input from published proteomics and microscopy data, as well as from previous spectroscopic and redox characterization of individual iron-containing proteins. Composite simulations were compared to experimentally determined spectra. Simulated MB spectra of non-proteinaceous iron pools in the cell were assumed to account for major differences between simulated and experimental spectra of whole cells and isolated mitochondria and vacuoles. Nuclei were predicted to contain ∼30 μM iron, mostly in the form of [Fe4S4] clusters. This was experimentally confirmed by isolating nuclei from 57Fe-enriched cells and obtaining the first MB spectra of the organelle. This study provides the first semi-quantitative estimate of all concentrations of iron-containing proteins and non-proteinaceous species in yeast, as well as a novel approach to spectroscopically characterizing LFePs.
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Affiliation(s)
- Paul A Lindahl
- Department of Chemistry, Texas A&M University, College Station, TX,USA
- Department of Biochemistry and Biophysics, Texas A&M University, College Station TX,USA
| | - Shaik Waseem Vali
- Department of Chemistry, Texas A&M University, College Station, TX,USA
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Fernandez S, Wofford JD, Shepherd RE, Vali SW, Dancis A, Lindahl PA. Yeast cells depleted of the frataxin homolog Yfh1 redistribute cellular iron: Studies using Mössbauer spectroscopy and mathematical modeling. J Biol Chem 2022; 298:101921. [PMID: 35413285 PMCID: PMC9130540 DOI: 10.1016/j.jbc.2022.101921] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2022] [Revised: 04/05/2022] [Accepted: 04/06/2022] [Indexed: 11/27/2022] Open
Abstract
The neurodegenerative disease Friedreich's ataxia arises from a deficiency of frataxin, a protein that promotes iron-sulfur cluster (ISC) assembly in mitochondria. Here, primarily using Mössbauer spectroscopy, we investigated the iron content of a yeast strain in which expression of yeast frataxin homolog 1 (Yfh1), oxygenation conditions, iron concentrations, and metabolic modes were varied. We found that aerobic fermenting Yfh1-depleted cells grew slowly and accumulated FeIII nanoparticles, unlike WT cells. Under hypoxic conditions, the same mutant cells grew at rates similar to WT cells, had similar iron content, and were dominated by FeII rather than FeIII nanoparticles. Furthermore, mitochondria from mutant hypoxic cells contained approximately the same levels of ISCs as WT cells, confirming that Yfh1 is not required for ISC assembly. These cells also did not accumulate excessive iron, indicating that iron accumulation into yfh1-deficient mitochondria is stimulated by O2. In addition, in aerobic WT cells, we found that vacuoles stored FeIII, whereas under hypoxic fermenting conditions, vacuolar iron was reduced to FeII. Under respiring conditions, vacuoles of Yfh1-deficient cells contained FeIII, and nanoparticles accumulated only under aerobic conditions. Taken together, these results informed a mathematical model of iron trafficking and regulation in cells that could semiquantitatively simulate the Yfh1-deficiency phenotype. Simulations suggested partially independent regulation in which cellular iron import is regulated by ISC activity in mitochondria, mitochondrial iron import is regulated by a mitochondrial FeII pool, and vacuolar iron import is regulated by cytosolic FeII and mitochondrial ISC activity.
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Affiliation(s)
- Salvador Fernandez
- Department of Chemistry, Texas A&M University, College Station, Texas, USA
| | - Joshua D Wofford
- Department of Chemistry, College of Science and Mathematics, Charleston Southern University, Charleston South Carolina, USA
| | - Rachel E Shepherd
- Department of Chemistry, Texas A&M University, College Station, Texas, USA
| | - Shaik Waseem Vali
- Department of Biochemistry and Biophysics, Texas A&M University, College Station, Texas, USA
| | - Andrew Dancis
- Department of Medicine, Division of Hematology-Oncology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, USA
| | - Paul A Lindahl
- Department of Chemistry, Texas A&M University, College Station, Texas, USA; Department of Biochemistry and Biophysics, Texas A&M University, College Station, Texas, USA.
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Palma M, Mondo S, Pereira M, Vieira É, Grigoriev IV, Sá-Correia I. Genome Sequence and Analysis of the Flavinogenic Yeast Candida membranifaciens IST 626. J Fungi (Basel) 2022; 8:jof8030254. [PMID: 35330255 PMCID: PMC8955749 DOI: 10.3390/jof8030254] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2022] [Revised: 02/26/2022] [Accepted: 02/27/2022] [Indexed: 02/04/2023] Open
Abstract
The ascomycetous yeast Candida membranifaciens has been isolated from diverse habitats, including humans, insects, and environmental sources, exhibiting a remarkable ability to use different carbon sources that include pentoses, melibiose, and inulin. In this study, we isolated four C. membranifaciens strains from soil and investigated their potential to overproduce riboflavin. C. membranifaciens IST 626 was found to produce the highest concentrations of riboflavin. The volumetric production of this vitamin was higher when C. membranifaciens IST 626 cells were cultured in a commercial medium without iron and when xylose was the available carbon source compared to the same basal medium with glucose. Supplementation of the growth medium with 2 g/L glycine favored the metabolization of xylose, leading to biomass increase and consequent enhancement of riboflavin volumetric production that reached 120 mg/L after 216 h of cultivation. To gain new insights into the molecular basis of riboflavin production and carbon source utilization in this species, the first annotated genome sequence of C. membranifaciens is reported in this article, as well as the result of a comparative genomic analysis with other relevant yeast species. A total of 5619 genes were predicted to be present in C. membranifaciens IST 626 genome sequence (11.5 Mbp). Among them are genes involved in riboflavin biosynthesis, iron homeostasis, and sugar uptake and metabolism. This work put forward C. membranifaciens IST 626 as a riboflavin overproducer and provides valuable molecular data for future development of superior producing strains capable of using the wide range of carbon sources, which is a characteristic trait of the species.
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Affiliation(s)
- Margarida Palma
- Institute for Bioengineering and Biosciences, Instituto Superior Técnico, Universidade de Lisboa, Av. Rovisco Pais, 1049-001 Lisboa, Portugal; (M.P.); (É.V.); (I.S.-C.)
- Department of Bioengineering, Instituto Superior Técnico, Universidade de Lisboa, Av. Rovisco Pais, 1049-001 Lisboa, Portugal
- Associate Laboratory i4HB—Institute for Health and Bioeconomy at Instituto Superior Técnico, Universidade de Lisboa, Av. Rovisco Pais, 1049-001 Lisboa, Portugal
- Correspondence:
| | - Stephen Mondo
- US Department of Energy Joint Genome Institute, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA; (S.M.); (I.V.G.)
- Department of Agricultural Biology, Colorado State University, Fort Collins, CO 80523, USA
| | - Mariana Pereira
- Institute for Bioengineering and Biosciences, Instituto Superior Técnico, Universidade de Lisboa, Av. Rovisco Pais, 1049-001 Lisboa, Portugal; (M.P.); (É.V.); (I.S.-C.)
- Department of Bioengineering, Instituto Superior Técnico, Universidade de Lisboa, Av. Rovisco Pais, 1049-001 Lisboa, Portugal
| | - Érica Vieira
- Institute for Bioengineering and Biosciences, Instituto Superior Técnico, Universidade de Lisboa, Av. Rovisco Pais, 1049-001 Lisboa, Portugal; (M.P.); (É.V.); (I.S.-C.)
- Department of Bioengineering, Instituto Superior Técnico, Universidade de Lisboa, Av. Rovisco Pais, 1049-001 Lisboa, Portugal
| | - Igor V. Grigoriev
- US Department of Energy Joint Genome Institute, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA; (S.M.); (I.V.G.)
- Department of Plant and Microbial Biology, University of California Berkeley, Berkeley, CA 94720, USA
| | - Isabel Sá-Correia
- Institute for Bioengineering and Biosciences, Instituto Superior Técnico, Universidade de Lisboa, Av. Rovisco Pais, 1049-001 Lisboa, Portugal; (M.P.); (É.V.); (I.S.-C.)
- Department of Bioengineering, Instituto Superior Técnico, Universidade de Lisboa, Av. Rovisco Pais, 1049-001 Lisboa, Portugal
- Associate Laboratory i4HB—Institute for Health and Bioeconomy at Instituto Superior Técnico, Universidade de Lisboa, Av. Rovisco Pais, 1049-001 Lisboa, Portugal
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Kamnev AA, Tugarova AV. Bioanalytical applications of Mössbauer spectroscopy. RUSSIAN CHEMICAL REVIEWS 2021. [DOI: 10.1070/rcr5006] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Abstract
Data on the applications of Mössbauer spectroscopy in the transmission (mainly on 57Fe nuclei) and emission (on 57Co nuclei) variants for analytical studies at the molecular level of metal-containing components in a wide range of biological objects (from biocomplexes and biomacromolecules to supramolecular structures, cells, tissues and organisms) and of objects that are participants or products of biological processes, published in the last 15 years are discussed and systematized. The prospects of the technique in its biological applications, including the developing fields (emission variant, use of synchrotron radiation), are formulated.
The bibliography includes 248 references.
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Abstract
Metal ions are essential to all living cells, as they can serve as cofactors of enzymes to drive catalysis of biochemical reactions. We present a constraint-based model of yeast that relates metabolism with metal ions via enzymes. The model is able to capture responses of metabolism and gene expression upon iron depletion, suggesting that yeast cells allocate iron resource in the way abiding to optimization principles. Interestingly, the model predicts up-regulation of several iron-containing enzymes that coincide with experiments, which raises the possibility that the decrease in activity due to limited iron could be compensated by elevated enzyme abundance. Moreover, the model paves the way for guiding biosynthesis of high-value compounds (e.g., p-coumaric acid) that relies on iron-containing enzymes. Metal ions are vital to metabolism, as they can act as cofactors on enzymes and thus modulate individual enzymatic reactions. Although many enzymes have been reported to interact with metal ions, the quantitative relationships between metal ions and metabolism are lacking. Here, we reconstructed a genome-scale metabolic model of the yeast Saccharomyces cerevisiae to account for proteome constraints and enzyme cofactors such as metal ions, named CofactorYeast. The model is able to estimate abundances of metal ions binding on enzymes in cells under various conditions, which are comparable to measured metal ion contents in biomass. In addition, the model predicts distinct metabolic flux distributions in response to reduced levels of various metal ions in the medium. Specifically, the model reproduces changes upon iron deficiency in metabolic and gene expression levels, which could be interpreted by optimization principles (i.e., yeast optimizes iron utilization based on metabolic network and enzyme kinetics rather than preferentially targeting iron to specific enzymes or pathways). At last, we show the potential of using the model for understanding cell factories that harbor heterologous iron-containing enzymes to synthesize high-value compounds such as p-coumaric acid. Overall, the model demonstrates the dependence of enzymes on metal ions and links metal ions to metabolism on a genome scale.
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An Internal Promoter Drives the Expression of a Truncated Form of CCC1 Capable of Protecting Yeast from Iron Toxicity. Microorganisms 2021; 9:microorganisms9061337. [PMID: 34203091 PMCID: PMC8235630 DOI: 10.3390/microorganisms9061337] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2021] [Revised: 06/11/2021] [Accepted: 06/15/2021] [Indexed: 11/17/2022] Open
Abstract
In yeast, iron storage and detoxification depend on the Ccc1 transporter that mediates iron accumulation in vacuoles. While deletion of the CCC1 gene renders cells unable to survive under iron overload conditions, the deletion of its previously identified regulators only partially affects survival, indicating that the mechanisms controlling iron storage and detoxification in yeast are still far from well understood. This work reveals that CCC1 is equipped with a complex transcriptional structure comprising several regulatory regions. One of these is located inside the coding sequence of the gene and drives the expression of a short transcript encoding an N-terminally truncated protein, designated as s-Ccc1. s-Ccc1, though less efficiently than Ccc1, is able to promote metal accumulation in the vacuole, protecting cells against iron toxicity. While the expression of the s-Ccc1 appears to be repressed in the normal genomic context, our current data clearly demonstrates that it is functional and has the capacity to play a role under iron overload conditions.
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Vali SW, Haja DK, Brand RA, Adams MWW, Lindahl PA. The Pyrococcus furiosus ironome is dominated by [Fe 4S 4] 2+ clusters or thioferrate-like iron depending on the availability of elemental sulfur. J Biol Chem 2021; 296:100710. [PMID: 33930466 PMCID: PMC8219758 DOI: 10.1016/j.jbc.2021.100710] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2021] [Revised: 04/12/2021] [Accepted: 04/22/2021] [Indexed: 11/28/2022] Open
Abstract
Pyrococcus furiosus is a hyperthermophilic anaerobic archaeon whose metabolism depends on whether elemental sulfur is (+S0) or is not (-S0) included in growth medium. Under +S0 conditions, expression of respiratory hydrogenase declines while respiratory membrane-bound sulfane reductase and the putative iron-storage protein IssA increase. Our objective was to investigate the iron content of WT and ΔIssA cells under these growth conditions using Mössbauer spectroscopy. WT-S0 cells contained ∼1 mM Fe, with ∼85% present as two spectroscopically distinct forms of S = 0 [Fe4S4]2+ clusters; the remainder was mainly high-spin FeII. WT+S0 cells contained 5 to 9 mM Fe, with 75 to 90% present as magnetically ordered thioferrate-like (TFL) iron nanoparticles. TFL iron was similar to chemically defined thioferrates; both consisted of FeIII ions coordinated by an S4 environment, and both exhibited strong coupling between particles causing high applied fields to have little spectral effect. At high temperatures with magnetic hyperfine interactions abolished, TFL iron exhibited two doublets overlapping those of [Fe4S4]2+ clusters in -S0 cells. This coincidence arose because of similar coordination environments of TFL iron and cluster iron. The TFL structure was more heterogeneous in the presence of IssA. Presented data suggest that IssA may coordinate insoluble iron sulfides as TFL iron, formed as a byproduct of anaerobic sulfur respiration under high iron conditions, which thereby reduces its toxicity to the cell. This was the first Mössbauer characterization of the ironome of an archaeon, and it illustrates differences relative to the iron content of better-studied bacteria such as Escherichia coli.
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Affiliation(s)
- Shaik Waseem Vali
- Department of Biochemistry and Biophysics, Texas A&M University, College Station, Texas, USA
| | - Dominik K Haja
- Department of Biochemistry and Molecular Biology, University of Georgia, Athens, Georgia, USA
| | - Richard A Brand
- Faculty of Physics, University of Duisburg-Essen, Duisburg, Germany; Institute of Nanotechnology, Karlsruhe Institute of Technology, Eggenstein-Leopoldshafen, Germany
| | - Michael W W Adams
- Department of Biochemistry and Molecular Biology, University of Georgia, Athens, Georgia, USA
| | - Paul A Lindahl
- Department of Biochemistry and Biophysics, Texas A&M University, College Station, Texas, USA; Department of Chemistry, Texas A&M University, College Station, Texas, USA.
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Čanadi Jurešić G, Ćurko-Cofek B, Barbarić M, Mumiši N, Blagović B, Jamnik P. Response of Saccharomyces cerevisiae W303 to Iron and Lead Toxicity in Overloaded Conditions. Curr Microbiol 2021; 78:1188-1201. [PMID: 33624192 DOI: 10.1007/s00284-021-02390-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2020] [Accepted: 02/07/2021] [Indexed: 11/29/2022]
Abstract
Yeast Saccharomyces cerevisiae is an ideal model organism for studying molecular mechanisms of the stress response provoked by metals. In this work, yeast cells response to iron (Fe3+) or lead (Pb2+) exposure was tested and compared. Survival test was used to determine testing doses of metal ions-for Fe3+ it was 4 mM and for Pb2+ 8 mM. These (high, over-loaded) doses provoked comparable values of growth inhibition, but different values in vitality measurement. The percentage of metabolically active cells, determined by fluorescent FUN-1 dye, was lower in Pb2+ than in Fe3+ treated cells. Besides, endogenous antioxidant defence systems in the cells treated with Pb2+ were less efficient compared to Fe3+. At the mitochondrial level, the effects of metal ions were in correlation with the results of cell metabolic activity. The mitochondrial proteome of Pb2+ treated cells showed the domination of protein downregulation. Yeast cells treated either with Fe3+ or Pb2+ shared 19 common significantly changed proteins. The affected proteins were involved in different cellular process and amongst them only five proteins belong to energy and carbohydrate metabolism, and protein biosynthesis. Based on all obtained results, it is possible to conclude that the effects of Fe3+ and Pb2+ on yeast cells show rather specific patterns of toxicity and stress response.
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Affiliation(s)
- Gordana Čanadi Jurešić
- Department of Medical Chemistry, Biochemistry and Clinical Chemistry, Faculty of Medicine, University of Rijeka, B. Branchetta 20, 51000, Rijeka, Croatia.
| | - Božena Ćurko-Cofek
- Department of Physiology and Immunology, Faculty of Medicine, University of Rijeka, B. Branchetta 20, 51000, Rijeka, Croatia
| | - Martina Barbarić
- Faculty of Medicine, University of Rijeka, B. Branchetta 20, 51000, Rijeka, Croatia
| | - Nermina Mumiši
- Faculty of Medicine, University of Rijeka, B. Branchetta 20, 51000, Rijeka, Croatia
| | - Branka Blagović
- Department of Medical Chemistry, Biochemistry and Clinical Chemistry, Faculty of Medicine, University of Rijeka, B. Branchetta 20, 51000, Rijeka, Croatia
| | - Polona Jamnik
- Biotechnical Faculty, University of Ljubljana, Jamnikarjeva 101, 1000, Ljubljana, Slovenia
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Kim JE, Vali SW, Nguyen TQ, Dancis A, Lindahl PA. Mössbauer and LC-ICP-MS investigation of iron trafficking between vacuoles and mitochondria in vma2ΔSaccharomyces cerevisiae. J Biol Chem 2020; 296:100141. [PMID: 33268384 PMCID: PMC7948489 DOI: 10.1074/jbc.ra120.015907] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2020] [Revised: 11/24/2020] [Accepted: 12/02/2020] [Indexed: 01/09/2023] Open
Abstract
Vacuoles are acidic organelles that store FeIII polyphosphate, participate in iron homeostasis, and have been proposed to deliver iron to mitochondria for iron–sulfur cluster (ISC) and heme biosynthesis. Vma2Δ cells have dysfunctional V-ATPases, rendering their vacuoles nonacidic. These cells have mitochondria that are iron-dysregulated, suggesting disruption of a putative vacuole-to-mitochondria iron trafficking pathway. To investigate this potential pathway, we examined the iron content of a vma2Δ mutant derived from W303 cells using Mössbauer and EPR spectroscopies and liquid chromatography interfaced with inductively-coupled-plasma mass spectrometry. Relative to WT cells, vma2Δ cells contained WT concentrations of iron but nonheme FeII dominated the iron content of fermenting and respiring vma2Δ cells, indicating that the vacuolar FeIII ions present in WT cells had been reduced. However, vma2Δ cells synthesized WT levels of ISCs/hemes and had normal aconitase activity. The iron content of vma2Δ mitochondria was similar to WT, all suggesting that iron delivery to mitochondria was not disrupted. Chromatograms of cytosolic flow–through solutions exhibited iron species with apparent masses of 600 and 800 Da for WT and vma2∆, respectively. Mutant cells contained high copper concentrations and high concentrations of a species assigned to metallothionein, indicating copper dysregulation. vma2Δ cells from previously studied strain BY4741 exhibited iron-associated properties more consistent with prior studies, suggesting subtle strain differences. Vacuoles with functional V-ATPases appear unnecessary in W303 cells for iron to enter mitochondria and be used in ISC/heme biosynthesis; thus, there appears to be no direct or dedicated vacuole-to-mitochondria iron trafficking pathway. The vma2Δ phenotype may arise from alterations in trafficking of iron directly from cytosol to mitochondria.
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Affiliation(s)
- Joshua E Kim
- Department of Chemistry, Texas A&M University, College Station, Texas, USA
| | - Shaik Waseem Vali
- Department of Biochemistry and Biophysics, Texas A&M University, College Station, Texas, USA
| | - Trang Q Nguyen
- Department of Chemistry, Texas A&M University, College Station, Texas, USA
| | - Andrew Dancis
- Department of Pharmacology, Physiology, and Neuroscience, New Jersey Medical School, Rutgers University, Newark, New Jersey, USA; Division of Hematology-Oncology, Department of Medicine, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, USA
| | - Paul A Lindahl
- Department of Chemistry, Texas A&M University, College Station, Texas, USA; Department of Biochemistry and Biophysics, Texas A&M University, College Station, Texas, USA.
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Sorribes-Dauden R, Peris D, Martínez-Pastor MT, Puig S. Structure and function of the vacuolar Ccc1/VIT1 family of iron transporters and its regulation in fungi. Comput Struct Biotechnol J 2020; 18:3712-3722. [PMID: 33304466 PMCID: PMC7714665 DOI: 10.1016/j.csbj.2020.10.044] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2020] [Revised: 10/28/2020] [Accepted: 10/31/2020] [Indexed: 02/06/2023] Open
Abstract
Iron is an essential micronutrient for most living beings since it participates as a redox active cofactor in many biological processes including cellular respiration, lipid biosynthesis, DNA replication and repair, and ribosome biogenesis and recycling. However, when present in excess, iron can participate in Fenton reactions and generate reactive oxygen species that damage cells at the level of proteins, lipids and nucleic acids. Organisms have developed different molecular strategies to protect themselves against the harmful effects of high concentrations of iron. In the case of fungi and plants, detoxification mainly occurs by importing cytosolic iron into the vacuole through the Ccc1/VIT1 iron transporter. New sequenced genomes and bioinformatic tools are facilitating the functional characterization, evolution and ecological relevance of metabolic pathways and homeostatic networks across the Tree of Life. Sequence analysis shows that Ccc1/VIT1 homologs are widely distributed among organisms with the exception of animals. The recent elucidation of the crystal structure of a Ccc1/VIT1 plant ortholog has enabled the identification of both conserved and species-specific motifs required for its metal transport mechanism. Moreover, recent studies in the yeast Saccharomyces cerevisiae have also revealed that multiple transcription factors including Yap5 and Msn2/Msn4 contribute to the expression of CCC1 in high-iron conditions. Interestingly, Malaysian S. cerevisiae strains express a partially functional Ccc1 protein that renders them sensitive to iron. Different regulatory mechanisms have been described for non-Saccharomycetaceae Ccc1 homologs. The characterization of Ccc1/VIT1 proteins is of high interest in the development of biofortified crops and the protection against microbial-derived diseases.
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Key Words
- BLOSUM, BLOcks SUbstitution Matrix
- CBC, CCAAT-binding core complex
- CRD, Cysteine-rich domain
- CS, Consistency score
- Ccc1
- Cg, Candida glabrata
- Eg, Eucalyptus grandis
- Fe, Iron
- Fungi
- H, Helix
- Hap, Heme activator protein
- ISC, Iron-sulfur luster
- Iron detoxification
- Iron regulation
- Iron transport
- MAFFT, Multiple Alignment using Fast Fourier Transform
- MBD, Metal-binding domain
- ML, Maximum-likelihood
- NRAMP, Natural Resistance-Associated Macrophage Protein
- Plants
- ROS, Reactive oxygen species
- TMD, Transmembrane domain
- VIT, Vacuolar iron transporter
- VIT1
- VTL, Vacuolar iron transporter-like
- Vacuole
- YRE, Yap response elements
- Yeast
- bZIP, basic leucine-zipper
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Affiliation(s)
- Raquel Sorribes-Dauden
- Departamento de Bioquímica y Biología Molecular, Universitat de València, Burjassot, Valencia, Spain
| | - David Peris
- Departamento de Biotecnología, Instituto de Agroquímica y Tecnología de Alimentos (IATA), Consejo Superior de Investigaciones Científicas (CSIC), Paterna, Valencia, Spain
| | | | - Sergi Puig
- Departamento de Biotecnología, Instituto de Agroquímica y Tecnología de Alimentos (IATA), Consejo Superior de Investigaciones Científicas (CSIC), Paterna, Valencia, Spain
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14
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Thévenod F, Lee WK, Garrick MD. Iron and Cadmium Entry Into Renal Mitochondria: Physiological and Toxicological Implications. Front Cell Dev Biol 2020; 8:848. [PMID: 32984336 PMCID: PMC7492674 DOI: 10.3389/fcell.2020.00848] [Citation(s) in RCA: 31] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2020] [Accepted: 08/07/2020] [Indexed: 12/15/2022] Open
Abstract
Regulation of body fluid homeostasis is a major renal function, occurring largely through epithelial solute transport in various nephron segments driven by Na+/K+-ATPase activity. Energy demands are greatest in the proximal tubule and thick ascending limb where mitochondrial ATP production occurs through oxidative phosphorylation. Mitochondria contain 20-80% of the cell's iron, copper, and manganese that are imported for their redox properties, primarily for electron transport. Redox reactions, however, also lead to reactive, toxic compounds, hence careful control of redox-active metal import into mitochondria is necessary. Current dogma claims the outer mitochondrial membrane (OMM) is freely permeable to metal ions, while the inner mitochondrial membrane (IMM) is selectively permeable. Yet we recently showed iron and manganese import at the OMM involves divalent metal transporter 1 (DMT1), an H+-coupled metal ion transporter. Thus, iron import is not only regulated by IMM mitoferrins, but also depends on the OMM to intermembrane space H+ gradient. We discuss how these mitochondrial transport processes contribute to renal injury in systemic (e.g., hemochromatosis) and local (e.g., hemoglobinuria) iron overload. Furthermore, the environmental toxicant cadmium selectively damages kidney mitochondria by "ionic mimicry" utilizing iron and calcium transporters, such as OMM DMT1 or IMM calcium uniporter, and by disrupting the electron transport chain. Consequently, unraveling mitochondrial metal ion transport may help develop new strategies to prevent kidney injury induced by metals.
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Affiliation(s)
- Frank Thévenod
- Faculty of Health, Centre for Biomedical Education and Research, Institute of Physiology, Pathophysiology and Toxicology, Witten/Herdecke University, Witten, Germany
| | - Wing-Kee Lee
- Faculty of Health, Centre for Biomedical Education and Research, Institute of Physiology, Pathophysiology and Toxicology, Witten/Herdecke University, Witten, Germany
| | - Michael D Garrick
- Department of Biochemistry, Jacobs School of Medicine and Biomedical Sciences, University at Buffalo, Buffalo, NY, United States
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15
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Hunsaker EW, McAuliffe KJ, Franz KJ. Fluconazole analogues with metal-binding motifs impact metal-dependent processes and demonstrate antifungal activity in Candida albicans. J Biol Inorg Chem 2020; 25:729-745. [PMID: 32542530 PMCID: PMC7415656 DOI: 10.1007/s00775-020-01796-x] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2020] [Accepted: 05/25/2020] [Indexed: 12/28/2022]
Abstract
Azole antifungals are an important class of antifungal drugs due to their low cost, ability to be administered orally, and broad-spectrum activity. However, their widespread and long-term use have given rise to adaptation mechanisms that render these compounds less effective against common fungal pathogens, including Candida albicans. New antifungals are desperately needed as drug-resistant strains become more prevalent. We recently showed that copper supplementation potentiates the activity of the azole antifungal fluconazole against the opportunistic fungal pathogen C. albicans. Here, we report eight new azole analogues derived from fluconazole in which one triazole group has been replaced with a metal-binding group, a strategy designed to enhance potentiation of azole antifungal activity by copper. The bioactivity of all eight compounds was tested and compared to that of fluconazole. Three of the analogues showed activity against C. albicans and two had lower levels of trailing growth. One compound, Flu-TSCZ, was found to impact the levels, speciation, and bioavailability of cellular metals.
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Affiliation(s)
- Elizabeth W Hunsaker
- Department of Chemistry, French Family Science Center, Duke University, 124 Science Drive, Durham, NC, 27708, USA
| | - Katherine J McAuliffe
- Department of Chemistry, French Family Science Center, Duke University, 124 Science Drive, Durham, NC, 27708, USA
| | - Katherine J Franz
- Department of Chemistry, French Family Science Center, Duke University, 124 Science Drive, Durham, NC, 27708, USA.
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16
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Hunsaker EW, Franz KJ. Candida albicans reprioritizes metal handling during fluconazole stress. Metallomics 2020; 11:2020-2032. [PMID: 31709426 DOI: 10.1039/c9mt00228f] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
Maintenance of metal homeostasis is critical to cell survival due to the multitude of cellular processes that depend on one or more metal cofactors. Here, we show that the opportunistic fungal pathogen Candida albicans extensively remodels its metal homeostasis networks to respond to treatment with the antifungal drug fluconazole. Disruption of the ergosterol biosynthetic pathway by fluconazole requires C. albicans adaptation, including increased Cu import and storage, increased retention of Fe, Mn, and Zn, altered utilization of Cu- and Mn-dependent enzymes, mobilization of Fe stores, and increased production of the heme prosthetic group utilized by the enzyme target of fluconazole. The findings offer a new perspective for thinking about fungal response to drug stress that pushes cells out of their metal homeostatic zones, leading them to enact metal-associated adaptation mechanisms to restore homeostasis to survive.
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Affiliation(s)
- Elizabeth W Hunsaker
- Department of Chemistry, Duke University, French Family Science Center, 124 Science Drive, Durham, North Carolina 27708, USA.
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17
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Nguyen TQ, Kim JE, Brawley HN, Lindahl PA. Chromatographic detection of low-molecular-mass metal complexes in the cytosol of Saccharomyces cerevisiae. Metallomics 2020; 12:1094-1105. [PMID: 32301942 PMCID: PMC7497409 DOI: 10.1039/c9mt00312f] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
Fluorescence-based chelators are commonly used to probe labile low-molecular-mass (LMM) metal pools in the cytosol of eukaryotic cells, but such chelators destroy the complexes of interest during detection. The objective of this study was to use chromatography to directly detect such complexes. Towards this end, 47 batches of cytosol were isolated from fermenting S. cerevisiae yeast cells and passed through a 10 kDa cut-off membrane. The metal contents of the cytosol and resulting flow-through solution (FTS) were determined. FTSs were applied to a size-exclusion LC column located in an anaerobic refrigerated glove box. The LC system was coupled to an online inductively-coupled-plasma mass spectrometer (ICP-MS) for detection of individual metals. Iron-detected chromatograms of cytosolic FTSs from WT cells exhibited 2-4 major species with apparent masses between 500-1300 Da. Increasing the iron concentration in the growth medium 40-fold increased the overall intensity of these peaks. Approximately 3 LMM cytosolic copper complexes with apparent masses between 300-1300 Da were also detected; their LC intensities were weak, but these increased with increasing concentrations of copper in the growth medium. Observed higher-mass copper-detected peaks were tentatively assigned to copper-bound metallothioneins Cup1 and Crs5. FTSs from strains in which Cup1 or the Cox17 copper chaperone were deleted altered the distribution of LMM copper complexes. LMM zinc- and manganese-detected species were also present in cytosol, albeit at low concentrations. Supplementing the growth medium with zinc increased the intensity of the zinc peak assigned to Crs5 but the intensities of LMM zinc complexes were unaffected. Phosphorus-detected chromatograms were dominated by peaks at apparent masses 400-800 Da, with minor peaks at 1000-1500 Da in some batches. Sulfur chromatograms contained a low-intensity peak that comigrated with a glutathione standard; quantification suggested a GSH concentration in the cytosol of ca. 13 mM. A second LMM sulfur peak that migrated at an apparent mass of 100 Da was also evident.
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Affiliation(s)
- Trang Q Nguyen
- Department of Chemistry, Texas A&M University, College Station, TX 77843-3255, USA.
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18
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Abstract
Iron is essential for nearly every organism, and mismanagement of its intracellular concentrations (either deficiency or excess) contributes to diminished virulence in human pathogens, necessitating intricate metalloregulatory mechanisms. To date, although several metal-responsive riboswitches have been identified in bacteria, none has been shown to respond to FeII. The czcD riboswitch, present in numerous human gut microbiota and pathogens, was recently shown to respond to NiII and CoII but thought not to respond to FeII, on the basis of aerobic, in vitro assays; its function in vivo is not well understood. We constructed a fluorescent sensor using this riboswitch fused to the RNA aptamer, Spinach2. When assayed anaerobically, the resulting sensor responds in vitro to FeII, as well as to MnII, CoII, NiII, and ZnII, but only in the cases of FeII and MnII do the apparent Kd values (0.4 and 11 μM, respectively) fall within the range of labile metal concentrations maintained by known metalloregulators. We also show that the sensor-which is, to the best of our knowledge, the first reversible genetically encoded fluorescent sensor for FeII-responds to iron in Escherichia coli cells. Finally, we demonstrate that the putative metal exporters directly downstream of two czcD riboswitches efficiently rescue iron toxicity in a heterologous expression system. Together, our results indicate that iron merits consideration as a plausible physiological ligand for czcD riboswitches, although a response to general metal stress cannot be ruled out at present.
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Affiliation(s)
- Jiansong Xu
- Department of Chemistry, The Pennsylvania State University, University Park, Pennsylvania 16802, United States
| | - Joseph A Cotruvo
- Department of Chemistry, The Pennsylvania State University, University Park, Pennsylvania 16802, United States
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19
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Ramos-Alonso L, Wittmaack N, Mulet I, Martínez-Garay CA, Fita-Torró J, Lozano MJ, Romero AM, García-Ferris C, Martínez-Pastor MT, Puig S. Molecular strategies to increase yeast iron accumulation and resistance. Metallomics 2019; 10:1245-1256. [PMID: 30137082 DOI: 10.1039/c8mt00124c] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
All eukaryotic organisms rely on iron as an essential micronutrient for life because it participates as a redox-active cofactor in multiple biological processes. However, excess iron can generate reactive oxygen species that damage cellular macromolecules. The low solubility of ferric iron under physiological conditions increases the prevalence of iron deficiency anemia. A common strategy to treat iron deficiency consists of dietary iron supplementation. The baker's yeast Saccharomyces cerevisiae is used as a model eukaryotic organism, but also as a feed supplement. In response to iron deficiency, the yeast Aft1 transcription factor activates cellular iron acquisition. However, when constitutively active, Aft1 inhibits growth probably due to iron toxicity. In this report, we have studied the consequences of using hyperactive AFT1 alleles, including AFT1-1UP, to increase yeast iron accumulation. We first characterized the iron sensitivity of cells expressing different constitutively active AFT1 alleles. We rescued the high iron sensitivity conferred by the AFT1 alleles by deleting the sphingolipid signaling kinase YPK1. We observed that the deletion of YPK1 exerts different effects on iron accumulation depending on the AFT1 allele and the environmental iron. Moreover, we determined that the impairment of the high-affinity iron transport system partially rescues the high iron toxicity of AFT1-1UP-expressing cells. Finally, we observed that AFT1-1UP inhibits oxygen consumption through activation of the RNA-binding protein Cth2. Deletion of CTH2 partially rescues the AFT1-1UP negative respiratory effect. Collectively, these results contribute to understand how the Aft1 transcription factor functions and the multiple consequences derived from its constitutive activation.
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Affiliation(s)
- Lucía Ramos-Alonso
- Departamento de Biotecnología, Instituto de Agroquímica y Tecnología de Alimentos (IATA), Consejo Superior de Investigaciones Científicas (CSIC), Paterna, Valencia, Spain.
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20
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Zhou DR, Eid R, Miller KA, Boucher E, Mandato CA, Greenwood MT. Intracellular second messengers mediate stress inducible hormesis and Programmed Cell Death: A review. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2019; 1866:773-792. [DOI: 10.1016/j.bbamcr.2019.01.016] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/10/2018] [Revised: 01/25/2019] [Accepted: 01/29/2019] [Indexed: 12/11/2022]
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21
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Zhou DR, Eid R, Boucher E, Miller KA, Mandato CA, Greenwood MT. Stress is an agonist for the induction of programmed cell death: A review. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2019; 1866:699-712. [DOI: 10.1016/j.bbamcr.2018.12.001] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/17/2018] [Revised: 09/17/2018] [Accepted: 12/01/2018] [Indexed: 02/07/2023]
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22
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Wofford JD, Lindahl PA. A mathematical model of iron import and trafficking in wild-type and Mrs3/4ΔΔ yeast cells. BMC SYSTEMS BIOLOGY 2019; 13:23. [PMID: 30791941 PMCID: PMC6385441 DOI: 10.1186/s12918-019-0702-2] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 04/11/2018] [Accepted: 02/06/2019] [Indexed: 12/03/2022]
Abstract
Background Iron plays crucial roles in the metabolism of eukaryotic cells. Much iron is trafficked into mitochondria where it is used for iron-sulfur cluster assembly and heme biosynthesis. A yeast strain in which Mrs3/4, the high-affinity iron importers on the mitochondrial inner membrane, are deleted exhibits a slow-growth phenotype when grown under iron-deficient conditions. However, these cells grow at WT rates under iron-sufficient conditions. The object of this study was to develop a mathematical model that could explain this recovery on the molecular level. Results A multi-tiered strategy was used to solve an ordinary-differential-equations-based mathematical model of iron import, trafficking, and regulation in growing Saccharomyces cerevisiae cells. At the simplest level of modeling, all iron in the cell was presumed to be a single species and the cell was considered to be a single homogeneous volume. Optimized parameters associated with the rate of iron import and the rate of dilution due to cell growth were determined. At the next level of complexity, the cell was divided into three regions, including cytosol, mitochondria, and vacuoles, each of which was presumed to contain a single form of iron. Optimized parameters associated with import into these regions were determined. At the final level of complexity, nine components were assumed within the same three cellular regions. Parameters obtained at simpler levels of complexity were used to help solve the more complex versions of the model; this was advantageous because the data used for solving the simpler model variants were more reliable and complete relative to those required for the more complex variants. The optimized full-complexity model simulated the observed phenotype of WT and Mrs3/4ΔΔ cells with acceptable fidelity, and the model exhibited some predictive power. Conclusions The developed model highlights the importance of an FeII mitochondrial pool and the necessary exclusion of O2 in the mitochondrial matrix for eukaryotic iron-sulfur cluster metabolism. Similar multi-tiered strategies could be used for any micronutrient in which concentrations and metabolic forms have been determined in different organelles within a growing eukaryotic cell. Electronic supplementary material The online version of this article (10.1186/s12918-019-0702-2) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Joshua D Wofford
- Texas A&M University, Department of Chemistry, College Station, TX, 77843-3255, USA
| | - Paul A Lindahl
- Texas A&M University, Department of Chemistry, College Station, TX, 77843-3255, USA. .,Texas A&M University, Department of Biochemistry & Biophysics, College Station, 77843-3255, USA.
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23
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Dikicioglu D, Oliver SG. Extension of the yeast metabolic model to include iron metabolism and its use to estimate global levels of iron-recruiting enzyme abundance from cofactor requirements. Biotechnol Bioeng 2019; 116:610-621. [PMID: 30578666 PMCID: PMC6492170 DOI: 10.1002/bit.26905] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2018] [Revised: 11/21/2018] [Accepted: 12/20/2018] [Indexed: 12/15/2022]
Abstract
Metabolic networks adapt to changes in their environment by modulating the activity of their enzymes and transporters; often by changing their abundance. Understanding such quantitative changes can shed light onto how metabolic adaptation works, or how it can fail and lead to a metabolically dysfunctional state. We propose a strategy to quantify metabolic protein requirements for cofactor‐utilising enzymes and transporters through constraint‐based modelling. The first eukaryotic genome‐scale metabolic model to comprehensively represent iron metabolism was constructed, extending the most recent community model of the Saccharomyces cerevisiae metabolic network. Partial functional impairment of the genes involved in the maturation of iron‐sulphur (Fe‐S) proteins was investigated employing the model and the in silico analysis revealed extensive rewiring of the fluxes in response to this functional impairment, despite its marginal phenotypic effect. The optimal turnover rate of enzymes bearing ion cofactors can be determined via this novel approach; yeast metabolism, at steady state, was determined to employ a constant turnover of its iron‐recruiting enzyme at a rate of 3.02 × 10
−11 mmol·(g biomass)
−1·h
−1.
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Affiliation(s)
- Duygu Dikicioglu
- Department of Chemical Engineering and Biotechnology, University of Cambridge, Cambridge, UK.,Cambridge Systems Biology Centre, University of Cambridge, Cambridge, UK
| | - Stephen G Oliver
- Cambridge Systems Biology Centre, University of Cambridge, Cambridge, UK.,Department of Biochemistry, University of Cambridge, Cambridge, UK
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24
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Abstract
Non-Saccharomyces yeasts are becoming important because most of them are considered as spoilage species in winemaking processes, among them the species Saccharomycodes ludwigii. This species is frequently isolated at the end of the fermentation process and/or during storage of the wine, i.e., it can to grow in the presence of high levels of ethanol. Besides, this species is adaptable to unfavorable conditions such as high concentrations of SO2 and is characterized by its capacity to produce high amounts of undesirable metabolites as acetoin, ethyl acetate or acetic acid. To the present, physical (gamma irradiation and continuous pulsed electric fields), chemical (inhibitory compounds such as chitosan and dimethyl dicarbonate) and biological (antagonistic biocontrol by killer yeasts) treatments have been developed in order to control the growth of this spoilage yeast in wines and other fruit derivatives. Therefore, this review is focused on the most relevant studies conducted to control contamination by S. ludwigii. Moreover, potential applications of S. ludwigii in alternative winemaking techniques, for example for ageing-on-lees and stabilization of red wines, and improvement of aromatic profile are also examined.
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25
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Moore MJ, Wofford JD, Dancis A, Lindahl PA. Recovery of mrs3Δmrs4Δ Saccharomyces cerevisiae Cells under Iron-Sufficient Conditions and the Role of Fe 580. Biochemistry 2018; 57:672-683. [PMID: 29228768 PMCID: PMC6468996 DOI: 10.1021/acs.biochem.7b01034] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
Mrs3 and Mrs4 are mitochondrial inner membrane proteins that deliver an unidentified cytosolic iron species into the matrix for use in iron-sulfur cluster (ISC) and heme biosynthesis. The Mrs3/4 double-deletion strain (ΔΔ) grew slowly in iron-deficient glycerol/ethanol medium but recovered to wild-type (WT) rates in iron-sufficient medium. ΔΔ cells grown under both iron-deficient and iron-sufficient respiring conditions acquired large amounts of iron relative to WT cells, indicating iron homeostatic dysregulation regardless of nutrient iron status. Biophysical spectroscopy (including Mössbauer, electron paramagnetic resonance, and electronic absorption) and bioanalytical methods (liquid chromatography with online inductively coupled plasma mass spectrometry detection) were used to characterize these phenotypes. Anaerobically isolated mitochondria contained a labile iron pool composed of a nonheme high-spin FeII complex with primarily O and N donor ligands, called Fe580. Fe580 likely serves as feedstock for ISC and heme biosynthesis. Mitochondria from respiring ΔΔ cells grown under iron-deficient conditions were devoid of Fe580, ISCs, and hemes; most iron was present as FeIII nanoparticles. O2 likely penetrates the matrix of slow-growing poorly respiring iron-deficient ΔΔ cells and reacts with Fe580 to form nanoparticles, thereby inhibiting ISC and heme biosynthesis. Mitochondria from iron-sufficient ΔΔ cells contained ISCs, hemes, and Fe580 at concentrations comparable to those of WT mitochondria. The matrix of these mutant cells was probably sufficiently anaerobic to protect Fe580 from degradation by O2. An ∼1100 Da manganese complex, an ∼1200 Da zinc complex, and an ∼5000 Da copper species were also present in ΔΔ and WT mitochondrial flow-through solutions. No lower-mass copper complex was evident.
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Affiliation(s)
- Michael J. Moore
- Department of Chemistry, Texas A&M University, College Station, Texas 77843, United States
| | - Joshua D. Wofford
- Department of Chemistry, Texas A&M University, College Station, Texas 77843, United States
| | - Andrew Dancis
- Department of Medicine, Division of Hematology-Oncology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania 19104, United States
| | - Paul A. Lindahl
- Department of Chemistry, Texas A&M University, College Station, Texas 77843, United States
- Department of Biochemistry and Biophysics, Texas A&M University, College Station, Texas 77843, United States
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26
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Garcia-Serres R, Clémancey M, Latour JM, Blondin G. Contribution of Mössbauer spectroscopy to the investigation of Fe/S biogenesis. J Biol Inorg Chem 2018; 23:635-644. [PMID: 29350298 PMCID: PMC6006220 DOI: 10.1007/s00775-018-1534-z] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2017] [Accepted: 01/04/2018] [Indexed: 10/27/2022]
Abstract
Fe/S cluster biogenesis involves a complex machinery comprising several mitochondrial and cytosolic proteins. Fe/S cluster biosynthesis is closely intertwined with iron trafficking in the cell. Defects in Fe/S cluster elaboration result in severe diseases such as Friedreich ataxia. Deciphering this machinery is a challenge for the scientific community. Because iron is a key player, 57Fe-Mössbauer spectroscopy is especially appropriate for the characterization of Fe species and monitoring the iron distribution. This minireview intends to illustrate how Mössbauer spectroscopy contributes to unravel steps in Fe/S cluster biogenesis. Studies were performed on isolated proteins that may be present in multiple protein complexes. Since a few decades, Mössbauer spectroscopy was also performed on whole cells or on isolated compartments such as mitochondria and vacuoles, affording an overview of the iron trafficking. This minireview aims at presenting selected applications of 57Fe-Mössbauer spectroscopy to Fe/S cluster biogenesis.
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Affiliation(s)
| | - Martin Clémancey
- Univ. Grenoble Alpes, CEA, CNRS, LCBM UMR 5249, pmb, 38000, Grenoble, France
| | - Jean-Marc Latour
- Univ. Grenoble Alpes, CEA, CNRS, LCBM UMR 5249, pmb, 38000, Grenoble, France
| | - Geneviève Blondin
- Univ. Grenoble Alpes, CEA, CNRS, LCBM UMR 5249, pmb, 38000, Grenoble, France. .,LCBM/pmb, CEA Bât C5, 17 Rue des Martyrs, 38054, Grenoble Cedex 9, France.
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27
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Wofford JD, Park J, McCormick SP, Chakrabarti M, Lindahl PA. Ferric ions accumulate in the walls of metabolically inactivating Saccharomyces cerevisiae cells and are reductively mobilized during reactivation. Metallomics 2017; 8:692-708. [PMID: 27188213 DOI: 10.1039/c6mt00070c] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
Mössbauer and EPR spectra of fermenting yeast cells before and after cell wall (CW) digestion revealed that CWs accumulated iron as cells transitioned from exponential to post-exponential growth. Most CW iron was mononuclear nonheme high-spin (NHHS) Fe(III), some was diamagnetic and some was superparamagnetic. A significant portion of CW Fe was removable by EDTA. Simulations using an ordinary-differential-equations-based model suggested that cells accumulate Fe as they become metabolically inactive. When dormant Fe-loaded cells were metabolically reactivated in Fe-deficient bathophenanthroline disulfonate (BPS)-treated medium, they grew using Fe that had been mobilized from their CWs AND using trace amounts of Fe in the Fe-deficient medium. When grown in Fe-deficient medium, Fe-starved cells contained the lowest cellular Fe concentrations reported for a eukaryotic cell. During metabolic reactivation of Fe-loaded dormant cells, Fe(III) ions in the CWs of these cells were mobilized by reduction to Fe(II), followed by release from the CW and reimport into the cell. BPS short-circuited this process by chelating mobilized and released Fe(II) ions before reimport; the resulting Fe(II)(BPS)3 complex adsorbed on the cell surface. NHHS Fe(II) ions appeared transiently during mobilization, suggesting that these ions were intermediates in this process. In the presence of chelators and at high pH, metabolically inactive cells leached CW Fe; this phenomenon probably differs from metabolic mobilization. The iron regulon, as reported by Fet3p levels, was not expressed during post-exponential conditions; Fet3p was maximally expressed in exponentially growing cells. Decreased expression of the iron regulon and metabolic decline combine to promote CW Fe accumulation.
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Affiliation(s)
- Joshua D Wofford
- Department of Chemistry, Texas A&M University, College Station, TX 77843-3255, USA.
| | - Jinkyu Park
- Department of Chemistry, Texas A&M University, College Station, TX 77843-3255, USA.
| | - Sean P McCormick
- Department of Chemistry, Texas A&M University, College Station, TX 77843-3255, USA.
| | - Mrinmoy Chakrabarti
- Department of Chemistry, Texas A&M University, College Station, TX 77843-3255, USA.
| | - Paul A Lindahl
- Department of Chemistry, Texas A&M University, College Station, TX 77843-3255, USA. and Department of Biochemistry and Biophysics, Texas A&M University, College Station, TX 77843, USA
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28
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Horie T, Kawamata T, Matsunami M, Ohsumi Y. Recycling of iron via autophagy is critical for the transition from glycolytic to respiratory growth. J Biol Chem 2017; 292:8533-8543. [PMID: 28320861 DOI: 10.1074/jbc.m116.762963] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2016] [Revised: 03/14/2017] [Indexed: 11/06/2022] Open
Abstract
Autophagy is a bulk degradation process conserved from yeast to mammals. To examine the roles of autophagy in cellular metabolism, we generated autophagy-defective (atg) mutants in the X2180-1B strain background. We compared the growth of wild-type (WT) and atg cells in minimal (synthetic dextrose, SD) and rich (yeast extract/peptone/dextrose, YEPD) medium, and we found that mutations in the core autophagy machinery result in defects in the diauxic shift, the transition from fermentation to respiratory growth upon glucose depletion, specifically in SD. Furthermore, we confirmed that autophagy was induced prior to the diauxic shift, implying that it plays a role in this process. In YEPD, atg mutants grew normally, so we assumed that the insufficiency of certain nutrients in SD was responsible for the defects. We ultimately identified iron, which is a necessary cofactor for respiratory activity, as the nutrient required for the diauxic shift in atg mutants. Indeed, atg mutants exhibited defects in respiration, which was rescued by supplementation with iron. Based on these data, we hypothesized that autophagy is involved in iron recycling during the diauxic shift. smf3Δfet5Δ or smf3Δftr1Δ cells, which are unable to export iron from the vacuole, also exhibit defects in the diauxic shift, so iron released from the vacuole is important for the shift in SD medium. Finally, we observed that smf3Δfet5Δ cells accumulated nearly twice as much vacuolar iron as smf3Δfet5Δatg2Δ cells, suggesting that autophagy is involved in iron recycling by the vacuolar transport and degradation of iron-containing cargos.
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Affiliation(s)
- Tetsuro Horie
- Research Unit for Cell Biology, Institute of Innovative Research, Tokyo Institute of Technology, Yokohama 226-8503; Research Center for Odontology, School of Life Dentistry at Tokyo, The Nippon Dental University, Chiyoda-ku, Tokyo 102-8159, Japan
| | - Tomoko Kawamata
- Research Unit for Cell Biology, Institute of Innovative Research, Tokyo Institute of Technology, Yokohama 226-8503
| | - Miou Matsunami
- Research Unit for Cell Biology, Institute of Innovative Research, Tokyo Institute of Technology, Yokohama 226-8503
| | - Yoshinori Ohsumi
- Research Unit for Cell Biology, Institute of Innovative Research, Tokyo Institute of Technology, Yokohama 226-8503.
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29
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Tenório RP, Barros W. Patterns in Saccharomyces cerevisiae yeast colonies via magnetic resonance imaging. Integr Biol (Camb) 2017; 9:68-75. [PMID: 27942686 DOI: 10.1039/c6ib00219f] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
We report the use of high-resolution magnetic resonance imaging methods to observe pattern formation in colonies of Saccharomyces cerevisiae. Our results indicate substantial signal loss localized in specific regions of the colony rendering useful imaging contrast. This imaging contrast is recognizable as being due to discontinuities in magnetic susceptibility (χ) between different spatial regions. At the microscopic pixel level, the local variations in the magnetic susceptibility (Δχ) induce a loss in the NMR signal, which was quantified via T2 and T2* maps, permitting estimation of Δχ values for different regions of the colony. Interestingly the typical petal/wrinkling patterns present in the colony have a high degree of correlation with the estimated susceptibility distribution. We conclude that the presence of magnetic susceptibility inclusions, together with their spatial arrangement within the colony, may be a potential cause of the susceptibility distribution and therefore the contrast observed on the images.
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Affiliation(s)
- Rômulo P Tenório
- Centro Regional de Ciências Nucleares do Nordeste, Comissão Nacional de Energia Nuclear, Av. Prof. Luiz Freire, 200, Cidade Universitária, 50740-540, Recife, Pernambuco, Brazil.
| | - Wilson Barros
- Departamento de Física, Universidade Federal de Pernambuco, Av. Prof. Luiz Freire, s/n, Cidade Universitária, 50670-901, Recife, Pernambuco, Brazil
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30
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Eid R, Boucher E, Gharib N, Khoury C, Arab NTT, Murray A, Young PG, Mandato CA, Greenwood MT. Identification of human ferritin, heavy polypeptide 1 (FTH1) and yeast RGI1 (YER067W) as pro-survival sequences that counteract the effects of Bax and copper in Saccharomyces cerevisiae. Exp Cell Res 2016; 342:52-61. [PMID: 26886577 DOI: 10.1016/j.yexcr.2016.02.010] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2015] [Revised: 02/09/2016] [Accepted: 02/12/2016] [Indexed: 02/06/2023]
Abstract
Ferritin is a sub-family of iron binding proteins that form multi-subunit nanotype iron storage structures and prevent oxidative stress induced apoptosis. Here we describe the identification and characterization of human ferritin, heavy polypeptide 1 (FTH1) as a suppressor of the pro-apoptotic murine Bax sequence in yeast. In addition we demonstrate that FTH1 is a general pro-survival sequence since it also prevents the cell death inducing effects of copper when heterologously expressed in yeast. Although ferritins are phylogenetically widely distributed and are present in most species of Bacteria, Archaea and Eukarya, ferritin is conspicuously absent in most fungal species including Saccharomyces cerevisiae. An in silico analysis of the yeast proteome lead to the identification of the 161 residue RGI1 (YER067W) encoded protein as a candidate for being a yeast ferritin. In addition to sharing 20% sequence identity with the 183 residue FTH1, RGI1 also has similar pro-survival properties as ferritin when overexpressed in yeast. Analysis of recombinant protein by SDS-PAGE and by electron microscopy revealed the expected formation of higher-order structures for FTH1 that was not observed with Rgi1p. Further analysis revealed that cells overexpressing RGI1 do not show increased resistance to iron toxicity and do not have enhanced capacity to store iron. In contrast, cells lacking RGI1 were found to be hypersensitive to the toxic effects of iron. Overall, our results suggest that Rgi1p is a novel pro-survival protein whose function is not related to ferritin but nevertheless it may have a role in regulating yeast sensitivity to iron stress.
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Affiliation(s)
- Rawan Eid
- Department of Chemistry and Chemical Engineering, Royal Military College, Kingston, Ontario, Canada; Department of Biology, Queen's University, Kingston, Ontario, Canada
| | - Eric Boucher
- Department of Anatomy and Cell Biology, McGill University, Montreal, Quebec, Canada
| | - Nada Gharib
- Department of Chemistry and Chemical Engineering, Royal Military College, Kingston, Ontario, Canada
| | - Chamel Khoury
- Department of Chemistry and Chemical Engineering, Royal Military College, Kingston, Ontario, Canada; Department of Biology, Queen's University, Kingston, Ontario, Canada; Department of Anatomy and Cell Biology, McGill University, Montreal, Quebec, Canada
| | - Nagla T T Arab
- Department of Chemistry and Chemical Engineering, Royal Military College, Kingston, Ontario, Canada; Department of Biology, Queen's University, Kingston, Ontario, Canada
| | - Alistair Murray
- Department of Anatomy and Cell Biology, McGill University, Montreal, Quebec, Canada
| | - Paul G Young
- Department of Biology, Queen's University, Kingston, Ontario, Canada
| | - Craig A Mandato
- Department of Anatomy and Cell Biology, McGill University, Montreal, Quebec, Canada
| | - Michael T Greenwood
- Department of Chemistry and Chemical Engineering, Royal Military College, Kingston, Ontario, Canada.
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31
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Cth2 Protein Mediates Early Adaptation of Yeast Cells to Oxidative Stress Conditions. PLoS One 2016; 11:e0148204. [PMID: 26824473 PMCID: PMC4732752 DOI: 10.1371/journal.pone.0148204] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2015] [Accepted: 01/14/2016] [Indexed: 11/19/2022] Open
Abstract
Cth2 is an mRNA-binding protein that participates in remodeling yeast cell metabolism in iron starvation conditions by promoting decay of the targeted molecules, in order to avoid excess iron consumption. This study shows that in the absence of Cth2 immediate upregulation of expression of several of the iron regulon genes (involved in high affinity iron uptake and intracellular iron redistribution) upon oxidative stress by hydroperoxide is more intense than in wild type conditions where Cth2 is present. The oxidative stress provokes a temporary increase in the levels of Cth2 (itself a member of the iron regulon). In such conditions Cth2 molecules accumulate at P bodies-like structures when the constitutive mRNA decay machinery is compromised. In addition, a null Δcth2 mutant shows defects, in comparison to CTH2 wild type cells, in exit from α factor-induced arrest at the G1 stage of the cell cycle when hydroperoxide treatment is applied. The cell cycle defects are rescued in conditions that compromise uptake of external iron into the cytosol. The observations support a role of Cth2 in modulating expression of diverse iron regulon genes, excluding those specifically involved in the reductive branch of the high-affinity transport. This would result in immediate adaptation of the yeast cells to an oxidative stress, by controlling uptake of oxidant-promoting iron cations.
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32
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Responses of Saccharomyces cerevisiae Strains from Different Origins to Elevated Iron Concentrations. Appl Environ Microbiol 2016; 82:1906-1916. [PMID: 26773083 DOI: 10.1128/aem.03464-15] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2015] [Accepted: 01/08/2016] [Indexed: 01/10/2023] Open
Abstract
Iron is an essential micronutrient for all eukaryotic organisms. However, the low solubility of ferric iron has tremendously increased the prevalence of iron deficiency anemia, especially in women and children, with dramatic consequences. Baker's yeast Saccharomyces cerevisiae is used as a model eukaryotic organism, a fermentative microorganism, and a feed supplement. In this report, we explore the genetic diversity of 123 wild and domestic strains of S. cerevisiae isolated from different geographical origins and sources to characterize how yeast cells respond to elevated iron concentrations in the environment. By using two different forms of iron, we selected and characterized both iron-sensitive and iron-resistant yeast strains. We observed that when the iron concentration in the medium increases, iron-sensitive strains accumulate iron more rapidly than iron-resistant isolates. We observed that, consistent with excess iron leading to oxidative stress, the redox state of iron-sensitive strains was more oxidized than that of iron-resistant strains. Growth assays in the presence of different oxidative reagents ruled out that this phenotype was due to alterations in the general oxidative stress protection machinery. It was noteworthy that iron-resistant strains were more sensitive to iron deficiency conditions than iron-sensitive strains, which suggests that adaptation to either high or low iron is detrimental for the opposite condition. An initial gene expression analysis suggested that alterations in iron homeostasis genes could contribute to the different responses of distant iron-sensitive and iron-resistant yeast strains to elevated environmental iron levels.
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33
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Wofford JD, Lindahl PA. Mitochondrial Iron-Sulfur Cluster Activity and Cytosolic Iron Regulate Iron Traffic in Saccharomyces cerevisiae. J Biol Chem 2015; 290:26968-26977. [PMID: 26306041 PMCID: PMC4646409 DOI: 10.1074/jbc.m115.676668] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2015] [Revised: 08/17/2015] [Indexed: 11/06/2022] Open
Abstract
An ordinary differential equation-based mathematical model was developed to describe trafficking and regulation of iron in growing fermenting budding yeast. Accordingly, environmental iron enters the cytosol and moves into mitochondria and vacuoles. Dilution caused by increasing cell volume is included. Four sites are regulated, including those in which iron is imported into the cytosol, mitochondria, and vacuoles, and the site at which vacuolar Fe(II) is oxidized to Fe(III). The objective of this study was to determine whether cytosolic iron (Fecyt) and/or a putative sulfur-based product of iron-sulfur cluster (ISC) activity was/were being sensed in regulation. The model assumes that the matrix of healthy mitochondria is anaerobic, and that in ISC mutants, O2 diffuses into the matrix where it reacts with nonheme high spin Fe(II) ions, oxidizing them to nanoparticles and generating reactive oxygen species. This reactivity causes a further decline in ISC/heme biosynthesis, which ultimately gives rise to the diseased state. The ordinary differential equations that define this model were numerically integrated, and concentrations of each component were plotted versus the concentration of iron in the growth medium and versus the rate of ISC/heme biosynthesis. Model parameters were optimized by fitting simulations to literature data. The model variant that assumed that both Fecyt and ISC biosynthesis activity were sensed in regulation mimicked observed behavior best. Such "dual sensing" probably arises in real cells because regulation involves assembly of an ISC on a cytosolic protein using Fecyt and a sulfur species generated in mitochondria during ISC biosynthesis and exported into the cytosol.
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Affiliation(s)
- Joshua D Wofford
- Departments of Chemistry, Texas A & M University, College Station, Texas 77843
| | - Paul A Lindahl
- Departments of Chemistry, Texas A & M University, College Station, Texas 77843; Departments of Chemistry, Biochemistry and Biophysics, Texas A & M University, College Station, Texas 77843.
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34
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McCormick SP, Moore MJ, Lindahl PA. Detection of Labile Low-Molecular-Mass Transition Metal Complexes in Mitochondria. Biochemistry 2015; 54:3442-53. [PMID: 26018429 DOI: 10.1021/bi5015437] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
Liquid chromatography was used with an online inductively coupled plasma mass spectrometer to detect low-molecular-mass (LMM) transition metal complexes in mitochondria isolated from fermenting yeast cells, human Jurkat cells, and mouse brain and liver. These complexes constituted 20-40% of total mitochondrial Mn, Fe, Zn, and Cu ions. The major LMM Mn complex in yeast mitochondria, called Mn1100, had a mass of ∼1100 Da and a concentration of ∼2 μM. Mammalian mitochondria contained a second Mn species with a mass of ∼2000 Da at a comparable concentration. The major Fe complex in mitochondria isolated from exponentially growing yeast cells had a mass of ∼580 Da; the concentration of Fe580 in mitochondria was ∼100 μM. When mitochondria were isolated from fermenting cells in postexponential phase, the mass of the dominant LMM Fe complex was ∼1100 Da. Upon incubation, the intensity of Fe1100 declined and that of Fe580 increased, suggesting that the two are interrelated. Mammalian mitochondria contained Fe580 and two other Fe species (Fe2000 and Fe1100) at concentrations of ∼50 μM each. The dominant LMM Zn species in mitochondria had a mass of ∼1200 Da and a concentration of ∼110 μM. Mammalian mitochondria contained a second major LMM Zn species at 1500 Da. The dominant LMM Cu species in yeast mitochondria had a mass of ∼5000 Da and a concentration in yeast mitochondria of ∼16 μM; Cu5000 was not observed in mammalian mitochondria. The dominant Co species in mitochondria, Co1200, had a concentration of 20 nM and was probably a cobalamin. Mammalian but not yeast mitochondria contained a LMM Mo species, Mo730, at a concentration of ∼1 μM. Increasing Mn, Fe, Cu, and Zn concentrations 10-fold in the medium increased the concentration of the same element in the corresponding isolated mitochondria. Treatment with metal chelators confirmed that these LMM species were labile. The dominant S species at 1100 Da was not free glutathione or glutathione disulfide.
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35
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Zhang C. Essential functions of iron-requiring proteins in DNA replication, repair and cell cycle control. Protein Cell 2014; 5:750-60. [PMID: 25000876 PMCID: PMC4180463 DOI: 10.1007/s13238-014-0083-7] [Citation(s) in RCA: 179] [Impact Index Per Article: 17.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2014] [Accepted: 05/04/2014] [Indexed: 02/06/2023] Open
Abstract
Eukaryotic cells contain numerous iron-requiring proteins such as iron-sulfur (Fe-S) cluster proteins, hemoproteins and ribonucleotide reductases (RNRs). These proteins utilize iron as a cofactor and perform key roles in DNA replication, DNA repair, metabolic catalysis, iron regulation and cell cycle progression. Disruption of iron homeostasis always impairs the functions of these iron-requiring proteins and is genetically associated with diseases characterized by DNA repair defects in mammals. Organisms have evolved multi-layered mechanisms to regulate iron balance to ensure genome stability and cell development. This review briefly provides current perspectives on iron homeostasis in yeast and mammals, and mainly summarizes the most recent understandings on iron-requiring protein functions involved in DNA stability maintenance and cell cycle control.
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Affiliation(s)
- Caiguo Zhang
- Department of Biochemistry and Molecular Genetics, University of Colorado School of Medicine, Aurora, CO, 80045, USA,
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36
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Park J, McCormick SP, Cockrell AL, Chakrabarti M, Lindahl PA. High-spin ferric ions in Saccharomyces cerevisiae vacuoles are reduced to the ferrous state during adenine-precursor detoxification. Biochemistry 2014; 53:3940-51. [PMID: 24919141 PMCID: PMC4072367 DOI: 10.1021/bi500148y] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
The majority of Fe in Fe-replete yeast cells is located in vacuoles. These acidic organelles store Fe for use under Fe-deficient conditions and they sequester it from other parts of the cell to avoid Fe-associated toxicity. Vacuolar Fe is predominantly in the form of one or more magnetically isolated nonheme high-spin (NHHS) Fe(III) complexes with polyphosphate-related ligands. Some Fe(III) oxyhydroxide nanoparticles may also be present in these organelles, perhaps in equilibrium with the NHHS Fe(III). Little is known regarding the chemical properties of vacuolar Fe. When grown on adenine-deficient medium (A↓), ADE2Δ strains of yeast such as W303 produce a toxic intermediate in the adenine biosynthetic pathway. This intermediate is conjugated with glutathione and shuttled into the vacuole for detoxification. The iron content of A↓ W303 cells was determined by Mössbauer and EPR spectroscopies. As they transitioned from exponential growth to stationary state, A↓ cells (supplemented with 40 μM Fe(III) citrate) accumulated two major NHHS Fe(II) species as the vacuolar NHHS Fe(III) species declined. This is evidence that vacuoles in A↓ cells are more reducing than those in adenine-sufficient cells. A↓ cells suffered less oxidative stress despite the abundance of NHHS Fe(II) complexes; such species typically promote Fenton chemistry. Most Fe in cells grown for 5 days with extra yeast-nitrogen-base, amino acids and bases in minimal medium was HS Fe(III) with insignificant amounts of nanoparticles. The vacuoles of these cells might be more acidic than normal and can accommodate high concentrations of HS Fe(III) species. Glucose levels and rapamycin (affecting the TOR system) affected cellular Fe content. This study illustrates the sensitivity of cellular Fe to changes in metabolism, redox state and pH. Such effects broaden our understanding of how Fe and overall cellular metabolism are integrated.
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Affiliation(s)
- Jinkyu Park
- Department of Chemistry, Texas A&M University , College Station, Texas 77843-3255, United States
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37
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Cockrell A, McCormick SP, Moore MJ, Chakrabarti M, Lindahl PA. Mössbauer, EPR, and modeling study of iron trafficking and regulation in Δccc1 and CCC1-up Saccharomyces cerevisiae. Biochemistry 2014; 53:2926-40. [PMID: 24785783 PMCID: PMC4025571 DOI: 10.1021/bi500002n] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
![]()
Strains lacking and overexpressing
the vacuolar iron (Fe) importer CCC1 were characterized
using Mössbauer and EPR spectroscopies.
Vacuolar Fe import is impeded in Δccc1 cells
and enhanced in CCC1-up cells, causing vacuolar Fe
in these strains to decline and accumulate, respectively, relative
to WT cells. Cytosolic Fe levels should behave oppositely. The Fe
content of Δccc1 cells grown under low-Fe conditions
was similar to that in WT cells. Most Fe was mitochondrial with some
nonheme high spin (NHHS) FeII present. Δccc1 cells grown with increasing Fe concentration in the medium contained
less total Fe, less vacuolar HS FeIII, and more NHHS FeII than in comparable WT cells. As the Fe concentration in
the growth medium increased, the concentration of HS FeIII in Δccc1 cells increased to just 60% of WT
levels, while NHHS FeII increased to twice WT levels, suggesting
that the NHHS FeII was cytosolic. Δccc1 cells suffered more oxidative damage than WT cells, suggesting that
the accumulated NHHS FeII promoted Fenton chemistry. The
Fe concentration in CCC1-up cells was higher than
in WT cells; the extra Fe was present as NHHS FeII and
FeIII and as FeIII oxyhydroxide nanoparticles.
These cells contained less mitochondrial Fe and exhibited less ROS
damage than Δccc1 cells. CCC1-up cells were adenine-deficient on minimal medium; supplementing with
adenine caused a decline of NHHS FeII suggesting that some
of the NHHS FeII that accumulated in these cells was associated
with adenine deficiency rather than the overexpression of CCC1. A mathematical model was developed that simulated
changes in Fe distributions. Simulations suggested that only a modest
proportion of the observed NHHS FeII in both strains was
the cytosolic form of Fe that is sensed by the Fe import regulatory
system. The remainder is probably generated by the reduction of the
vacuolar NHHS FeIII species.
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Affiliation(s)
- Allison Cockrell
- Department of Biochemistry and Biophysics, Texas A&M University , College Station, Texas 77843-2128, United States
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38
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Oro L, Ciani M, Comitini F. Antimicrobial activity of Metschnikowia pulcherrima on wine yeasts. J Appl Microbiol 2014; 116:1209-17. [PMID: 24443784 DOI: 10.1111/jam.12446] [Citation(s) in RCA: 130] [Impact Index Per Article: 13.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2013] [Revised: 12/04/2013] [Accepted: 01/09/2014] [Indexed: 12/25/2022]
Abstract
AIMS In the present study, it was investigated the antagonistic behaviour of Metschnikowia pulcherrima, as biocontrol agent, against the main wine yeast species involved in the winemaking process. METHODS AND RESULTS Seven strains of M. pulcherrima were evaluated for the antimicrobial activity against 114 yeast strains belonging to Pichia, Candida, Hanseniaspora, Kluyveromyces, Saccharomycodes, Torulaspora, Brettanomyces and Saccharomyces genera. Results showed both different inter-generic and intra-generic responses to the antimicrobial action of M. pulcherrima strains. Interestingly, the antimicrobial activity of M. pulcherrima did not have any influence on the growth of Saccharomyces cerevisiae. Instead, M. pulcherrima displayed a broad and effective antimicrobial action on undesired wild spoilage yeasts, such as Brettanomyces/Dekkera, Hanseniaspora and Pichia genera. Fermentation trials carried out in synthetic grape must confirmed the antimicrobial activity of M. pulcherrima, determining the early death of the non-Saccharomyces co-inoculated cultures. CONCLUSIONS The antimicrobial activity of M. pulcherrima does not seem due to proteinaceous compounds such as killer phenomenon, but to the pulcherriminic acid (the precursor of pulcherrimin pigment) that depletes iron present in the medium, making it not available to the other yeasts. SIGNIFICANCE AND IMPACT OF THE STUDY These data agree with and further support the potential use of selected M. pulcherrima strains in controlled multistarter fermentations with S. cerevisiae starter cultures.
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Affiliation(s)
- L Oro
- Dipartimento Scienze della Vita e dell'Ambiente, Università Politecnica delle Marche, Ancona, Italy
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39
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The role of iron and reactive oxygen species in cell death. Nat Chem Biol 2014; 10:9-17. [PMID: 24346035 DOI: 10.1038/nchembio.1416] [Citation(s) in RCA: 1477] [Impact Index Per Article: 147.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2013] [Accepted: 11/19/2013] [Indexed: 02/06/2023]
Abstract
The transition metal iron is essential for life, yet potentially toxic iron-catalyzed reactive oxygen species (ROS) are unavoidable in an oxygen-rich environment. Iron and ROS are increasingly recognized as important initiators and mediators of cell death in a variety of organisms and pathological situations. Here, we review recent discoveries regarding the mechanism by which iron and ROS participate in cell death. We describe the different roles of iron in triggering cell death, targets of iron-dependent ROS that mediate cell death and a new form of iron-dependent cell death termed ferroptosis. Recent advances in understanding the role of iron and ROS in cell death offer unexpected surprises and suggest new therapeutic avenues to treat cancer, organ damage and degenerative disease.
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40
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Holmes-Hampton GP, Tong WH, Rouault TA. Biochemical and biophysical methods for studying mitochondrial iron metabolism. Methods Enzymol 2014; 547:275-307. [PMID: 25416363 DOI: 10.1016/b978-0-12-801415-8.00015-1] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Iron is a heavily utilized element in organisms and numerous mechanisms accordingly regulate the trafficking, metabolism, and storage of iron. Despite the high regulation of iron homeostasis, several diseases and mutations can lead to the misregulation and often accumulation of iron in the cytosol or mitochondria of tissues. To understand the genesis of iron overload, it is necessary to employ various techniques to quantify iron in organisms and mitochondria. This chapter discusses techniques for determining the total iron content of tissue samples, ranging from colorimetric determination of iron concentrations, atomic absorption spectroscopy, inductively coupled plasma-optical emission spectroscopy, and inductively coupled plasma-mass spectrometry. In addition, we discuss in situ techniques for analyzing iron including electron microscopic nonheme iron histochemistry, electron energy loss spectroscopy, synchrotron X-ray fluorescence imaging, and confocal Raman microscopy. Finally, we discuss biophysical methods for studying iron in isolated mitochondria, including ultraviolet-visible, electron paramagnetic resonance, X-ray absorbance, and Mössbauer spectroscopies. This chapter should aid researchers to select and interpret mitochondrial iron quantifications.
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Affiliation(s)
- Gregory P Holmes-Hampton
- Molecular Medicine Program, Eunice Kennedy Shriver National Institute of Child Health and Human Development, Bethesda, Maryland, USA
| | - Wing-Hang Tong
- Molecular Medicine Program, Eunice Kennedy Shriver National Institute of Child Health and Human Development, Bethesda, Maryland, USA
| | - Tracey A Rouault
- Molecular Medicine Program, Eunice Kennedy Shriver National Institute of Child Health and Human Development, Bethesda, Maryland, USA.
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41
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Park J, McCormick SP, Chakrabarti M, Lindahl PA. Insights into the iron-ome and manganese-ome of Δmtm1 Saccharomyces cerevisiae mitochondria. Metallomics 2013; 5:656-72. [PMID: 23598994 DOI: 10.1039/c3mt00041a] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Biophysical spectroscopies and LC-ICP-MS were used to evaluate the iron-ome and manganese-ome of mitochondria from Δmtm1 yeast cells. Deleting the mitochondrial carrier gene MTM1 causes Fe to accumulate in mitochondria and Mn superoxide dismutase (SOD2) activity to decline. One explanation for this is that some accumulated Fe misincorporates into apo-Sod2p. Mössbauer spectroscopy revealed that most of the accumulated Fe was Fe(III) nanoparticles which are unlikely to misincorporate into apo-Sod2p. Under anaerobic conditions, Fe did not accumulate yet SOD2 activity remained low, suggesting that the two phenomena are independent. Mn concentrations were two-fold higher in Δmtm1 mitochondria than in WT mitochondria. Soluble extracts from such samples were subjected to size-exclusion LC and fractions were analyzed with an on-line ICP-MS. Two major Mn peaks were observed, one due to MnSod2p and the other to a Mn species with a mass of 2-3 kDa (called Mn2-3). Mn2-3 may deliver Mn into apo-Sod2p. Most Mn in WT mitochondria was associated with MnSod2p, whereas most Mn in Δmtm1 mitochondria was associated with Mn2-3. The [Mn2-3] increased in cells grown on high MnCl2 while the MnSod2p concentration remained unchanged. Corresponding Fe traces showed numerous peaks, including a complex of ~3 kDa which may be the form of Fe that misincorporates, and an Fe peak with the molecular mass of Sod2p that may correspond to FeSod2p. The intensity of this peak suggests that deleting MTM1 probably diminishes SOD2 activity by some means other than Fe misincorporation. A portion of Sod2p in Δmtm1 mitochondria might be unfolded or immature. Mtm1p may import a species required for apo-Sod2p maturation, activity or stability.
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Affiliation(s)
- Jinkyu Park
- Texas A&M University, Department of Chemistry, College Station, TX 77843, USA
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42
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Park J, McCormick SP, Chakrabarti M, Lindahl PA. The lack of synchronization between iron uptake and cell growth leads to iron overload in Saccharomyces cerevisiae during post-exponential growth modes. Biochemistry 2013; 52:9413-25. [PMID: 24344915 DOI: 10.1021/bi4010304] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
Fermenting cells growing exponentially on rich (YPAD) medium underwent a transition to a slow-growing state as glucose levels declined and their metabolism shifted to respiration. During exponential growth, Fe import and cell-growth rates were matched, affording an approximately invariant cellular Fe concentration. During the transition period, the high-affinity Fe import rate declined slower than the cell-growth rate declined, causing Fe to accumulate, initially as Fe(III) oxyhydroxide nanoparticles but eventually as mitochondrial and vacuolar Fe. Once the cells had reached slow-growth mode, Fe import and cell-growth rates were again matched, and the cellular Fe concentration was again approximately invariant. Fermenting cells grown on minimal medium (MM) grew more slowly during the exponential phase and underwent a transition to a true stationary state as glucose levels declined. The Fe concentration of MM cells that just entered the stationary state was similar to that of YPAD cells, but MM cells continued to accumulate Fe in the stationary state. Fe initially accumulated as nanoparticles and high-spin Fe(II) species, but vacuolar Fe(III) also eventually accumulated. Surprisingly, Fe-packed 5-day-old MM cells suffered no more reactive oxygen species (ROS) damage than younger cells, suggesting that the Fe concentration alone does not accurately predict the extent of ROS damage. The mode and rate of growth at the time of harvesting dramatically affected cellular Fe content. A mathematical model of Fe metabolism in a growing cell was developed. The model included the import of Fe via a regulated high-affinity pathway and an unregulated low-affinity pathway. The import of Fe from the cytosol to vacuoles and mitochondria and nanoparticle formation were also included. The model captured essential trafficking behavior, demonstrating that cells regulate Fe import in accordance with their overall growth rate and that they misregulate Fe import when nanoparticles accumulate. The lack of regulation of Fe in yeast is perhaps unique compared to the tight regulation of other cellular metabolites. This phenomenon likely derives from the unique chemistry associated with Fe nanoparticle formation.
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Affiliation(s)
- Jinkyu Park
- Department of Chemistry, Texas A&M University , College Station, Texas 77843-3255, United States
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Jhurry ND, Chakrabarti M, McCormick SP, Gohil VM, Lindahl PA. Mössbauer study and modeling of iron import and trafficking in human jurkat cells. Biochemistry 2013; 52:7926-42. [PMID: 24180611 DOI: 10.1021/bi401015t] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
The Fe content of Jurkat cells grown on transferrin-bound iron (TBI) and Fe(III) citrate (FC) was characterized using Mössbauer, electron paramagnetic resonance, and UV-vis spectroscopies, as well as electron and inductively coupled plasma mass spectrometry. Isolated mitochondria were similarly characterized. Fe-limited cells contained ~100 μM essential Fe, mainly as mitochondrial Fe and nonmitochondrial non-heme high-spin Fe(II). Cells replete with Fe also contained ferritin-bound Fe and Fe(III) oxyhydroxide nanoparticles. Only 400 ± 100 Fe ions were loaded per ferritin complex, regardless of the growth medium Fe concentration. Ferritin regulation thus appears to be more complex than is commonly assumed. The magnetic and structural properties of Jurkat nanoparticles differed from those of yeast mitochondria. They were smaller and may be located in the cytosol. The extent of nanoparticle formation scaled nonlinearly with the concentration of Fe in the medium. Nanoparticle formation was not strongly correlated with reactive oxygen species (ROS) damage. Cells could utilize nanoparticle Fe, converting such aggregates into essential Fe forms. Cells grown on galactose rather than glucose respired faster, grew slower, exhibited more ROS damage, and generally contained more nanoparticles. Cells grown with TBI rather than FC contained less Fe overall, more ferritin, and fewer nanoparticles. Cells in which the level of transferrin receptor expression was increased contained more ferritin Fe. Frataxin-deficient cells contained more nanoparticles than comparable wild-type cells. Data were analyzed by a chemically based mathematical model. Although simple, it captured essential features of Fe import, trafficking, and regulation. TBI import was highly regulated, but FC import was not. Nanoparticle formation was not regulated, but the rate was third-order in cytosolic Fe.
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Affiliation(s)
- Nema D Jhurry
- Department of Biochemistry and Biophysics, Texas A&M University , College Station, Texas 77843-2128, United States
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Outten CE, Albetel AN. Iron sensing and regulation in Saccharomyces cerevisiae: Ironing out the mechanistic details. Curr Opin Microbiol 2013; 16:662-8. [PMID: 23962819 DOI: 10.1016/j.mib.2013.07.020] [Citation(s) in RCA: 103] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2013] [Accepted: 07/29/2013] [Indexed: 01/26/2023]
Abstract
Regulation of iron metabolism in Saccharomyces cerevisiae is achieved at the transcriptional level by low (Aft1 and Aft2) and high iron-sensing (Yap5) transcription factors, and at the post-transcriptional level by mRNA-binding proteins (Cth1 and Cth2). In this review we highlight recent studies unveiling the critical role that iron-sulfur clusters play in control of Aft1/2 and Yap5 activity, as well as the complex relationship between iron homeostasis and thiol redox metabolism. In addition, new insights into the localization and regulation of Cth1/Cth2 have added another layer of complexity to the cell's adaptation to iron deficiency. Finally, biophysical studies on subcellular iron speciation changes in response to environmental and genetic factors have further illuminated the elaborate control mechanisms required to manage iron bioavailability in the cell.
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Affiliation(s)
- Caryn E Outten
- Department of Chemistry and Biochemistry, University of South Carolina, 631 Sumter St., Columbia, SC 29208, USA.
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