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Bak DW, Weerapana E. Proteomic strategies to interrogate the Fe-S proteome. BIOCHIMICA ET BIOPHYSICA ACTA. MOLECULAR CELL RESEARCH 2024; 1871:119791. [PMID: 38925478 DOI: 10.1016/j.bbamcr.2024.119791] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/29/2024] [Revised: 05/23/2024] [Accepted: 06/19/2024] [Indexed: 06/28/2024]
Abstract
Iron‑sulfur (Fe-S) clusters, inorganic cofactors composed of iron and sulfide, participate in numerous essential redox, non-redox, structural, and regulatory biological processes within the cell. Though structurally and functionally diverse, the list of all proteins in an organism capable of binding one or more Fe-S clusters is referred to as its Fe-S proteome. Importantly, the Fe-S proteome is highly dynamic, with continuous cluster synthesis and delivery by complex Fe-S cluster biogenesis pathways. This cluster delivery is balanced out by processes that can result in loss of Fe-S cluster binding, such as redox state changes, iron availability, and oxygen sensitivity. Despite continued expansion of the Fe-S protein catalogue, it remains a challenge to reliably identify novel Fe-S proteins. As such, high-throughput techniques that can report on native Fe-S cluster binding are required to both identify new Fe-S proteins, as well as characterize the in vivo dynamics of Fe-S cluster binding. Due to the recent rapid growth in mass spectrometry, proteomics, and chemical biology, there has been a host of techniques developed that are applicable to the study of native Fe-S proteins. This review will detail both the current understanding of the Fe-S proteome and Fe-S cluster biology as well as describing state-of-the-art proteomic strategies for the study of Fe-S clusters within the context of a native proteome.
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Affiliation(s)
- Daniel W Bak
- Department of Chemistry, Boston College, Chestnut Hill, MA, United States of America.
| | - Eranthie Weerapana
- Department of Chemistry, Boston College, Chestnut Hill, MA, United States of America.
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2
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Lamačová LJ, Trnka J. Chelating mitochondrial iron and copper: Recipes, pitfalls and promise. Mitochondrion 2024; 78:101903. [PMID: 38777220 DOI: 10.1016/j.mito.2024.101903] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2023] [Revised: 05/10/2024] [Accepted: 05/15/2024] [Indexed: 05/25/2024]
Abstract
Iron and copper chelation therapy plays a crucial role in treating conditions associated with metal overload, such as hemochromatosis or Wilson's disease. However, conventional chelators face challenges in reaching the core of iron and copper metabolism - the mitochondria. Mitochondria-targeted chelators can specifically target and remove metal ions from mitochondria, showing promise in treating diseases linked to mitochondrial dysfunction, including neurodegenerative diseases and cancer. Additionally, they serve as specific mitochondrial metal sensors. However, designing these new molecules presents its own set of challenges. Depending on the chelator's intended use to prevent or to promote redox cycling of the metals, the chelating moiety must possess different donor atoms and an optimal value of the electrode potential of the chelator-metal complex. Various targeting moieties can be employed for selective delivery into the mitochondria. This review also provides an overview of the current progress in the design of mitochondria-targeted chelators and their biological activity investigation.
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Affiliation(s)
- Lucie J Lamačová
- Department of Biochemistry, Cell and Molecular Biology, Third Faculty of Medicine, Charles University, Ruská 87, 100 00 Praha, Czech Republic
| | - Jan Trnka
- Department of Biochemistry, Cell and Molecular Biology, Third Faculty of Medicine, Charles University, Ruská 87, 100 00 Praha, Czech Republic.
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3
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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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4
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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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5
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Shepherd RE, Kreinbrink AC, Njimoh CL, Vali SW, Lindahl PA. Yeast Mitochondria Import Aqueous Fe II and, When Activated for Iron-Sulfur Cluster Assembly, Export or Release Low-Molecular-Mass Iron and Also Export Iron That Incorporates into Cytosolic Proteins. J Am Chem Soc 2023. [PMID: 37339084 DOI: 10.1021/jacs.2c13439] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/22/2023]
Abstract
Iron-sulfur cluster (ISC) assembly occurs in both mitochondria and cytosol. Mitochondria are thought to export a low-molecular-mass (LMM) iron and/or sulfur species which is used as a substrate for cytosolic ISC assembly. This species, called X-S or (Fe-S)int, has not been directly detected. Here, an assay was developed in which mitochondria were isolated from 57Fe-enriched cells and incubated in various buffers. Thereafter, mitochondria were separated from the supernatant, and both fractions were investigated by ICP-MS-detected size exclusion liquid chromatography. Aqueous 54FeII in the buffer declined upon exposure to intact 57Fe-enriched mitochondria. Some 54Fe was probably surface-absorbed but some was incorporated into mitochondrial iron-containing proteins when mitochondria were activated for ISC biosynthesis. When activated, mitochondria exported/released two LMM nonproteinaceous iron complexes. One species, which comigrated with an Fe-ATP complex, developed faster than the other Fe species, which also comigrated with phosphorus. Both were enriched in 54Fe and 57Fe, suggesting that the added 54Fe entered a pre-existing pool of 57Fe, which was also the source of the exported species. When 54Fe-loaded 57Fe-enriched mitochondria were mixed with isolated cytosol and activated, multiple cytosolic proteins became enriched with Fe. No incorporation was observed when 54Fe was added directly to the cytosol in the absence of mitochondria. This suggests that a different Fe source in mitochondria, the one enriched mainly with 57Fe, was used to export a species that was ultimately incorporated into cytosolic proteins. Iron from buffer was imported into mitochondria fastest, followed by mitochondrial ISC assembly, LMM iron export, and cytosolic ISC assembly.
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Affiliation(s)
- Rachel E Shepherd
- Department of Chemistry, Texas A&M University, College Station, Texas 77843-3255, United States
| | - Alexia C Kreinbrink
- Department of Biochemistry and Biophysics, Texas A&M University, College Station Texas 77843, United States
| | - Cybele Lemuh Njimoh
- Department of Biochemistry and Biophysics, Texas A&M University, College Station Texas 77843, United States
| | - Shaik Waseem Vali
- Department of Biochemistry and Biophysics, Texas A&M University, College Station Texas 77843, United States
| | - Paul A Lindahl
- Department of Chemistry, Texas A&M University, College Station, Texas 77843-3255, United States
- Department of Biochemistry and Biophysics, Texas A&M University, College Station Texas 77843, United States
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6
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Kim J, Lindahl PA. CUP1 Metallothionein from Healthy Saccharomyces cerevisiae Colocalizes to the Cytosol and Mitochondrial Intermembrane Space. Biochemistry 2023; 62:62-74. [PMID: 36503220 PMCID: PMC9813906 DOI: 10.1021/acs.biochem.2c00481] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2022] [Revised: 10/26/2022] [Indexed: 12/14/2022]
Abstract
Liquid chromatography, mass spectrometry, and metal analyses of cytosol and mitochondrial filtrates from healthy copper-replete Saccharomyces cerevisiae cells revealed that metallothionein CUP1 was a notable copper-containing species in both compartments, with its abundance dependent upon the level of copper supplementation in the growth media. Electrospray ionization mass spectrometry of cytosol and soluble mitochondrial filtrates displayed a full isotopologue pattern of CUP1 in which the first eight amino acid residues were truncated and eight copper ions were bound. Neither apo-CUP1 nor intermediate copper-bound forms were detected, but chelator treatment could generate apo-CUP1. Mitoplasting revealed that mitochondrial CUP1 was located in the intermembrane space. Fluorescence microscopy demonstrated that 34 kDa CUP1-GFP entered the organelle, discounting the possibility that 7 kDa CUP1 enters folded and metalated through outer membrane pores. How CUP1 enters mitochondria remains unclear, as does its role within the organelle. Although speculative, mitochondrial CUP1 may limit the concentrations of low-molecular-mass copper complexes in the organelle.
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Affiliation(s)
- Joshua
E. Kim
- Department
of Chemistry, Texas A&M University, College Station, Texas 77843-3255, United States
| | - Paul A. Lindahl
- Department
of Chemistry, Texas A&M University, College Station, Texas 77843-3255, United States
- Department
of Biochemistry and Biophysics, Texas A&M
University, College Station, Texas 77843, United States
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7
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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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Kurt F, Kurt B, Filiz E, Yildiz K, Akbudak MA. Mitochondrial iron transporter (MIT) gene in potato (Solanum tuberosum): comparative bioinformatics, physiological and expression analyses in response to drought and salinity. Biometals 2022; 35:875-887. [PMID: 35764832 DOI: 10.1007/s10534-022-00411-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2021] [Accepted: 06/11/2022] [Indexed: 11/26/2022]
Abstract
Mitochondrial iron transporter (MIT) genes are essential for mitochondrial acquisition/import of iron and vital to proper functioning of mitochondria. Unlike other organisms, research on the MITs in plants is limited. The present study provides comparative bioinformatics assays for the potato MIT gene (StMIT) as well as gene expression analyses. The phylogenetic analyses revealed monocots-dicot divergence in MIT proteins and it was also found clade specific motif diversity. In addition, docking analyses indicated that Asp172 and Gly100 residues to be identified as the closest residues binding to ferrous iron. The percentage of structure overlap of the StMIT 3D protein model with Arabidopsis, maize and rice MIT proteins was found between 80.18% and 85.71%. The transcript analyses exhibited that the expression of StMIT was triggered under drought and salinity stresses. The findings of the present study would provide valuable leads for further studies targeting specifically the MIT gene and generally the plant iron metabolism.
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Affiliation(s)
- Firat Kurt
- Faculty of Applied Sciences, Plant Production and Technologies, Mus Alparslan University, Muş, Turkey
| | - Baris Kurt
- Department of Mathematics, Faculty of Education, Mus Alparslan University, Muş, Turkey
| | - Ertugrul Filiz
- Department of Crop and Animal Production, Cilimli Vocational School, Duzce University, Cilimli, Duzce, Turkey.
| | - Kubra Yildiz
- Department of Agricultural Biotechnology, Akdeniz University, Antalya, Turkey
| | - M Aydın Akbudak
- Department of Agricultural Biotechnology, Akdeniz University, Antalya, Turkey.
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9
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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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10
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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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11
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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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12
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Abstract
Iron–sulfur (Fe–S) clusters are protein cofactors of a multitude of enzymes performing essential biological functions. Specialized multi-protein machineries present in all types of organisms support their biosynthesis. These machineries encompass a scaffold protein on which Fe–S clusters are assembled and a cysteine desulfurase that provides sulfur in the form of a persulfide. The sulfide ions are produced by reductive cleavage of the persulfide, which involves specific reductase systems. Several other components are required for Fe–S biosynthesis, including frataxin, a key protein of controversial function and accessory components for insertion of Fe–S clusters in client proteins. Fe–S cluster biosynthesis is thought to rely on concerted and carefully orchestrated processes. However, the elucidation of the mechanisms of their assembly has remained a challenging task due to the biochemical versatility of iron and sulfur and the relative instability of Fe–S clusters. Nonetheless, significant progresses have been achieved in the past years, using biochemical, spectroscopic and structural approaches with reconstituted system in vitro. In this paper, we review the most recent advances on the mechanism of assembly for the founding member of the Fe–S cluster family, the [2Fe2S] cluster that is the building block of all other Fe–S clusters. The aim is to provide a survey of the mechanisms of iron and sulfur insertion in the scaffold proteins by examining how these processes are coordinated, how sulfide is produced and how the dinuclear [2Fe2S] cluster is formed, keeping in mind the question of the physiological relevance of the reconstituted systems. We also cover the latest outcomes on the functional role of the controversial frataxin protein in Fe–S cluster biosynthesis.
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13
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Fernie AR, Cavalcanti JHF, Nunes-Nesi A. Metabolic Roles of Plant Mitochondrial Carriers. Biomolecules 2020; 10:E1013. [PMID: 32650612 PMCID: PMC7408384 DOI: 10.3390/biom10071013] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2020] [Revised: 06/28/2020] [Accepted: 06/29/2020] [Indexed: 02/07/2023] Open
Abstract
Mitochondrial carriers (MC) are a large family (MCF) of inner membrane transporters displaying diverse, yet often redundant, substrate specificities, as well as differing spatio-temporal patterns of expression; there are even increasing examples of non-mitochondrial subcellular localization. The number of these six trans-membrane domain proteins in sequenced plant genomes ranges from 39 to 141, rendering the size of plant families larger than that found in Saccharomyces cerevisiae and comparable with Homo sapiens. Indeed, comparison of plant MCs with those from these better characterized species has been highly informative. Here, we review the most recent comprehensive studies of plant MCFs, incorporating the torrent of genomic data emanating from next-generation sequencing techniques. As such we present a more current prediction of the substrate specificities of these carriers as well as review the continuing quest to biochemically characterize this feature of the carriers. Taken together, these data provide an important resource to guide direct genetic studies aimed at addressing the relevance of these vital carrier proteins.
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Affiliation(s)
- Alisdair R. Fernie
- Max-Planck-Instiute of Molecular Plant Physiology, 14476 Postdam-Golm, Germany
| | - João Henrique F. Cavalcanti
- Instituto de Educação, Agricultura e Ambiente, Universidade Federal do Amazonas, Humaitá 69800-000, Amazonas, Brazil;
| | - Adriano Nunes-Nesi
- Departamento de Biologia Vegetal, Universidade Federal de Viçosa, Viçosa 36570-900, Minas Gerais, Brazil
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14
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Lewis BE, Mason Z, Rodrigues AV, Nuth M, Dizin E, Cowan JA, Stemmler TL. Unique roles of iron and zinc binding to the yeast Fe-S cluster scaffold assembly protein "Isu1". Metallomics 2019; 11:1820-1835. [PMID: 31532427 DOI: 10.1039/c9mt00172g] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
Mitochondrial Fe-S cluster biosynthesis is accomplished within yeast utilizing the biophysical attributes of the "Isu1" scaffold assembly protein. As a member of a highly homologous protein family, Isu1 has sequence conservation between orthologs and a conserved ability to assemble [2Fe-2S] clusters. Regardless of species, scaffold orthologs have been shown to exist in both "disordered" and "structured" conformations, a structural architecture that is directly related to conformations utilized during Fe-S cluster assembly. During assembly, the scaffold helps direct the delivery and utilization of Fe(ii) and persulfide substrates to produce [2Fe-2S] clusters, however Zn(ii) binding alters the activity of the scaffold while at the same time stabilizes the protein in its structured state. Additional studies confirm Zn binds to the scaffold's Cys rich active site, and has an impact on the protein's ability to make Fe-S clusters. Understanding the interplay between Fe(ii) and Zn(ii) binding to Isu1 in vitro may help clarify metal loading events that occur during Fe-S cluster assembly in vivo. Here we determine the metal : protein stoichiometry for Isu1 Zn and Fe binding to be 1 : 1 and 2 : 1, respectively. As expected, while Zn binding shifts the Isu1 to its structured state, folding is not influenced by Fe(ii) binding. X-ray absorption spectroscopy (XAS) confirms Zn(ii) binds to the scaffold's cysteine rich active site but Fe(ii) binds at a location distinct from the active site. XAS results show Isu1 binding initially of either Fe(ii) or Zn(ii) does not significantly perturb the metal site structure of alternate metal. XAS confirmed that four scaffold orthologs bind iron as high-spin Fe(ii) at a site composed of ca. 6 oxygen and nitrogen nearest neighbor ligands. Finally, in our report Zn binding dramatically reduces the Fe-S cluster assembly activity of Isu1 even in the presence of frataxin. Given the Fe-binding activity we report for Isu1 and its orthologs here, a possible mechanism involving Fe(ii) transport to the scaffold's active site during cluster assembly has been considered.
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Affiliation(s)
- Brianne E Lewis
- Department of Pharmaceutical Science, Wayne State University, Detroit, MI 48201, USA.
| | - Zachary Mason
- Department of Pharmaceutical Science, Wayne State University, Detroit, MI 48201, USA.
| | - Andria V Rodrigues
- Department of Pharmaceutical Science, Wayne State University, Detroit, MI 48201, USA.
| | - Manunya Nuth
- Department of Chemistry, The Ohio State University, Columbus, OH 43210, USA
| | - Eric Dizin
- Department of Chemistry, The Ohio State University, Columbus, OH 43210, USA
| | - J A Cowan
- Department of Chemistry, The Ohio State University, Columbus, OH 43210, USA
| | - Timothy L Stemmler
- Department of Pharmaceutical Science, Wayne State University, Detroit, MI 48201, USA.
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15
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Lindahl PA. A comprehensive mechanistic model of iron metabolism in Saccharomyces cerevisiae. Metallomics 2019; 11:1779-1799. [PMID: 31531508 DOI: 10.1039/c9mt00199a] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
The ironome of budding yeast (circa 2019) consists of approximately 139 proteins and 5 nonproteinaceous species. These proteins were grouped according to location in the cell, type of iron center(s), and cellular function. The resulting 27 groups were used, along with an additional 13 nonprotein components, to develop a mesoscale mechanistic model that describes the import, trafficking, metallation, and regulation of iron within growing yeast cells. The model was designed to be simultaneously mutually autocatalytic and mutually autoinhibitory - a property called autocatinhibitory that should be most realistic for simulating cellular biochemical processes. The model was assessed at the systems' level. General conclusions are presented, including a new perspective on understanding regulatory mechanisms in cellular systems. Some unsettled issues are described. This model, once fully developed, has the potential to mimic the phenotype (at a coarse-grain level) of all iron-related genetic mutations in this simple and well-studied eukaryote.
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Affiliation(s)
- Paul A Lindahl
- Departments of Chemistry and of Biochemistry and Biophysics, Texas A&M University, College Station, TX 77843-3255, USA.
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16
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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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17
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Abstract
A host of critical metalloproteins reside in mitochondria, where metallation occurs within the organelle after protein import. Although the pathways by which proteins are imported into the mitochondria are well known, the mechanisms by which their metal partners are imported are more obscure. A new study by Boulet et al. demonstrates that the mammalian SLC25A3 inner membrane transporter, previously known as a phosphate carrier, is also a functional Cu(I) importer, clarifying the source of mitochondrial copper and raising new questions about cellular copper homeostasis.
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Affiliation(s)
- Dennis R Winge
- From the Departments of Internal Medicine and Biochemistry, University of Utah Health Sciences Center, Salt Lake City, Utah 84132
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18
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Knight SAB, Yoon H, Pandey AK, Pain J, Pain D, Dancis A. Splitting the functions of Rim2, a mitochondrial iron/pyrimidine carrier. Mitochondrion 2019; 47:256-265. [PMID: 30660752 DOI: 10.1016/j.mito.2018.12.005] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2018] [Revised: 11/29/2018] [Accepted: 12/28/2018] [Indexed: 10/27/2022]
Abstract
Rim2 is an unusual mitochondrial carrier protein capable of transporting both iron and pyrimidine nucleotides. Here we characterize two point mutations generated in the predicted substrate-binding site, finding that they yield disparate effects on iron and pyrimidine transport. The Rim2 (E248A) mutant was deficient in mitochondrial iron transport activity. By contrast, the Rim2 (K299A) mutant specifically abrogated pyrimidine nucleotide transport and exchange, while leaving iron transport activity largely unaffected. Strikingly, E248A preserved TTP/TTP homoexchange but interfered with TTP/TMP heteroexchange, perhaps because proton coupling was dependent on the E248 acidic residue. Rim2-dependent iron transport was unaffected by pyrimidine nucleotides. Rim2-dependent pyrimidine transport was competed by Zn2+ but not by Fe2+, Fe3+ or Cu2+. The iron and pyrimidine nucleotide transport processes displayed different salt requirements; pyrimidine transport was dependent on the salt content of the buffer whereas iron transport was salt independent. In mitochondria containing Rim2 (E248A), iron proteins were decreased, including aconitase (Fe-S), pyruvate dehydrogenase (lipoic acid containing) and cytochrome c (heme protein). Additionally, the rate of Fe-S cluster synthesis in isolated and intact mitochondria was decreased compared with the K299A mutant, consistent with the impairment of iron-dependent functions in that mutant. In summary, mitochondrial iron transport and pyrimidine transport by Rim2 occur separately and independently. Rim2 could be a bifunctional carrier protein.
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Affiliation(s)
- Simon A B Knight
- Department of Medicine, Division of Hematology-Oncology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA
| | - Heeyong Yoon
- Department of Medicine, Division of Hematology-Oncology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA
| | - Ashutosh K Pandey
- Department of Pharmacology, Physiology, and Neuroscience, New Jersey Medical School, Rutgers University, Newark, NJ 07103, USA
| | - Jayashree Pain
- Department of Pharmacology, Physiology, and Neuroscience, New Jersey Medical School, Rutgers University, Newark, NJ 07103, USA
| | - Debkumar Pain
- Department of Pharmacology, Physiology, and Neuroscience, New Jersey Medical School, Rutgers University, Newark, NJ 07103, USA
| | - Andrew Dancis
- Department of Medicine, Division of Hematology-Oncology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA.
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19
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Jain A, Dashner ZS, Connolly EL. Mitochondrial Iron Transporters (MIT1 and MIT2) Are Essential for Iron Homeostasis and Embryogenesis in Arabidopsis thaliana. FRONTIERS IN PLANT SCIENCE 2019; 10:1449. [PMID: 31850005 PMCID: PMC6889801 DOI: 10.3389/fpls.2019.01449] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/19/2019] [Accepted: 10/17/2019] [Indexed: 05/08/2023]
Abstract
Iron (Fe) is an essential nutrient for virtually all organisms, where it functions in critical electron transfer processes, like those involved in respiration. Photosynthetic organisms have special requirements for Fe due to its importance in photosynthesis. While the importance of Fe for mitochondria- and chloroplast-localized processes is clear, our understanding of the molecular mechanisms that underlie the trafficking of Fe to these compartments is not complete. Here, we describe the Arabidopsis mitochondrial iron transporters, MIT1 and MIT2, that belong to the mitochondrial carrier family (MCF) of transport proteins. MIT1 and MIT2 display considerable homology with known mitochondrial Fe transporters of other organisms. Expression of MIT1 or MIT2 rescues the phenotype of the yeast mrs3mrs4 mutant, which is defective in mitochondrial iron transport. Although the Arabidopsis mit1 and mit2 single mutants do not show any significant visible phenotypes, the double mutant mit1mit2 displays embryo lethality. Analysis of a mit1 -- /mit2 + - line revealed that MIT1 and MIT2 are essential for iron acquisition by mitochondria and proper mitochondrial function. In addition, loss of MIT function results in mislocalization of Fe, which in turn causes upregulation of the root high affinity Fe uptake pathway. Thus, MIT1 and MIT2 are required for the maintenance of both mitochondrial and whole plant Fe homeostasis, which, in turn, is important for the proper growth and development of the plant.
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Affiliation(s)
- Anshika Jain
- Department of Biological Sciences, University of South Carolina, Columbia, SC, United States
| | - Zachary S. Dashner
- Department of Plant Science, The Pennsylvania State University, University Park, PA, United States
| | - Erin L. Connolly
- Department of Biological Sciences, University of South Carolina, Columbia, SC, United States
- Department of Plant Science, The Pennsylvania State University, University Park, PA, United States
- *Correspondence: Erin L. Connolly,
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20
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Wofford JD, Bolaji N, Dziuba N, Outten FW, Lindahl PA. Evidence that a respiratory shield in Escherichia coli protects a low-molecular-mass Fe II pool from O 2-dependent oxidation. J Biol Chem 2018; 294:50-62. [PMID: 30337367 DOI: 10.1074/jbc.ra118.005233] [Citation(s) in RCA: 30] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2018] [Revised: 10/16/2018] [Indexed: 11/06/2022] Open
Abstract
Iron is critical for virtually all organisms, yet major questions remain regarding the systems-level understanding of iron in whole cells. Here, we obtained Mössbauer and EPR spectra of Escherichia coli cells prepared under different nutrient iron concentrations, carbon sources, growth phases, and O2 concentrations to better understand their global iron content. We investigated WT cells and those lacking Fur, FtnA, Bfr, and Dps proteins. The coarse-grain iron content of exponentially growing cells consisted of iron-sulfur clusters, variable amounts of nonheme high-spin FeII species, and an unassigned residual quadrupole doublet. The iron in stationary-phase cells was dominated by magnetically ordered FeIII ions due to oxyhydroxide nanoparticles. Analysis of cytosolic extracts by size-exclusion chromatography detected by an online inductively coupled plasma mass spectrometer revealed a low-molecular-mass (LMM) FeII pool consisting of two iron complexes with masses of ∼500 (major) and ∼1300 (minor) Da. They appeared to be high-spin FeII species with mostly oxygen donor ligands, perhaps a few nitrogen donors, and probably no sulfur donors. Surprisingly, the iron content of E. coli and its reactivity with O2 were remarkably similar to those of mitochondria. In both cases, a "respiratory shield" composed of membrane-bound iron-rich respiratory complexes may protect the LMM FeII pool from reacting with O2 When exponentially growing cells transition to stationary phase, the shield deactivates as metabolic activity declines. Given the universality of oxidative phosphorylation in aerobic biology, the iron content and respiratory shield in other aerobic prokaryotes might be similar to those of E. coli and mitochondria.
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Affiliation(s)
- Joshua D Wofford
- Department of Chemistry, Texas A&M University, College Station, Texas 77843
| | - Naimah Bolaji
- Department of Chemistry and Biochemistry, University of South Carolina, Columbia, South Carolina 29208
| | - Nathaniel Dziuba
- Department of Biochemistry and Biophysics, Texas A&M University, College Station, Texas 77843
| | - F Wayne Outten
- Department of Chemistry and Biochemistry, University of South Carolina, Columbia, South Carolina 29208
| | - Paul A Lindahl
- Department of Chemistry, Texas A&M University, College Station, Texas 77843; Department of Biochemistry and Biophysics, Texas A&M University, College Station, Texas 77843.
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