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García-Guerrero AE, Marvin RG, Blackwell AM, Sigala PA. Biogenesis of cytochromes c and c 1 in the electron transport chain of malaria parasites. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.02.01.575742. [PMID: 38352463 PMCID: PMC10862854 DOI: 10.1101/2024.02.01.575742] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/16/2024]
Abstract
Plasmodium malaria parasites retain an essential mitochondrional electron transport chain (ETC) that is critical for growth within humans and mosquitoes and a key antimalarial drug target. ETC function requires cytochromes c and c 1 that are unusual among heme proteins due to their covalent binding to heme via conserved CXXCH sequence motifs. Heme attachment to these proteins in most eukaryotes requires the mitochondrial enzyme holocytochrome c synthase (HCCS) that binds heme and the apo cytochrome to facilitate biogenesis of the mature cytochrome c or c 1. Although humans encode a single bifunctional HCCS that attaches heme to both proteins, Plasmodium parasites are like yeast and encode two separate HCCS homologs thought to be specific for heme attachment to cyt c (HCCS) or cyt c 1 (HCC1S). To test the function and specificity of P. falciparum HCCS and HCC1S, we used CRISPR/Cas9 to tag both genes for conditional expression. HCC1S knockdown selectively impaired cyt c 1 biogenesis and caused lethal ETC dysfunction that was not reversed by over-expression of HCCS. Knockdown of HCCS caused a more modest growth defect but strongly sensitized parasites to mitochondrial depolarization by proguanil, revealing key defects in ETC function. These results and prior heterologous studies in E. coli of cyt c hemylation by P. falciparum HCCS and HCC1S strongly suggest that both homologs are essential for mitochondrial ETC function and have distinct specificities for biogenesis of cyt c and c 1, respectively, in parasites. This study lays a foundation to develop novel strategies to selectively block ETC function in malaria parasites.
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Affiliation(s)
| | - Rebecca G. Marvin
- Department of Biochemistry, University of Utah School of Medicine, Salt Lake City, UT, USA
| | - Amanda Mixon Blackwell
- Department of Biochemistry, University of Utah School of Medicine, Salt Lake City, UT, USA
| | - Paul A. Sigala
- Department of Biochemistry, University of Utah School of Medicine, Salt Lake City, UT, USA
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2
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Grunow AL, Carroll SC, Kreiman AN, Sutherland MC. Structure-function analysis of the heme-binding WWD domain in the bacterial holocytochrome c synthase, CcmFH. mBio 2023; 14:e0150923. [PMID: 37929956 PMCID: PMC10746174 DOI: 10.1128/mbio.01509-23] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2023] [Accepted: 09/26/2023] [Indexed: 11/07/2023] Open
Abstract
IMPORTANCE Heme is an essential co-factor for proteins involved with critical cellular functions, such as energy production and oxygen transport. Thus, understanding how heme interacts with proteins and is moved through cells is a fundamental biological question. This work studies the System I cytochrome c biogenesis pathway, which in some species (including Escherichia coli) is composed of eight integral membrane or membrane-associated proteins called CcmA-H that are proposed to function in two steps to transport and attach heme to apocytochrome c. Cytochrome c requires this heme attachment to function in electron transport chains to generate cellular energy. A conserved WWD heme-handling domain in CcmFH is analyzed and residues critical for heme interaction and holocytochrome c synthase activity are identified. CcmFH is the third member of the WWD domain-containing heme-handling protein family to undergo a comprehensive structure-function analysis, allowing for comparison of heme interaction across this protein family.
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Affiliation(s)
- Amber L. Grunow
- Department of Biological Sciences, University of Delaware, Newark, Delaware, USA
| | - Susan C. Carroll
- Department of Biological Sciences, University of Delaware, Newark, Delaware, USA
| | - Alicia N. Kreiman
- Department of Biological Sciences, University of Delaware, Newark, Delaware, USA
| | - Molly C. Sutherland
- Department of Biological Sciences, University of Delaware, Newark, Delaware, USA
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3
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Genceroglu MY, Cavdar C, Manioglu S, Bayraktar H. Genetically Encoded Fluorescent Probe for Detection of Heme-Induced Conformational Changes in Cytochrome c. BIOSENSORS 2023; 13:890. [PMID: 37754124 PMCID: PMC10526477 DOI: 10.3390/bios13090890] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/08/2023] [Revised: 09/11/2023] [Accepted: 09/14/2023] [Indexed: 09/28/2023]
Abstract
Cytochrome c (Cytc) is a key redox protein for energy metabolism and apoptosis in cells. The activation of Cytc is composed of several steps, including its transfer to the mitochondrial membrane, binding to cytochrome c heme lyase (CCHL) and covalent attachment to heme. The spectroscopic methods are often applied to study the structural changes of Cytc. However, they require the isolation of Cytc from cells and have limited availability under physiological conditions. Despite recent studies to elucidate the tightly regulated folding mechanism of Cytc, the role of these events and their association with different conformational states remain elusive. Here, we provide a genetically encoded fluorescence method that allows monitoring of the conformational changes of Cytc upon binding to heme and CCHL. Cerulean and Venus fluorescent proteins attached at the N and C terminals of Cytc can be used to determine its unfolded, intermediate, and native states by measuring FRET amplitude. We found that the noncovalent interaction of heme in the absence of CCHL induced a shift in the FRET signal, indicating the formation of a partially folded state. The higher concentration of heme and coexpression of CCHL gave rise to the recovery of Cytc native structure. We also found that Cytc was weakly associated with CCHL in the absence of heme. As a result, a FRET-based fluorescence approach was demonstrated to elucidate the mechanism of heme-induced Cytc conformational changes with spatiotemporal resolution and can be applied to study its interaction with small molecules and other protein partners in living cells.
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Affiliation(s)
- Mehmet Yunus Genceroglu
- Department of Molecular Biology and Genetics, Istanbul Technical University, Istanbul 34467, Turkey
| | - Cansu Cavdar
- Department of Molecular Biology and Genetics, Istanbul Technical University, Istanbul 34467, Turkey
| | - Selen Manioglu
- Biomedical Science and Engineering Program, Koç University, Istanbul 34450, Turkey
| | - Halil Bayraktar
- Department of Molecular Biology and Genetics, Istanbul Technical University, Istanbul 34467, Turkey
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4
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Kessi J, Turner RJ, Zannoni D. Tellurite and Selenite: how can these two oxyanions be chemically different yet so similar in the way they are transformed to their metal forms by bacteria? Biol Res 2022; 55:17. [PMID: 35382884 PMCID: PMC8981825 DOI: 10.1186/s40659-022-00378-2] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2021] [Accepted: 02/06/2022] [Indexed: 12/26/2022] Open
Abstract
This opinion review explores the microbiology of tellurite, TeO32− and selenite, SeO32− oxyanions, two similar Group 16 chalcogen elements, but with slightly different physicochemical properties that lead to intriguing biological differences. Selenium, Se, is a required trace element compared to tellurium, Te, which is not. Here, the challenges around understanding the uptake transport mechanisms of these anions, as reflected in the model organisms used by different groups, are described. This leads to a discussion around how these oxyanions are subsequently reduced to nanomaterials, which mechanistically, has controversies between ideas around the molecule chemistry, chemical reactions involving reduced glutathione and reactive oxygen species (ROS) production along with the bioenergetics at the membrane versus the cytoplasm. Of particular interest is the linkage of glutathione and thioredoxin chemistry from the cytoplasm through the membrane electron transport chain (ETC) system/quinones to the periplasm. Throughout the opinion review we identify open and unanswered questions about the microbial physiology under selenite and tellurite exposure. Thus, demonstrating how far we have come, yet the exciting research directions that are still possible. The review is written in a conversational manner from three long-term researchers in the field, through which to play homage to the late Professor Claudio Vásquez.
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Affiliation(s)
- Janine Kessi
- Until 2018 - Dept of Plant and Microbial Biology, University of Zurich, Zurich, Switzerland
| | - Raymond J Turner
- Dept of Biological Sciences, University of Calgary, Calgary, AB, Canada.
| | - Davide Zannoni
- Dept of Pharmacy and Biotechnology, University of Bologna, Bologna, Italy
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5
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Gatica-Soria LM, Ceriotti LF, Garcia LE, Virginia Sanchez-Puerta M. Native and foreign mitochondrial and nuclear encoded proteins conform the OXPHOS complexes of a holoparasitic plant. Gene 2022; 817:146176. [PMID: 35031426 DOI: 10.1016/j.gene.2021.146176] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2021] [Revised: 11/02/2021] [Accepted: 12/06/2021] [Indexed: 12/31/2022]
Abstract
The intimate contact between the holoparasitic plant Lophophytum mirabile (Balanophoraceae) and its host plant (Fabaceae) facilitates the exchange of genetic information, increasing the frequency of horizontal gene transfer (HGT). Lophophytum stands out because it acquired a large number of mitochondrial genes (greater than 20) from its legume host that replaced the majority of the native homologs. These foreign genes code for proteins that form multisubunit enzyme complexes, such as those in the oxidative phosphorylation system (OXPHOS) and cytochrome c maturation (ccm) system, together with dozens of nuclear-encoded subunits. However, the existence and the origin of the nuclear subunits that form the major part of the OXPHOS and ccm system in Lophophytum remain unknown. It was proposed that nuclear-encoding genes whose products interact with foreign mitochondrial proteins are also foreign, minimizing the incompatibilities that could arise in the assembly and functioning of these multiprotein complexes. We identified a nearly complete set of OXPHOS and ccm system subunits evolving under selective constraints in the transcriptome of Lophophytum, indicating that OXPHOS is functional and resembles that of free-living angiosperms. Maximum Likelihood phylogenetic analyses revealed a single case of HGT in the nuclear genes, which results in mosaic OXPHOS and ccm system in Lophophytum. These observations raise new questions about the evolution and physiology of this parasitic plant. A putative case of cooperation between two foreign (one mitochondrial and one nuclear) genes is presented.
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Affiliation(s)
- Leonardo M Gatica-Soria
- IBAM, Universidad Nacional de Cuyo, CONICET, Facultad de Ciencias Agrarias, Almirante Brown 500, Chacras de Coria, M5528AHB Mendoza, Argentina; Facultad de Ciencias Exactas y Naturales, Padre Jorge Contreras 1300, Universidad Nacional de Cuyo, M5502JMA Mendoza, Argentina
| | - Luis F Ceriotti
- IBAM, Universidad Nacional de Cuyo, CONICET, Facultad de Ciencias Agrarias, Almirante Brown 500, Chacras de Coria, M5528AHB Mendoza, Argentina; Facultad de Ciencias Exactas y Naturales, Padre Jorge Contreras 1300, Universidad Nacional de Cuyo, M5502JMA Mendoza, Argentina
| | - Laura E Garcia
- IBAM, Universidad Nacional de Cuyo, CONICET, Facultad de Ciencias Agrarias, Almirante Brown 500, Chacras de Coria, M5528AHB Mendoza, Argentina; Facultad de Ciencias Exactas y Naturales, Padre Jorge Contreras 1300, Universidad Nacional de Cuyo, M5502JMA Mendoza, Argentina
| | - M Virginia Sanchez-Puerta
- IBAM, Universidad Nacional de Cuyo, CONICET, Facultad de Ciencias Agrarias, Almirante Brown 500, Chacras de Coria, M5528AHB Mendoza, Argentina; Facultad de Ciencias Exactas y Naturales, Padre Jorge Contreras 1300, Universidad Nacional de Cuyo, M5502JMA Mendoza, Argentina.
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6
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Przybyla-Toscano J, Boussardon C, Law SR, Rouhier N, Keech O. Gene atlas of iron-containing proteins in Arabidopsis thaliana. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2021; 106:258-274. [PMID: 33423341 DOI: 10.1111/tpj.15154] [Citation(s) in RCA: 21] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/19/2020] [Revised: 12/17/2020] [Accepted: 01/04/2021] [Indexed: 05/27/2023]
Abstract
Iron (Fe) is an essential element for the development and physiology of plants, owing to its presence in numerous proteins involved in central biological processes. Here, we established an exhaustive, manually curated inventory of genes encoding Fe-containing proteins in Arabidopsis thaliana, and summarized their subcellular localization, spatiotemporal expression and evolutionary age. We have currently identified 1068 genes encoding potential Fe-containing proteins, including 204 iron-sulfur (Fe-S) proteins, 446 haem proteins and 330 non-Fe-S/non-haem Fe proteins (updates of this atlas are available at https://conf.arabidopsis.org/display/COM/Atlas+of+Fe+containing+proteins). A fourth class, containing 88 genes for which iron binding is uncertain, is indexed as 'unclear'. The proteins are distributed in diverse subcellular compartments with strong differences per category. Interestingly, analysis of the gene age index showed that most genes were acquired early in plant evolutionary history and have progressively gained regulatory elements, to support the complex organ-specific and development-specific functions necessitated by the emergence of terrestrial plants. With this gene atlas, we provide a valuable and updateable tool for the research community that supports the characterization of the molecular actors and mechanisms important for Fe metabolism in plants. This will also help in selecting relevant targets for breeding or biotechnological approaches aiming at Fe biofortification in crops.
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Affiliation(s)
| | - Clément Boussardon
- Department of Plant Physiology, Umeå Plant Science Centre, Umeå University, Umeå, S-90187, Sweden
| | - Simon R Law
- Department of Plant Physiology, Umeå Plant Science Centre, Umeå University, Umeå, S-90187, Sweden
| | | | - Olivier Keech
- Department of Plant Physiology, Umeå Plant Science Centre, Umeå University, Umeå, S-90187, Sweden
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7
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Nishimura Y, Kume K, Sonehara K, Tanifuji G, Shiratori T, Ishida KI, Hashimoto T, Inagaki Y, Ohkuma M. Mitochondrial Genomes of Hemiarma marina and Leucocryptos marina Revised the Evolution of Cytochrome c Maturation in Cryptista. Front Ecol Evol 2020. [DOI: 10.3389/fevo.2020.00140] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
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8
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Laleve A, Panozzo C, Kühl I, Bourand-Plantefol A, Ostojic J, Sissoko A, Tribouillard-Tanvier D, Cornu D, Burg A, Meunier B, Blondel M, Clain J, Bonnefoy N, Duval R, Dujardin G. Artemisinin and its derivatives target mitochondrial c-type cytochromes in yeast and human cells. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2020; 1867:118661. [PMID: 31987792 DOI: 10.1016/j.bbamcr.2020.118661] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/03/2019] [Revised: 01/17/2020] [Accepted: 01/23/2020] [Indexed: 12/27/2022]
Abstract
Artemisinin and its derivatives kill malaria parasites and inhibit the proliferation of cancer cells. In both processes, heme was shown to play a key role in artemisinin bioactivation. We found that artemisinin and clinical artemisinin derivatives are able to compensate for a mutation in the yeast Bcs1 protein, a key chaperon involved in biogenesis of the mitochondrial respiratory complex III. The equivalent Bcs1 variant causes an encephalopathy in human by affecting complex III assembly. We show that artemisinin derivatives decrease the content of mitochondrial cytochromes and disturb the maturation of the complex III cytochrome c1. This last effect is likely responsible for the compensation by decreasing the detrimental over-accumulation of the inactive pre-complex III observed in the bcs1 mutant. We further show that a fluorescent dihydroartemisinin probe rapidly accumulates in the mitochondrial network and targets cytochromes c and c1 in yeast, human cells and isolated mitochondria. In vitro this probe interacts with purified cytochrome c only under reducing conditions and we detect cytochrome c-dihydroartemisinin covalent adducts by mass spectrometry analyses. We propose that reduced mitochondrial c-type cytochromes act as both targets and mediators of artemisinin bioactivation in yeast and human cells.
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Affiliation(s)
- Anais Laleve
- Université Paris-Saclay, CEA, CNRS, Institute for Integrative Biology of the Cell (I2BC), 91198 Gif-sur-Yvette, France.
| | - Cristina Panozzo
- Université Paris-Saclay, CEA, CNRS, Institute for Integrative Biology of the Cell (I2BC), 91198 Gif-sur-Yvette, France
| | - Inge Kühl
- Université Paris-Saclay, CEA, CNRS, Institute for Integrative Biology of the Cell (I2BC), 91198 Gif-sur-Yvette, France
| | - Alexa Bourand-Plantefol
- Université Paris-Saclay, CEA, CNRS, Institute for Integrative Biology of the Cell (I2BC), 91198 Gif-sur-Yvette, France
| | - Jelena Ostojic
- Université Paris-Saclay, CEA, CNRS, Institute for Integrative Biology of the Cell (I2BC), 91198 Gif-sur-Yvette, France
| | - Abdoulaye Sissoko
- Université de Paris, MERIT, IRD, 4 Avenue de l'Observatoire, 75006 Paris, France
| | - Déborah Tribouillard-Tanvier
- Inserm UMR1078, Université de Bretagne Occidentale, Faculté de Médecine et des Sciences de la Santé; Etablissement Français du Sang (EFS) Bretagne; CHRU Brest, Hôpital Morvan, Laboratoire de Génétique Moléculaire, 22 avenue Camille Desmoulins, 29200 Brest, France
| | - David Cornu
- Université Paris-Saclay, CEA, CNRS, Institute for Integrative Biology of the Cell (I2BC), 91198 Gif-sur-Yvette, France
| | - Angélique Burg
- Université Paris-Saclay, CEA, CNRS, Institute for Integrative Biology of the Cell (I2BC), 91198 Gif-sur-Yvette, France
| | - Brigitte Meunier
- Université Paris-Saclay, CEA, CNRS, Institute for Integrative Biology of the Cell (I2BC), 91198 Gif-sur-Yvette, France
| | - Marc Blondel
- Inserm UMR1078, Université de Bretagne Occidentale, Faculté de Médecine et des Sciences de la Santé; Etablissement Français du Sang (EFS) Bretagne; CHRU Brest, Hôpital Morvan, Laboratoire de Génétique Moléculaire, 22 avenue Camille Desmoulins, 29200 Brest, France
| | - Jerome Clain
- Université de Paris, MERIT, IRD, 4 Avenue de l'Observatoire, 75006 Paris, France
| | - Nathalie Bonnefoy
- Université Paris-Saclay, CEA, CNRS, Institute for Integrative Biology of the Cell (I2BC), 91198 Gif-sur-Yvette, France
| | - Romain Duval
- Université de Paris, MERIT, IRD, 4 Avenue de l'Observatoire, 75006 Paris, France
| | - Geneviève Dujardin
- Université Paris-Saclay, CEA, CNRS, Institute for Integrative Biology of the Cell (I2BC), 91198 Gif-sur-Yvette, France.
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9
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Alvarez-Paggi D, Hannibal L, Castro MA, Oviedo-Rouco S, Demicheli V, Tórtora V, Tomasina F, Radi R, Murgida DH. Multifunctional Cytochrome c: Learning New Tricks from an Old Dog. Chem Rev 2017; 117:13382-13460. [DOI: 10.1021/acs.chemrev.7b00257] [Citation(s) in RCA: 135] [Impact Index Per Article: 19.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Affiliation(s)
- Damián Alvarez-Paggi
- Departamento
de Química Inorgánica, Analítica y Química
Física and INQUIMAE (CONICET-UBA), Facultad de Ciencias Exactas
y Naturales, Universidad de Buenos Aires, Ciudad Universitaria, Pab. 2, piso 1, Buenos Aires C1428EHA, Argentina
| | - Luciana Hannibal
- Department
of Pediatrics, Universitätsklinikum Freiburg, Mathildenstrasse 1, Freiburg 79106, Germany
- Departamento
de Bioquímica and Center for Free Radical and Biomedical Research,
Facultad de Medicina, Universidad de la República, Av.
Gral. Flores 2125, Montevideo 11800, Uruguay
| | - María A. Castro
- Departamento
de Química Inorgánica, Analítica y Química
Física and INQUIMAE (CONICET-UBA), Facultad de Ciencias Exactas
y Naturales, Universidad de Buenos Aires, Ciudad Universitaria, Pab. 2, piso 1, Buenos Aires C1428EHA, Argentina
| | - Santiago Oviedo-Rouco
- Departamento
de Química Inorgánica, Analítica y Química
Física and INQUIMAE (CONICET-UBA), Facultad de Ciencias Exactas
y Naturales, Universidad de Buenos Aires, Ciudad Universitaria, Pab. 2, piso 1, Buenos Aires C1428EHA, Argentina
| | - Veronica Demicheli
- Departamento
de Bioquímica and Center for Free Radical and Biomedical Research,
Facultad de Medicina, Universidad de la República, Av.
Gral. Flores 2125, Montevideo 11800, Uruguay
| | - Veronica Tórtora
- Departamento
de Bioquímica and Center for Free Radical and Biomedical Research,
Facultad de Medicina, Universidad de la República, Av.
Gral. Flores 2125, Montevideo 11800, Uruguay
| | - Florencia Tomasina
- Departamento
de Bioquímica and Center for Free Radical and Biomedical Research,
Facultad de Medicina, Universidad de la República, Av.
Gral. Flores 2125, Montevideo 11800, Uruguay
| | - Rafael Radi
- Departamento
de Bioquímica and Center for Free Radical and Biomedical Research,
Facultad de Medicina, Universidad de la República, Av.
Gral. Flores 2125, Montevideo 11800, Uruguay
| | - Daniel H. Murgida
- Departamento
de Química Inorgánica, Analítica y Química
Física and INQUIMAE (CONICET-UBA), Facultad de Ciencias Exactas
y Naturales, Universidad de Buenos Aires, Ciudad Universitaria, Pab. 2, piso 1, Buenos Aires C1428EHA, Argentina
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10
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Babbitt SE, Hsu J, Mendez DL, Kranz RG. Biosynthesis of Single Thioether c-Type Cytochromes Provides Insight into Mechanisms Intrinsic to Holocytochrome c Synthase (HCCS). Biochemistry 2017; 56:3337-3346. [PMID: 28617588 DOI: 10.1021/acs.biochem.7b00286] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
Abstract
C-type cytochromes (cyts c) are generally characterized by the presence of two thioether attachments between heme and two cysteine residues within a highly conserved CXXCH motif. Most eukaryotes use the System III cyt c biogenesis pathway composed of holocytochrome c synthase (HCCS) to catalyze thioether formation. Some protozoan organisms express a functionally equivalent, natural variant of cyt c with an XXXCH heme-attachment motif, resulting in a single covalent attachment. Previous studies have shown that recombinant HCCS can produce low levels of the XXXCH single thioether variant. However, cyt c variants containing substitutions at the C-terminal cysteine of the heme-attachment site (i.e., resulting in CXXXH) have never been observed in nature, and attempts to biosynthesize a recombinant version of this cyt c variant have been largely unsuccessful. In this study, we report the biochemical analyses of an HCCS-matured CXXXH cyt c variant, comparing its biosynthesis and properties to those of the XXXCH variant. The results indicate that although HCCS mediates heme attachment to the N-terminal cysteine in CXXXH cyt c variants, up to 50% of the cyt c produced is modified in an oxygen-dependent manner, resulting in a mixed population of cyt c. Since this aerobic modification occurs only in the context of CXXXH, we also propose that natural HCCS-mediated heme attachment to CXXCH likely initiates at the C-terminal cysteine.
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Affiliation(s)
- Shalon E Babbitt
- Department of Biology, Washington University , St. Louis, Missouri 63130, United States
| | - Jennifer Hsu
- Department of Biology, Washington University , St. Louis, Missouri 63130, United States
| | - Deanna L Mendez
- Department of Biology, Washington University , St. Louis, Missouri 63130, United States
| | - Robert G Kranz
- Department of Biology, Washington University , St. Louis, Missouri 63130, United States
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11
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Gabilly ST, Hamel PP. Maturation of Plastid c-type Cytochromes. FRONTIERS IN PLANT SCIENCE 2017; 8:1313. [PMID: 28798763 PMCID: PMC5526843 DOI: 10.3389/fpls.2017.01313] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/16/2017] [Accepted: 07/12/2017] [Indexed: 05/07/2023]
Abstract
Cytochromes c are hemoproteins, with the prosthetic group covalently linked to the apoprotein, which function as electron carriers. A class of cytochromes c is defined by a CXXCH heme-binding motif where the cysteines form thioether bonds with the vinyl groups of heme. Plastids are known to contain up to three cytochromes c. The membrane-bound cytochrome f and soluble cytochrome c6 operate in photosynthesis while the activity of soluble cytochrome c6A remains unknown. Conversion of apo- to holocytochrome c occurs in the thylakoid lumen and requires the independent transport of apocytochrome and heme across the thylakoid membrane followed by the stereospecific attachment of ferroheme via thioether linkages. Attachment of heme to apoforms of plastid cytochromes c is dependent upon the products of the CCS (for cytochrome csynthesis) genes, first uncovered via genetic analysis of photosynthetic deficient mutants in the green alga Chlamydomonas reinhardtii. The CCS pathway also occurs in cyanobacteria and several bacteria. CcsA and CCS1, the signature components of the CCS pathway are polytopic membrane proteins proposed to operate in the delivery of heme from the stroma to the lumen, and also in the catalysis of the heme ligation reaction. CCDA, CCS4, and CCS5 are components of trans-thylakoid pathways that deliver reducing equivalents in order to maintain the heme-binding cysteines in a reduced form prior to thioether bond formation. While only four CCS components are needed in bacteria, at least eight components are required for plastid cytochrome c assembly, suggesting the biochemistry of thioether formation is more nuanced in the plastid system.
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Affiliation(s)
- Stéphane T. Gabilly
- Department of Molecular Genetics and Department of Biological Chemistry and Pharmacology, The Ohio State University, ColumbusOH, United States
- Molecular and Cellular Developmental Biology Graduate Program, The Ohio State University, ColumbusOH, United States
| | - Patrice P. Hamel
- Department of Molecular Genetics and Department of Biological Chemistry and Pharmacology, The Ohio State University, ColumbusOH, United States
- Molecular and Cellular Developmental Biology Graduate Program, The Ohio State University, ColumbusOH, United States
- *Correspondence: Patrice P. Hamel,
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12
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Cline SG, Laughbaum IA, Hamel PP. CCS2, an Octatricopeptide-Repeat Protein, Is Required for Plastid Cytochrome c Assembly in the Green Alga Chlamydomonas reinhardtii. FRONTIERS IN PLANT SCIENCE 2017. [PMID: 28824661 DOI: 10.3389/fpls.2017.0130] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Subscribe] [Scholar Register] [Indexed: 05/08/2023]
Abstract
In bacteria and energy generating organelles, c-type cytochromes are a class of universal electron carriers with a heme cofactor covalently linked via one or two thioether bonds to a heme binding site. The covalent attachment of heme to apocytochromes is a catalyzed process, taking place via three evolutionarily distinct assembly pathways (Systems I, II, III). System II was discovered in the green alga Chlamydomonas reinhardtii through the genetic analysis of the ccs mutants (cytochrome csynthesis), which display a block in the apo- to holo- form conversion of cytochrome f and c6, the thylakoid lumen resident c-type cytochromes functioning in photosynthesis. Here we show that the gene corresponding to the CCS2 locus encodes a 1,719 amino acid polypeptide and identify the molecular lesions in the ccs2-1 to ccs2-5 alleles. The CCS2 protein displays seven degenerate amino acid repeats, which are variations of the octatricopeptide-repeat motif (OPR) recently recognized in several nuclear-encoded proteins controlling the maturation, stability, or translation of chloroplast transcripts. A plastid site of action for CCS2 is inferred from the finding that GFP fused to the first 100 amino acids of the algal protein localizes to chloroplasts in Nicotiana benthamiana. We discuss the possible functions of CCS2 in the heme attachment reaction.
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Affiliation(s)
- Sara G Cline
- Department of Molecular Genetics and Department of Biological Chemistry and Pharmacology, The Ohio State University, ColumbusOH, United States
- Plant Cellular and Molecular Biology Graduate Program, The Ohio State University, ColumbusOH, United States
| | - Isaac A Laughbaum
- Department of Molecular Genetics and Department of Biological Chemistry and Pharmacology, The Ohio State University, ColumbusOH, United States
| | - Patrice P Hamel
- Department of Molecular Genetics and Department of Biological Chemistry and Pharmacology, The Ohio State University, ColumbusOH, United States
- Plant Cellular and Molecular Biology Graduate Program, The Ohio State University, ColumbusOH, United States
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Cline SG, Laughbaum IA, Hamel PP. CCS2, an Octatricopeptide-Repeat Protein, Is Required for Plastid Cytochrome c Assembly in the Green Alga Chlamydomonas reinhardtii. FRONTIERS IN PLANT SCIENCE 2017; 8:1306. [PMID: 28824661 PMCID: PMC5541062 DOI: 10.3389/fpls.2017.01306] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/16/2017] [Accepted: 07/12/2017] [Indexed: 05/19/2023]
Abstract
In bacteria and energy generating organelles, c-type cytochromes are a class of universal electron carriers with a heme cofactor covalently linked via one or two thioether bonds to a heme binding site. The covalent attachment of heme to apocytochromes is a catalyzed process, taking place via three evolutionarily distinct assembly pathways (Systems I, II, III). System II was discovered in the green alga Chlamydomonas reinhardtii through the genetic analysis of the ccs mutants (cytochrome csynthesis), which display a block in the apo- to holo- form conversion of cytochrome f and c6, the thylakoid lumen resident c-type cytochromes functioning in photosynthesis. Here we show that the gene corresponding to the CCS2 locus encodes a 1,719 amino acid polypeptide and identify the molecular lesions in the ccs2-1 to ccs2-5 alleles. The CCS2 protein displays seven degenerate amino acid repeats, which are variations of the octatricopeptide-repeat motif (OPR) recently recognized in several nuclear-encoded proteins controlling the maturation, stability, or translation of chloroplast transcripts. A plastid site of action for CCS2 is inferred from the finding that GFP fused to the first 100 amino acids of the algal protein localizes to chloroplasts in Nicotiana benthamiana. We discuss the possible functions of CCS2 in the heme attachment reaction.
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Affiliation(s)
- Sara G. Cline
- Department of Molecular Genetics and Department of Biological Chemistry and Pharmacology, The Ohio State University, ColumbusOH, United States
- Plant Cellular and Molecular Biology Graduate Program, The Ohio State University, ColumbusOH, United States
| | - Isaac A. Laughbaum
- Department of Molecular Genetics and Department of Biological Chemistry and Pharmacology, The Ohio State University, ColumbusOH, United States
| | - Patrice P. Hamel
- Department of Molecular Genetics and Department of Biological Chemistry and Pharmacology, The Ohio State University, ColumbusOH, United States
- Plant Cellular and Molecular Biology Graduate Program, The Ohio State University, ColumbusOH, United States
- *Correspondence: Patrice P. Hamel,
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Nishimura Y, Tanifuji G, Kamikawa R, Yabuki A, Hashimoto T, Inagaki Y. Mitochondrial Genome of Palpitomonas bilix: Derived Genome Structure and Ancestral System for Cytochrome c Maturation. Genome Biol Evol 2016; 8:3090-3098. [PMID: 27604877 PMCID: PMC5174734 DOI: 10.1093/gbe/evw217] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
We here reported the mitochondrial (mt) genome of one of the heterotrophic microeukaryotes related to cryptophytes, Palpitomonas bilix. The P. bilix mt genome was found to be a linear molecule composed of “single copy region” (∼16 kb) and repeat regions (∼30 kb) arranged in an inverse manner at both ends of the genome. Linear mt genomes with large inverted repeats are known for three distantly related eukaryotes (including P. bilix), suggesting that this particular mt genome structure has emerged at least three times in the eukaryotic tree of life. The P. bilix mt genome contains 47 protein-coding genes including ccmA, ccmB, ccmC, and ccmF, which encode protein subunits involved in the system for cytochrome c maturation inherited from a bacterium (System I). We present data indicating that the phylogenetic relatives of P. bilix, namely, cryptophytes, goniomonads, and kathablepharids, utilize an alternative system for cytochrome c maturation, which has most likely emerged during the evolution of eukaryotes (System III). To explain the distribution of Systems I and III in P. bilix and its phylogenetic relatives, two scenarios are possible: (i) System I was replaced by System III on the branch leading to the common ancestor of cryptophytes, goniomonads, and kathablepharids, and (ii) the two systems co-existed in their common ancestor, and lost differentially among the four descendants.
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Affiliation(s)
- Yuki Nishimura
- Graduate School of Life and Environmental Sciences, University of Tsukuba, Tsukuba, Japan Present address: Japan Collection of Microorganisms/Microbe Division, RIKEN BioResource Center, Japan Collection of Microorganisms Microbe Division, Tsukuba, Japan
| | - Goro Tanifuji
- Graduate School of Life and Environmental Sciences, University of Tsukuba, Tsukuba, Japan Present address: Department of Zoology, National Museum of Nature and Science, Tsukuba, Japan
| | - Ryoma Kamikawa
- Graduate School of Global Environmental Studies and Graduate School of Human and Environmental Studies, Kyoto University, Kyoto, Japan
| | - Akinori Yabuki
- Japan Agency for Marine-Earth Science and Technology (JAMSTEC), Yokosuka, Japan
| | - Tetsuo Hashimoto
- Graduate School of Life and Environmental Sciences, University of Tsukuba, Tsukuba, Japan Center for Computational Sciences, University of Tsukuba, Tsukuba, Japan
| | - Yuji Inagaki
- Graduate School of Life and Environmental Sciences, University of Tsukuba, Tsukuba, Japan Center for Computational Sciences, University of Tsukuba, Tsukuba, Japan
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Posayapisit N, Songsungthong W, Koonyosying P, Falade MO, Uthaipibull C, Yuthavong Y, Shaw PJ, Kamchonwongpaisan S. Cytochrome c and c1 heme lyases are essential in Plasmodium berghei. Mol Biochem Parasitol 2016; 210:32-36. [PMID: 27520480 DOI: 10.1016/j.molbiopara.2016.08.003] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2016] [Revised: 08/04/2016] [Accepted: 08/08/2016] [Indexed: 10/21/2022]
Abstract
Malaria parasites possess a de novo heme synthetic pathway. Interestingly, this pathway is dispensable during the blood stages of development in mammalian hosts. The assembly of the two most important hemeproteins, cytochromes c and c1, is mediated by cytochrome heme lyase enzymes. Plasmodium spp. possess two cytochrome heme lyases encoded by separate genes. Given the redundancy of heme synthesis, we sought to determine if heme lyase function also exhibits redundancy. To answer this question, we performed gene knockout experiments. We found that the PBANKA_143950 and PBANKA_0602600 Plasmodium berghei genes encoding cytochrome c (Pbcchl) and cytochrome c1 (Pbcc1hl) heme lyases, respectively, can only be disrupted when a complementary gene is present. In contrast, four genes in the de novo heme synthesis pathway can be disrupted without complementation. This work provides evidence that Pbcchl and Pbcc1hl are both essential and thus may be antimalarial targets.
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Affiliation(s)
- Navaporn Posayapisit
- National Center for Genetic Engineering and Biotechnology (BIOTEC), National Science and Technology Development Agency (NSTDA), 113 Thailand Science Park, Thanon Phahonyothin, Tambon Khlong Neung, Amphoe Khlong Luang, Pathum Thani 12120, Thailand
| | - Warangkhana Songsungthong
- National Center for Genetic Engineering and Biotechnology (BIOTEC), National Science and Technology Development Agency (NSTDA), 113 Thailand Science Park, Thanon Phahonyothin, Tambon Khlong Neung, Amphoe Khlong Luang, Pathum Thani 12120, Thailand
| | - Pongpisid Koonyosying
- National Center for Genetic Engineering and Biotechnology (BIOTEC), National Science and Technology Development Agency (NSTDA), 113 Thailand Science Park, Thanon Phahonyothin, Tambon Khlong Neung, Amphoe Khlong Luang, Pathum Thani 12120, Thailand
| | - Mofolusho O Falade
- National Center for Genetic Engineering and Biotechnology (BIOTEC), National Science and Technology Development Agency (NSTDA), 113 Thailand Science Park, Thanon Phahonyothin, Tambon Khlong Neung, Amphoe Khlong Luang, Pathum Thani 12120, Thailand
| | - Chairat Uthaipibull
- National Center for Genetic Engineering and Biotechnology (BIOTEC), National Science and Technology Development Agency (NSTDA), 113 Thailand Science Park, Thanon Phahonyothin, Tambon Khlong Neung, Amphoe Khlong Luang, Pathum Thani 12120, Thailand
| | - Yongyuth Yuthavong
- National Center for Genetic Engineering and Biotechnology (BIOTEC), National Science and Technology Development Agency (NSTDA), 113 Thailand Science Park, Thanon Phahonyothin, Tambon Khlong Neung, Amphoe Khlong Luang, Pathum Thani 12120, Thailand
| | - Philip J Shaw
- National Center for Genetic Engineering and Biotechnology (BIOTEC), National Science and Technology Development Agency (NSTDA), 113 Thailand Science Park, Thanon Phahonyothin, Tambon Khlong Neung, Amphoe Khlong Luang, Pathum Thani 12120, Thailand.
| | - Sumalee Kamchonwongpaisan
- National Center for Genetic Engineering and Biotechnology (BIOTEC), National Science and Technology Development Agency (NSTDA), 113 Thailand Science Park, Thanon Phahonyothin, Tambon Khlong Neung, Amphoe Khlong Luang, Pathum Thani 12120, Thailand.
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Babbitt SE, Hsu J, Kranz RG. Molecular Basis Behind Inability of Mitochondrial Holocytochrome c Synthase to Mature Bacterial Cytochromes: DEFINING A CRITICAL ROLE FOR CYTOCHROME c α HELIX-1. J Biol Chem 2016; 291:17523-34. [PMID: 27387500 DOI: 10.1074/jbc.m116.741231] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2016] [Indexed: 11/06/2022] Open
Abstract
Mitochondrial holocytochrome c synthase (HCCS) is required for cytochrome c (cyt c) maturation and therefore respiration. HCCS efficiently attaches heme via two thioethers to CXXCH of mitochondrial but not bacterial cyt c even though they are functionally conserved. This inability is due to residues in the bacterial cyt c N terminus, but the molecular basis is unknown. Human cyts c with deletions of single residues in α helix-1, which mimic bacterial cyt c, are poorly matured by human HCCS. Focusing on ΔM13 cyt c, we co-purified this variant with HCCS, demonstrating that HCCS recognizes the bacterial-like cytochrome. Although an HCCS-WT cyt c complex contains two covalent links, HCCS-ΔM13 cyt c contains only one thioether attachment. Using multiple approaches, we show that the single attachment is to the second thiol of C(15)SQC(18)H, indicating that α helix-1 is required for positioning the first cysteine for covalent attachment, whereas the histidine of CXXCH positions the second cysteine. Modeling of the N-terminal structure suggested that the serine residue (of CSQCH) would be anchored where the first cysteine should be in ΔM13 cyt c An engineered cyt c with a CQCH motif in the ΔM13 background is matured at higher levels (2-3-fold), providing further evidence for α helix-1 positioning the first cysteine. Bacterial cyt c biogenesis pathways (Systems I and II) appear to recognize simply the CXXCH motif, not requiring α helix-1. Results here explain mechanistically how HCCS (System III) requires an extended region adjacent to CXXCH for maturation.
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Affiliation(s)
- Shalon E Babbitt
- From the Department of Biology, Washington University, St. Louis, Missouri 63130
| | - Jennifer Hsu
- From the Department of Biology, Washington University, St. Louis, Missouri 63130
| | - Robert G Kranz
- From the Department of Biology, Washington University, St. Louis, Missouri 63130
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17
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Sutherland MC, Rankin JA, Kranz RG. Heme Trafficking and Modifications during System I Cytochrome c Biogenesis: Insights from Heme Redox Potentials of Ccm Proteins. Biochemistry 2016; 55:3150-6. [PMID: 27198710 DOI: 10.1021/acs.biochem.6b00427] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Cytochromes c require covalent attachment of heme via two thioether bonds at conserved CXXCH motifs, a process accomplished in prokaryotes by eight integral membrane proteins (CcmABCDEFGH), termed System I. Heme is trafficked from inside the cell to outside (via CcmABCD) and chaperoned (holoCcmE) to the cytochrome c synthetase (CcmF/H). Purification of key System I pathway intermediates allowed the determination of heme redox potentials. The data support a model whereby heme is oxidized to form holoCcmE and subsequently reduced by CcmF/H for thioether formation, with Fe(2+) being required for attachment to CXXCH. Results provide insight into mechanisms for the oxidation and reduction of heme in vivo.
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Affiliation(s)
- Molly C Sutherland
- Department of Biology, Washington University , St. Louis, Missouri 63130, United States
| | - Joel A Rankin
- Department of Biology, Washington University , St. Louis, Missouri 63130, United States
| | - Robert G Kranz
- Department of Biology, Washington University , St. Louis, Missouri 63130, United States
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18
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Barupala DP, Dzul SP, Riggs-Gelasco PJ, Stemmler TL. Synthesis, delivery and regulation of eukaryotic heme and Fe-S cluster cofactors. Arch Biochem Biophys 2016; 592:60-75. [PMID: 26785297 PMCID: PMC4784227 DOI: 10.1016/j.abb.2016.01.010] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2015] [Revised: 01/13/2016] [Accepted: 01/14/2016] [Indexed: 11/25/2022]
Abstract
In humans, the bulk of iron in the body (over 75%) is directed towards heme- or Fe-S cluster cofactor synthesis, and the complex, highly regulated pathways in place to accomplish biosynthesis have evolved to safely assemble and load these cofactors into apoprotein partners. In eukaryotes, heme biosynthesis is both initiated and finalized within the mitochondria, while cellular Fe-S cluster assembly is controlled by correlated pathways both within the mitochondria and within the cytosol. Iron plays a vital role in a wide array of metabolic processes and defects in iron cofactor assembly leads to human diseases. This review describes progress towards our molecular-level understanding of cellular heme and Fe-S cluster biosynthesis, focusing on the regulation and mechanistic details that are essential for understanding human disorders related to the breakdown in these essential pathways.
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Affiliation(s)
- Dulmini P Barupala
- Departments of Biochemistry and Molecular Biology, and Pharmaceutical Sciences, Wayne State University, Detroit, MI 48201, USA
| | - Stephen P Dzul
- Departments of Biochemistry and Molecular Biology, and Pharmaceutical Sciences, Wayne State University, Detroit, MI 48201, USA
| | | | - Timothy L Stemmler
- Departments of Biochemistry and Molecular Biology, and Pharmaceutical Sciences, Wayne State University, Detroit, MI 48201, USA.
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Khalfaoui-Hassani B, Verissimo AF, Shroff NP, Ekici S, Trasnea PI, Utz M, Koch HG, Daldal F. Biogenesis of Cytochrome c Complexes: From Insertion of Redox Cofactors to Assembly of Different Subunits. ADVANCES IN PHOTOSYNTHESIS AND RESPIRATION 2016. [DOI: 10.1007/978-94-017-7481-9_27] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
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20
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Babbitt SE, Sutherland MC, San Francisco B, Mendez DL, Kranz RG. Mitochondrial cytochrome c biogenesis: no longer an enigma. Trends Biochem Sci 2015; 40:446-55. [PMID: 26073510 DOI: 10.1016/j.tibs.2015.05.006] [Citation(s) in RCA: 85] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2015] [Revised: 05/13/2015] [Accepted: 05/18/2015] [Indexed: 12/31/2022]
Abstract
Cytochromes c (cyt c) and c1 are heme proteins that are essential for aerobic respiration. Release of cyt c from mitochondria is an important signal in apoptosis initiation. Biogenesis of c-type cytochromes involves covalent attachment of heme to two cysteines (at a conserved CXXCH sequence) in the apocytochrome. Heme attachment is catalyzed in most mitochondria by holocytochrome c synthase (HCCS), which is also necessary for the import of apocytochrome c (apocyt c). Thus, HCCS affects cellular levels of cyt c, impacting mitochondrial physiology and cell death. Here, we review the mechanisms of HCCS function and the roles of heme and residues in the CXXCH motif. Additionally, we consider concepts emerging within the two prokaryotic cytochrome c biogenesis pathways.
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Affiliation(s)
- Shalon E Babbitt
- Department of Biology, Washington University, St Louis, MO 63130, USA
| | | | | | - Deanna L Mendez
- Department of Biology, Washington University, St Louis, MO 63130, USA
| | - Robert G Kranz
- Department of Biology, Washington University, St Louis, MO 63130, USA.
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Babbitt SE, San Francisco B, Mendez DL, Lukat-Rodgers GS, Rodgers KR, Bretsnyder EC, Kranz RG. Mechanisms of mitochondrial holocytochrome c synthase and the key roles played by cysteines and histidine of the heme attachment site, Cys-XX-Cys-His. J Biol Chem 2014; 289:28795-807. [PMID: 25170082 DOI: 10.1074/jbc.m114.593509] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Mitochondrial cytochrome c assembly requires the covalent attachment of heme by thioether bonds between heme vinyl groups and a conserved CXXCH motif of cytochrome c/c1. The enzyme holocytochrome c synthase (HCCS) binds heme and apocytochrome c substrate to catalyze this attachment, subsequently releasing holocytochrome c for proper folding to its native structure. We address mechanisms of assembly using a functional Escherichia coli recombinant system expressing human HCCS. Human cytochrome c variants with individual cysteine, histidine, double cysteine, and triple cysteine/histidine substitutions (of CXXCH) were co-purified with HCCS. Single and double mutants form a complex with HCCS but not the triple mutant. Resonance Raman and UV-visible spectroscopy support the proposal that heme puckering induced by both thioether bonds facilitate release of holocytochrome c from the complex. His-19 (of CXXCH) supplies the second axial ligand to heme in the complex, the first axial ligand was previously shown to be from HCCS residue His-154. Substitutions of His-19 in cytochrome c to seven other residues (Gly, Ala, Met, Arg, Lys, Cys, and Tyr) were used with various approaches to establish other roles played by His-19. Three roles for His-19 in HCCS-mediated assembly are suggested: (i) to provide the second axial ligand to the heme iron in preparation for covalent attachment; (ii) to spatially position the two cysteinyl sulfurs adjacent to the two heme vinyl groups for thioether formation; and (iii) to aid in release of the holocytochrome c from the HCCS active site. Only H19M is able to carry out these three roles, albeit at lower efficiencies than the natural His-19.
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Affiliation(s)
- Shalon E Babbitt
- From the Department of Biology, Washington University, St. Louis, Missouri 63130 and
| | - Brian San Francisco
- From the Department of Biology, Washington University, St. Louis, Missouri 63130 and
| | - Deanna L Mendez
- From the Department of Biology, Washington University, St. Louis, Missouri 63130 and
| | - Gudrun S Lukat-Rodgers
- the Department of Chemistry and Biochemistry, North Dakota State University, Fargo, North Dakota 58102
| | - Kenton R Rodgers
- the Department of Chemistry and Biochemistry, North Dakota State University, Fargo, North Dakota 58102
| | - Eric C Bretsnyder
- From the Department of Biology, Washington University, St. Louis, Missouri 63130 and
| | - Robert G Kranz
- From the Department of Biology, Washington University, St. Louis, Missouri 63130 and
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Babbitt SE, San Francisco B, Bretsnyder EC, Kranz RG. Conserved residues of the human mitochondrial holocytochrome c synthase mediate interactions with heme. Biochemistry 2014; 53:5261-71. [PMID: 25054239 PMCID: PMC4139152 DOI: 10.1021/bi500704p] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
C-type cytochromes are distinguished by the covalent attachment of a heme cofactor, a modification that is typically required for its subsequent folding, stability, and function. Heme attachment takes place in the mitochondrial intermembrane space and, in most eukaryotes, is mediated by holocytochrome c synthase (HCCS). HCCS is the primary component of the eukaryotic cytochrome c biogenesis pathway, known as System III. The catalytic function of HCCS depends on its ability to coordinate interactions between its substrates: heme and cytochrome c. Recent advancements in the recombinant expression and purification of HCCS have facilitated comprehensive analyses of the roles of conserved residues in HCCS, as demonstrated in this study. Previously, we proposed a four-step model describing HCCS-mediated cytochrome c assembly, identifying a conserved histidine residue (His154) as an axial ligand to the heme iron. In this study, we performed a systematic mutational analysis of 17 conserved residues in HCCS, and we provide evidence that the enzyme contains two heme-binding domains. Our data indicate that heme contacts mediated by residues within these domains modulate the dynamics of heme binding and contribute to the stability of the HCCS-heme-cytochrome c steady state ternary complex. While some residues are essential for initial heme binding (step 1), others impact the subsequent release of the holocytochrome c product (step 4). Certain HCCS mutants that were defective in heme binding were corrected for function by exogenous aminolevulinic acid (ALA, the precursor to heme). This chemical "correction" supports the proposed role of heme binding for the corresponding residues.
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Affiliation(s)
- Shalon E Babbitt
- Department of Biology, Washington University , St. Louis, Missouri 63130, United States
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23
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San Francisco B, Kranz RG. Interaction of holoCcmE with CcmF in heme trafficking and cytochrome c biosynthesis. J Mol Biol 2014; 426:570-85. [PMID: 24513106 DOI: 10.1016/j.jmb.2013.10.025] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2013] [Revised: 10/10/2013] [Accepted: 10/17/2013] [Indexed: 10/26/2022]
Abstract
The periplasmic heme chaperone holoCcmE is essential for heme trafficking in the cytochrome c biosynthetic pathway in many bacteria, archaea, and plant mitochondria. This pathway, called system I, involves two steps: (i) formation and release of holoCcmE (by the ABC-transporter complex CcmABCD) and (ii) delivery of the heme in holoCcmE to the putative cytochrome c heme lyase complex, CcmFH. CcmFH is believed to facilitate the final covalent attachment of heme (from holoCcmE) to the apocytochrome c. Although most models for system I propose that holoCcmE delivers heme directly to CcmF, no interaction between holoCcmE and CcmF has been demonstrated. Here, a complex between holoCcmE and CcmF is “trapped”, purified, and characterized. HoloCcmE must be released from the ABC-transporter complex CcmABCD to interact with CcmF, and the holo-form of CcmE interacts with CcmF at levels at least 20-fold higher than apoCcmE. Two conserved histidines (here termed P-His1 and P-His2) in separate periplasmic loops in CcmF are required for interaction with holoCcmE, and evidence that P-His1 and P-His2 function as heme-binding ligands is presented. These results show that heme in holoCcmE is essential for complex formation with CcmF and that the heme of holoCcmE is coordinated by P-His1 and P-His2 within the WWD domain of CcmF. These features are strikingly similar to formation of the CcmC:heme:CcmE ternary complex [Richard-Fogal C, Kranz RG. The CcmC:heme:CcmE complex in heme trafficking and cytochrome c biosynthesis. J Mol Biol 2010;401:350–62] and suggest common mechanistic and structural aspects.
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Verissimo AF, Daldal F. Cytochrome c biogenesis System I: an intricate process catalyzed by a maturase supercomplex? BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2014; 1837:989-98. [PMID: 24631867 DOI: 10.1016/j.bbabio.2014.03.003] [Citation(s) in RCA: 47] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/11/2014] [Revised: 03/03/2014] [Accepted: 03/06/2014] [Indexed: 11/16/2022]
Abstract
Cytochromes c are ubiquitous heme proteins that are found in most living organisms and are essential for various energy production pathways as well as other cellular processes. Their biosynthesis relies on a complex post-translational process, called cytochrome c biogenesis, responsible for the formation of stereo-specific thioether bonds between the vinyl groups of heme b (protoporphyrin IX-Fe) and the thiol groups of apocytochromes c heme-binding site (C1XXC2H) cysteine residues. In some organisms this process involves up to nine (CcmABCDEFGHI) membrane proteins working together to achieve heme ligation, designated the Cytochrome c maturation (Ccm)-System I. Here, we review recent findings related to the Ccm-System I found in bacteria, archaea and plant mitochondria, with an emphasis on protein interactions between the Ccm components and their substrates (apocytochrome c and heme). We discuss the possibility that the Ccm proteins may form a multi subunit supercomplex (dubbed "Ccm machine"), and based on the currently available data, we present an updated version of a mechanistic model for Ccm. This article is part of a Special Issue entitled: 18th European Bioenergetic Conference.
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Affiliation(s)
- Andreia F Verissimo
- Department of Biology, University of Pennsylvania, Philadelphia, PA 19104-6019, USA
| | - Fevzi Daldal
- Department of Biology, University of Pennsylvania, Philadelphia, PA 19104-6019, USA.
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25
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San Francisco B, Sutherland MC, Kranz RG. The CcmFH complex is the system I holocytochrome c synthetase: engineering cytochrome c maturation independent of CcmABCDE. Mol Microbiol 2014; 91:996-1008. [PMID: 24397552 DOI: 10.1111/mmi.12510] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 01/04/2014] [Indexed: 01/03/2023]
Abstract
Cytochrome c maturation (ccm) in many bacteria, archaea and plant mitochondria requires eight membrane proteins, CcmABCDEFGH, called system I. This pathway delivers and attaches haem covalently to two cysteines (of Cys-Xxx-Xxx-Cys-His) in the cytochrome c. All models propose that CcmFH facilitates covalent attachment of haem to the apocytochrome; namely, that it is the synthetase. However, holocytochrome c synthetase activity has not been directly demonstrated for CcmFH. We report formation of holocytochromes c by CcmFH and CcmG, a periplasmic thioredoxin, independent of CcmABCDE (we term this activity CcmFGH-only). Cytochrome c produced in the absence of CcmABCDE is indistinguishable from cytochrome c produced by the full system I, with a cleaved signal sequence and two covalent bonds to haem. We engineered increased cytochrome c production by CcmFGH-only, with yields approaching those from the full system I. Three conserved histidines in CcmF (TM-His1, TM-His2 and P-His1) are required for activity, as are the conserved cysteine pairs in CcmG and CcmH. Our findings establish that CcmFH is the system I holocytochrome c synthetase. Although we discuss why this engineering would likely not replace the need for CcmABCDE in nature, these results provide unique mechanistic and evolutionary insights into cytochrome c biosynthesis.
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Affiliation(s)
- Brian San Francisco
- Department of Biology, Washington University in St. Louis, St. Louis, MO, 63130, USA
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Ferousi C, Speth DR, Reimann J, Op den Camp HJM, Allen JWA, Keltjens JTM, Jetten MSM. Identification of the type II cytochrome c maturation pathway in anammox bacteria by comparative genomics. BMC Microbiol 2013; 13:265. [PMID: 24267221 PMCID: PMC4222556 DOI: 10.1186/1471-2180-13-265] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2013] [Accepted: 11/18/2013] [Indexed: 11/10/2022] Open
Abstract
Background Anaerobic ammonium oxidizing (anammox) bacteria may contribute up to 50% to the global nitrogen production, and are, thus, key players of the global nitrogen cycle. The molecular mechanism of anammox was recently elucidated and is suggested to proceed through a branched respiratory chain. This chain involves an exceptionally high number of c-type cytochrome proteins which are localized within the anammoxosome, a unique subcellular organelle. During transport into the organelle the c-type cytochrome apoproteins need to be post-translationally processed so that heme groups become covalently attached to them, resulting in mature c-type cytochrome proteins. Results In this study, a comparative genome analysis was performed to identify the cytochrome c maturation system employed by anammox bacteria. Our results show that all available anammox genome assemblies contain a complete type II cytochrome c maturation system. Conclusions Our working model suggests that this machinery is localized at the anammoxosome membrane which is assumed to be the locus of anammox catabolism. These findings will stimulate further studies in dissecting the molecular and cellular basis of cytochrome c biogenesis in anammox bacteria.
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Affiliation(s)
- Christina Ferousi
- Department of Microbiology, Institute for Water and Wetland Research, Radboud University Nijmegen, Heyendaalseweg 135, 6525, AJ, Nijmegen, the Netherlands.
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Yoon JY, Kim J, An DR, Lee SJ, Kim HS, Im HN, Yoon HJ, Kim JY, Kim SJ, Han BW, Suh SW. Structural and functional characterization of HP0377, a thioredoxin-fold protein from Helicobacter pylori. ACTA CRYSTALLOGRAPHICA SECTION D: BIOLOGICAL CRYSTALLOGRAPHY 2013; 69:735-46. [PMID: 23633582 DOI: 10.1107/s0907444913001236] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/11/2012] [Accepted: 01/12/2013] [Indexed: 12/16/2022]
Abstract
Maturation of cytochrome c is carried out in the bacterial periplasm, where specialized thiol-disulfide oxidoreductases provide the correct reduction of oxidized apocytochrome c before covalent haem attachment. HP0377 from Helicobacter pylori is a thioredoxin-fold protein that has been implicated as a component of system II for cytochrome c assembly and shows limited sequence similarity to Escherichia coli DsbC, a disulfide-bond isomerase. To better understand the role of HP0377, its crystal structures have been determined in both reduced and partially oxidized states, which are highly similar to each other. Sedimentation-equilibrium experiments indicate that HP0377 is monomeric in solution. HP0377 adopts a thioredoxin fold but shows distinctive variations as in other thioredoxin-like bacterial periplasmic proteins. The active site of HP0377 closely resembles that of E. coli DsbC. A reductase assay suggests that HP0377 may play a role as a reductase in the biogenesis of holocytochrome c553 (HP1227). Binding experiments indicate that it can form a covalent complex with HP0518, a putative L,D-transpeptidase with a catalytic cysteine residue, via a disulfide bond. Furthermore, physicochemical properties of HP0377 and its R86A variant have been determined. These results suggest that HP0377 may perform multiple functions as a reductase in H. pylori.
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Affiliation(s)
- Ji Young Yoon
- Department of Chemistry, College of Natural Sciences, Seoul National University, Seoul 151-742, Republic of Korea
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Mavridou DAI, Ferguson SJ, Stevens JM. Cytochrome c assembly. IUBMB Life 2013; 65:209-16. [PMID: 23341334 DOI: 10.1002/iub.1123] [Citation(s) in RCA: 48] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2012] [Accepted: 11/29/2012] [Indexed: 11/08/2022]
Abstract
Cytochromes c are central proteins in energy transduction processes by virtue of their functions in electron transfer in respiration and photosynthesis. They have heme covalently attached to a characteristic CXXCH motif via protein-catalyzed post-translational modification reactions. Several systems with diverse constituent proteins have been identified in different organisms and are required to perform the heme attachment and associated functions. The necessary steps are translocation of the apocytochrome polypeptide to the site of heme attachment, transport and provision of heme to the appropriate compartment, reduction and chaperoning of the apocytochrome, and finally, formation of the thioether bonds between heme and two cysteines in the cytochrome. Here we summarize the established classical models for these processes and present recent progress in our understanding of the individual steps within the different cytochrome c biogenesis systems.
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Travaglini-Allocatelli C. Protein Machineries Involved in the Attachment of Heme to Cytochrome c: Protein Structures and Molecular Mechanisms. SCIENTIFICA 2013; 2013:505714. [PMID: 24455431 PMCID: PMC3884852 DOI: 10.1155/2013/505714] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/21/2013] [Accepted: 11/24/2013] [Indexed: 05/09/2023]
Abstract
Cytochromes c (Cyt c) are ubiquitous heme-containing proteins, mainly involved in electron transfer processes, whose structure and functions have been and still are intensely studied. Surprisingly, our understanding of the molecular mechanism whereby the heme group is covalently attached to the apoprotein (apoCyt) in the cell is still largely unknown. This posttranslational process, known as Cyt c biogenesis or Cyt c maturation, ensures the stereospecific formation of the thioether bonds between the heme vinyl groups and the cysteine thiols of the apoCyt heme binding motif. To accomplish this task, prokaryotic and eukaryotic cells have evolved distinctive protein machineries composed of different proteins. In this review, the structural and functional properties of the main maturation apparatuses found in gram-negative and gram-positive bacteria and in the mitochondria of eukaryotic cells will be presented, dissecting the Cyt c maturation process into three functional steps: (i) heme translocation and delivery, (ii) apoCyt thioreductive pathway, and (iii) apoCyt chaperoning and heme ligation. Moreover, current hypotheses and open questions about the molecular mechanisms of each of the three steps will be discussed, with special attention to System I, the maturation apparatus found in gram-negative bacteria.
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Affiliation(s)
- Carlo Travaglini-Allocatelli
- Department of Biochemical Sciences, University of Rome “Sapienza”, P.le A. Moro 5, 00185 Rome, Italy
- *Carlo Travaglini-Allocatelli:
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Karamoko M, Gabilly ST, Hamel PP. Operation of trans-thylakoid thiol-metabolizing pathways in photosynthesis. FRONTIERS IN PLANT SCIENCE 2013; 4:476. [PMID: 24348486 PMCID: PMC3842002 DOI: 10.3389/fpls.2013.00476] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/15/2013] [Accepted: 11/04/2013] [Indexed: 05/08/2023]
Abstract
Thiol oxidation to disulfides and the reverse reaction, i.e., disulfide reduction to free thiols, are under the control of catalysts in vivo. Enzymatically assisted thiol-disulfide chemistry is required for the biogenesis of all energy-transducing membrane systems. However, until recently, this had only been demonstrated for the bacterial plasma membrane. Long considered to be vacant, the thylakoid lumen has now moved to the forefront of photosynthesis research with the realization that its proteome is far more complicated than initially anticipated. Several lumenal proteins are known to be disulfide bonded in Arabidopsis, highlighting the importance of sulfhydryl oxidation in the thylakoid lumen. While disulfide reduction in the plastid stroma is known to activate several enzymatic activities, it appears that it is the reverse reaction, i.e., thiol oxidation that is required for the activity of several lumen-resident proteins. This paradigm for redox regulation in the thylakoid lumen has opened a new frontier for research in the field of photosynthesis. Of particular significance in this context is the discovery of trans-thylakoid redox pathways controlling disulfide bond formation and reduction, which are required for photosynthesis.
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Affiliation(s)
- Mohamed Karamoko
- Department of Molecular Genetics, The Ohio State UniversityColumbus, OH, USA
- Department of Molecular and Cellular Biochemistry, The Ohio State UniversityColumbus, OH, USA
| | - Stéphane T. Gabilly
- Department of Molecular Genetics, The Ohio State UniversityColumbus, OH, USA
- Department of Molecular and Cellular Biochemistry, The Ohio State UniversityColumbus, OH, USA
| | - Patrice P. Hamel
- Department of Molecular Genetics, The Ohio State UniversityColumbus, OH, USA
- Department of Molecular and Cellular Biochemistry, The Ohio State UniversityColumbus, OH, USA
- *Correspondence: Patrice P. Hamel, Department of Molecular Genetics, The Ohio State University, 500 Aronoff Laboratory, 318 West 12th Avenue, 43210 Columbus, OH, USA e-mail:
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Miethke M. Molecular strategies of microbial iron assimilation: from high-affinity complexes to cofactor assembly systems. Metallomics 2013. [DOI: 10.1039/c2mt20193c] [Citation(s) in RCA: 87] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
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Human mitochondrial holocytochrome c synthase's heme binding, maturation determinants, and complex formation with cytochrome c. Proc Natl Acad Sci U S A 2012; 110:E788-97. [PMID: 23150584 DOI: 10.1073/pnas.1213897109] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Abstract
Proper functioning of the mitochondrion requires the orchestrated assembly of respiratory complexes with their cofactors. Cytochrome c, an essential electron carrier in mitochondria and a critical component of the apoptotic pathway, contains a heme cofactor covalently attached to the protein at a conserved CXXCH motif. Although it has been known for more than two decades that heme attachment requires the mitochondrial protein holocytochrome c synthase (HCCS), the mechanism remained unknown. We purified membrane-bound human HCCS with endogenous heme and in complex with its cognate human apocytochrome c. Spectroscopic analyses of HCCS alone and complexes of HCCS with site-directed variants of cytochrome c revealed the fundamental steps of heme attachment and maturation. A conserved histidine in HCCS (His154) provided the key ligand to the heme iron. Formation of the HCCS:heme complex served as the platform for interaction with apocytochrome c. Heme was the central molecule mediating contact between HCCS and apocytochrome c. A conserved histidine in apocytochrome c (His19 of CXXCH) supplied the second axial ligand to heme in the trapped HCCS:heme:cytochrome c complex. We also examined the substrate specificity of human HCCS and converted a bacterial cytochrome c into a robust substrate for the HCCS. The results allow us to describe the molecular mechanisms underlying the HCCS reaction.
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Kim HJ, Khalimonchuk O, Smith PM, Winge DR. Structure, function, and assembly of heme centers in mitochondrial respiratory complexes. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2012; 1823:1604-16. [PMID: 22554985 DOI: 10.1016/j.bbamcr.2012.04.008] [Citation(s) in RCA: 154] [Impact Index Per Article: 12.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/14/2012] [Revised: 04/11/2012] [Accepted: 04/13/2012] [Indexed: 10/28/2022]
Abstract
The sequential flow of electrons in the respiratory chain, from a low reduction potential substrate to O(2), is mediated by protein-bound redox cofactors. In mitochondria, hemes-together with flavin, iron-sulfur, and copper cofactors-mediate this multi-electron transfer. Hemes, in three different forms, are used as a protein-bound prosthetic group in succinate dehydrogenase (complex II), in bc(1) complex (complex III) and in cytochrome c oxidase (complex IV). The exact function of heme b in complex II is still unclear, and lags behind in operational detail that is available for the hemes of complex III and IV. The two b hemes of complex III participate in the unique bifurcation of electron flow from the oxidation of ubiquinol, while heme c of the cytochrome c subunit, Cyt1, transfers these electrons to the peripheral cytochrome c. The unique heme a(3), with Cu(B), form a catalytic site in complex IV that binds and reduces molecular oxygen. In addition to providing catalytic and electron transfer operations, hemes also serve a critical role in the assembly of these respiratory complexes, which is just beginning to be understood. In the absence of heme, the assembly of complex II is impaired, especially in mammalian cells. In complex III, a covalent attachment of the heme to apo-Cyt1 is a prerequisite for the complete assembly of bc(1), whereas in complex IV, heme a is required for the proper folding of the Cox 1 subunit and subsequent assembly. In this review, we provide further details of the aforementioned processes with respect to the hemes of the mitochondrial respiratory complexes. This article is part of a Special Issue entitled: Cell Biology of Metals.
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Affiliation(s)
- Hyung J Kim
- University of Utah Health Sciences Center, Department of Medicine, Salt Lake City, UT 84132, USA
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Welchen E, Hildebrandt TM, Lewejohann D, Gonzalez DH, Braun HP. Lack of cytochrome c in Arabidopsis decreases stability of Complex IV and modifies redox metabolism without affecting Complexes I and III. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2012; 1817:990-1001. [PMID: 22551905 DOI: 10.1016/j.bbabio.2012.04.008] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/07/2012] [Revised: 04/09/2012] [Accepted: 04/11/2012] [Indexed: 12/12/2022]
Abstract
We studied the role of cytochrome c (CYTc), which mediates electron transfer between Complexes III and IV, in cellular events related with mitochondrial respiration, plant development and redox homeostasis. We analyzed single and double homozygous mutants in both CYTc-encoding genes from Arabidopsis: CYTC-1 and CYTC-2. While individual mutants were similar to wild-type, knock-out of both genes produced an arrest of embryo development, showing that CYTc function is essential at early stages of plant development. Mutants in which CYTc levels were extremely reduced respective to wild-type had smaller rosettes with a pronounced decrease in parenchymatic cell size and an overall delay in development. Mitochondria from these mutants had lower respiration rates and a relative increase in alternative respiration. Furthermore, the decrease in CYTc severely affected the activity and the amount of Complex IV, without affecting Complexes I and III. Reactive oxygen species levels were reduced in these mutants, which showed induction of genes encoding antioxidant enzymes. Ascorbic acid levels were not affected, suggesting that a small amount of CYTc is enough to support its normal synthesis. We postulate that, in addition to its role as an electron carrier between Complexes III and IV, CYTc influences Complex IV levels in plants, probably reflecting a role of this protein in Complex IV stability. This double function of CYTc most likely explains why it is essential for plant survival.
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Affiliation(s)
- Elina Welchen
- Instituto de Agrobiotecnología del Litoral (IAL), CONICET, Universidad Nacional del Litoral, Santa Fe, Argentina.
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Corvest V, Murrey DA, Hirasawa M, Knaff DB, Guiard B, Hamel PP. The flavoprotein Cyc2p, a mitochondrial cytochrome c assembly factor, is a NAD(P)H-dependent haem reductase. Mol Microbiol 2012; 83:968-80. [PMID: 22257001 DOI: 10.1111/j.1365-2958.2012.07981.x] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Cytochrome c assembly requires sulphydryls at the CXXCH haem binding site on the apoprotein and also chemical reduction of the haem co-factor. In yeast mitochondria, the cytochrome haem lyases (CCHL, CC(1) HL) and Cyc2p catalyse covalent haem attachment to apocytochromes c and c(1) . An in vivo indication that Cyc2p controls a reductive step in the haem attachment reaction is the finding that the requirement for its function can be bypassed by exogenous reductants. Although redox titrations of Cyc2p flavin (E(m) = -290 mV) indicate that reduction of a disulphide at the CXXCH site of apocytochrome c (E(m) = -265 mV) is a thermodynamically favourable reaction, Cyc2p does not act as an apocytochrome c or c(1) CXXCH disulphide reductase in vitro. In contrast, Cyc2p is able to catalyse the NAD(P)H-dependent reduction of hemin, an indication that the protein's role may be to control the redox state of the iron in the haem attachment reaction to apocytochromes c. Using two-hybrid analysis, we show that Cyc2p interacts with CCHL and also with apocytochromes c and c(1) . We postulate that Cyc2p, possibly in a complex with CCHL, reduces the haem iron prior to haem attachment to the apoforms of cytochrome c and c(1) .
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Affiliation(s)
- Vincent Corvest
- Departments of Molecular Genetics and Molecular and Cellular Biochemistry, The Ohio State University, Columbus, OH 43210, USA
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Mavridou DAI, Stevens JM, Mönkemeyer L, Daltrop O, di Gleria K, Kessler BM, Ferguson SJ, Allen JWA. A pivotal heme-transfer reaction intermediate in cytochrome c biogenesis. J Biol Chem 2011; 287:2342-52. [PMID: 22121193 PMCID: PMC3268396 DOI: 10.1074/jbc.m111.313692] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022] Open
Abstract
c-Type cytochromes are widespread proteins, fundamental for respiration or photosynthesis in most cells. They contain heme covalently bound to protein in a highly conserved, highly stereospecific post-translational modification. In many bacteria, mitochondria, and archaea this heme attachment is catalyzed by the cytochrome c maturation (Ccm) proteins. Here we identify and characterize a covalent, ternary complex between the heme chaperone CcmE, heme, and cytochrome c. Formation of the complex from holo-CcmE occurs in vivo and in vitro and involves the specific heme-binding residues of both CcmE and apocytochrome c. The enhancement and attenuation of the amounts of this complex correlates completely with known consequences of mutations in genes for other Ccm proteins. We propose the complex is a trapped catalytic intermediate in the cytochrome c biogenesis process, at the point of heme transfer from CcmE to the cytochrome, the key step in the maturation pathway.
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Affiliation(s)
- Despoina A I Mavridou
- Department of Biochemistry, University of Oxford, South Parks Road, Oxford OX1 3QU, United Kingdom
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San Francisco B, Bretsnyder EC, Rodgers KR, Kranz RG. Heme ligand identification and redox properties of the cytochrome c synthetase, CcmF. Biochemistry 2011; 50:10974-85. [PMID: 22066495 DOI: 10.1021/bi201508t] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Cytochrome c maturation in many bacteria, archaea, and plant mitochondria involves the integral membrane protein CcmF, which is thought to function as a cytochrome c synthetase by facilitating the final covalent attachment of heme to the apocytochrome c. We previously reported that the E. coli CcmF protein contains a b-type heme that is stably and stoichiometrically associated with the protein and is not the heme attached to apocytochrome c. Here, we show that mutation of either of two conserved transmembrane histidines (His261 or His491) impairs stoichiometric b-heme binding in CcmF and results in spectral perturbations in the remaining heme. Exogeneous imidazole is able to correct cytochrome c maturation for His261 and His491 substitutions with small side chains (Ala or Gly), suggesting that a "cavity" is formed in these CcmF mutants in which imidazole binds and acts as a functional ligand to the b-heme. The results of resonance Raman spectroscopy on wild-type CcmF are consistent with a hexacoordinate low-spin b-heme with at least one endogeneous axial His ligand. Analysis of purified recombinant CcmF proteins from diverse prokaryotes reveals that the b-heme in CcmF is widely conserved. We have also determined the reduction potential of the CcmF b-heme (E(m,7) = -147 mV). We discuss these results in the context of CcmF structure and functions as a heme reductase and cytochrome c synthetase.
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Affiliation(s)
- Brian San Francisco
- Department of Biology, Washington University in St. Louis, St. Louis, Missouri 63130, United States
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Jonietz C, Forner J, Hildebrandt T, Binder S. RNA PROCESSING FACTOR3 is crucial for the accumulation of mature ccmC transcripts in mitochondria of Arabidopsis accession Columbia. PLANT PHYSIOLOGY 2011; 157:1430-9. [PMID: 21875896 PMCID: PMC3252130 DOI: 10.1104/pp.111.181552] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/04/2023]
Abstract
RNA PROCESSING FACTOR1 (RPF1) and RPF2 are pentatricopeptide repeat (PPR) proteins involved in 5' processing of different mitochondrial mRNAs in Arabidopsis (Arabidopsis thaliana). Both factors are highly similar to RESTORERS OF FERTILITY (RF), which are part of cytoplasmic male sterility/restoration systems in various plant species. These findings suggest a predominant role of RF-like PPR proteins in posttranscriptional 5' processing. To further explore the functions of this group of proteins, we examined a number of T-DNA lines carrying insertions in the corresponding PPR genes. This screening identified a nearly complete absence of mature ccmC transcripts in an At1g62930 T-DNA insertion line, a phenotype that could be restored by the introduction of the intact At1g62930 gene into the mutant. The insertion in this nuclear gene, which we now call RPF3, also leads to a severe reduction of the CcmC protein in mitochondria. The analysis of C24/rpf3-1 F2 hybrids lacking functional RPF3 genes revealed that this gene has less influence on the generation of the mature ccmC 5' transcript end derived from a distinct ccmC 5' upstream configuration found in mitochondrial DNAs from C24 and other accessions. These data show that a particular function of an RF-like protein is required only in connection with a distinct mtDNA configuration. Our new results further substantiate the fundamental role of RF-like PPR proteins in the posttranscriptional generation of plant mitochondrial 5' transcript termini.
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Richard-Fogal CL, San Francisco B, Frawley ER, Kranz RG. Thiol redox requirements and substrate specificities of recombinant cytochrome c assembly systems II and III. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2011; 1817:911-9. [PMID: 21945855 DOI: 10.1016/j.bbabio.2011.09.008] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/17/2011] [Revised: 09/01/2011] [Accepted: 09/12/2011] [Indexed: 02/05/2023]
Abstract
The reconstitution of biosynthetic pathways from heterologous hosts can help define the minimal genetic requirements for pathway function and facilitate detailed mechanistic studies. Each of the three pathways for the assembly of cytochrome c in nature (called systems I, II, and III) has been shown to function recombinantly in Escherichia coli, covalently attaching heme to the cysteine residues of a CXXCH motif of a c-type cytochrome. However, recombinant systems I (CcmABCDEFGH) and II (CcsBA) function in the E. coli periplasm, while recombinant system III (CCHL) attaches heme to its cognate receptor in the cytoplasm of E. coli, which makes direct comparisons between the three systems difficult. Here we show that the human CCHL (with a secretion signal) attaches heme to the human cytochrome c (with a signal sequence) in the E. coli periplasm, which is bioenergetically (p-side) analogous to the mitochondrial intermembrane space. The human CCHL is specific for the human cytochrome c, whereas recombinant system II can attach heme to multiple non-cognate c-type cytochromes (possessing the CXXCH motif.) We also show that the recombinant periplasmic systems II and III use components of the natural E. coli periplasmic DsbC/DsbD thiol-reduction pathway. This article is part of a Special Issue entitled: Biogenesis/Assembly of Respiratory Enzyme Complexes.
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Mitochondrial cytochromecsynthase: CP motifs are not necessary for heme attachment to apocytochromec. FEBS Lett 2011; 585:3415-9. [DOI: 10.1016/j.febslet.2011.08.042] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2011] [Revised: 08/25/2011] [Accepted: 08/26/2011] [Indexed: 11/20/2022]
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Abstract
In c-type cytochromes, heme becomes covalently attached to the polypeptide chain by a reaction between the vinyl groups of the heme and cysteine thiols from the protein. There are two such cytochromes in mitochondria: cytochrome c and cytochrome c(1). The heme attachment is a post-translational modification that is catalysed by different biogenesis proteins in different organisms. Three types of biogenesis system are found or predicted in mitochondria: System I (the cytochrome c maturation system); System III (termed holocytochrome c synthase (HCCS) or heme lyase); and System V. This review focuses primarily on cytochrome c maturation in mitochondria containing HCCS (System III). It describes what is known about the enzymology and substrate specificity of HCCS; the role of HCCS in human disease; import of HCCS into mitochondria; import of apocytochromes c and c(1) into mitochondria and the close relationships with HCCS-dependent heme attachment; and the role of the fungal cytochrome c biogenesis accessory protein Cyc2. System V is also discussed; this is the postulated mitochondrial cytochrome c biogenesis system of trypanosomes and related organisms. No cytochrome c biogenesis proteins have been identified in the genomes of these organisms whose c-type cytochromes also have a unique mode of heme attachment.
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Affiliation(s)
- James W A Allen
- Department of Biochemistry, University of Oxford, Oxford, UK.
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Kim S, Lee Y, Lazar P, Son M, Baek A, Thangapandian S, Jeong NY, Yoo YH, Lee KW. Binding conformation prediction between human acetylcholinesterase and cytochrome c using molecular modeling methods. J Mol Graph Model 2011; 29:996-1005. [PMID: 21570330 DOI: 10.1016/j.jmgm.2011.04.006] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2011] [Revised: 04/15/2011] [Accepted: 04/18/2011] [Indexed: 11/19/2022]
Abstract
The acetylcholinesterase (AChE) is important to terminate acetylcholine-mediated neurotransmission at cholinergic synapses. The pivotal role of AChE in apoptosome formation through the interactions with cytochrome c (Cyt c) was demonstrated in recent study. In order to investigate the proper binding conformation between the human AChE (hAChE) and human Cyt c (hCyt c), macro-molecular docking simulation was performed using DOT 2.0 program. The hCyt c was bound to peripheral anionic site (PAS) on hAChE and binding mode of the docked conformation was very similar to the reported crystal structure of the AChE and fasciculin-II (Fas-II) complex. Two 10ns molecular dynamics (MD) simulations were carried out to refine the binding mode of docked structure and to observe the differences of the binding conformations between the absent (Apo) and presence (Holo) of heme group. The key hydrogen bonding residues between hAChE and hCyt c proteins were found in Apo and Holo systems, as well as each Tyr341 and Trp286 residue of hAChE was participated in cation-pi (π) interactions with Lys79 of hCyt c in Apo and Holo systems, respectively. From the present study, although the final structures of the Apo and Holo systems have similar binding pattern, several differences were investigated in flexibilities, interface interactions, and interface accessible surface areas. Based on these results, we were able to predict the reasonable binding conformation which is indispensable for apoptosome formation.
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Affiliation(s)
- Songmi Kim
- Division of Applied Life Science (BK21 Program), Research Institute of Natural Science (RINS), Plant Molecular Biology and Biotechnology Research Center (PMBBRC), Gyeongsang National University, Jinju 660-701, Republic of Korea
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A novel component of the disulfide-reducing pathway required for cytochrome c assembly in plastids. Genetics 2011; 187:793-802. [PMID: 21220358 DOI: 10.1534/genetics.110.125369] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
In plastids, the conversion of energy in the form of light to ATP requires key electron shuttles, the c-type cytochromes, which are defined by the covalent attachment of heme to a CXXCH motif. Plastid c-type cytochrome biogenesis occurs in the thylakoid lumen and requires a system for transmembrane transfer of reductants. Previously, CCDA and CCS5/HCF164, found in all plastid-containing organisms, have been proposed as two components of the disulfide-reducing pathway. In this work, we identify a small novel protein, CCS4, as a third component in this pathway. CCS4 was genetically identified in the green alga Chlamydomonas reinhardtii on the basis of the rescue of the ccs4 mutant, which is blocked in the synthesis of holoforms of plastid c-type cytochromes, namely cytochromes f and c(6). Although CCS4 does not display sequence motifs suggestive of redox or heme-binding function, biochemical and genetic complementation experiments suggest a role in the disulfide-reducing pathway required for heme attachment to apoforms of cytochromes c. Exogenous thiols partially rescue the growth phenotype of the ccs4 mutant concomitant with recovery of holocytochrome f accumulation, as does expression of an ectopic copy of the CCDA gene, encoding a trans-thylakoid transporter of reducing equivalents. We suggest that CCS4 might function to stabilize CCDA or regulate its activity.
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44
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Bonnard G, Corvest V, Meyer EH, Hamel PP. Redox processes controlling the biogenesis of c-type cytochromes. Antioxid Redox Signal 2010; 13:1385-401. [PMID: 20214494 DOI: 10.1089/ars.2010.3161] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
In mitochondria, two mono heme c-type cytochromes are essential electron shuttles of the respiratory chain. They are characterized by the covalent attachment of their heme C to a CXXCH motif in the apoproteins. This post-translational modification occurs in the intermembrane space compartment. Dedicated assembly pathways have evolved to achieve this chemical reaction that requires a strict reducing environment. In mitochondria, two unrelated machineries operate, the rather simple System III in yeast and animals and System I in plants and some protozoans. System I is also found in bacteria and shares some common features with System II that operates in bacteria and plastids. This review aims at presenting how different systems control the chemical requirements for the heme ligation in the compartments where cytochrome c maturation takes place. A special emphasis will be given on the redox processes that are required for the heme attachment reaction onto apocytochromes c.
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Affiliation(s)
- Géraldine Bonnard
- Institut de Biologie Moléculaire des Plantes, CNRS UPR-Université de Strasbourg, France.
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45
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Abstract
Mitochondria contain two aqueous compartments: the matrix and the intermembrane space. Whereas many of the biologic functions of the matrix were well characterized in the past, it became clear very recently that the intermembrane space plays a pivotal role in the coordination of mitochondrial activities with other cellular processes. These activities include the exchange of proteins, lipids, or metal ions between the matrix and the cytosol, the regulated initiation of apoptotic cascades, signalling pathways that regulate respiration and metabolic functions, the prevention of reactive oxygen species produced by the respiratory chain, or the control of mitochondrial morphogenesis. We focus on the different biologic functions of the intermembrane space and discuss the relevance of this fascinating compartment for cellular physiology and human health.
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Di Matteo A, Calosci N, Gianni S, Jemth P, Brunori M, Travaglini-Allocatelli C. Structural and functional characterization of CcmG from Pseudomonas aeruginosa, a key component of the bacterial cytochrome c maturation apparatus. Proteins 2010; 78:2213-21. [PMID: 20544959 DOI: 10.1002/prot.22733] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
The cytochrome c maturation process is carried out in the bacterial periplasm, where some specialized thiol-disulfide oxidoreductases work in close synergy for the correct reduction of oxidized apocytochrome before covalent heme attachment. We present a structural and functional characterization of the soluble periplasmic domain of CcmG from the opportunistic pathogen P. aeruginosa (Pa-CcmG), a component of the protein machinery involved in cyt c maturation in gram-negative bacteria. X-ray crystallography reveals that Pa-CcmG is a TRX-like protein; high-resolution crystal structures show that the oxidized and the reduced forms of the enzyme are identical except for the active-site disulfide. The standard redox potential was calculated to be E(0') = -0.213 V at pH 7.0; the pK(a) of the active site thiols were pK(a) = 6.13 +/- 0.05 for the N-terminal Cys74 and pK(a) = 10.5 +/- 0.17 for the C-terminal Cys77. Experiments were carried out to characterize and isolate the mixed disulfide complex between Pa-CcmG and Pa-CcmH (the other redox active component of System I in P. aeruginosa). Our data indicate that the target disulfide of this TRX-like protein is not the intramolecular disulfide of oxidized Pa-CcmH, but the intermolecular disulfide formed between Cys28 of Pa-CcmH and DTNB used for the in vitro experiments. This observation suggests that, in vivo, the physiological substrate of Pa-CcmG may be the mixed-disulfide complex between Pa-CcmH and apo-cyt.
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Affiliation(s)
- Adele Di Matteo
- Dipartimento di Scienze Biochimiche, Istituto di Biologia e Patologia Molecolari del CNR, Sapienza-Università di Roma, Piazzale A. Moro 5, 00185, Roma, Italy
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47
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c-type cytochrome assembly in Saccharomyces cerevisiae: a key residue for apocytochrome c1/lyase interaction. Genetics 2010; 186:561-71. [PMID: 20697122 DOI: 10.1534/genetics.110.120022] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The electron transport chains in the membranes of bacteria and organelles generate proton-motive force essential for ATP production. The c-type cytochromes, defined by the covalent attachment of heme to a CXXCH motif, are key electron carriers in these energy-transducing membranes. In mitochondria, cytochromes c and c(1) are assembled by the cytochrome c heme lyases (CCHL and CC(1)HL) and by Cyc2p, a putative redox protein. A cytochrome c(1) mutant with a CAPCH heme-binding site instead of the wild-type CAACH is strictly dependent upon Cyc2p for assembly. In this context, we found that overexpression of CC(1)HL, as well as mutations of the proline in the CAPCH site to H, L, S, or T residues, can bypass the absence of Cyc2p. The P mutation was postulated to shift the CXXCH motif to an oxidized form, which must be reduced in a Cyc2p-dependent reaction before heme ligation. However, measurement of the redox midpoint potential of apocytochrome c(1) indicates that neither the P nor the T residues impact the thermodynamic propensity of the CXXCH motif to occur in a disulfide vs. dithiol form. We show instead that the identity of the second intervening residue in the CXXCH motif is key in determining the CCHL-dependent vs. CC(1)HL-dependent assembly of holocytochrome c(1). We also provide evidence that Cyc2p is dedicated to the CCHL pathway and is not required for the CC(1)HL-dependent assembly of cytochrome c(1).
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Gabilly ST, Dreyfuss BW, Karamoko M, Corvest V, Kropat J, Page MD, Merchant SS, Hamel PP. CCS5, a thioredoxin-like protein involved in the assembly of plastid c-type cytochromes. J Biol Chem 2010; 285:29738-49. [PMID: 20628047 DOI: 10.1074/jbc.m109.099069] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The c-type cytochromes are metalloproteins with a heme molecule covalently linked to the sulfhydryls of a CXXCH heme-binding site. In plastids, at least six assembly factors are required for heme attachment to the apo-forms of cytochrome f and cytochrome c(6) in the thylakoid lumen. CCS5, controlling plastid cytochrome c assembly, was identified through insertional mutagenesis in the unicellular green alga Chlamydomonas reinhardtii. The complementing gene encodes a protein with similarity to Arabidopsis thaliana HCF164, which is a thylakoid membrane-anchored protein with a lumen-facing thioredoxin-like domain. HCF164 is required for cytochrome b(6)f biogenesis, but its activity and site of action in the assembly process has so far remained undeciphered. We show that CCS5 is a component of a trans-thylakoid redox pathway and operates by reducing the CXXCH heme-binding site of apocytochrome c prior to the heme ligation reaction. The proposal is based on the following findings: 1) the ccs5 mutant is rescued by exogenous thiols; 2) CCS5 interacts with apocytochrome f and c(6) in a yeast two-hybrid assay; and 3) recombinant CCS5 is able to reduce a disulfide in the CXXCH heme-binding site of apocytochrome f.
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Affiliation(s)
- Stéphane T Gabilly
- From the Department of Molecular Genetics and Department of Molecular Cellular Biochemistry and
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49
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Richard-Fogal C, Kranz RG. The CcmC:heme:CcmE complex in heme trafficking and cytochrome c biosynthesis. J Mol Biol 2010; 401:350-62. [PMID: 20599545 DOI: 10.1016/j.jmb.2010.06.041] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2010] [Revised: 06/16/2010] [Accepted: 06/21/2010] [Indexed: 10/19/2022]
Abstract
A superfamily of integral membrane proteins is characterized by a conserved tryptophan-rich region (called the WWD domain) in an external loop at the inner membrane surface. The three major members of this family (CcmC, CcmF, and CcsBA) are each involved in cytochrome c biosynthesis, yet the function of the WWD domain is unknown. It has been hypothesized that the WWD domain binds heme to present it to an acceptor protein (apoCcmE for CcmC or apocytochrome c for CcmF and CcsBA) such that the heme vinyl group(s) covalently attaches to the acceptors. Alternative proposals suggest that the WWD domain interacts directly with the acceptor protein (e.g., apoCcmE for CcmC). Here, it is shown that CcmC is only trapped with heme when its cognate acceptor protein CcmE is present. It is demonstrated that CcmE only interacts stably with CcmC when heme is present; thus, specific residues in each protein provide sites of interaction with heme to form this very stable complex. For the first time, evidence that the external WWD domain of CcmC interacts directly with heme is presented. Single and multiple substitutions of completely conserved residues in the WWD domain of CcmC alter the spectral properties of heme in the stable CcmC:heme:CcmE complexes. Moreover, some mutations reduce the binding of heme up to 100%. It is likely that endogenously synthesized heme enters the external WWD domain of CcmC either via a channel within this six-transmembrane-spanning protein or from the membrane. The data suggest that a specific heme channel (i.e., heme binding site within membrane spanning helices) is not present in CcmC, in contrast to the CcsBA protein. We discuss the likelihood that it is not important to protect the heme via trafficking in CcmC whereas it is critical in CcsBA.
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Affiliation(s)
- Cynthia Richard-Fogal
- Department of Biology, Washington University, Campus Box 1137, 1 Brookings Drive, St Louis, MO 63130, USA
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50
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Goddard AD, Stevens JM, Rao F, Mavridou DAI, Chan W, Richardson DJ, Allen JWA, Ferguson SJ. c-Type cytochrome biogenesis can occur via a natural Ccm system lacking CcmH, CcmG, and the heme-binding histidine of CcmE. J Biol Chem 2010; 285:22882-9. [PMID: 20466730 DOI: 10.1074/jbc.m110.133421] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The Ccm cytochrome c maturation System I catalyzes covalent attachment of heme to apocytochromes c in many bacterial species and some mitochondria. A covalent, but transient, bond between heme and a conserved histidine in CcmE along with an interaction between CcmH and the apocytochrome have been previously indicated as core aspects of the Ccm system. Here, we show that in the Ccm system from Desulfovibrio desulfuricans, no CcmH is required, and the holo-CcmE covalent bond occurs via a cysteine residue. These observations call for reconsideration of the accepted models of System I-mediated c-type cytochrome biogenesis.
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Affiliation(s)
- Alan D Goddard
- Department of Biochemistry, University of Oxford, South Parks Road, Oxford OX1 3QU, United Kingdom
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