1
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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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2
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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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3
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Yang J, Cui Y, Zhang X, Yang Z, Lai J, Song W, Liang J, Li X. Maize PPR278 Functions in Mitochondrial RNA Splicing and Editing. Int J Mol Sci 2022; 23:ijms23063035. [PMID: 35328469 PMCID: PMC8949463 DOI: 10.3390/ijms23063035] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2022] [Revised: 03/03/2022] [Accepted: 03/08/2022] [Indexed: 02/01/2023] Open
Abstract
Pentatricopeptide repeat (PPR) proteins are a large protein family in higher plants and play important roles during seed development. Most reported PPR proteins function in mitochondria. However, some PPR proteins localize to more than one organelle; functional characterization of these proteins remains limited in maize (Zea mays L.). Here, we cloned and analyzed the function of a P-subfamily PPR protein, PPR278. Loss-function of PPR278 led to a lower germination rate and other defects at the seedling stage, as well as smaller kernels compared to the wild type. PPR278 was expressed in all investigated tissues. Furthermore, we determined that PPR278 is involved in the splicing of two mitochondrial transcripts (nad2 intron 4 and nad5 introns 1 and 4), as well as RNA editing of C-to-U sites in 10 mitochondrial transcripts. PPR278 localized to the nucleus, implying that it may function as a transcriptional regulator during seed development. Our data indicate that PPR278 is involved in maize seed development via intron splicing and RNA editing in mitochondria and has potential regulatory roles in the nucleus.
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Affiliation(s)
- Jing Yang
- National Engineering Laboratory for Crop Molecular Breeding, Institute of Crop Science, Chinese Academy of Agricultural Sciences, Beijing 100081, China;
- State Key Laboratory of Plant Physiology and Biochemistry, China Agricultural University, Beijing 100193, China; (Y.C.); (X.Z.); (Z.Y.); (J.L.); (W.S.)
- National Maize Improvement Center, Department of Plant Genetics and Breeding, China Agricultural University, Beijing 100193, China
| | - Yang Cui
- State Key Laboratory of Plant Physiology and Biochemistry, China Agricultural University, Beijing 100193, China; (Y.C.); (X.Z.); (Z.Y.); (J.L.); (W.S.)
- National Maize Improvement Center, Department of Plant Genetics and Breeding, China Agricultural University, Beijing 100193, China
| | - Xiangbo Zhang
- State Key Laboratory of Plant Physiology and Biochemistry, China Agricultural University, Beijing 100193, China; (Y.C.); (X.Z.); (Z.Y.); (J.L.); (W.S.)
- National Maize Improvement Center, Department of Plant Genetics and Breeding, China Agricultural University, Beijing 100193, China
| | - Zhijia Yang
- State Key Laboratory of Plant Physiology and Biochemistry, China Agricultural University, Beijing 100193, China; (Y.C.); (X.Z.); (Z.Y.); (J.L.); (W.S.)
- National Maize Improvement Center, Department of Plant Genetics and Breeding, China Agricultural University, Beijing 100193, China
| | - Jinsheng Lai
- State Key Laboratory of Plant Physiology and Biochemistry, China Agricultural University, Beijing 100193, China; (Y.C.); (X.Z.); (Z.Y.); (J.L.); (W.S.)
- National Maize Improvement Center, Department of Plant Genetics and Breeding, China Agricultural University, Beijing 100193, China
| | - Weibin Song
- State Key Laboratory of Plant Physiology and Biochemistry, China Agricultural University, Beijing 100193, China; (Y.C.); (X.Z.); (Z.Y.); (J.L.); (W.S.)
- National Maize Improvement Center, Department of Plant Genetics and Breeding, China Agricultural University, Beijing 100193, China
| | - Jingang Liang
- Development Center of Science and Technology, Ministry of Agriculture and Rural Affairs, Beijing 100176, China
- Correspondence: (J.L.); (X.L.)
| | - Xinhai Li
- National Engineering Laboratory for Crop Molecular Breeding, Institute of Crop Science, Chinese Academy of Agricultural Sciences, Beijing 100081, China;
- Correspondence: (J.L.); (X.L.)
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4
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Brausemann A, Zhang L, Ilcu L, Einsle O. Architecture of the membrane-bound cytochrome c heme lyase CcmF. Nat Chem Biol 2021; 17:800-805. [PMID: 33958791 PMCID: PMC7611092 DOI: 10.1038/s41589-021-00793-8] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2020] [Accepted: 04/06/2021] [Indexed: 02/02/2023]
Abstract
The covalent attachment of one or multiple heme cofactors to cytochrome c protein chains enables cytochrome c proteins to be used in electron transfer and redox catalysis in extracytoplasmic environments. A dedicated heme maturation machinery, whose core component is a heme lyase, scans nascent peptides after Sec-dependent translocation for CXnCH-binding motifs. Here we report the three-dimensional (3D) structure of the heme lyase CcmF, a 643-amino acid integral membrane protein, from Thermus thermophilus. CcmF contains a heme b cofactor at the bottom of a large cavity that opens toward the extracellular side to receive heme groups from the heme chaperone CcmE for cytochrome maturation. A surface groove on CcmF may guide the extended apoprotein to heme attachment at or near a loop containing the functionally essential WXWD motif, which is situated above the putative cofactor binding pocket. The structure suggests heme delivery from within the membrane, redefining the role of the chaperone CcmE.
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5
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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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6
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Kolli R, Engstler C, Akbaş Ş, Mower JP, Soll J, Carrie C. The OXA2a Insertase of Arabidopsis Is Required for Cytochrome c Maturation. PLANT PHYSIOLOGY 2020; 184:1042-1055. [PMID: 32759271 PMCID: PMC7536658 DOI: 10.1104/pp.19.01248] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/07/2019] [Accepted: 07/28/2020] [Indexed: 06/02/2023]
Abstract
In yeast (Saccharomyces cerevisiae) and human (Homo sapiens) mitochondria, Oxidase assembly protein1 (Oxa1) is the general insertase for protein insertion from the matrix side into the inner membrane while Cytochrome c oxidase assembly protein18 (Cox18/Oxa2) is specifically involved in the topogenesis of the complex IV subunit, Cox2. Arabidopsis (Arabidopsis thaliana) mitochondria contain four OXA homologs: OXA1a, OXA1b, OXA2a, and OXA2b. OXA2a and OXA2b are unique members of the Oxa1 superfamily, in that they possess a tetratricopeptide repeat (TPR) domain at their C termini. Here, we determined the role of OXA2a by studying viable mutant plants generated by partial complementation of homozygous lethal OXA2a transfer-DNA insertional mutants using the developmentally regulated ABSCISIC ACID INSENSITIVE3 (ABI3) promoter. The ABI3p:OXA2a plants displayed growth retardation due to a reduction in the steady-state abundances of both c-type cytochromes, cytochrome c 1 and cytochrome c The observed reduction in the steady-state abundance of complex III could be attributed to cytochrome c 1 being one of its subunits. Expression of a soluble heme lyase from an organism with cytochrome c maturation system III could functionally complement the lack of OXA2a. This implies that OXA2a is required for the system I cytochrome c maturation of Arabidopsis. Due to the interaction of OXA2a with Cytochrome c maturation protein CcmF C-terminal-like protein (CCMFC) in a yeast split-ubiquitin based interaction assay, we propose that OXA2a aids in the membrane insertion of CCMFC, which is presumed to form the heme lyase component of the cytochrome c maturation pathway. In contrast with the crucial role played by the TPR domain of OXA2b, the TPR domain of OXA2a is not essential for its functionality.
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Affiliation(s)
- Renuka Kolli
- Department Biologie I - Botanik, Ludwig-Maximilians-Universität München, Planegg-Martinsried, 82152, Germany
| | - Carina Engstler
- Department Biologie I - Botanik, Ludwig-Maximilians-Universität München, Planegg-Martinsried, 82152, Germany
| | - Şebnem Akbaş
- Department Biologie I - Botanik, Ludwig-Maximilians-Universität München, Planegg-Martinsried, 82152, Germany
| | - Jeffrey P Mower
- Center for Plant Science Innovation, University of Nebraska, Lincoln, Nebraska 68588
- Department of Agronomy and Horticulture, University of Nebraska, Lincoln, Nebraska 68583
| | - Jürgen Soll
- Department Biologie I - Botanik, Ludwig-Maximilians-Universität München, Planegg-Martinsried, 82152, Germany
- Munich Centre for Integrated Protein Science, CIPSM, Ludwig-Maximilians-Universität München, Munich, 81377, Germany
| | - Chris Carrie
- Department Biologie I - Botanik, Ludwig-Maximilians-Universität München, Planegg-Martinsried, 82152, Germany
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7
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Gupta D, Sutherland MC, Rengasamy K, Meacham JM, Kranz RG, Bose A. Photoferrotrophs Produce a PioAB Electron Conduit for Extracellular Electron Uptake. mBio 2019; 10:e02668-19. [PMID: 31690680 PMCID: PMC6831781 DOI: 10.1128/mbio.02668-19] [Citation(s) in RCA: 35] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2019] [Accepted: 10/10/2019] [Indexed: 11/20/2022] Open
Abstract
Photoferrotrophy is a form of anoxygenic photosynthesis whereby bacteria utilize soluble or insoluble forms of ferrous iron as an electron donor to fix carbon dioxide using light energy. They can also use poised electrodes as their electron donor via phototrophic extracellular electron uptake (phototrophic EEU). The electron uptake mechanisms underlying these processes are not well understood. Using Rhodopseudomonas palustris TIE-1 as a model, we show that a single periplasmic decaheme cytochrome c, PioA, and an outer membrane porin, PioB, form a complex allowing extracellular electron uptake across the outer membrane from both soluble iron and poised electrodes. We observe that PioA undergoes postsecretory proteolysis of its N terminus to produce a shorter heme-attached PioA (holo-PioAC, where PioAC represents the C terminus of PioA), which can exist both freely in the periplasm and in a complex with PioB. The extended N-terminal peptide controls heme attachment, and its processing is required to produce wild-type levels of holo-PioAC and holo-PioACB complex. It is also conserved in PioA homologs from other phototrophs. The presence of PioAB in these organisms correlate with their ability to perform photoferrotrophy and phototrophic EEU.IMPORTANCE Some anoxygenic phototrophs use soluble iron, insoluble iron minerals (such as rust), or their proxies (poised electrodes) as electron donors for photosynthesis. However, the underlying electron uptake mechanisms are not well established. Here, we show that these phototrophs use a protein complex made of an outer membrane porin and a periplasmic decaheme cytochrome (electron transfer protein) to harvest electrons from both soluble iron and poised electrodes. This complex has two unique characteristics: (i) it lacks an extracellular cytochrome c, and (ii) the periplasmic decaheme cytochrome c undergoes proteolytic cleavage to produce a functional electron transfer protein. These characteristics are conserved in phototrophs harboring homologous proteins.
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Affiliation(s)
- Dinesh Gupta
- Department of Biology, Washington University in St. Louis, St. Louis, Missouri, USA
| | - Molly C Sutherland
- Department of Biology, Washington University in St. Louis, St. Louis, Missouri, USA
| | | | - J Mark Meacham
- Department of Mechanical Engineering and Materials Science, Washington University in St. Louis, St. Louis, Missouri, USA
- Institute of Materials Science and Engineering, Washington University in St. Louis, St. Louis, Missouri, USA
| | - Robert G Kranz
- Department of Biology, Washington University in St. Louis, St. Louis, Missouri, USA
| | - Arpita Bose
- Department of Biology, Washington University in St. Louis, St. Louis, Missouri, USA
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8
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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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9
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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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10
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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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11
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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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12
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Sun F, Wang X, Bonnard G, Shen Y, Xiu Z, Li X, Gao D, Zhang Z, Tan BC. Empty pericarp7 encodes a mitochondrial E-subgroup pentatricopeptide repeat protein that is required for ccmFN editing, mitochondrial function and seed development in maize. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2015; 84:283-95. [PMID: 26303363 DOI: 10.1111/tpj.12993] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/11/2015] [Revised: 08/07/2015] [Accepted: 08/13/2015] [Indexed: 05/02/2023]
Abstract
RNA editing, converting cytidines (C) to uridines (U) at specific sites in the transcripts of mitochondria and plastids, plays a critical role in organelle gene expression in land plants. Recently pentatricopeptide repeat (PPR) proteins were identified as site-specific recognition factors for RNA editing. In this study, we characterized an empty pericarp7 mutant (emp7) in Zea mays (maize), which confers an embryo-lethal phenotype. In emp7 mutants, mitochondrial functions are seriously perturbed, resulting in a strikingly reduced respiration rate. Emp7 encodes an E-subgroup PPR protein that is localized exclusively in the mitochondrion. Null mutation of Emp7 abolishes the C → U editing of ccmF(N) transcript solely at position 1553. CcmF(N) is coding for a subunit of heme lyase complex in the cytochrome c maturation pathway. The resulting Phe → Ser substitution in CcmF(N) leads to the loss of CcmF(N) protein and a strikingly reduced c-type cytochrome. Consequently, the mitochondrial cytochrome-linked respiratory chain is impaired as a result of the disassembly of complex III in the emp7 mutant. These results indicate that the PPR-E subgroup protein EMP7 is required for C → U editing of ccmF(N) -1553 at a position essential for cytochrome c maturation and mitochondrial oxidative phosphorylation, and hence is essential to embryo and endosperm development in maize.
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Affiliation(s)
- Feng Sun
- Key Laboratory of Plant Cell Engineering and Germplasm Innovation, Ministry of Education, School of Life Sciences, Shandong University, Jinan, 250100, China
| | - Xiaomin Wang
- Key Laboratory of Cell Activities and Stress Adaptations, Ministry of Education, School of Life Sciences, Lanzhou University, Lanzhou, 730000, China
| | - Géraldine Bonnard
- Institut de biologie moléculaire des plantes CNRS, Associé à l'Université de Strasbourg, 12 rue du Général Zimmer, 67084, Strasbourg, France
| | - Yun Shen
- School of Life Sciences, The Chinese University of Hong Kong, N.T, Hong Kong
| | - Zhihui Xiu
- School of Life Sciences, The Chinese University of Hong Kong, N.T, Hong Kong
| | - Xiaojie Li
- School of Life Sciences, The Chinese University of Hong Kong, N.T, Hong Kong
| | - Dahai Gao
- Key Laboratory of Experimental Marine Biology, Institute of Oceanology, Chinese Academy of Sciences, Qingdao, 266071, China
| | - Zhonghang Zhang
- School of Life Sciences, The Chinese University of Hong Kong, N.T, Hong Kong
| | - Bao-Cai Tan
- Key Laboratory of Plant Cell Engineering and Germplasm Innovation, Ministry of Education, School of Life Sciences, Shandong University, Jinan, 250100, China
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13
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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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14
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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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15
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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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16
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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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17
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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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18
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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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19
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Efimov I, Parkin G, Millett ES, Glenday J, Chan CK, Weedon H, Randhawa H, Basran J, Raven EL. A simple method for the determination of reduction potentials in heme proteins. FEBS Lett 2014; 588:701-4. [PMID: 24440354 PMCID: PMC3999514 DOI: 10.1016/j.febslet.2013.12.030] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2013] [Revised: 12/20/2013] [Accepted: 12/24/2013] [Indexed: 11/28/2022]
Abstract
A simple method for determination of heme protein reduction potentials is described. We use the method to determine reduction potentials for human NPAS2 and human CLOCK. The method can be easily applied to other heme proteins.
We describe a simple method for the determination of heme protein reduction potentials. We use the method to determine the reduction potentials for the PAS-A domains of the regulatory heme proteins human NPAS2 (Em = −115 mV ± 2 mV, pH 7.0) and human CLOCK (Em = −111 mV ± 2 mV, pH 7.0). We suggest that the method can be easily and routinely applied to the determination of reduction potentials across the family of heme proteins.
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Affiliation(s)
- Igor Efimov
- Department of Chemistry, Henry Wellcome Building, University of Leicester, University Road, Leicester LE1 7RH, United Kingdom
| | - Gary Parkin
- Department of Chemistry, Henry Wellcome Building, University of Leicester, University Road, Leicester LE1 7RH, United Kingdom
| | - Elizabeth S Millett
- Department of Chemistry, Henry Wellcome Building, University of Leicester, University Road, Leicester LE1 7RH, United Kingdom
| | - Jennifer Glenday
- Department of Chemistry, Henry Wellcome Building, University of Leicester, University Road, Leicester LE1 7RH, United Kingdom
| | - Cheuk K Chan
- Department of Chemistry, Henry Wellcome Building, University of Leicester, University Road, Leicester LE1 7RH, United Kingdom
| | - Holly Weedon
- Department of Chemistry, Henry Wellcome Building, University of Leicester, University Road, Leicester LE1 7RH, United Kingdom
| | - Harpreet Randhawa
- Department of Chemistry, Henry Wellcome Building, University of Leicester, University Road, Leicester LE1 7RH, United Kingdom
| | - Jaswir Basran
- Department of Biochemistry, Henry Wellcome Building, University of Leicester, University Road, Leicester LE1 9HN, United Kingdom
| | - Emma L Raven
- Department of Chemistry, Henry Wellcome Building, University of Leicester, University Road, Leicester LE1 7RH, United Kingdom.
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20
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Mavridou DAI, Clark MN, Choulat C, Ferguson SJ, Stevens JM. Probing heme delivery processes in cytochrome c biogenesis System I. Biochemistry 2013; 52:7262-70. [PMID: 24044352 PMCID: PMC3806149 DOI: 10.1021/bi400398t] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
![]()
Cytochromes c comprise
a diverse and widespread
family of proteins containing covalently bound heme that are central
to the life of most organisms. In many bacteria and in certain mitochondria,
the synthesis of cytochromes c is performed by a
complex post-translational modification apparatus called System I
(or cytochrome c maturation, Ccm, system). In Escherichia coli, there are eight maturation proteins,
several of which are involved in heme handling, but the mechanism
of heme transfer from one protein to the next is not known. Attachment
of the heme to the apocytochrome occurs via a novel covalent bond
to a histidine residue of the heme chaperone CcmE. The discovery of
a variant maturation system (System I*) has provided a new tool for
studying cytochrome c assembly because the variant
CcmE functions via a cysteine residue in the place of the histidine
of System I. In this work, we use site-directed mutagenesis on both
maturation systems to probe the function of the individual component
proteins as well as their concerted action in transferring heme to
the cytochrome c substrate. The roles of CcmA, CcmC,
CcmE, and CcmF in the heme delivery process are compared between Systems
I and I*. We show that a previously proposed quinone-binding site
on CcmF is not essential for either system. Significant differences
in the heme chemistry involved in the formation of cytochromes c in the variant system add new pieces to the cytochrome c biogenesis puzzle.
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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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21
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Di Silvio E, Di Matteo A, Malatesta F, Travaglini-Allocatelli C. Recognition and binding of apocytochrome c to P. aeruginosa CcmI, a component of cytochrome c maturation machinery. BIOCHIMICA ET BIOPHYSICA ACTA-PROTEINS AND PROTEOMICS 2013; 1834:1554-61. [PMID: 23648553 DOI: 10.1016/j.bbapap.2013.04.027] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/12/2013] [Revised: 04/23/2013] [Accepted: 04/25/2013] [Indexed: 01/13/2023]
Abstract
The biogenesis of c-type cytochromes (Cytc) is a process that in Gram-negative bacteria demands the coordinated action of different periplasmic proteins (CcmA-I), whose specific roles are still being investigated. Activities of Ccm proteins span from the chaperoning of heme b in the periplasm to the specific reduction of oxidized apocytochrome (apoCyt) cysteine residues and to chaperoning and recognition of the unfolded apoCyt before covalent attachment of the heme to the cysteine thiols can occur. We present here the functional characterization of the periplasmic domain of CcmI from the pathogen Pseudomonas aeruginosa (Pa-CcmI*). Pa-CcmI* is composed of a TPR domain and a peculiar C-terminal domain. Pa-CcmI* fulfills both the ability to recognize and bind to P. aeruginosa apo-cytochrome c551 (Pa-apoCyt) and a chaperoning activity towards unfolded proteins, as it prevents citrate synthase aggregation in a concentration-dependent manner. Equilibrium and kinetic experiments with Pa-CcmI*, or its isolated domains, with peptides mimicking portions of Pa-apoCyt sequence allow us to quantify the molecular details of the interaction between Pa-apoCyt and Pa-CcmI*. Binding experiments show that the interaction occurs at the level of the TPR domain and that the recognition is mediated mainly by the C-terminal sequence of Pa-apoCyt. The affinity of Pa-CcmI* to full-length Pa-apoCyt or to its C-terminal sequence is in the range expected for a component of a multi-protein complex, whose task is to receive the apoCyt and to deliver it to other components of the apoCyt:heme b ligation protein machinery.
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Affiliation(s)
- Eva Di Silvio
- Department of Biochemical Sciences, Università di Roma La Sapienza, Roma, Italy
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22
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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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23
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Verissimo AF, Mohtar MA, Daldal F. The heme chaperone ApoCcmE forms a ternary complex with CcmI and apocytochrome c. J Biol Chem 2013; 288:6272-83. [PMID: 23319598 DOI: 10.1074/jbc.m112.440024] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Cytochrome c maturation (Ccm) is a post-translational process that occurs after translocation of apocytochromes c to the positive (p) side of energy-transducing membranes. Ccm is responsible for the formation of covalent bonds between the thiol groups of two cysteines residues at the heme-binding sites of the apocytochromes and the vinyl groups of heme b (protoporphyrin IX-Fe). Among the proteins (CcmABCDEFGHI and CcdA) required for this process, CcmABCD are involved in loading heme b to apoCcmE. The holoCcmE thus formed provides heme b to the apocytochromes. Catalysis of the thioether bonds between the apocytochromes c and heme b is mediated by the heme ligation core complex, which in Rhodobacter capsulatus contains at least the CcmF, CcmH, and CcmI components. In this work we show that the heme chaperone apoCcmE binds to the apocytochrome c and the apocytochrome c chaperone CcmI to yield stable binary and ternary complexes in the absence of heme in vitro. We found that during these protein-protein interactions, apoCcmE favors the presence of a disulfide bond at the apocytochrome c heme-binding site. We also establish using detergent-dispersed membranes that apoCcmE interacts directly with CcmI and CcmH of the heme ligation core complex CcmFHI. Implications of these findings are discussed with respect to heme transfer from CcmE to the apocytochromes c during heme ligation assisted by the core complex CcmFHI.
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Affiliation(s)
- Andreia F Verissimo
- Department of Biology, University of Pennsylvania, Philadelphia, Pennsylvania 19014-6019, USA
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24
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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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25
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Continued surprises in the cytochrome c biogenesis story. Protein Cell 2012; 3:405-9. [PMID: 22723177 DOI: 10.1007/s13238-012-2912-x] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2012] [Accepted: 03/21/2012] [Indexed: 10/28/2022] Open
Abstract
Cytochromes c covalently bind their heme prosthetic groups through thioether bonds between the vinyl groups of the heme and the thiols of a CXXCH motif within the protein. In Gram-negative bacteria, this process is catalyzed by the Ccm (cytochrome c maturation) proteins, also called System I. The Ccm proteins are found in the bacterial inner membrane, but some (CcmE, CcmG, CcmH, and CcmI) also have soluble functional domains on the periplasmic face of the membrane. Elucidation of the mechanisms involved in the transport and relay of heme and the apocytochrome from the bacterial cytosol into the periplasm, and their subsequent reaction, has proved challenging due to the fact that most of the proteins involved are membrane-associated, but recent progress in understanding some key components has thrown up some surprises. In this Review, we discuss advances in our understanding of this process arising from a substrate's point of view and from recent structural information about individual components.
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26
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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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