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Pandey AK, Yoon H, Pain J, Dancis A, Pain D. Mitochondrial acyl carrier protein, Acp1, required for iron-sulfur cluster assembly in mitochondria and cytoplasm in Saccharomyces cerevisiae. Mitochondrion 2024:101955. [PMID: 39251117 DOI: 10.1016/j.mito.2024.101955] [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: 05/29/2024] [Revised: 08/07/2024] [Accepted: 08/31/2024] [Indexed: 09/11/2024]
Abstract
Mitochondria perform vital biosynthetic processes, including fatty acid synthesis and iron-sulfur (FeS) cluster biogenesis. In Saccharomyces cerevisiae mitochondria, the acyl carrier protein Acp1 participates in type II fatty acid synthesis, requiring a 4-phosphopantetheine (PP) prosthetic group. Acp1 also interacts with the mitochondrial FeS cluster assembly complex that contains the cysteine desulfurase Nfs1. Here we investigated the role of Acp1 in FeS cluster biogenesis in mitochondria and cytoplasm. In the Acp1-depleted (Acp1↓) cells, biogenesis of mitochondrial FeS proteins was impaired, likely due to greatly reduced Nfs1 protein and/or its persulfide-forming activity. Formation of cytoplasmic FeS proteins was also deficient, suggesting a disruption in generating the (Fe-S)int intermediate, that is exported from mitochondria and is utilized for cytoplasmic FeS cluster assembly. Iron homeostasis was perturbed, with enhanced iron uptake into the cells and accumulation of iron in mitochondria. The Δppt2 strain, lacking the mitochondrial ability to add PP to Acp1, phenocopied the Acp1↓ cells. These data suggest that the holo form of Acp1 with the PP-conjugated acyl chain is required for stability of the Nfs1 protein and/or stimulation of its persulfide-forming activity. Thus, mitochondria lacking Acp1 (or Ppt2) cannot support FeS cluster biogenesis in mitochondria or cytoplasm, leading to disrupted iron homeostasis.
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Affiliation(s)
- Ashutosh K Pandey
- Department of Pharmacology, Physiology and Neuroscience, New Jersey Medical School, Rutgers University, Newark, NJ 07103, United States
| | - Heeyong Yoon
- Department of Medicine, Division of Hematology-Oncology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104, United States
| | - Jayashree Pain
- Department of Pharmacology, Physiology and Neuroscience, New Jersey Medical School, Rutgers University, Newark, NJ 07103, United States
| | - Andrew Dancis
- Department of Medicine, Division of Hematology-Oncology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104, United States
| | - Debkumar Pain
- Department of Pharmacology, Physiology and Neuroscience, New Jersey Medical School, Rutgers University, Newark, NJ 07103, United States.
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Pandey AK, Pain J, J B, Dancis A, Pain D. Essential mitochondrial role in iron-sulfur cluster assembly of the cytoplasmic isopropylmalate isomerase Leu1 in Saccharomyces cerevisiae. Mitochondrion 2023; 69:104-115. [PMID: 36773733 DOI: 10.1016/j.mito.2023.02.006] [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: 11/11/2022] [Revised: 01/30/2023] [Accepted: 02/04/2023] [Indexed: 02/11/2023]
Abstract
Iron-sulfur (Fe-S) cluster assembly in mitochondria and cytoplasm is essential for cell viability. In the yeast S. cerevisiae, Leu1 [4Fe-4S] is the cytoplasmic isopropylmalate isomerase involved in leucine biosynthesis. Using permeabilized Δleu1 cells and recombinant apo-Leu1R, here we show that the [4Fe-4S] cluster assembly on Leu1R can be reconstituted in a physiologic manner requiring both mitochondria and cytoplasm, as judged by conversion of the inactive enzyme to an active form. The mitochondrial contribution to this reconstitution assay is abrogated by inactivating mutations in the mitochondrial ISC (iron-sulfur cluster assembly) machinery components (such as Nfs1 cysteine desulfurase and Ssq1 chaperone) or the mitochondrial exporter Atm1. Likewise, depletion of a CIA (cytoplasmic iron-sulfur protein assembly) component Dre2 leads to impaired Leu1R reconstitution. Mitochondria likely make and export an intermediate, called X-S or (Fe-S)int, that is needed for cytoplasmic Fe-S cluster biosynthesis. Here we show that once exported, the same intermediate can be used for both [2Fe-2S] and [4Fe-4S] cluster biogenesis in the cytoplasm, with no further requirement of mitochondria. Our data also suggest that the exported intermediate can activate defective/latent CIA components in cytoplasm isolated from nfs1 or Δatm1 mutant cells. These findings may provide a way to isolate X-S or (Fe-S)int.
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Affiliation(s)
- Ashutosh K Pandey
- Department of Pharmacology, Physiology and Neuroscience, New Jersey Medical School, Rutgers University, Newark, NJ 07103, United States
| | - Jayashree Pain
- Department of Pharmacology, Physiology and Neuroscience, New Jersey Medical School, Rutgers University, Newark, NJ 07103, United States
| | - Brindha J
- Department of Pharmacology, Physiology and Neuroscience, New Jersey Medical School, Rutgers University, Newark, NJ 07103, United States
| | - Andrew Dancis
- Department of Pharmacology, Physiology and Neuroscience, New Jersey Medical School, Rutgers University, Newark, NJ 07103, United States
| | - Debkumar Pain
- Department of Pharmacology, Physiology and Neuroscience, New Jersey Medical School, Rutgers University, Newark, NJ 07103, United States.
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Fujihara KM, Zhang BZ, Jackson TD, Ogunkola MO, Nijagal B, Milne JV, Sallman DA, Ang CS, Nikolic I, Kearney CJ, Hogg SJ, Cabalag CS, Sutton VR, Watt S, Fujihara AT, Trapani JA, Simpson KJ, Stojanovski D, Leimkühler S, Haupt S, Phillips WA, Clemons NJ. Eprenetapopt triggers ferroptosis, inhibits NFS1 cysteine desulfurase, and synergizes with serine and glycine dietary restriction. SCIENCE ADVANCES 2022; 8:eabm9427. [PMID: 36103522 PMCID: PMC9473576 DOI: 10.1126/sciadv.abm9427] [Citation(s) in RCA: 31] [Impact Index Per Article: 15.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/08/2023]
Abstract
The mechanism of action of eprenetapopt (APR-246, PRIMA-1MET) as an anticancer agent remains unresolved, although the clinical development of eprenetapopt focuses on its reported mechanism of action as a mutant-p53 reactivator. Using unbiased approaches, this study demonstrates that eprenetapopt depletes cellular antioxidant glutathione levels by increasing its turnover, triggering a nonapoptotic, iron-dependent form of cell death known as ferroptosis. Deficiency in genes responsible for supplying cancer cells with the substrates for de novo glutathione synthesis (SLC7A11, SHMT2, and MTHFD1L), as well as the enzymes required to synthesize glutathione (GCLC and GCLM), augments the activity of eprenetapopt. Eprenetapopt also inhibits iron-sulfur cluster biogenesis by limiting the cysteine desulfurase activity of NFS1, which potentiates ferroptosis and may restrict cellular proliferation. The combination of eprenetapopt with dietary serine and glycine restriction synergizes to inhibit esophageal xenograft tumor growth. These findings reframe the canonical view of eprenetapopt from a mutant-p53 reactivator to a ferroptosis inducer.
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Affiliation(s)
- Kenji M. Fujihara
- Gastrointestinal Cancer Program, Cancer Research Division, Peter MacCallum Cancer Centre, Melbourne, Victoria, Australia
- Sir Peter MacCallum Department of Oncology, The University of Melbourne, Parkville, Victoria, Australia
- Corresponding author. (N.J.C.); (K.M.F.)
| | - Bonnie Z. Zhang
- Gastrointestinal Cancer Program, Cancer Research Division, Peter MacCallum Cancer Centre, Melbourne, Victoria, Australia
- Sir Peter MacCallum Department of Oncology, The University of Melbourne, Parkville, Victoria, Australia
| | - Thomas D. Jackson
- Department of Biochemistry and Pharmacology, The University of Melbourne, Parkville, Victoria, Australia
- Bio21 Molecular Science and Biotechnology Institute, The University of Melbourne, Parkville, Victoria, Australia
| | - Moses O. Ogunkola
- Institute of Biochemistry and Biology Department for Molecular Enzymology, University of Potsdam, Potsdam, Germany
| | - Brunda Nijagal
- Metabolomics Australia, The Bio21 Institute of Molecular Science and Biotechnology, The University of Melbourne, Parkville, Victoria, Australia
| | - Julia V. Milne
- Gastrointestinal Cancer Program, Cancer Research Division, Peter MacCallum Cancer Centre, Melbourne, Victoria, Australia
- Sir Peter MacCallum Department of Oncology, The University of Melbourne, Parkville, Victoria, Australia
| | - David A. Sallman
- Malignant Hematology Department, H. Lee Moffitt Cancer Center and Research Institute, Tampa, FL, USA
| | - Ching-Seng Ang
- Bio21 Molecular Science and Biotechnology Institute, The University of Melbourne, Parkville, Victoria, Australia
| | - Iva Nikolic
- Victorian Centre for Functional Genomics, Peter MacCallum Cancer Centre, Melbourne, Victoria, Australia
| | - Conor J. Kearney
- Sir Peter MacCallum Department of Oncology, The University of Melbourne, Parkville, Victoria, Australia
- Translational Hematology Program, Cancer Research Division, Peter MacCallum Cancer Centre, Melbourne, Victoria, Australia
| | - Simon J. Hogg
- Sir Peter MacCallum Department of Oncology, The University of Melbourne, Parkville, Victoria, Australia
- Translational Hematology Program, Cancer Research Division, Peter MacCallum Cancer Centre, Melbourne, Victoria, Australia
- Human Oncology and Pathogenesis Program, Memorial Sloan Kettering Cancer Center, New York, NY, USA
| | - Carlos S. Cabalag
- Gastrointestinal Cancer Program, Cancer Research Division, Peter MacCallum Cancer Centre, Melbourne, Victoria, Australia
- Sir Peter MacCallum Department of Oncology, The University of Melbourne, Parkville, Victoria, Australia
- Department of Surgical Oncology, Peter MacCallum Cancer Centre, Melbourne, Victoria, Australia
| | - Vivien R. Sutton
- Sir Peter MacCallum Department of Oncology, The University of Melbourne, Parkville, Victoria, Australia
- Cancer Immunology Program, Peter MacCallum Cancer Centre, Melbourne, Victoria, Australia
| | - Sally Watt
- Sir Peter MacCallum Department of Oncology, The University of Melbourne, Parkville, Victoria, Australia
- Cancer Immunology Program, Peter MacCallum Cancer Centre, Melbourne, Victoria, Australia
| | - Asuka T. Fujihara
- Gastrointestinal Cancer Program, Cancer Research Division, Peter MacCallum Cancer Centre, Melbourne, Victoria, Australia
| | - Joseph A. Trapani
- Sir Peter MacCallum Department of Oncology, The University of Melbourne, Parkville, Victoria, Australia
- Cancer Immunology Program, Peter MacCallum Cancer Centre, Melbourne, Victoria, Australia
| | - Kaylene J. Simpson
- Sir Peter MacCallum Department of Oncology, The University of Melbourne, Parkville, Victoria, Australia
- Victorian Centre for Functional Genomics, Peter MacCallum Cancer Centre, Melbourne, Victoria, Australia
| | - Diana Stojanovski
- Department of Biochemistry and Pharmacology, The University of Melbourne, Parkville, Victoria, Australia
| | - Silke Leimkühler
- Institute of Biochemistry and Biology Department for Molecular Enzymology, University of Potsdam, Potsdam, Germany
| | - Sue Haupt
- Sir Peter MacCallum Department of Oncology, The University of Melbourne, Parkville, Victoria, Australia
- Tumor Suppression and Cancer Sex Disparity Laboratory, Peter MacCallum Cancer Centre, Melbourne, Victoria, Australia
| | - Wayne A. Phillips
- Gastrointestinal Cancer Program, Cancer Research Division, Peter MacCallum Cancer Centre, Melbourne, Victoria, Australia
- Sir Peter MacCallum Department of Oncology, The University of Melbourne, Parkville, Victoria, Australia
- Department of Surgery (St. Vincent’s Hospital), The University of Melbourne, Parkville, Victoria, Australia
- Department of Biochemistry and Molecular Biology, Monash University, Clayton, Victoria, Australia
| | - Nicholas J. Clemons
- Gastrointestinal Cancer Program, Cancer Research Division, Peter MacCallum Cancer Centre, Melbourne, Victoria, Australia
- Sir Peter MacCallum Department of Oncology, The University of Melbourne, Parkville, Victoria, Australia
- Corresponding author. (N.J.C.); (K.M.F.)
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ODELADE KA, OLADEJI OS. Isolation of phytopathogenic fungi associated with the post-harvest deterioration of watermelon fruits. SCIENTIFIC AFRICAN 2020. [DOI: 10.1016/j.sciaf.2020.e00366] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022] Open
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Pandey AK, Pain J, Dancis A, Pain D. Mitochondria export iron-sulfur and sulfur intermediates to the cytoplasm for iron-sulfur cluster assembly and tRNA thiolation in yeast. J Biol Chem 2019; 294:9489-9502. [PMID: 31040179 DOI: 10.1074/jbc.ra119.008600] [Citation(s) in RCA: 41] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2019] [Revised: 04/26/2019] [Indexed: 12/28/2022] Open
Abstract
Iron-sulfur clusters are essential cofactors of proteins. In eukaryotes, iron-sulfur cluster biogenesis requires a mitochondrial iron-sulfur cluster machinery (ISC) and a cytoplasmic iron-sulfur protein assembly machinery (CIA). Here we used mitochondria and cytoplasm isolated from yeast cells, and [35S]cysteine to detect cytoplasmic Fe-35S cluster assembly on a purified apoprotein substrate. We showed that mitochondria generate an intermediate, called (Fe-S)int, needed for cytoplasmic iron-sulfur cluster assembly. The mitochondrial biosynthesis of (Fe-S)int required ISC components such as Nfs1 cysteine desulfurase, Isu1/2 scaffold, and Ssq1 chaperone. Mitochondria then exported (Fe-S)int via the Atm1 transporter in the inner membrane, and we detected (Fe-S)int in active form. When (Fe-S)int was added to cytoplasm, CIA utilized it for iron-sulfur cluster assembly without any further help from the mitochondria. We found that both iron and sulfur for cytoplasmic iron-sulfur cluster assembly originate from the mitochondria, revealing a surprising and novel mitochondrial role. Mitochondrial (Fe-S)int export was most efficient in the presence of cytoplasm containing an apoprotein substrate, suggesting that mitochondria respond to the cytoplasmic demand for iron-sulfur cluster synthesis. Of note, the (Fe-S)int is distinct from the sulfur intermediate called Sint, which is also made and exported by mitochondria but is instead used for cytoplasmic tRNA thiolation. In summary, our findings establish a direct and vital role of mitochondria in cytoplasmic iron-sulfur cluster assembly in yeast cells.
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Affiliation(s)
- Ashutosh K Pandey
- From the Department of Pharmacology, Physiology and Neuroscience, New Jersey Medical School, Rutgers University, Newark, New Jersey 07103 and
| | - Jayashree Pain
- From the Department of Pharmacology, Physiology and Neuroscience, New Jersey Medical School, Rutgers University, Newark, New Jersey 07103 and
| | - Andrew Dancis
- the Department of Medicine, Division of Hematology-Oncology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania 19104
| | - Debkumar Pain
- From the Department of Pharmacology, Physiology and Neuroscience, New Jersey Medical School, Rutgers University, Newark, New Jersey 07103 and
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Pandey A, Pain J, Dziuba N, Pandey AK, Dancis A, Lindahl PA, Pain D. Mitochondria Export Sulfur Species Required for Cytosolic tRNA Thiolation. Cell Chem Biol 2018; 25:738-748.e3. [PMID: 29706592 PMCID: PMC6014917 DOI: 10.1016/j.chembiol.2018.04.002] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2018] [Revised: 03/09/2018] [Accepted: 04/03/2018] [Indexed: 12/15/2022]
Abstract
In eukaryotes, mitochondria have been hypothesized to generate sulfur species required for tRNA thiolation in the cytosol, although no direct evidence thus far exists. Here we have detected these sulfur species, making use of our observation that isolated yeast cytosol alone is unable to thiolate tRNAs but can do so upon addition of mitochondria. Mitochondria were found to utilize the cysteine desulfurase Nfs1 to produce sulfur-containing species with masses ranging from 700 to 1,100 Da. Mitochondria exported these species via the Atm1 transporter in the inner membrane. Once exported to the cytosol, these sulfur species promoted cytosolic tRNA thiolation with no further requirement of mitochondria. Furthermore, we found that the Isu1/2 scaffolds but not the Ssq1 chaperone of the mitochondrial iron-sulfur cluster machinery were required for cytosolic tRNA thiolation, and thus the sulfur utilization pathway bifurcates at the Isu1/2 site for intra-organellar use in mitochondria or export to the cytosol.
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Affiliation(s)
- Alok 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
| | - Nathaniel Dziuba
- Department of Biochemistry and Biophysics, Texas A&M University, College Station, TX 77843, USA
| | - Ashutosh K Pandey
- 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
| | - Paul A Lindahl
- Department of Biochemistry and Biophysics, Texas A&M University, College Station, TX 77843, USA; Department of Chemistry, Texas A&M University, College Station, TX 77843, USA
| | - Debkumar Pain
- Department of Pharmacology, Physiology and Neuroscience, New Jersey Medical School, Rutgers University, Newark, NJ 07103, USA.
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Rocha AG, Knight SAB, Pandey A, Yoon H, Pain J, Pain D, Dancis A. Cysteine desulfurase is regulated by phosphorylation of Nfs1 in yeast mitochondria. Mitochondrion 2018; 40:29-41. [PMID: 28941588 PMCID: PMC5858965 DOI: 10.1016/j.mito.2017.09.003] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2017] [Revised: 08/30/2017] [Accepted: 09/13/2017] [Indexed: 01/13/2023]
Abstract
The cysteine desulfurase Nfs1/Isd11 uses the amino acid cysteine as the substrate and its activity is absolutely required for contributing persulfide sulfur to the essential process of iron-sulfur (Fe-S) cluster assembly in mitochondria. Here we describe a novel regulatory process involving phosphorylation of Nfs1 in mitochondria. Phosphorylation enhanced cysteine desulfurase activity, while dephosphorylation decreased its activity. Nfs1 phosphopeptides were identified, and the corresponding phosphosite mutants showed impaired persulfide formation. Nfs1 pull down from mitochondria recovered an associated kinase activity, and Yck2, a kinase present in the pull down, was able to phosphorylate Nfs1 in vitro and stimulate cysteine desulfurase activity. Yck2 exhibited an eclipsed distribution in the mitochondrial matrix, although other cellular localizations have been previously described. Mitochondria lacking the Yck2 protein kinase (∆yck2) showed less phosphorylating activity for Nfs1. Compared with wild-type mitochondria, ∆yck2 mitochondria revealed slower persulfide formation on Nfs1 consistent with a role of Yck2 in regulating mitochondrial cysteine desulfurase activity. We propose that Nfs1 phosphorylation may provide a means of rapid adaptation to increased metabolic demand for sulfur and Fe-S clusters within mitochondria.
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Affiliation(s)
- Agostinho G Rocha
- Department of Medicine, Division of Hematology-Oncology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, United States
| | - Simon A B Knight
- Department of Medicine, Division of Hematology-Oncology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, United States
| | - Alok Pandey
- Department of Pharmacology, Physiology and Neuroscience, New Jersey Medical School, Rutgers University, Newark, NJ, United States
| | - Heeyong Yoon
- Department of Medicine, Division of Hematology-Oncology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, United States
| | - Jayashree Pain
- Department of Pharmacology, Physiology and Neuroscience, New Jersey Medical School, Rutgers University, Newark, NJ, United States
| | - Debkumar Pain
- Department of Pharmacology, Physiology and Neuroscience, New Jersey Medical School, Rutgers University, Newark, NJ, United States
| | - Andrew Dancis
- Department of Medicine, Division of Hematology-Oncology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, United States.
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Fox NG, Das D, Chakrabarti M, Lindahl PA, Barondeau DP. Frataxin Accelerates [2Fe-2S] Cluster Formation on the Human Fe-S Assembly Complex. Biochemistry 2015; 54:3880-9. [PMID: 26016518 PMCID: PMC4675465 DOI: 10.1021/bi5014497] [Citation(s) in RCA: 57] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
Iron-sulfur (Fe-S) clusters function as protein cofactors for a wide variety of critical cellular reactions. In human mitochondria, a core Fe-S assembly complex [called SDUF and composed of NFS1, ISD11, ISCU2, and frataxin (FXN) proteins] synthesizes Fe-S clusters from iron, cysteine sulfur, and reducing equivalents and then transfers these intact clusters to target proteins. In vitro assays have relied on reducing the complexity of this complicated Fe-S assembly process by using surrogate electron donor molecules and monitoring simplified reactions. Recent studies have concluded that FXN promotes the synthesis of [4Fe-4S] clusters on the mammalian Fe-S assembly complex. Here the kinetics of Fe-S synthesis reactions were determined using different electron donation systems and by monitoring the products with circular dichroism and absorbance spectroscopies. We discovered that common surrogate electron donor molecules intercepted Fe-S cluster intermediates and formed high-molecular weight species (HMWS). The HMWS are associated with iron, sulfide, and thiol-containing proteins and have properties of a heterogeneous solubilized mineral with spectroscopic properties remarkably reminiscent of those of [4Fe-4S] clusters. In contrast, reactions using physiological reagents revealed that FXN accelerates the formation of [2Fe-2S] clusters rather than [4Fe-4S] clusters as previously reported. In the preceding paper [Fox, N. G., et al. (2015) Biochemistry 54, DOI: 10.1021/bi5014485], [2Fe-2S] intermediates on the SDUF complex were shown to readily transfer to uncomplexed ISCU2 or apo acceptor proteins, depending on the reaction conditions. Our results indicate that FXN accelerates a rate-limiting sulfur transfer step in the synthesis of [2Fe-2S] clusters on the human Fe-S assembly complex.
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Affiliation(s)
- Nicholas G. Fox
- Department of Chemistry, Texas A&M University, College Station, Texas 77843-3255, United States
| | - Deepika Das
- Department of Chemistry, Texas A&M University, College Station, Texas 77843-3255, United States
| | - Mrinmoy Chakrabarti
- 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 77843-2128, United States
| | - David P. Barondeau
- Department of Chemistry, Texas A&M University, College Station, Texas 77843-3255, United States
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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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Yoon H, Knight SAB, Pandey A, Pain J, Turkarslan S, Pain D, Dancis A. Turning Saccharomyces cerevisiae into a Frataxin-Independent Organism. PLoS Genet 2015; 11:e1005135. [PMID: 25996596 PMCID: PMC4440810 DOI: 10.1371/journal.pgen.1005135] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2014] [Accepted: 03/10/2015] [Indexed: 01/08/2023] Open
Abstract
Frataxin (Yfh1 in yeast) is a conserved protein and deficiency leads to the neurodegenerative disease Friedreich's ataxia. Frataxin is a critical protein for Fe-S cluster assembly in mitochondria, interacting with other components of the Fe-S cluster machinery, including cysteine desulfurase Nfs1, Isd11 and the Isu1 scaffold protein. Yeast Isu1 with the methionine to isoleucine substitution (M141I), in which the E. coli amino acid is inserted at this position, corrected most of the phenotypes that result from lack of Yfh1 in yeast. This suppressor Isu1 behaved as a genetic dominant. Furthermore frataxin-bypass activity required a completely functional Nfs1 and correlated with the presence of efficient scaffold function. A screen of random Isu1 mutations for frataxin-bypass activity identified only M141 substitutions, including Ile, Cys, Leu, or Val. In each case, mitochondrial Nfs1 persulfide formation was enhanced, and mitochondrial Fe-S cluster assembly was improved in the absence of frataxin. Direct targeting of the entire E. coli IscU to ∆yfh1 mitochondria also ameliorated the mutant phenotypes. In contrast, expression of IscU with the reverse substitution i.e. IscU with Ile to Met change led to worsening of the ∆yfh1 phenotypes, including severely compromised growth, increased sensitivity to oxygen, deficiency in Fe-S clusters and heme, and impaired iron homeostasis. A bioinformatic survey of eukaryotic Isu1/prokaryotic IscU database entries sorted on the amino acid utilized at the M141 position identified unique groupings, with virtually all of the eukaryotic scaffolds using Met, and the preponderance of prokaryotic scaffolds using other amino acids. The frataxin-bypassing amino acids Cys, Ile, Leu, or Val, were found predominantly in prokaryotes. This amino acid position 141 is unique in Isu1, and the frataxin-bypass effect likely mimics a conserved and ancient feature of the prokaryotic Fe-S cluster assembly machinery.
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Affiliation(s)
- Heeyong Yoon
- Department of Medicine, Division of Hematology-Oncology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, United States of America
| | - Simon A. B. Knight
- Department of Medicine, Division of Hematology-Oncology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, United States of America
| | - Alok Pandey
- Department of Pharmacology and Physiology, New Jersey Medical School, Rutgers University, Newark, New Jersey, United States of America
| | - Jayashree Pain
- Department of Pharmacology and Physiology, New Jersey Medical School, Rutgers University, Newark, New Jersey, United States of America
| | - Serdar Turkarslan
- Institute for Systems Biology, Seattle, Washington, United States of America
| | - Debkumar Pain
- Department of Pharmacology and Physiology, New Jersey Medical School, Rutgers University, Newark, New Jersey, United States of America
| | - Andrew Dancis
- Department of Medicine, Division of Hematology-Oncology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, United States of America
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Parent A, Elduque X, Cornu D, Belot L, Le Caer JP, Grandas A, Toledano MB, D'Autréaux B. Mammalian frataxin directly enhances sulfur transfer of NFS1 persulfide to both ISCU and free thiols. Nat Commun 2015; 6:5686. [PMID: 25597503 DOI: 10.1038/ncomms6686] [Citation(s) in RCA: 119] [Impact Index Per Article: 13.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2014] [Accepted: 10/28/2014] [Indexed: 02/08/2023] Open
Abstract
Friedreich's ataxia is a severe neurodegenerative disease caused by the decreased expression of frataxin, a mitochondrial protein that stimulates iron-sulfur (Fe-S) cluster biogenesis. In mammals, the primary steps of Fe-S cluster assembly are performed by the NFS1-ISD11-ISCU complex via the formation of a persulfide intermediate on NFS1. Here we show that frataxin modulates the reactivity of NFS1 persulfide with thiols. We use maleimide-peptide compounds along with mass spectrometry to probe cysteine-persulfide in NFS1 and ISCU. Our data reveal that in the presence of ISCU, frataxin enhances the rate of two similar reactions on NFS1 persulfide: sulfur transfer to ISCU leading to the accumulation of a persulfide on the cysteine C104 of ISCU, and sulfur transfer to small thiols such as DTT, L-cysteine and GSH leading to persulfuration of these thiols and ultimately sulfide release. These data raise important questions on the physiological mechanism of Fe-S cluster assembly and point to a unique function of frataxin as an enhancer of sulfur transfer within the NFS1-ISD11-ISCU complex.
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Affiliation(s)
- Aubérie Parent
- Institut de Chimie des Substances Naturelles, UPR2301, Centre de Recherche de Gif, Centre National de la Recherche Scientifique, 1 avenue de la terrasse, 91191 Gif Sur Yvette, France
| | - Xavier Elduque
- Departament de Química Orgànica i IBUB, Facultat de Química, Universitat de Barcelona, Marti i Franques 1-11, E-08028 Barcelona, Spain
| | - David Cornu
- Plateforme IMAGIF, Centre de Recherche de Gif, Centre National de la Recherche Scientifique, 1 avenue de le terrasse, 91191 Gif Sur Yvette, France
| | - Laura Belot
- Institut de Chimie des Substances Naturelles, UPR2301, Centre de Recherche de Gif, Centre National de la Recherche Scientifique, 1 avenue de la terrasse, 91191 Gif Sur Yvette, France
| | - Jean-Pierre Le Caer
- Institut de Chimie des Substances Naturelles, UPR2301, Centre de Recherche de Gif, Centre National de la Recherche Scientifique, 1 avenue de la terrasse, 91191 Gif Sur Yvette, France
| | - Anna Grandas
- Departament de Química Orgànica i IBUB, Facultat de Química, Universitat de Barcelona, Marti i Franques 1-11, E-08028 Barcelona, Spain
| | - Michel B Toledano
- Laboratoire Stress Oxydant et Cancer, Service de Biologie Intégrative et de Génétique Moléculaire, Institut de Biologie et de Technologie de Saclay, Commissariat à l'Energie Atomique et aux Energies Alternatives, F-91191 Gif Sur Yvette, France
| | - Benoit D'Autréaux
- Institut de Chimie des Substances Naturelles, UPR2301, Centre de Recherche de Gif, Centre National de la Recherche Scientifique, 1 avenue de la terrasse, 91191 Gif Sur Yvette, France
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12
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Pandey A, Pain J, Ghosh AK, Dancis A, Pain D. Fe-S cluster biogenesis in isolated mammalian mitochondria: coordinated use of persulfide sulfur and iron and requirements for GTP, NADH, and ATP. J Biol Chem 2014; 290:640-57. [PMID: 25398879 DOI: 10.1074/jbc.m114.610402] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
Iron-sulfur (Fe-S) clusters are essential cofactors, and mitochondria contain several Fe-S proteins, including the [4Fe-4S] protein aconitase and the [2Fe-2S] protein ferredoxin. Fe-S cluster assembly of these proteins occurs within mitochondria. Although considerable data exist for yeast mitochondria, this biosynthetic process has never been directly demonstrated in mammalian mitochondria. Using [(35)S]cysteine as the source of sulfur, here we show that mitochondria isolated from Cath.A-derived cells, a murine neuronal cell line, can synthesize and insert new Fe-(35)S clusters into aconitase and ferredoxins. The process requires GTP, NADH, ATP, and iron, and hydrolysis of both GTP and ATP is necessary. Importantly, we have identified the (35)S-labeled persulfide on the NFS1 cysteine desulfurase as a genuine intermediate en route to Fe-S cluster synthesis. In physiological settings, the persulfide sulfur is released from NFS1 and transferred to a scaffold protein, where it combines with iron to form an Fe-S cluster intermediate. We found that the release of persulfide sulfur from NFS1 requires iron, showing that the use of iron and sulfur for the synthesis of Fe-S cluster intermediates is a highly coordinated process. The release of persulfide sulfur also requires GTP and NADH, probably mediated by a GTPase and a reductase, respectively. ATP, a cofactor for a multifunctional Hsp70 chaperone, is not required at this step. The experimental system described here may help to define the biochemical basis of diseases that are associated with impaired Fe-S cluster biogenesis in mitochondria, such as Friedreich ataxia.
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Affiliation(s)
- Alok Pandey
- From the Department of Pharmacology and Physiology, New Jersey Medical School, Rutgers University, Newark, New Jersey 07101 and
| | - Jayashree Pain
- From the Department of Pharmacology and Physiology, New Jersey Medical School, Rutgers University, Newark, New Jersey 07101 and
| | - Arnab K Ghosh
- From the Department of Pharmacology and Physiology, New Jersey Medical School, Rutgers University, Newark, New Jersey 07101 and
| | - Andrew Dancis
- the Department of Medicine, Division of Hematology-Oncology, University of Pennsylvania, Philadelphia, Pennsylvania 19104
| | - Debkumar Pain
- From the Department of Pharmacology and Physiology, New Jersey Medical School, Rutgers University, Newark, New Jersey 07101 and
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13
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Bridwell-Rabb J, Fox N, Tsai CL, Winn AM, Barondeau DP. Human frataxin activates Fe-S cluster biosynthesis by facilitating sulfur transfer chemistry. Biochemistry 2014; 53:4904-13. [PMID: 24971490 PMCID: PMC4215901 DOI: 10.1021/bi500532e] [Citation(s) in RCA: 121] [Impact Index Per Article: 12.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2014] [Revised: 06/26/2014] [Indexed: 01/11/2023]
Abstract
Iron-sulfur clusters are ubiquitous protein cofactors with critical cellular functions. The mitochondrial Fe-S assembly complex, which consists of the cysteine desulfurase NFS1 and its accessory protein (ISD11), the Fe-S assembly protein (ISCU2), and frataxin (FXN), converts substrates l-cysteine, ferrous iron, and electrons into Fe-S clusters. The physiological function of FXN has received a tremendous amount of attention since the discovery that its loss is directly linked to the neurodegenerative disease Friedreich's ataxia. Previous in vitro results revealed a role for human FXN in activating the cysteine desulfurase and Fe-S cluster biosynthesis activities of the Fe-S assembly complex. Here we present radiolabeling experiments that indicate FXN accelerates the accumulation of sulfur on ISCU2 and that the resulting persulfide species is viable in the subsequent synthesis of Fe-S clusters. Additional mutagenesis, enzyme kinetic, UV-visible, and circular dichroism spectroscopic studies suggest conserved ISCU2 residue C104 is critical for FXN activation, whereas C35, C61, and C104 are all essential for Fe-S cluster formation on the assembly complex. These results cannot be fully explained by the hypothesis that FXN functions as an iron donor for Fe-S cluster biosynthesis, and further support an allosteric regulator role for FXN. Together, these results lead to an activation model in which FXN accelerates persulfide formation on NFS1 and favors a helix-to-coil interconversion on ISCU2 that facilitates the transfer of sulfur from NFS1 to ISCU2 as an initial step in Fe-S cluster biosynthesis.
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Affiliation(s)
- Jennifer Bridwell-Rabb
- Department of Chemistry, Texas A&M
University, College Station, Texas 77842, United States
| | - Nicholas
G. Fox
- Department of Chemistry, Texas A&M
University, College Station, Texas 77842, United States
| | - Chi-Lin Tsai
- Department of Chemistry, Texas A&M
University, College Station, Texas 77842, United States
| | - Andrew M. Winn
- Department of Chemistry, Texas A&M
University, College Station, Texas 77842, United States
| | - David P. Barondeau
- Department of Chemistry, Texas A&M
University, College Station, Texas 77842, United States
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14
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Yoon H, Knight SAB, Pandey A, Pain J, Zhang Y, Pain D, Dancis A. Frataxin-bypassing Isu1: characterization of the bypass activity in cells and mitochondria. Biochem J 2014; 459:71-81. [PMID: 24433162 PMCID: PMC4021491 DOI: 10.1042/bj20131273] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Frataxin is a conserved mitochondrial protein, and deficiency underlies the neurodegenerative disease Friedreich's ataxia. Frataxin interacts with the core machinery for Fe-S cluster assembly in mitochondria. Recently we reported that in frataxin-deleted yeast strains, a spontaneously occurring mutation in one of two genes encoding redundant Isu scaffold proteins, bypassed the mutant phenotypes. In the present study we created strains expressing a single scaffold protein, either Isu1 or the bypass mutant M107I Isu1. Our results show that in the frataxin-deletion strain expressing the bypass mutant Isu1, cell growth, Fe-S cluster protein activities, haem proteins and iron homoeostasis were restored to normal or close to normal. The bypass effects were not mediated by changes in Isu1 expression level. The persulfide-forming activity of the cysteine desulfurase was diminished in the frataxin deletion (∆yfh1 ISU1) and was improved by expression of the bypass Isu1 (∆yfh1 M107I ISU1). The addition of purified bypass M107I Isu1 protein to a ∆yfh1 lysate conferred similar enhancement of cysteine desulfurase as did frataxin, suggesting that this effect contributed to the bypass mechanism. Fe-S cluster-forming activity in isolated mitochondria was stimulated by the bypass Isu1, albeit at a lower rate. The rescuing effects of the bypass Isu1 point to ways that the core defects in Friedreich's ataxia mitochondria can be restored.
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Affiliation(s)
- Heeyong Yoon
- Division of Hematology-Oncology, Department of Medicine, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104, U.S.A
| | - Simon A. B. Knight
- Division of Hematology-Oncology, Department of Medicine, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104, U.S.A
| | - Alok Pandey
- Department of Pharmacology and Physiology, New Jersey Medical School, Rutgers University, Newark, NJ 07101, U.S.A
| | - Jayashree Pain
- Department of Pharmacology and Physiology, New Jersey Medical School, Rutgers University, Newark, NJ 07101, U.S.A
| | - Yan Zhang
- Division of Hematology-Oncology, Department of Medicine, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104, U.S.A
| | - Debkumar Pain
- Department of Pharmacology and Physiology, New Jersey Medical School, Rutgers University, Newark, NJ 07101, U.S.A
| | - Andrew Dancis
- Division of Hematology-Oncology, Department of Medicine, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104, U.S.A
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15
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Pandey A, Gordon DM, Pain J, Stemmler TL, Dancis A, Pain D. Frataxin directly stimulates mitochondrial cysteine desulfurase by exposing substrate-binding sites, and a mutant Fe-S cluster scaffold protein with frataxin-bypassing ability acts similarly. J Biol Chem 2013; 288:36773-86. [PMID: 24217246 PMCID: PMC3873537 DOI: 10.1074/jbc.m113.525857] [Citation(s) in RCA: 76] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2013] [Revised: 11/09/2013] [Indexed: 01/17/2023] Open
Abstract
For iron-sulfur (Fe-S) cluster synthesis in mitochondria, the sulfur is derived from the amino acid cysteine by the cysteine desulfurase activity of Nfs1. The enzyme binds the substrate cysteine in the pyridoxal phosphate-containing site, and a persulfide is formed on the active site cysteine in a manner depending on the accessory protein Isd11. The persulfide is then transferred to the scaffold Isu, where it combines with iron to form the Fe-S cluster intermediate. Frataxin is implicated in the process, although it is unclear where and how, and deficiency causes Friedreich ataxia. Using purified proteins and isolated mitochondria, we show here that the yeast frataxin homolog (Yfh1) directly and specifically stimulates cysteine binding to Nfs1 by exposing substrate-binding sites. This novel function of frataxin does not require iron, Isu1, or Isd11. Once bound to Nfs1, the substrate cysteine is the source of the Nfs1 persulfide, but this step is independent of frataxin and strictly dependent on Isd11. Recently, a point mutation in Isu1 was found to bypass many frataxin functions. The data presented here show that the Isu1 suppressor mimics the frataxin effects on Nfs1, explaining the bypassing activity. We propose a regulatory mechanism for the Nfs1 persulfide-forming activity. Specifically, at least two separate conformational changes must occur in the enzyme for optimum activity as follows: one is mediated by frataxin interaction that exposes the "buried" substrate-binding sites, and the other is mediated by Isd11 interaction that brings the bound substrate cysteine and the active site cysteine in proximity for persulfide formation.
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Affiliation(s)
- Alok Pandey
- From the Department of Pharmacology and Physiology, New Jersey Medical School, Rutgers University, Newark, New Jersey 07101
| | - Donna M. Gordon
- From the Department of Pharmacology and Physiology, New Jersey Medical School, Rutgers University, Newark, New Jersey 07101
| | - Jayashree Pain
- From the Department of Pharmacology and Physiology, New Jersey Medical School, Rutgers University, Newark, New Jersey 07101
| | - Timothy L. Stemmler
- the Department of Pharmaceutical Sciences, Wayne State University, Detroit, Michigan 48201, and
| | - Andrew Dancis
- the Department of Medicine, Division of Hematology-Oncology, University of Pennsylvania, Philadelphia, Pennsylvania 19104
| | - Debkumar Pain
- From the Department of Pharmacology and Physiology, New Jersey Medical School, Rutgers University, Newark, New Jersey 07101
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16
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McCormick SP, Chakrabarti M, Cockrell AL, Park J, Lindahl LS, Lindahl PA. Low-molecular-mass metal complexes in the mouse brain. Metallomics 2013; 5:232-41. [PMID: 23443205 DOI: 10.1039/c3mt00009e] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
The presence of labile low-molecular-mass (LMM, defined as <10 kDa) metal complexes in cells and super-cellular structures such as the brain has been inferred from chelation studies, but direct evidence is lacking. To evaluate the presence of LMM metal complexes in the brain, supernatant fractions of fresh mouse brain homogenates were passed through a 10 kDa cutoff membrane and subjected to size-exclusion liquid chromatography under anaerobic refrigerated conditions. Fractions were monitored for Mn, Fe, Co, Cu, Zn, Mo, S and P using an on-line ICP-MS. At least 30 different LMM metal complexes were detected along with numerous P- and S- containing species. Reproducibility was assessed by performing the experiment 13 times, using different buffers, and by examining whether complexes changed with time. Eleven Co, 2 Cu, 5 Mn, 4 Mo, 3 Fe and 2 Zn complexes with molecular masses <4 kDa were detected. One LMM Mo complex comigrated with the molybdopterin cofactor. Most Cu and Zn complexes appeared to be protein-bound with masses ranging from 4-20 kDa. Co was the only metal for which the "free" or aqueous complex was reproducibly observed. Aqueous Co may be sufficiently stable in this environment due to its relatively slow water-exchange kinetics. Attempts were made to assign some of these complexes, but further efforts will be required to identify them unambiguously and to determine their functions. This is among the first studies to detect low-molecular-mass transition metal complexes in the mouse brain using LC-ICP-MS.
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Affiliation(s)
- Sean P McCormick
- Texas A&M University, Department of Chemistry, College Station, TX 77843, USA
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17
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Persulfide formation on mitochondrial cysteine desulfurase: enzyme activation by a eukaryote-specific interacting protein and Fe-S cluster synthesis. Biochem J 2012; 448:171-87. [PMID: 22928949 DOI: 10.1042/bj20120951] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Cysteine desulfurases abstract sulfur from the substrate cysteine, generate a covalent persulfide on the active site cysteine of the enzyme, and then donate the persulfide sulfur to various recipients such as Fe-S clusters. In Saccharomyces cerevisiae, the Nfs1p protein is the only known cysteine desulfurase, and it forms a complex with Isd11p (Nfs1p·Isd11p). Both of these proteins are found primarily in mitochondria and both are essential for cell viability. In the present study we show, using the results of experiments with isolated mitochondria and purified proteins, that Isd11p is required for the cysteine desulfurase activity of Nfs1p. Whereas Nfs1p by itself was inactive, the Nfs1p·Isd11p complex formed persulfide and was active as a cysteine desulfurase. In the absence of Isd11p, Nfs1p was able to bind the substrate cysteine but failed to form a persulfide. Addition of Isd11p allowed Nfs1p with bound substrate to generate a covalent persulfide. We suggest that Isd11p induces an activating conformational change in Nfs1p to bring the bound substrate and the active site cysteine in proximity for persulfide formation. Thus mitochondrial Nfs1p is different from bacterial cysteine desulfurases that are active in the absence of accessory proteins. Isd11p may serve to regulate cysteine desulfurase activity in mitochondria.
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