101
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McClelland LJ, Steele HBB, Whitby FG, Mou TC, Holley D, Alexander Ross JB, Sprang SR, Bowler BE. Cytochrome c Can Form a Well-Defined Binding Pocket for Hydrocarbons. J Am Chem Soc 2016; 138:16770-16778. [PMID: 27990813 PMCID: PMC5564421 DOI: 10.1021/jacs.6b10745] [Citation(s) in RCA: 35] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
Cytochrome c can acquire peroxidase activity when it binds to cardiolipin in mitochondrial membranes. The resulting oxygenation of cardiolipin by cytochrome c provides an early signal for the onset of apoptosis. The structure of this enzyme-substrate complex is a matter of considerable debate. We present three structures at 1.7-2.0 Å resolution of a domain-swapped dimer of yeast iso-1-cytochrome c with the detergents, CYMAL-5, CYMAL-6, and ω-undecylenyl-β-d-maltopyranoside, bound in a channel that places the hydrocarbon moieties of these detergents next to the heme. The heme is poised for peroxidase activity with water bound in place of Met80, which serves as the axial heme ligand when cytochrome c functions as an electron carrier. The hydroxyl group of Tyr67 sits 3.6-4.0 Å from the nearest carbon of the detergents, positioned to act as a relay in radical abstraction during peroxidase activity. Docking studies with linoleic acid, the most common fatty acid component of cardiolipin, show that C11 of linoleic acid can sit adjacent to Tyr67 and the heme, consistent with the oxygenation pattern observed in lipidomics studies. The well-defined hydrocarbon binding pocket provides atomic resolution evidence for the extended lipid anchorage model for cytochrome c/cardiolipin binding. Dimer dissociation/association kinetics for yeast versus equine cytochrome c indicate that formation of mammalian cytochrome c dimers in vivo would require catalysis. However, the dimer structure shows that only a modest deformation of monomeric cytochrome c would suffice to form the hydrocarbon binding site occupied by these detergents.
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Affiliation(s)
- Levi J. McClelland
- Department of Chemistry & Biochemistry, University of Montana, Missoula, Montana, 59812, United States
- Division of Biological Sciences, University of Montana, Missoula, Montana, 59812, United States
- Center for Biomolecular Structure & Dynamics, University of Montana, Missoula, Montana, 59812, United States
| | - Harmen B. B. Steele
- Department of Chemistry & Biochemistry, University of Montana, Missoula, Montana, 59812, United States
- Center for Biomolecular Structure & Dynamics, University of Montana, Missoula, Montana, 59812, United States
| | - Frank G. Whitby
- Department of Biochemistry, University of Utah School of Medicine, Salt Lake City, Utah, 84112, United States
| | - Tung-Chung Mou
- Division of Biological Sciences, University of Montana, Missoula, Montana, 59812, United States
- Center for Biomolecular Structure & Dynamics, University of Montana, Missoula, Montana, 59812, United States
| | - David Holley
- Center for Biomolecular Structure & Dynamics, University of Montana, Missoula, Montana, 59812, United States
| | - J. B. Alexander Ross
- Department of Chemistry & Biochemistry, University of Montana, Missoula, Montana, 59812, United States
- Center for Biomolecular Structure & Dynamics, University of Montana, Missoula, Montana, 59812, United States
| | - Stephen R. Sprang
- Division of Biological Sciences, University of Montana, Missoula, Montana, 59812, United States
- Center for Biomolecular Structure & Dynamics, University of Montana, Missoula, Montana, 59812, United States
| | - Bruce E. Bowler
- Department of Chemistry & Biochemistry, University of Montana, Missoula, Montana, 59812, United States
- Center for Biomolecular Structure & Dynamics, University of Montana, Missoula, Montana, 59812, United States
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102
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Malyshka D, Schweitzer-Stenner R. Ferrocyanide-Mediated Photoreduction of Ferricytochrome C Utilized to Selectively Probe Non-native Conformations Induced by Binding to Cardiolipin-Containing Liposomes. Chemistry 2016; 23:1151-1156. [PMID: 27859757 DOI: 10.1002/chem.201604992] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2016] [Indexed: 01/29/2023]
Abstract
Ferricytochrome c binding to cardiolipin-containing liposomes produces a heterogeneous distribution of conformations comprising native-like and non-native misfolded proteins. We utilized the photoreduction of native ferricytochrome c in the presence of potassium ferrocyanide and resonance Raman spectroscopy to probe the population of native and misfolded cytochrome c on liposomes with 20 % tetraoleylcardiolipin (TOCL)/80 % dioleylphosphocholine (DOPC) and with 100 % TOCL as a function of TOCL concentration. Our data provided strong support for an earlier model, which predicts that the equilibrium between native and non-native conformations is shifted to the latter with decreasing protein occupation of liposomes.
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Affiliation(s)
- Dmitry Malyshka
- Department of Chemistry, Drexel University, 3141 Chestnut Street, Philadelphia, PA, 19104, USA
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103
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Conformational status of cytochrome c upon N-homocysteinylation: Implications to cytochrome c release. Arch Biochem Biophys 2016; 614:23-27. [PMID: 28003096 DOI: 10.1016/j.abb.2016.12.006] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2016] [Revised: 12/14/2016] [Accepted: 12/16/2016] [Indexed: 11/21/2022]
Abstract
One of the proposed mechanisms of homocysteine (Hcy) toxicity is the post-translational modification of proteins by its metabolite, homocysteine thiolactone (HTL). Incubation of proteins with HTL has been shown to form covalent adducts with ε-amino group of lysine residues of protein (called N-homocysteinylation) which ultimately results in structural and functional alterations of the modified proteins. In the present study, the effects of HTL on the conformational and heme status of cytochrome c (cyt c) were investigated. Spectroscopic analyses revealed that HTL-modified cyt c undergoes certain conformational alterations leading to disturbed heme-Trp distance and packing of the apolar groups. These alterations were accompanied with the reduction of the heme moiety and activation of peroxidase-like function of cyt c, which is known to be a crucial event for initiation of the intrinsic apoptotic pathway. Further structural characterization revealed that disruption of the heme-Met80 interaction, thereby converting the hexa-coordinate cyt c to a penta-coordinate species (with a free heme ligand), was responsible for the activation of the peroxidase activity. The study provides insights for the possible role of cyt c N-homocysteinylation in eliciting its toxicity and cell death.
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104
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Wu LB, Du KJ, Nie CM, Gao SQ, Wen GB, Tan X, Lin YW. Peroxidase activity enhancement of myoglobin by two cooperative distal histidines and a channel to the heme pocket. ACTA ACUST UNITED AC 2016. [DOI: 10.1016/j.molcatb.2016.08.018] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
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105
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Serpas L, Milorey B, Pandiscia LA, Addison AW, Schweitzer-Stenner R. Autoxidation of Reduced Horse Heart Cytochrome c Catalyzed by Cardiolipin-Containing Membranes. J Phys Chem B 2016; 120:12219-12231. [PMID: 27934230 DOI: 10.1021/acs.jpcb.6b05620] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
Visible circular dichroism, absorption, and fluorescence spectroscopy were used to probe the binding of horse heart ferrocytochrome c to anionic cardiolipin (CL) head groups on the surface of 1,1',2,2'-tetraoleoyl cardiolipin (TOCL)/1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC) (20%:80%) liposomes in an aerobic environment. We found that ferrocytochrome c undergoes a conformational transition upon binding that leads to complete oxidation of the protein at intermediate and high CL concentrations. At low lipid concentrations, the protein maintains a structure that is only slightly different from its native one, whereas an ensemble of misligated predominantly hexacoordinated low-spin states become increasingly populated at high lipid concentrations. A minor fraction of conformations with either high- or quantum-mixed-spin states were detected at a CL to protein ratio of 200 (the largest one investigated). The population of the non-native state is less pronounced than that found for cytochrome c-CL interactions initiated with oxidized cytochrome c. Under anaerobic conditions, the protein maintains its reduced state but still undergoes some conformational change upon binding to CL head groups on the liposome surface. Our data suggest that CL-containing liposomes function as catalysts by reducing the activation barrier for a Fe2+ → O2 electron transfer. Adding NaCl to the existing cytochrome-liposome mixtures under aerobic conditions inhibits protein autoxidation of ferrocytochrome c and stabilizes the reduced state of the membrane-bound protein.
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Affiliation(s)
- Lee Serpas
- Department of Chemistry, Drexel University , 3141 Chestnut Street, Philadelphia, Pennsylvania 19104, United States
| | - Bridget Milorey
- Department of Chemistry, Drexel University , 3141 Chestnut Street, Philadelphia, Pennsylvania 19104, United States
| | - Leah A Pandiscia
- Department of Chemistry, Drexel University , 3141 Chestnut Street, Philadelphia, Pennsylvania 19104, United States
| | - Anthony W Addison
- Department of Chemistry, Drexel University , 3141 Chestnut Street, Philadelphia, Pennsylvania 19104, United States
| | - Reinhard Schweitzer-Stenner
- Department of Chemistry, Drexel University , 3141 Chestnut Street, Philadelphia, Pennsylvania 19104, United States
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106
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Zeng L, Wu L, Liu L, Jiang X. Analyzing Structural Properties of Heterogeneous Cardiolipin-Bound Cytochrome C and Their Regulation by Surface-Enhanced Infrared Absorption Spectroscopy. Anal Chem 2016; 88:11727-11733. [DOI: 10.1021/acs.analchem.6b03360] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Affiliation(s)
- Li Zeng
- State
Key Laboratory of Electroanalytical Chemistry, Changchun Institute
of Applied Chemistry, Chinese Academy of Sciences, Changchun, Jilin 130022, China
- University of Chinese Academy of Sciences, Beijing 100049, China
| | - Lie Wu
- State
Key Laboratory of Electroanalytical Chemistry, Changchun Institute
of Applied Chemistry, Chinese Academy of Sciences, Changchun, Jilin 130022, China
| | - Li Liu
- State
Key Laboratory of Electroanalytical Chemistry, Changchun Institute
of Applied Chemistry, Chinese Academy of Sciences, Changchun, Jilin 130022, China
| | - Xiue Jiang
- State
Key Laboratory of Electroanalytical Chemistry, Changchun Institute
of Applied Chemistry, Chinese Academy of Sciences, Changchun, Jilin 130022, China
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107
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Sinibaldi F, Milazzo L, Howes BD, Piro MC, Fiorucci L, Polticelli F, Ascenzi P, Coletta M, Smulevich G, Santucci R. The key role played by charge in the interaction of cytochrome c with cardiolipin. J Biol Inorg Chem 2016; 22:19-29. [PMID: 27826772 DOI: 10.1007/s00775-016-1404-5] [Citation(s) in RCA: 38] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2016] [Accepted: 10/17/2016] [Indexed: 12/27/2022]
Abstract
Cytochrome c undergoes structural variations upon binding of cardiolipin, one of the phospholipids constituting the mitochondrial membrane. Although several mechanisms governing cytochrome c/cardiolipin (cyt c/CL) recognition have been proposed, the interpretation of the process remains, at least in part, unknown. To better define the steps characterizing the cyt c-CL interaction, the role of Lys72 and Lys73, two residues thought to be important in the protein/lipid binding interaction, were recently investigated by mutagenesis. The substitution of the two (positively charged) Lys residues with Asn revealed that such mutations cancel the CL-dependent peroxidase activity of cyt c; furthermore, CL does not interact with the Lys72Asn mutant. In the present paper, we extend our study to the Lys → Arg mutants to investigate the influence exerted by the charge possessed by the residues located at positions 72 and 73 on the cyt c/CL interaction. On the basis of the present work a number of overall conclusions can be drawn: (i) position 72 must be occupied by a positively charged residue to assure cyt c/CL recognition; (ii) the Arg residues located at positions 72 and 73 permit cyt c to react with CL; (iii) the replacement of Lys72 with Arg weakens the second (low-affinity) binding transition; (iv) the Lys73Arg mutation strongly increases the peroxidase activity of the CL-bound protein.
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Affiliation(s)
- Federica Sinibaldi
- Department of Experimental Medicine and Surgery, University of Rome 'Tor Vergata', Via Montpellier 1, 00133, Rome, Italy
| | - Lisa Milazzo
- Department of Chemistry "Ugo Schiff", University of Florence, Via della Lastruccia 3-13, 50019, Sesto Fiorentino (Fi), Italy
| | - Barry D Howes
- Department of Chemistry "Ugo Schiff", University of Florence, Via della Lastruccia 3-13, 50019, Sesto Fiorentino (Fi), Italy
| | - Maria Cristina Piro
- Department of Experimental Medicine and Surgery, University of Rome 'Tor Vergata', Via Montpellier 1, 00133, Rome, Italy
| | - Laura Fiorucci
- Department of Clinical Sciences and Translational Medicine, University of Rome 'Tor Vergata', Via Montpellier 1, 00133, Rome, Italy
| | - Fabio Polticelli
- Department of Sciences, Roma Tre University, Viale Marconi 446, 00146, Rome, Italy
- National Institute of Nuclear Physics, 'Roma Tre' Section, Via della Vasca Navale 84, 00146, Rome, Italy
| | - Paolo Ascenzi
- Interdepartmental Laboratory for Electron Microscopy, Roma Tre University, Via della Vasca Navale 79, 00146, Rome, Italy
| | - Massimo Coletta
- Department of Clinical Sciences and Translational Medicine, University of Rome 'Tor Vergata', Via Montpellier 1, 00133, Rome, Italy
| | - Giulietta Smulevich
- Department of Chemistry "Ugo Schiff", University of Florence, Via della Lastruccia 3-13, 50019, Sesto Fiorentino (Fi), Italy.
| | - Roberto Santucci
- Department of Clinical Sciences and Translational Medicine, University of Rome 'Tor Vergata', Via Montpellier 1, 00133, Rome, Italy.
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108
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Structural and thermodynamic characterisation of L94F mutant of horse cytochrome c. Int J Biol Macromol 2016; 92:202-212. [DOI: 10.1016/j.ijbiomac.2016.06.096] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2016] [Revised: 06/24/2016] [Accepted: 06/30/2016] [Indexed: 12/11/2022]
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109
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Kobayashi H, Nagao S, Hirota S. Characterization of the Cytochrome c
Membrane-Binding Site Using Cardiolipin-Containing Bicelles with NMR. Angew Chem Int Ed Engl 2016. [DOI: 10.1002/ange.201607419] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Affiliation(s)
- Hisashi Kobayashi
- Graduate School of Materials Science; Nara Institute of Science and Technology; 8916-5 Takayama, Ikoma Nara 630-0192 Japan
| | - Satoshi Nagao
- Graduate School of Materials Science; Nara Institute of Science and Technology; 8916-5 Takayama, Ikoma Nara 630-0192 Japan
| | - Shun Hirota
- Graduate School of Materials Science; Nara Institute of Science and Technology; 8916-5 Takayama, Ikoma Nara 630-0192 Japan
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110
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Kobayashi H, Nagao S, Hirota S. Characterization of the Cytochrome c Membrane-Binding Site Using Cardiolipin-Containing Bicelles with NMR. Angew Chem Int Ed Engl 2016; 55:14019-14022. [PMID: 27723218 DOI: 10.1002/anie.201607419] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2016] [Revised: 09/16/2016] [Indexed: 12/12/2022]
Abstract
Cytochrome (cyt) c transports electrons from Complex III to Complex IV in mitochondria. Cyt c is ordinarily anchored to the mitochondrial membrane through interaction with cardiolipin (CL), however its release into the cytosol initiates apoptosis. The cyt c interaction site with CL-containing bicelles was characterized by NMR spectroscopy. Chemical shift perturbations in cyt c signals upon interaction with bicelles revealed that a relatively wide region, which includes the A-site, the CXXCH motif, and the N- and C-terminal helices, and contains multiple Lys residues, interacts cooperatively with CL. The specific cyt c-CL interaction increased with increasing CL molecules in the bicelles. The location of the cyt c interaction site for CL was similar to those for Complex III and Complex IV, thus indicating that cyt c recognizes lipids and partner proteins in a similar way. In addition to elucidating the cyt c membrane-binding site, these results provide insight into the dynamic aspect of cyt c interactions in mitochondria.
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Affiliation(s)
- Hisashi Kobayashi
- Graduate School of Materials Science, Nara Institute of Science and Technology, 8916-5 Takayama, Ikoma, Nara, 630-0192, Japan
| | - Satoshi Nagao
- Graduate School of Materials Science, Nara Institute of Science and Technology, 8916-5 Takayama, Ikoma, Nara, 630-0192, Japan.
| | - Shun Hirota
- Graduate School of Materials Science, Nara Institute of Science and Technology, 8916-5 Takayama, Ikoma, Nara, 630-0192, Japan.
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111
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Structural Changes and Proapoptotic Peroxidase Activity of Cardiolipin-Bound Mitochondrial Cytochrome c. Biophys J 2016; 109:1873-84. [PMID: 26536264 DOI: 10.1016/j.bpj.2015.09.016] [Citation(s) in RCA: 62] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2015] [Revised: 08/11/2015] [Accepted: 09/18/2015] [Indexed: 01/19/2023] Open
Abstract
The cellular process of intrinsic apoptosis relies on the peroxidation of mitochondrial lipids as a critical molecular signal. Lipid peroxidation is connected to increases in mitochondrial reactive oxygen species, but there is also a required role for mitochondrial cytochrome c (cyt-c). In apoptotic mitochondria, cyt-c gains a new function as a lipid peroxidase that catalyzes the reactive oxygen species-mediated chemical modification of the mitochondrial lipid cardiolipin (CL). This peroxidase activity is caused by a conformational change in the protein, resulting from interactions between cyt-c and CL. The nature of the conformational change and how it causes this gain-of-function remain uncertain. Via a combination of functional, structural, and biophysical experiments we investigate the structure and peroxidase activity of cyt-c in its membrane-bound state. We reconstituted cyt-c with CL-containing lipid vesicles, and determined the increase in peroxidase activity resulting from membrane binding. We combined these assays of CL-induced proapoptotic activity with structural and dynamic studies of the membrane-bound protein via solid-state NMR and optical spectroscopy. Multidimensional magic angle spinning (MAS) solid-state NMR of uniformly (13)C,(15)N-labeled protein was used to detect site-specific conformational changes in oxidized and reduced horse heart cyt-c bound to CL-containing lipid bilayers. MAS NMR and Fourier transform infrared measurements show that the peripherally membrane-bound cyt-c experiences significant dynamics, but also retains most or all of its secondary structure. Moreover, in two-dimensional and three-dimensional MAS NMR spectra the CL-bound cyt-c displays a spectral resolution, and thus structural homogeneity, that is inconsistent with extensive membrane-induced unfolding. Cyt-c is found to interact primarily with the membrane interface, without significantly disrupting the lipid bilayer. Thus, membrane binding results in cyt-c gaining the increased peroxidase activity that represents its pivotal proapoptotic function, but we do not observe evidence for large-scale unfolding or penetration into the membrane core.
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112
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Bren KL. Going with the Electron Flow: Heme Electronic Structure and Electron Transfer in Cytochrome
c. Isr J Chem 2016. [DOI: 10.1002/ijch.201600021] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Affiliation(s)
- Kara L. Bren
- Department of Chemistry University of Rochester Rochester NY 14627-0216 USA
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113
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Firsov AM, Kotova EA, Orlov VN, Antonenko YN, Skulachev VP. A mitochondria-targeted antioxidant can inhibit peroxidase activity of cytochromecby detachment of the protein from liposomes. FEBS Lett 2016; 590:2836-43. [DOI: 10.1002/1873-3468.12319] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2016] [Revised: 07/14/2016] [Accepted: 07/14/2016] [Indexed: 11/08/2022]
Affiliation(s)
- Alexander M. Firsov
- Belozersky Institute of Physico-Chemical Biology; Lomonosov Moscow State University; Russia
- Department of Bioengineering and Bioinformatics; Lomonosov Moscow State University; Russia
| | - Elena A. Kotova
- Belozersky Institute of Physico-Chemical Biology; Lomonosov Moscow State University; Russia
| | - Viktor N. Orlov
- Belozersky Institute of Physico-Chemical Biology; Lomonosov Moscow State University; Russia
| | - Yuri N. Antonenko
- Belozersky Institute of Physico-Chemical Biology; Lomonosov Moscow State University; Russia
| | - Vladimir P. Skulachev
- Belozersky Institute of Physico-Chemical Biology; Lomonosov Moscow State University; Russia
- Department of Bioengineering and Bioinformatics; Lomonosov Moscow State University; Russia
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114
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Known unknowns of cardiolipin signaling: The best is yet to come. Biochim Biophys Acta Mol Cell Biol Lipids 2016; 1862:8-24. [PMID: 27498292 PMCID: PMC5323096 DOI: 10.1016/j.bbalip.2016.08.001] [Citation(s) in RCA: 91] [Impact Index Per Article: 11.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2016] [Revised: 07/27/2016] [Accepted: 08/01/2016] [Indexed: 12/11/2022]
Abstract
Since its discovery 75years ago, a wealth of knowledge has accumulated on the role of cardiolipin, the hallmark phospholipid of mitochondria, in bioenergetics and particularly on the structural organization of the inner mitochondrial membrane. A surge of interest in this anionic doubly-charged tetra-acylated lipid found in both prokaryotes and mitochondria has emerged based on its newly discovered signaling functions. Cardiolipin displays organ, tissue, cellular and transmembrane distribution asymmetries. A collapse of the membrane asymmetry represents a pro-mitophageal mechanism whereby externalized cardiolipin acts as an "eat-me" signal. Oxidation of cardiolipin's polyunsaturated acyl chains - catalyzed by cardiolipin complexes with cytochrome c. - is a pro-apoptotic signal. The messaging functions of myriads of cardiolipin species and their oxidation products are now being recognized as important intracellular and extracellular signals for innate and adaptive immune systems. This newly developing field of research exploring cardiolipin signaling is the main subject of this review. This article is part of a Special Issue entitled: Lipids of Mitochondria edited by Guenther Daum.
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115
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The nitrite reductase activity of horse heart carboxymethylated-cytochrome c is modulated by cardiolipin. J Biol Inorg Chem 2016; 21:421-32. [DOI: 10.1007/s00775-016-1351-1] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2015] [Accepted: 02/28/2016] [Indexed: 10/22/2022]
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116
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Hannibal L, Tomasina F, Capdevila DA, Demicheli V, Tórtora V, Alvarez-Paggi D, Jemmerson R, Murgida DH, Radi R. Alternative Conformations of Cytochrome c: Structure, Function, and Detection. Biochemistry 2016; 55:407-28. [DOI: 10.1021/acs.biochem.5b01385] [Citation(s) in RCA: 89] [Impact Index Per Article: 11.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Affiliation(s)
- Luciana Hannibal
- Departamento
de Bioquímica, Facultad de Medicina, Universidad de la República, Avda. General Flores 2125, 11800 Montevideo, Uruguay
- Centro
de Investigaciones Biomédicas (CEINBIO), Facultad de Medicina, Universidad de la República, Avda. General Flores 2125, 11800 Montevideo, Uruguay
- Center
for Pediatrics and Adolescent Medicine, Medical Center, University of Freiburg, Mathildenstrasse 1, Freiburg D-79106, Germany
| | - Florencia Tomasina
- Departamento
de Bioquímica, Facultad de Medicina, Universidad de la República, Avda. General Flores 2125, 11800 Montevideo, Uruguay
- Centro
de Investigaciones Biomédicas (CEINBIO), Facultad de Medicina, Universidad de la República, Avda. General Flores 2125, 11800 Montevideo, Uruguay
| | - Daiana A. Capdevila
- Departamento
de Química Inorgánica, Analítica y Química
Física/INQUIMAE, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Pabellón 2, Ciudad Universitaria, C1428EHA Buenos Aires, Argentina
| | - Verónica Demicheli
- Departamento
de Bioquímica, Facultad de Medicina, Universidad de la República, Avda. General Flores 2125, 11800 Montevideo, Uruguay
- Centro
de Investigaciones Biomédicas (CEINBIO), Facultad de Medicina, Universidad de la República, Avda. General Flores 2125, 11800 Montevideo, Uruguay
| | - Verónica Tórtora
- Departamento
de Bioquímica, Facultad de Medicina, Universidad de la República, Avda. General Flores 2125, 11800 Montevideo, Uruguay
- Centro
de Investigaciones Biomédicas (CEINBIO), Facultad de Medicina, Universidad de la República, Avda. General Flores 2125, 11800 Montevideo, Uruguay
| | - Damián Alvarez-Paggi
- Departamento
de Química Inorgánica, Analítica y Química
Física/INQUIMAE, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Pabellón 2, Ciudad Universitaria, C1428EHA Buenos Aires, Argentina
| | - Ronald Jemmerson
- Department
of Microbiology and Immunology, University of Minnesota, MMC 196,
420 Delaware Street, Southeast, Minneapolis, Minnesota 55455, United States
| | - Daniel H. Murgida
- Departamento
de Química Inorgánica, Analítica y Química
Física/INQUIMAE, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Pabellón 2, Ciudad Universitaria, C1428EHA Buenos Aires, Argentina
| | - Rafael Radi
- Departamento
de Bioquímica, Facultad de Medicina, Universidad de la República, Avda. General Flores 2125, 11800 Montevideo, Uruguay
- Centro
de Investigaciones Biomédicas (CEINBIO), Facultad de Medicina, Universidad de la República, Avda. General Flores 2125, 11800 Montevideo, Uruguay
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117
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O'Brien ES, Nucci NV, Fuglestad B, Tommos C, Wand AJ. Defining the Apoptotic Trigger: THE INTERACTION OF CYTOCHROME c AND CARDIOLIPIN. J Biol Chem 2015; 290:30879-87. [PMID: 26487716 PMCID: PMC4692216 DOI: 10.1074/jbc.m115.689406] [Citation(s) in RCA: 51] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2015] [Revised: 10/14/2015] [Indexed: 11/06/2022] Open
Abstract
The interaction between cytochrome c and the anionic lipid cardiolipin has been proposed as a primary event in the apoptotic signaling cascade. Numerous studies that have examined the interaction of cytochrome c with cardiolipin embedded in a variety of model phospholipid membranes have suggested that partial unfolding of the protein is a precursor to the apoptotic response. However, these studies lacked site resolution and used model systems with negligible or a positive membrane curvature, which is distinct from the large negative curvature of the invaginations of the inner mitochondrial membrane where cytochrome c resides. We have used reverse micelle encapsulation to mimic the potential effects of confinement on the interaction of cytochrome c with cardiolipin. Encapsulation of oxidized horse cytochrome c in 1-decanoyl-rac-glycerol/lauryldimethylamine-N-oxide/hexanol reverse micelles prepared in pentane yields NMR spectra essentially identical to the protein in free aqueous solution. The structure of encapsulated ferricytochrome c was determined to high precision (bb ∼ 0.23 Å) using NMR-based methods and is closely similar to the cryogenic crystal structure (bb ∼ 1.2 Å). Incorporation of cardiolipin into the reverse micelle surfactant shell causes localized chemical shift perturbations of the encapsulated protein, providing the first view of the cardiolipin/cytochrome c interaction interface at atomic resolution. Three distinct sites of interaction are detected: the so-called A- and L-sites, plus a previously undocumented interaction centered on residues Phe-36, Gly-37, Thr-58, Trp-59, and Lys-60. Importantly, in distinct contrast to earlier studies of this interaction, the protein is not significantly disturbed by the binding of cardiolipin in the context of the reverse micelle.
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Affiliation(s)
- Evan S O'Brien
- From the Johnson Research Foundation and Department of Biochemistry and Biophysics, University of Pennsylvania, Philadelphia, Pennsylvania 19104-6059
| | - Nathaniel V Nucci
- From the Johnson Research Foundation and Department of Biochemistry and Biophysics, University of Pennsylvania, Philadelphia, Pennsylvania 19104-6059
| | - Brian Fuglestad
- From the Johnson Research Foundation and Department of Biochemistry and Biophysics, University of Pennsylvania, Philadelphia, Pennsylvania 19104-6059
| | - Cecilia Tommos
- From the Johnson Research Foundation and Department of Biochemistry and Biophysics, University of Pennsylvania, Philadelphia, Pennsylvania 19104-6059
| | - A Joshua Wand
- From the Johnson Research Foundation and Department of Biochemistry and Biophysics, University of Pennsylvania, Philadelphia, Pennsylvania 19104-6059
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118
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Capdevila DA, Oviedo Rouco S, Tomasina F, Tortora V, Demicheli V, Radi R, Murgida DH. Active Site Structure and Peroxidase Activity of Oxidatively Modified Cytochrome c Species in Complexes with Cardiolipin. Biochemistry 2015; 54:7491-504. [PMID: 26620444 DOI: 10.1021/acs.biochem.5b00922] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
We report a resonance Raman and UV-vis characterization of the active site structure of oxidatively modified forms of cytochrome c (Cyt-c) free in solution and in complexes with cardiolipin (CL). The studied post-translational modifications of Cyt-c include methionine sulfoxidation and tyrosine nitration, which lead to altered heme axial ligation and increased peroxidase activity with respect to those of the wild-type protein. In spite of the structural and activity differences between the protein variants free in solution, binding to CL liposomes induces in all cases the formation of a spectroscopically identical bis-His axial coordination conformer that more efficiently promotes lipid peroxidation. The spectroscopic results indicate that the bis-His form is in equilibrium with small amounts of high-spin species, thus suggesting a labile distal His ligand as the basis for the CL-induced increase in enzymatic activity observed for all protein variants. For Cyt-c nitrated at Tyr74 and sulfoxidized at Met80, the measured apparent binding affinities for CL are ∼4 times larger than for wild-type Cyt-c. On the basis of these results, we propose that these post-translational modifications may amplify the pro-apoptotic signal of Cyt-c under oxidative stress conditions at CL concentrations lower than for the unmodified protein.
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Affiliation(s)
- Daiana A Capdevila
- 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, C1428EHA Buenos Aires, 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, C1428EHA Buenos Aires, Argentina
| | - Florencia Tomasina
- Departamento de Bioquímica and Center for Free Radical and Biomedical Research, Facultad de Medicina, Universidad de la República , Montevideo, Uruguay
| | - Verónica Tortora
- Departamento de Bioquímica and Center for Free Radical and Biomedical Research, Facultad de Medicina, Universidad de la República , Montevideo, Uruguay
| | - Verónica Demicheli
- Departamento de Bioquímica and Center for Free Radical and Biomedical Research, Facultad de Medicina, Universidad de la República , Montevideo, Uruguay
| | - Rafael Radi
- Departamento de Bioquímica and Center for Free Radical and Biomedical Research, Facultad de Medicina, Universidad de la República , Montevideo, 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, C1428EHA Buenos Aires, Argentina
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119
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Marchenkova MA, Dyakova YA, Tereschenko EY, Kovalchuk MV, Vladimirov YA. Cytochrome c Complexes with Cardiolipin Monolayer Formed under Different Surface Pressure. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2015; 31:12426-12436. [PMID: 26488458 DOI: 10.1021/acs.langmuir.5b03155] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
The formation of the complex of cytochrome c (Cytc) with a phospholipid cardiolipin (CL) in mitochondria is a crucial event in apoptosis development. There are two viewpoints on the structure of the complex. (1) Cytc is bound on the surface of the lipid bilayer. (2) The complex is a hydrophobic nanoparticle Cytc-CL formed by Cytc molten globule, covered by CL monolayer.1 In the present work, we attempted to bridge the gap between these two structures. We investigated the interaction between Cytc and Langmuir monolayers of CL. The surface pressure increase during incorporation of Cytc into CL monolayer obeys the equation: π = π0 + Δπ∞[1 - exp(-βt)], where β is pseudo-first-order rate constant of Cytc binding, directly proportional to the initial Cytc concentration c0. Parameters Δπ∞ and the rate β measured in different conditions were virtually equal for natural bovine CL and peroxidation-resistant tetraoleoyl CL in all experiments. Surface area-surface pressure isotherms of Cytc alone and in combination with a CL monolayer were similar in shape. Apparently, the protein exposes hydrophilic groups to the water phase and hydrophobic to the air or to the hydrocarbon chains of CL. The 30% ethanol dramatically accelerated the adsorption of Cytc on the water surface. The protein-lipid surface films showed, in compression-expansion cycles, that hysteresis loops were observed always when Cytc present, reproducible in repeating cycles. Taken together, our data show that when incorporated in a lipid monolayer or after adsorption on the water-air interface, Cytc undergoes conformational transition. In that, one part of the globule sphere becomes predominantly hydrophobic and the other, hydrophilic and charged ("stratified" Cytc). We hypothesize that in CL-containing bilayer membranes, Cytc incorporation into the lipid monolayer would result in membrane folding with subsequent formation of either catalytically reactive "bubbles" inside the bilayer, formed by Cytc-CL, or the appearance of hydrophilic pores. The role of lipid peroxidation catalyzed by Cytc-CL in the appearance of pores and apoptosis is also discussed.
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Affiliation(s)
- Margarita A Marchenkova
- Shubnikov Institute of Crystallography of Russian Academy of Sciences , 119333 Moscow, Russian Federation
- National Research Centre "Kurchatov Institute" , 123182 Moscow, Russian Federation
| | - Yulia A Dyakova
- Shubnikov Institute of Crystallography of Russian Academy of Sciences , 119333 Moscow, Russian Federation
- National Research Centre "Kurchatov Institute" , 123182 Moscow, Russian Federation
| | - Elena Yu Tereschenko
- Shubnikov Institute of Crystallography of Russian Academy of Sciences , 119333 Moscow, Russian Federation
- National Research Centre "Kurchatov Institute" , 123182 Moscow, Russian Federation
| | - Mikhail V Kovalchuk
- Shubnikov Institute of Crystallography of Russian Academy of Sciences , 119333 Moscow, Russian Federation
- National Research Centre "Kurchatov Institute" , 123182 Moscow, Russian Federation
- St. Petersburg State University , 199034 St. Petersburg, Russian Federation
| | - Yury A Vladimirov
- M.V. Lomonosov Moscow State University , 119991 Moscow, Russian Federation
- Pirogov Russian National Research Medical University , 117997 Moscow, Russian Federation
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120
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Karsisiotis AI, Deacon OM, Rajagopal BS, Macdonald C, Blumenschein TMA, Moore GR, Worrall JAR. Backbone resonance assignments of ferric human cytochrome c and the pro-apoptotic G41S mutant in the ferric and ferrous states. BIOMOLECULAR NMR ASSIGNMENTS 2015; 9:415-419. [PMID: 26123826 DOI: 10.1007/s12104-015-9621-3] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/14/2015] [Accepted: 06/26/2015] [Indexed: 06/04/2023]
Abstract
Human cytochrome c is a multi-functional protein with key roles in both the mitochondrial electron transfer chain and in apoptosis. In the latter, a complex formed between the mitochondrial phospholipid cardiolipin and cytochrome c is crucial for instigating the release of pro-apoptotic factors, including cytochrome c, from the mitochondrion into the cytosol. The G41S mutant of human cytochrome c is the only known disease-related variant of cytochrome c and causes increased apoptotic activity in patients with autosomal dominant thrombocytopenia. NMR spectroscopy can be used to investigate the interaction of human cytochrome c with cardiolipin and the structural and dynamic factors, which may contribute to enhanced apoptotic activity for the G41S mutant. We present here essentially full backbone amide resonance assignments for ferric human cytochrome c (98 %) as well as assignments of both the ferric (92 %) and ferrous (95 %) forms of the G41S mutant. Backbone amide chemical shift differences between the wild type and G41S mutant in the ferric state reveals significant changes around the mutation site, with many other amides also affected. This suggests the possibility of increased dynamics and/or a change in the paramagnetic susceptibility tensor of the G41S mutant relative to the wild type protein.
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Affiliation(s)
| | - Oliver M Deacon
- School of Biological Sciences, University of Essex, Wivenhoe Park, Colchester, CO4 3SQ, UK
| | - Badri S Rajagopal
- School of Biological Sciences, University of Essex, Wivenhoe Park, Colchester, CO4 3SQ, UK
| | - Colin Macdonald
- School of Chemistry, University of East Anglia, Norwich Research Park, Norwich, NR4 7TJ, UK
| | | | - Geoffrey R Moore
- School of Chemistry, University of East Anglia, Norwich Research Park, Norwich, NR4 7TJ, UK
| | - Jonathan A R Worrall
- School of Biological Sciences, University of Essex, Wivenhoe Park, Colchester, CO4 3SQ, UK.
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121
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Pandiscia LA, Schweitzer-Stenner R. Coexistence of Native-Like and Non-Native Cytochrome c on Anionic Liposomes with Different Cardiolipin Content. J Phys Chem B 2015; 119:12846-59. [PMID: 26369421 DOI: 10.1021/acs.jpcb.5b07328] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
We employed a combination of fluorescence, visible circular dichroism, and absorption spectroscopy to study the conformational changes of ferricytochrome c upon its binding to cardiolipin-containing small unilamellar vesicles. The measurements were performed as a function of the cardiolipin concentration, the cardiolipin content of the liposomes, and the NaCl concentration of the solvent. The data were analyzed with a novel model that combines a single binding step with a conformational equilibrium between native-like and non-native-like proteins bound to the membrane surface. The equilibrium between the two conformations, which themselves are comprised of structurally slightly different subconformations, shifts to the more non-native-like conformation with increasing cardiolipin concentration. For the binding isotherms described in this paper, we explicitly considered the enthalpic and entropic contributions of molecular crowding to protein binding at low lipid concentrations and high occupancy of the liposome surface. Increasing the CL content of liposomes increases the overall binding affinity but makes the conformational distribution much more susceptible to the influence of sodium and chloride ions, which shifts the equilibrium toward the more native-like state and directly inhibits binding, particularly to liposomes with 100% cardiolipin content. Spectroscopic evidence further suggests that a fraction of the non-native conformers adopts a pentacoordinated state similar to those obtained in class C peroxidases. On the basis of our results, we propose a hypothesis that describes the balance between facilitating and impeding forces controlling the peroxidase activity of cytochrome c in the inner membrane space of mitochondria.
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Affiliation(s)
- Leah A Pandiscia
- Department of Chemistry, Drexel University , 3141 Chestnut Street, Philadelphia, Pennsylvania 19104, United States
| | - Reinhard Schweitzer-Stenner
- Department of Chemistry, Drexel University , 3141 Chestnut Street, Philadelphia, Pennsylvania 19104, United States
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122
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Lightowlers RN, Taylor RW, Turnbull DM. Mutations causing mitochondrial disease: What is new and what challenges remain? Science 2015; 349:1494-9. [PMID: 26404827 DOI: 10.1126/science.aac7516] [Citation(s) in RCA: 211] [Impact Index Per Article: 23.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Mitochondrial diseases are among the most common and most complex of all inherited genetic diseases. The involvement of both the mitochondrial and nuclear genome presents unique challenges, but despite this there have been some remarkable advances in our knowledge of mitochondrial diseases over the past few years. A greater understanding of mitochondrial genetics has led to improved diagnosis as well as novel ways to prevent transmission of severe mitochondrial disease. These and other advances have had a major impact on patient care, but considerable challenges remain, particularly in the areas of therapies for those patients manifesting clinical symptoms associated with mitochondrial dysfunction and the tissue specificity seen in many mitochondrial disorders. This review highlights some important recent advances in mitochondrial disease but also stresses the areas where progress is essential.
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Affiliation(s)
- Robert N Lightowlers
- Wellcome Trust Centre for Mitochondrial Research, Institute for Cell and Molecular Biosciences and Institute of Neuroscience, Medical School, Newcastle University, Newcastle upon Tyne NE2 4HH, UK
| | - Robert W Taylor
- Wellcome Trust Centre for Mitochondrial Research, Institute for Cell and Molecular Biosciences and Institute of Neuroscience, Medical School, Newcastle University, Newcastle upon Tyne NE2 4HH, UK
| | - Doug M Turnbull
- Wellcome Trust Centre for Mitochondrial Research, Institute for Cell and Molecular Biosciences and Institute of Neuroscience, Medical School, Newcastle University, Newcastle upon Tyne NE2 4HH, UK.
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123
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Wang Z, Ando Y, Nugraheni AD, Ren C, Nagao S, Hirota S. Self-oxidation of cytochrome c at methionine80 with molecular oxygen induced by cleavage of the Met-heme iron bond. MOLECULAR BIOSYSTEMS 2015; 10:3130-7. [PMID: 25224641 DOI: 10.1039/c4mb00285g] [Citation(s) in RCA: 36] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
Met80 of cytochrome c (cyt c) has been shown to dissociate from its heme iron when cyt c interacts with cardiolipin (CL), which triggers the release of cyt c into the cytosol initiating apoptosis. We found that the mass of human cyt c increases by 16 Da in the Met80-Lys86 region by reaction with molecular oxygen in the presence of CL-containing liposomes and dithiothreitol (DTT). To investigate the effect of Met80 dissociation on the reaction of cyt c with molecular oxygen without affecting its secondary structures, a human cyt c mutant (Δ8384 cyt c) was constructed by removing two amino acids (Val83 and Gly84) from the loop containing Met80. According to MALDI-TOF-MS and tandem mass measurements, Met80 of Δ8384 cyt c was modified site-specifically to methionine sulfoxide when purified in the presence of molecular oxygen, whereas Met80 was not modified in the absence of molecular oxygen. A red-shift of the Soret band from 406 to 412 nm and absorption increase at ∼536 and ∼568 nm were observed for Δ8384 cyt c when it reacted with DTT and molecular oxygen, followed by a further red-shift of the Soret band to 416 nm and absorption increase at ∼620 and ∼650 nm. These results indicate that Met80 of cyt c is oxidized site-specifically by formation of the oxy and subsequent compound I-like species when Met80 dissociates from the heme iron, where the Met80 modification may affect its peroxidase activity related to apoptosis.
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Affiliation(s)
- Zhonghua Wang
- Graduate School of Materials Science, Nara Institute of Science and Technology, 8916-5 Takayama, Ikoma, Nara 630-0192, Japan.
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124
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Kleingardner JG, Bren KL. Biological significance and applications of heme c proteins and peptides. Acc Chem Res 2015; 48:1845-52. [PMID: 26083801 DOI: 10.1021/acs.accounts.5b00106] [Citation(s) in RCA: 70] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
Hemes are ubiquitous in biology and carry out a wide range of functions. The heme group is largely invariant across proteins with different functions, although there are a few variations seen in nature. The most common variant is heme c, which is formed by a post-translational modification in which heme is covalently linked to two Cys residues on the polypeptide via thioether bonds. In this Account, the influence of this covalent attachment on heme c properties and function is discussed, and examples of how covalent attachment has been used in selected applications are presented. Proteins that bind heme c are among the most well-characterized proteins in biochemistry. Most of these proteins are cytochromes c (cyts c) that serve as electron carriers in photosynthesis and respiration. Despite the intense study of cyts c, the functional significance of heme covalent attachment has remained elusive. One observation is that heme c reaches a lower reduction potential in nature than its noncovalently linked counterpart, heme b, when comparing proteins with the same axial ligands. Furthermore, covalent attachment is known to enhance protein stability and allow the heme to be relatively solvent exposed. However, an inorganic chemistry perspective on the effects of covalent attachment has been lacking. Spectroscopic measurements and computations on cyts c and model systems reveal a number of effects of covalent attachment on heme electronic structure and reactivity. One is that the predominant nonplanar ruffling distortion seen in heme c lowers heme reduction potential. Another is that covalent attachment influences the interaction of the heme iron with the proximal His ligand. Heme ruffling also has been shown to influence electronic coupling to redox partners and, therefore, electron transfer rates by altering the distribution of the orbital hole on the porphyrin in oxidized cyt c. Another consequence of heme covalent attachment is the strong vibrational coupling seen between the iron and the protein surface as revealed by nuclear resonance vibrational spectroscopy studies. Finally, heme covalent attachment is proposed to be an important feature supporting multiple roles of cyt c in programmed cell death (apoptosis). Heme covalent attachment is not only vital for the biological functions of cyt c but also provides a useful handle in a number of applications. For one, the engineering of heme c onto an exposed portion of a protein of interest has been shown to provide a visible affinity purification tag. In addition, peptides with covalently attached heme, known as microperoxidases, have been studied as model compounds and oxidation catalysts and, more recently, in applications for energy conversion and storage. The wealth of insight gained about heme c through fundamental studies of cyts c forms a basis for future efforts toward engineering natural and artificial cytochromes for a variety of applications.
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Affiliation(s)
- Jesse G. Kleingardner
- Department
of Chemistry, Ithaca College, Ithaca, New York 14850, United States
- Department
of Chemistry, University of Rochester, Rochester, New York 14618, United States
| | - Kara L. Bren
- Department
of Chemistry, University of Rochester, Rochester, New York 14618, United States
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125
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Amacher JF, Zhong F, Lisi GP, Zhu MQ, Alden SL, Hoke KR, Madden DR, Pletneva EV. A Compact Structure of Cytochrome c Trapped in a Lysine-Ligated State: Loop Refolding and Functional Implications of a Conformational Switch. J Am Chem Soc 2015; 137:8435-49. [PMID: 26038984 DOI: 10.1021/jacs.5b01493] [Citation(s) in RCA: 56] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
It has been suggested that the alkaline form of cytochrome c (cyt c) regulates function of this protein as an electron carrier in oxidative phosphorylation and as a peroxidase that reacts with cardiolipin (CL) during apoptosis. In this form, Met80, the native ligand to the heme iron, is replaced by a Lys. While it has become clear that the structure of cyt c changes, the extent and sequence of conformational rearrangements associated with this ligand replacement remain a subject of debate. Herein we report a high-resolution crystal structure of a Lys73-ligated cyt c conformation that reveals intricate change in the heme environment upon this switch in the heme iron ligation. The structure is surprisingly compact, and the heme coordination loop refolds into a β-hairpin with a turn formed by the highly conserved residues Pro76 and Gly77. Repositioning of residue 78 modifies the intraprotein hydrogen-bonding network and, together with adjustments of residues 52 and 74, increases the volume of the heme pocket to allow for insertion of one of the CL acyl moieties next to Asn52. Derivatization of Cys78 with maleimide creates a solution mimic of the Lys-ligated cyt c that has enhanced peroxidase activity, adding support for a role of the Lys-ligated cyt c in the apoptotic mechanism. Experiments with the heme peptide microperoxidase-8 and engineered model proteins provide a thermodynamic rationale for the switch to Lys ligation upon perturbations in the protein scaffold.
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Affiliation(s)
- Jeanine F Amacher
- †Department of Biochemistry, Geisel School of Medicine, Hanover, New Hampshire 03755, United States
| | - Fangfang Zhong
- ‡Department of Chemistry, Dartmouth College, Hanover, New Hampshire 03755, United States
| | - George P Lisi
- ‡Department of Chemistry, Dartmouth College, Hanover, New Hampshire 03755, United States
| | - Michael Q Zhu
- ‡Department of Chemistry, Dartmouth College, Hanover, New Hampshire 03755, United States
| | - Stephanie L Alden
- ‡Department of Chemistry, Dartmouth College, Hanover, New Hampshire 03755, United States
| | - Kevin R Hoke
- §Department of Chemistry, Berry College, Mount Berry, Georgia 30149, United States
| | - Dean R Madden
- †Department of Biochemistry, Geisel School of Medicine, Hanover, New Hampshire 03755, United States
| | - Ekaterina V Pletneva
- †Department of Biochemistry, Geisel School of Medicine, Hanover, New Hampshire 03755, United States.,‡Department of Chemistry, Dartmouth College, Hanover, New Hampshire 03755, United States
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126
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Bakan A, Kapralov AA, Bayir H, Hu F, Kagan VE, Bahar I. Inhibition of Peroxidase Activity of Cytochrome c: De Novo Compound Discovery and Validation. Mol Pharmacol 2015; 88:421-7. [PMID: 26078313 DOI: 10.1124/mol.115.097816] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2015] [Accepted: 06/15/2015] [Indexed: 12/22/2022] Open
Abstract
Cytochrome c (cyt c) release from mitochondria is accepted to be the point of no return for eliciting a cascade of interactions that lead to apoptosis. A strategy for containing sustained apoptosis is to reduce the mitochondrial permeability pore opening. Pore opening is enhanced by peroxidase activity of cyt c gained upon its complexation with cardiolipin in the presence of reactive oxygen species. Blocking access to the heme group has been proposed as an effective intervention method for reducing, if not eliminating, the peroxidase activity of cyt c. In the present study, using a combination of druggability simulations, pharmacophore modeling, virtual screening, and in vitro fluorescence measurements to probe peroxidase activity, we identified three repurposable drugs and seven compounds that are validated to effectively inhibit the peroxidase activity of cyt c.
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Affiliation(s)
- Ahmet Bakan
- Department of Computational and Systems Biology, School of Medicine (A.B., F.H., I.B.), and Department of Environmental and Occupational Health (A.A.K., H.B., V.E.K.), University of Pittsburgh, Pittsburgh, Pennsylvania
| | - Alexandr A Kapralov
- Department of Computational and Systems Biology, School of Medicine (A.B., F.H., I.B.), and Department of Environmental and Occupational Health (A.A.K., H.B., V.E.K.), University of Pittsburgh, Pittsburgh, Pennsylvania
| | - Hulya Bayir
- Department of Computational and Systems Biology, School of Medicine (A.B., F.H., I.B.), and Department of Environmental and Occupational Health (A.A.K., H.B., V.E.K.), University of Pittsburgh, Pittsburgh, Pennsylvania
| | - Feizhou Hu
- Department of Computational and Systems Biology, School of Medicine (A.B., F.H., I.B.), and Department of Environmental and Occupational Health (A.A.K., H.B., V.E.K.), University of Pittsburgh, Pittsburgh, Pennsylvania
| | - Valerian E Kagan
- Department of Computational and Systems Biology, School of Medicine (A.B., F.H., I.B.), and Department of Environmental and Occupational Health (A.A.K., H.B., V.E.K.), University of Pittsburgh, Pittsburgh, Pennsylvania
| | - Ivet Bahar
- Department of Computational and Systems Biology, School of Medicine (A.B., F.H., I.B.), and Department of Environmental and Occupational Health (A.A.K., H.B., V.E.K.), University of Pittsburgh, Pittsburgh, Pennsylvania
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127
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Paul SS, Sil P, Haldar S, Mitra S, Chattopadhyay K. Subtle Change in the Charge Distribution of Surface Residues May Affect the Secondary Functions of Cytochrome c. J Biol Chem 2015; 290:14476-90. [PMID: 25873393 DOI: 10.1074/jbc.m114.607010] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2014] [Indexed: 11/06/2022] Open
Abstract
Although the primary function of cytochrome c (cyt c) is electron transfer, the protein caries out an additional secondary function involving its interaction with membrane cardiolipin (CDL), its peroxidase activity, and the initiation of apoptosis. Whereas the primary function of cyt c is essentially conserved, its secondary function varies depending on the source of the protein. We report here a detailed experimental and computational study, which aims to understand, at the molecular level, the difference in the secondary functions of cyt c obtained from horse heart (mammalian) and Saccharomyces cerevisiae (yeast). The conformational landscape of cyt c has been found to be heterogeneous, consisting of an equilibrium between the compact and extended conformers as well as the oligomeric species. Because the determination of relative populations of these conformers is difficult to obtain by ensemble measurements, we used fluorescence correlation spectroscopy (FCS), a method that offers single-molecule resolution. The population of different species is found to depend on multiple factors, including the protein source, the presence of CDL and urea, and their concentrations. The complex interplay between the conformational distribution and oligomerization plays a crucial role in the variation of the pre-apoptotic regulation of cyt c observed from different sources. Finally, computational studies reveal that the variation in the charge distribution at the surface and the charge reversal sites may be the key determinant of the conformational stability of cyt c.
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Affiliation(s)
- Simanta Sarani Paul
- From the Protein Folding and Dynamics Laboratory, Structural Biology and Bioinformatics Division, Council of Scientific and Industrial Research (CSIR)-Indian Institute of Chemical Biology, Kolkata 700032, India
| | - Pallabi Sil
- From the Protein Folding and Dynamics Laboratory, Structural Biology and Bioinformatics Division, Council of Scientific and Industrial Research (CSIR)-Indian Institute of Chemical Biology, Kolkata 700032, India
| | - Shubhasis Haldar
- From the Protein Folding and Dynamics Laboratory, Structural Biology and Bioinformatics Division, Council of Scientific and Industrial Research (CSIR)-Indian Institute of Chemical Biology, Kolkata 700032, India
| | - Samaresh Mitra
- From the Protein Folding and Dynamics Laboratory, Structural Biology and Bioinformatics Division, Council of Scientific and Industrial Research (CSIR)-Indian Institute of Chemical Biology, Kolkata 700032, India
| | - Krishnananda Chattopadhyay
- From the Protein Folding and Dynamics Laboratory, Structural Biology and Bioinformatics Division, Council of Scientific and Industrial Research (CSIR)-Indian Institute of Chemical Biology, Kolkata 700032, India
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128
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Ascenzi P, Coletta M, Wilson MT, Fiorucci L, Marino M, Polticelli F, Sinibaldi F, Santucci R. Cardiolipin-cytochrome c complex: Switching cytochrome c from an electron-transfer shuttle to a myoglobin- and a peroxidase-like heme-protein. IUBMB Life 2015; 67:98-109. [PMID: 25857294 DOI: 10.1002/iub.1350] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2014] [Accepted: 01/11/2015] [Indexed: 12/18/2022]
Abstract
Cytochrome c (cytc) is a small heme-protein located in the space between the inner and the outer membrane of the mitochondrion that transfers electrons from cytc-reductase to cytc-oxidase. The hexa-coordinated heme-Fe atom of cytc displays a very low reactivity toward ligands and does not exhibit significant catalytic properties. However, upon cardiolipin (CL) binding, cytc achieves ligand binding and catalytic properties reminiscent of those of myoglobin and peroxidase. In particular, the peroxidase activity of the cardiolipin-cytochrome c complex (CL-cytc) is critical for the redistribution of CL from the inner to the outer mitochondrial membranes and is essential for the execution and completion of the apoptotic program. On the other hand, the capability of CL-cytc to bind NO and CO and the heme-Fe-based scavenging of reactive nitrogen and oxygen species may affect apoptosis. Here, the ligand binding and catalytic properties of CL-cytc are analyzed in parallel with those of CL-free cytc, myoglobin, and peroxidase to dissect the potential mechanisms of CL in modulating the pro- and anti-apoptotic actions of cytc.
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Affiliation(s)
- Paolo Ascenzi
- Interdepartmental Laboratory for Electron Microscopy, Roma Tre University, Roma, Italy
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129
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Bandi S, Bowler BE. Effect of an Ala81His mutation on the Met80 loop dynamics of iso-1-cytochrome c. Biochemistry 2015; 54:1729-42. [PMID: 25671560 PMCID: PMC5065065 DOI: 10.1021/bi501252z] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
An A81H variant of yeast iso-1-cytochrome c is prepared to test the hypothesis that the steric size of the amino acid at sequence position 81 of cytochrome c, which has evolved from Ala in yeast to Ile in mammals, slows the dynamics of the opening of the heme crevice. The A81H mutation is used both to increase steric size and to provide a probe of the dynamics of the heme crevice through measurement of the thermodynamics and kinetics of the His81-mediated alkaline conformational transition of A81H iso-1-cytochrome c. Thermodynamic measurements show that the native conformer is more stable than the His81-heme alkaline conformer for A81H iso-1-cytochrome c. ΔGu°(H2O) is approximately 1.9 kcal/mol for formation of the His81-heme alkaline conformer. By contrast, for K79H iso-1-cytochrome c, the native conformer is less stable than the His79-heme alkaline conformer. ΔGu°(H2O) is approximately -0.34 kcal/mol for formation of the His79-heme alkaline conformer. pH jump and gated electron transfer kinetics demonstrate that this stabilization of the native conformer in A81H iso-1-cytochrome c arises primarily from a decrease in the rate constant for formation of the His81-heme alkaline conformer, kf,His81, relative to kf,His79 for formation of the His79-heme alkaline conformer, which forms by a mechanism similar to that observed for the His81-heme alkaline conformer. The result is discussed in terms of the effect of global protein stability on protein dynamics and in terms of optimization of the sequence of cytochrome c for its role as a peroxidase in the early stages of apoptosis in higher eukaryotes.
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Affiliation(s)
| | - Bruce E. Bowler
- Department of Chemistry & Biochemistry, Center for Biomolecular Structure and Dynamics, University of Montana, Missoula, Montana 59812
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130
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Peroxidative permeabilization of liposomes induced by cytochrome c/cardiolipin complex. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2015; 1848:767-74. [DOI: 10.1016/j.bbamem.2014.11.027] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/08/2014] [Revised: 11/21/2014] [Accepted: 11/25/2014] [Indexed: 01/23/2023]
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131
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The hydrogen-peroxide-induced radical behaviour in human cytochrome c-phospholipid complexes: implications for the enhanced pro-apoptotic activity of the G41S mutant. Biochem J 2015; 456:441-52. [PMID: 24099549 DOI: 10.1042/bj20130758] [Citation(s) in RCA: 70] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
We have investigated whether the pro-apoptotic properties of the G41S mutant of human cytochrome c can be explained by a higher than wild-type peroxidase activity triggered by phospholipid binding. A key complex in mitochondrial apoptosis involves cytochrome c and the phospholipid cardiolipin. In this complex cytochrome c has its native axial Met(80) ligand dissociated from the haem-iron, considerably augmenting the peroxidase capability of the haem group upon H2O2 binding. By EPR spectroscopy we reveal that the magnitude of changes in the paramagnetic haem states, as well as the yield of protein-bound free radical, is dependent on the phospholipid used and is considerably greater in the G41S mutant. A high-resolution X-ray crystal structure of human cytochrome c was determined and, in combination with the radical EPR signal analysis, two tyrosine residues, Tyr(46) and Tyr(48), have been rationalized to be putative radical sites. Subsequent single and double tyrosine-to-phenylalanine mutations revealed that the EPR signal of the radical, found to be similar in all variants, including G41S and wild-type, originates not from a single tyrosine residue, but is instead a superimposition of multiple EPR signals from different radical sites. We propose a mechanism of multiple radical formations in the cytochrome c-phospholipid complexes under H2O2 treatment, consistent with the stabilization of the radical in the G41S mutant, which elicits a greater peroxidase activity from cytochrome c and thus has implications in mitochondrial apoptosis.
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132
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Yarman A, Dechtrirat D, Bosserdt M, Jetzschmann KJ, Gajovic-Eichelmann N, Scheller FW. Cytochrome c-Derived Hybrid Systems Based on Moleculary Imprinted Polymers. ELECTROANAL 2015. [DOI: 10.1002/elan.201400592] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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133
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Pandiscia LA, Schweitzer-Stenner R. Coexistence of Native-like and Non-Native Partially Unfolded Ferricytochrome c on the Surface of Cardiolipin-Containing Liposomes. J Phys Chem B 2015; 119:1334-49. [DOI: 10.1021/jp5104752] [Citation(s) in RCA: 42] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
Affiliation(s)
- Leah A. Pandiscia
- Department
of Chemistry, Drexel University, Philadelphia, PA 19104, United States
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134
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Nguyen KT. An electronically enhanced chiral sum frequency generation vibrational spectroscopy study of lipid-bound cytochrome c. Chem Commun (Camb) 2015; 51:195-7. [DOI: 10.1039/c4cc06916a] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Electronically enhanced chiral SFG spectroscopy was employed to study the lipid bound cyt c in situ. It was directly observed that upon interacting with anionic phospholipids, the amino acid residues around the heme adopted the β-sheet conformation. In addition, the orientation of this newly formed β-sheet structure was found to be sensitive to the bulk pH.
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Affiliation(s)
- Khoi Tan Nguyen
- School of Chemical Engineering
- The University of Queensland
- Brisbane
- Australia
- School of Biotechnology
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135
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Wang ZP, Ding XZ, Wang J, Li YM. Double-edged sword in cells: chemical biology studies of the vital role of cytochrome c in the intrinsic pre-apoptotic mitochondria leakage pathway. RSC Adv 2015. [DOI: 10.1039/c4ra16856a] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023] Open
Abstract
Besides functioning as an electron transporter in the mitochondrial electron transport chain, cytochrome c (cyt c) is also one of the determinants in the execution of cell death.
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Affiliation(s)
- Zhi-Peng Wang
- School of Medical Engineering
- Hefei University of Technology
- Hefei
- China
- Department of Chemistry
| | - Xiao-Zhe Ding
- Department of Chemistry
- School of Life Sciences
- Tsinghua University
- Beijing 100084
- China
| | - Jun Wang
- School of Medical Engineering
- Hefei University of Technology
- Hefei
- China
| | - Yi-Ming Li
- School of Medical Engineering
- Hefei University of Technology
- Hefei
- China
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136
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Levin BD, Walsh KA, Sullivan KK, Bren KL, Elliott SJ. Methionine ligand lability of homologous monoheme cytochromes c. Inorg Chem 2014; 54:38-46. [PMID: 25490149 DOI: 10.1021/ic501186h] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Direct electrochemical analysis of adsorbed bacterial monoheme cytochromes c has revealed a phenomenological loss of the axial methionine when examined using pyrolytic "edge-plane" graphite (EPG) electrodes. While prior findings have reported that the Met-loss state may be quantitatively understood using the cytochrome c from Hydrogenobacter thermophilus as a model system, here we demonstrate that the formation of the Met-loss state upon EPG electrodes can be observed for a range of cytochrome orthologs. Through an electrochemical comparison of the wild-type proteins from organisms of varying growth temperature optima, we establish that Met-ligand losses at graphite surfaces have similar energetics to the "foldons" for known protein folding pathways. Furthermore, a downward shift in reduction potential to approximately -100 mV vs standard hydrogen electrode was observed, similar to that of the alkaline transition found in mitochondrial cytochromes c. Pourbaix diagrams for the Met-loss forms of each cytochrome, considered here in comparison to mutants where the Met-ligand has been substituted to His or Ala, suggest that the nature of the Met-loss state is distinct from either a His-/aquo- or a bis-His-ligated heme center, yet more closely matches the pKa values found for bis-His-ligated hemes., We find the propensity for adoption of the Met-loss state in bacterial monoheme cytochromes c scales with their overall thermal stability, though not with the specific stability of the Fe-Met bond.
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Affiliation(s)
- Benjamin D Levin
- Department of Chemistry, Boston University , 590 Commonwealth Avenue, Boston, Massachusetts 02215, United States
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137
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Capdevila DA, Álvarez-Paggi D, Castro MA, Tórtora V, Demicheli V, Estrín DA, Radi R, Murgida DH. Coupling of tyrosine deprotonation and axial ligand exchange in nitrocytochrome c. Chem Commun (Camb) 2014; 50:2592-4. [PMID: 24471160 DOI: 10.1039/c3cc47207h] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
Here we report a spectroscopic, electrochemical and computational study of cytochrome c showing that nitration of Tyr74 induces Tyr deprotonation, which is coupled to Met/Lys axial ligand exchange, and results in concomitant gain of peroxidatic activity at physiological pH.
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Affiliation(s)
- Daiana A Capdevila
- Departamento de Química Inorgánica, Analítica y Química Física and INQUIMAE, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires-CONICET, Argentina.
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138
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Szeto HH, Liu S, Soong Y, Birk AV. Improving mitochondrial bioenergetics under ischemic conditions increases warm ischemia tolerance in the kidney. Am J Physiol Renal Physiol 2014; 308:F11-21. [PMID: 25339695 DOI: 10.1152/ajprenal.00366.2014] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
Ischemia time during partial nephrectomy is strongly associated with acute and chronic renal injury. ATP depletion during warm ischemia inhibits ATP-dependent processes, resulting in cell swelling, cytoskeletal breakdown, and cell death. The duration of ischemia tolerated by the kidney depends on the amount of ATP that can be produced with residual substrates and oxygen in the tissue to sustain cell function. We previously reported that the rat can tolerate 30-min ischemia quite well but 45-min ischemia results in acute kidney injury and progressive interstitial fibrosis. Here, we report that pretreatment with SS-20 30 min before warm ischemia in the rat increased ischemia tolerance from 30 to 45 min. Histological examination of kidney tissues revealed that SS-20 reduced cytoskeletal breakdown and cell swelling after 45-min ischemia. Electron microscopy showed that SS-20 reduced mitochondrial matrix swelling and preserved cristae membranes, suggesting that SS-20 enhanced mitochondrial ATP synthesis under ischemic conditions. Studies with isolated kidney mitochondria showed dramatic reduction in state 3 respiration and respiratory control ratio after 45-min ischemia, and this was significantly improved by SS-20 treatment. These results suggest that SS-20 increases efficiency of the electron transport chain and improves coupling of oxidative phosphorylation. SS-20 treatment after ischemia also significantly reduced interstitial fibrosis. These new findings reveal that enhancing mitochondrial bioenergetics may be an important target for improving ischemia tolerance, and SS-20 may serve well for minimizing acute kidney injury and chronic kidney disease following surgical procedures such as partial nephrectomy and transplantation.
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Affiliation(s)
- Hazel H Szeto
- Research Program in Mitochondrial Therapeutics, Department of Pharmacology, Joan and Sanford I. Weill Medical College of Cornell University, New York, New York
| | - Shaoyi Liu
- Research Program in Mitochondrial Therapeutics, Department of Pharmacology, Joan and Sanford I. Weill Medical College of Cornell University, New York, New York
| | - Yi Soong
- Research Program in Mitochondrial Therapeutics, Department of Pharmacology, Joan and Sanford I. Weill Medical College of Cornell University, New York, New York
| | - Alexander V Birk
- Research Program in Mitochondrial Therapeutics, Department of Pharmacology, Joan and Sanford I. Weill Medical College of Cornell University, New York, New York
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139
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Wu FG, Sun HY, Zhou Y, Wu RG, Yu ZW. Full picture of the thermotropic phase behavior of cardiolipin bilayer in water: identification of a metastable subgel phase. RSC Adv 2014. [DOI: 10.1039/c4ra09158b] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
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140
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Szeto HH, Birk AV. Serendipity and the discovery of novel compounds that restore mitochondrial plasticity. Clin Pharmacol Ther 2014; 96:672-83. [PMID: 25188726 DOI: 10.1038/clpt.2014.174] [Citation(s) in RCA: 124] [Impact Index Per Article: 12.4] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2014] [Accepted: 08/23/2014] [Indexed: 01/10/2023]
Abstract
The mitochondrial electron transport chain (ETC) plays a central role in energy generation in the cell. Mitochondrial dysfunctions diminish adenosine triphosphate (ATP) production and result in insufficient energy to maintain cell function. As energy output declines, the most energetic tissues are preferentially affected. To satisfy cellular energy demands, the mitochondrial ETC needs to be able to elevate its capacity to produce ATP at times of increased metabolic demand or decreased fuel supply. This mitochondrial plasticity is reduced in many age-associated diseases. In this review, we describe the serendipitous discovery of a novel class of compounds that selectively target cardiolipin on the inner mitochondrial membrane to optimize efficiency of the ETC and thereby restore cellular bioenergetics in aging and diverse disease models, without any effect on the normal healthy organism. The first of these compounds, SS-31, is currently in multiple clinical trials.
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Affiliation(s)
- H H Szeto
- Research Program in Mitochondrial Therapeutics, Department of Pharmacology, Weill Cornell Medical College, New York, New York, USA
| | - A V Birk
- Research Program in Mitochondrial Therapeutics, Department of Pharmacology, Weill Cornell Medical College, New York, New York, USA
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141
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Capdevila DA, Marmisollé WA, Tomasina F, Demicheli V, Portela M, Radi R, Murgida DH. Specific methionine oxidation of cytochrome c in complexes with zwitterionic lipids by hydrogen peroxide: potential implications for apoptosis. Chem Sci 2014; 6:705-713. [PMID: 30154994 PMCID: PMC6085654 DOI: 10.1039/c4sc02181a] [Citation(s) in RCA: 42] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2014] [Accepted: 09/01/2014] [Indexed: 11/21/2022] Open
Abstract
The rise of H2O2 concentration that characterizes the initiation of apoptosis can specifically oxidize Met80 in cytochrome c bound to zwitterionic phospholipids, yielding a stable peroxidase.
Cytochrome c (Cyt-c) has been previously shown to participate in cardiolipin (CL) oxidation and, therefore, in mitochondrial membrane permeabilization during the early events of apoptosis. The gain in this function has been ascribed to specific CL/Cyt-c interactions. Here we report that the cationic protein Cyt-c is also able to interact electrostatically with the main lipid components of the mitochondrial membranes, the zwitterionic lipids phosphatidylcholine (PC) and phosphatidylethanolamine (PE), through the mediation of phosphate anions that bind specifically to amino groups in the surfaces of protein and model membranes. In these complexes, Cyt-c reacts efficiently with H2O2 at submillimolar levels, which oxidizes the sulfur atom of the axial ligand Met80. The modified protein is stable and presents significantly enhanced peroxidatic activity. Based on these results, we postulate that the rise of H2O2 concentrations to the submillimolar levels registered during initiation of the apoptotic program may represent one signaling event that triggers the gain in peroxidatic function of the Cyt-c molecules bound to the abundant PE and PC membrane components. As the activated protein is a chemically stable species, it can potentially bind and oxidize important targets, such as CL.
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Affiliation(s)
- Daiana A Capdevila
- 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 , C1428EHA-Buenos Aires , Argentina .
| | - Waldemar A Marmisollé
- 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 , C1428EHA-Buenos Aires , Argentina .
| | - Florencia Tomasina
- Departamento de Bioquímica and Center for Free Radical and Biomedical Research , Facultad de Medicina , Universidad de la República , Montevideo , Uruguay
| | - Verónica Demicheli
- Departamento de Bioquímica and Center for Free Radical and Biomedical Research , Facultad de Medicina , Universidad de la República , Montevideo , Uruguay
| | - Magdalena Portela
- Unidad de Bioquímica y Proteómica Analíticas , Institut Pasteur de Montevideo , Montevideo , Uruguay
| | - Rafael Radi
- Departamento de Bioquímica and Center for Free Radical and Biomedical Research , Facultad de Medicina , Universidad de la República , Montevideo , 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 , C1428EHA-Buenos Aires , Argentina .
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142
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Cytochrome c: A Multifunctional Protein Combining Conformational Rigidity with Flexibility. ACTA ACUST UNITED AC 2014. [DOI: 10.1155/2014/484538] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Cytochrome has served as a model system for studying redox reactions, protein folding, and more recently peroxidase activity induced by partial unfolding on membranes. This review illuminates some important aspects of the research on this biomolecule. The first part summarizes the results of structural analyses of its active site. Owing to heme-protein interactions the heme group is subject to both in-plane and out-of-plane deformations. The unfolding of the protein as discussed in detail in the second part of this review can be induced by changes of pH and temperature and most prominently by the addition of denaturing agents. Both the kinetic and thermodynamic folding and unfolding involve intermediate states with regard to all unfolding conditions. If allowed to sit at alkaline pH (11.5) for a week, the protein does not return to its folding state when the solvent is switched back to neutral pH. It rather adopts a misfolded state that is prone to aggregation via domain swapping. On the surface of cardiolipin containing liposomes, the protein can adopt a variety of partially unfolded states. Apparently, ferricytochrome c can perform biological functions even if it is only partially folded.
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143
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Jiang J, Bakan A, Kapralov AA, Ishara Silva K, Huang Z, Amoscato AA, Peterson J, Krishna Garapati V, Saxena S, Bayir H, Atkinson J, Bahar I, Kagan VE. Designing inhibitors of cytochrome c/cardiolipin peroxidase complexes: mitochondria-targeted imidazole-substituted fatty acids. Free Radic Biol Med 2014; 71:221-230. [PMID: 24631490 PMCID: PMC4216591 DOI: 10.1016/j.freeradbiomed.2014.02.029] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/20/2013] [Revised: 02/27/2014] [Accepted: 02/28/2014] [Indexed: 01/17/2023]
Abstract
Mitochondria have emerged as the major regulatory platform responsible for the coordination of numerous metabolic reactions as well as cell death processes, whereby the execution of intrinsic apoptosis includes the production of reactive oxygen species fueling oxidation of cardiolipin (CL) catalyzed by cytochrome (Cyt) c. As this oxidation occurs within the peroxidase complex of Cyt c with CL, the latter represents a promising target for the discovery and design of drugs with antiapoptotic mechanisms of action. In this work, we designed and synthesized a new group of mitochondria-targeted imidazole-substituted analogs of stearic acid TPP-n-ISAs with various positions of the attached imidazole group on the fatty acid (n = 6, 8, 10, 13, and 14). By using a combination of absorption spectroscopy and EPR protocols (continuous wave electron paramagnetic resonance and electron spin echo envelope modulation) we demonstrated that TPP-n-ISAs indeed were able to potently suppress CL-induced structural rearrangements in Cyt c, paving the way to its peroxidase competence. TPP-n-ISA analogs preserved the low-spin hexa-coordinated heme-iron state in Cyt c/CL complexes whereby TPP-6-ISA displayed a significantly more effective preservation pattern than TPP-14-ISA. Elucidation of these intermolecular stabilization mechanisms of Cyt c identified TPP-6-ISA as an effective inhibitor of the peroxidase function of Cyt c/CL complexes with a significant antiapoptotic potential realized in mouse embryonic cells exposed to ionizing irradiation. These experimental findings were detailed and supported by all-atom molecular dynamics simulations. Based on the experimental data and computation predictions, we identified TPP-6-ISA as a candidate drug with optimized antiapoptotic potency.
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Affiliation(s)
- Jianfei Jiang
- Center for Free Radical and Antioxidant Health and Center for Medical Countermeasures against Radiation, University of Pittsburgh, Pittsburgh, PA 15219, USA; Department of Environmental and Occupational Health, University of Pittsburgh, Pittsburgh, PA 15219, USA
| | - Ahmet Bakan
- Department of Computational and System Biology, University of Pittsburgh, Pittsburgh, PA 15219, USA
| | - Alexandr A Kapralov
- Center for Free Radical and Antioxidant Health and Center for Medical Countermeasures against Radiation, University of Pittsburgh, Pittsburgh, PA 15219, USA; Department of Environmental and Occupational Health, University of Pittsburgh, Pittsburgh, PA 15219, USA
| | - K Ishara Silva
- Department of Chemistry, University of Pittsburgh, Pittsburgh, PA 15219, USA
| | - Zhentai Huang
- Center for Free Radical and Antioxidant Health and Center for Medical Countermeasures against Radiation, University of Pittsburgh, Pittsburgh, PA 15219, USA; Department of Environmental and Occupational Health, University of Pittsburgh, Pittsburgh, PA 15219, USA
| | - Andrew A Amoscato
- Center for Free Radical and Antioxidant Health and Center for Medical Countermeasures against Radiation, University of Pittsburgh, Pittsburgh, PA 15219, USA; Department of Environmental and Occupational Health, University of Pittsburgh, Pittsburgh, PA 15219, USA
| | - James Peterson
- Department of Environmental and Occupational Health, University of Pittsburgh, Pittsburgh, PA 15219, USA
| | - Venkata Krishna Garapati
- Department of Chemistry & Centre for Biotechnology, Brock University, St. Catharines, ON L2S 3A1, Canada
| | - Sunil Saxena
- Department of Chemistry, University of Pittsburgh, Pittsburgh, PA 15219, USA
| | - Hülya Bayir
- Center for Free Radical and Antioxidant Health and Center for Medical Countermeasures against Radiation, University of Pittsburgh, Pittsburgh, PA 15219, USA; Department of Environmental and Occupational Health, University of Pittsburgh, Pittsburgh, PA 15219, USA; Department of Critical Care Medicine, University of Pittsburgh, Pittsburgh, PA 15219, USA
| | - Jeffrey Atkinson
- Department of Chemistry & Centre for Biotechnology, Brock University, St. Catharines, ON L2S 3A1, Canada
| | - Ivet Bahar
- Department of Computational and System Biology, University of Pittsburgh, Pittsburgh, PA 15219, USA
| | - Valerian E Kagan
- Center for Free Radical and Antioxidant Health and Center for Medical Countermeasures against Radiation, University of Pittsburgh, Pittsburgh, PA 15219, USA; Department of Environmental and Occupational Health, University of Pittsburgh, Pittsburgh, PA 15219, USA; Department of Chemistry, University of Pittsburgh, Pittsburgh, PA 15219, USA; Department of Pharmacology and Chemical Biology, and University of Pittsburgh, Pittsburgh, PA 15219, USA; Department of Radiation Oncology, University of Pittsburgh, Pittsburgh, PA 15219, USA.
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144
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Structure of a mitochondrial cytochrome c conformer competent for peroxidase activity. Proc Natl Acad Sci U S A 2014; 111:6648-53. [PMID: 24760830 DOI: 10.1073/pnas.1323828111] [Citation(s) in RCA: 88] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
At the onset of apoptosis, the peroxidation of cardiolipin at the inner mitochondrial membrane by cytochrome c requires an open coordination site on the heme. We report a 1.45-Å resolution structure of yeast iso-1-cytochrome c with the Met80 heme ligand swung out of the heme crevice and replaced by a water molecule. This conformational change requires modest adjustments to the main chain of the heme crevice loop and is facilitated by a trimethyllysine 72-to-alanine mutation. This mutation also enhances the peroxidase activity of iso-1-cytochrome c. The structure shows a buried water channel capable of facilitating peroxide access to the active site and of moving protons produced during peroxidase activity to the protein surface. Alternate positions of the side chain of Arg38 appear to mediate opening and closing of the buried water channel. In addition, two buried water molecules can adopt alternate positions that change the network of hydrogen bonds in the buried water channel. Taken together, these observations suggest that low and high proton conductivity states may mediate peroxidase function. Comparison of yeast and mammalian cytochrome c sequences, in the context of the steric factors that permit opening of the heme crevice, suggests that higher organisms have evolved to inhibit peroxidase activity, providing a more stringent barrier to the onset of apoptosis.
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145
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Szeto HH. First-in-class cardiolipin-protective compound as a therapeutic agent to restore mitochondrial bioenergetics. Br J Pharmacol 2014; 171:2029-50. [PMID: 24117165 PMCID: PMC3976620 DOI: 10.1111/bph.12461] [Citation(s) in RCA: 360] [Impact Index Per Article: 36.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2013] [Revised: 09/06/2013] [Accepted: 10/01/2013] [Indexed: 12/16/2022] Open
Abstract
A decline in energy is common in aging, and the restoration of mitochondrial bioenergetics may offer a common approach for the treatment of numerous age-associated diseases. Cardiolipin is a unique phospholipid that is exclusively expressed on the inner mitochondrial membrane where it plays an important structural role in cristae formation and the organization of the respiratory complexes into supercomplexes for optimal oxidative phosphorylation. The interaction between cardiolipin and cytochrome c determines whether cytochrome c acts as an electron carrier or peroxidase. Cardiolipin peroxidation and depletion have been reported in a variety of pathological conditions associated with energy deficiency, and cardiolipin has been identified as a target for drug development. This review focuses on the discovery and development of the first cardiolipin-protective compound as a therapeutic agent. SS-31 is a member of the Szeto-Schiller (SS) peptides known to selectively target the inner mitochondrial membrane. SS-31 binds selectively to cardiolipin via electrostatic and hydrophobic interactions. By interacting with cardiolipin, SS-31 prevents cardiolipin from converting cytochrome c into a peroxidase while protecting its electron carrying function. As a result, SS-31 protects the structure of mitochondrial cristae and promotes oxidative phosphorylation. SS-31 represents a new class of compounds that can recharge the cellular powerhouse and restore bioenergetics. Extensive animal studies have shown that targeting such a fundamental mechanism can benefit highly complex diseases that share a common pathogenesis of bioenergetics failure. This review summarizes the mechanisms of action and therapeutic potential of SS-31 and provides an update of its clinical development programme.
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Affiliation(s)
- Hazel H Szeto
- Research Program in Mitochondrial Therapeutics, Department of Pharmacology, Joan and Sanford I. Weill Medical College of Cornell UniversityNew York, NY, USA
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Birk AV, Chao WM, Bracken C, Warren JD, Szeto HH. Targeting mitochondrial cardiolipin and the cytochrome c/cardiolipin complex to promote electron transport and optimize mitochondrial ATP synthesis. Br J Pharmacol 2014; 171:2017-28. [PMID: 24134698 PMCID: PMC3976619 DOI: 10.1111/bph.12468] [Citation(s) in RCA: 214] [Impact Index Per Article: 21.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2013] [Revised: 09/19/2013] [Accepted: 10/09/2013] [Indexed: 12/11/2022] Open
Abstract
BACKGROUND AND PURPOSE Cardiolipin plays an important role in mitochondrial respiration and cardiolipin peroxidation is associated with age-related diseases. Hydrophobic interactions between cytochrome c and cardiolipin converts cytochrome c from an electron carrier to a peroxidase. In addition to cardiolipin peroxidation, this impedes electron flux and inhibits mitochondrial ATP synthesis. SS-31 (D-Arg-dimethylTyr-Lys-Phe-NH2 ) selectively binds to cardiolipin and inhibits cytochrome c peroxidase activity. Here, we examined whether SS-31 also protected the electron carrier function of cytochrome c. EXPERIMENTAL APPROACH Interactions of SS-31 with cardiolipin were studied using liposomes and bicelles containing phosphatidylcholine alone or with cardiolipin. Structural interactions were assessed by fluorescence spectroscopy, turbidity and nuclear magnetic resonance. Effects of cardiolipin on electron transfer kinetics of cytochrome c were determined by cytochrome c reduction in vitro and oxygen consumption using mitoplasts, frozen and fresh mitochondria. KEY RESULTS SS-31 interacted only with liposomes and bicelles containing cardiolipin in about 1:1 ratio. NMR studies demonstrated that the aromatic residues of SS-31 penetrated deep into cardiolipin-containing bilayers. SS-31 restored cytochrome c reduction and mitochondrial oxygen consumption in the presence of added cardiolipin. In fresh mitochondria, SS-31 increased state 3 respiration and efficiency of ATP synthesis. CONCLUSIONS AND IMPLICATIONS SS-31 selectively targeted cardiolipin and modulated its interaction with cytochrome c. SS-31 inhibited the cytochrome c/cardiolipin complex peroxidase activity while protecting its ability to serve as an electron carrier, thus optimizing mitochondrial electron transport and ATP synthesis. This novel class of cardiolipin therapeutics has the potential to restore mitochondrial bioenergetics for treatment of numerous age-related diseases.
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Affiliation(s)
- A V Birk
- Department of Pharmacology, Joan and Sanford I. Weill Medical College of Cornell UniversityNew York, NY, USA
| | - W M Chao
- Department of Pharmacology, Joan and Sanford I. Weill Medical College of Cornell UniversityNew York, NY, USA
| | - C Bracken
- Department of Biochemistry, Joan and Sanford I. Weill Medical College of Cornell UniversityNew York, NY, USA
- Nuclear Magnetic Resonance Core Facility, Joan and Sanford I. Weill Medical College of Cornell UniversityNew York, NY, USA
| | - J D Warren
- Department of Biochemistry, Joan and Sanford I. Weill Medical College of Cornell UniversityNew York, NY, USA
- Milstein Chemistry Core Facility, Joan and Sanford I. Weill Medical College of Cornell UniversityNew York, NY, USA
| | - H H Szeto
- Department of Pharmacology, Joan and Sanford I. Weill Medical College of Cornell UniversityNew York, NY, USA
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147
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Enhancing the peroxidase activity of cytochrome c by mutation of residue 41: implications for the peroxidase mechanism and cytochrome c release. Biochem J 2014; 458:259-65. [DOI: 10.1042/bj20131386] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
Enzymatic and mitochondrial release analyses of residue 41 variants of native and cardiolipin-bound mammalian cytochromes c implicate mobility of the 40–57 Ω loop in induction of peroxidase activity, but show that loss of axial Fe co-ordination is not essential.
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148
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Junedi S, Yasuhara K, Nagao S, Kikuchi JI, Hirota S. Morphological Change of Cell Membrane by Interaction with Domain-Swapped CytochromecOligomers. Chembiochem 2014; 15:517-21. [DOI: 10.1002/cbic.201300728] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2013] [Indexed: 01/17/2023]
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149
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Redox-dependent stability, protonation, and reactivity of cysteine-bound heme proteins. Proc Natl Acad Sci U S A 2014; 111:E306-15. [PMID: 24398520 DOI: 10.1073/pnas.1317173111] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023] Open
Abstract
Cysteine-bound hemes are key components of many enzymes and biological sensors. Protonation (deprotonation) of the Cys ligand often accompanies redox transformations of these centers. To characterize these phenomena, we have engineered a series of Thr78Cys/Lys79Gly/Met80X mutants of yeast cytochrome c (cyt c) in which Cys78 becomes one of the axial ligands to the heme. At neutral pH, the protonation state of the coordinated Cys differs for the ferric and ferrous heme species, with Cys binding as a thiolate and a thiol, respectively. Analysis of redox-dependent stability and alkaline transitions of these model proteins, as well as comparisons to Cys binding studies with the minimalist heme peptide microperoxidase-8, demonstrate that the protein scaffold and solvent interactions play important roles in stabilizing a particular Cys-heme coordination. The increased stability of ferric thiolate compared with ferrous thiol arises mainly from entropic factors. This robust cyt c model system provides access to all four forms of Cys-bound heme, including the ferric thiol. Protein motions control the rates of heme redox reactions, and these effects are amplified at low pH, where the proteins are less stable. Thermodynamic signatures and redox reactivity of the model Cys-bound hemes highlight the critical role of the protein scaffold and its dynamics in modulating redox-linked transitions between thiols and thiolates.
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150
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Hough MA, Silkstone G, Worrall JAR, Wilson MT. NO binding to the proapoptotic cytochrome c-cardiolipin complex. VITAMINS AND HORMONES 2014; 96:193-209. [PMID: 25189388 DOI: 10.1016/b978-0-12-800254-4.00008-8] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Cytochrome c is a heme protein that is localized in the compartment between the inner and outer mitochondrial membranes where it functions to transfer electrons between complex III and complex IV of the respiratory chain. It can also form an intimate association with the mitochondrion-specific phospholipid cardiolipin that induces a conformational change in the protein enabling it to act as a peroxidase catalyzing the oxidation of cardiolipin and thereby instigating a chain of events that leads to apoptosis. Unlike the native protein, cytochrome c within the complex binds ligands rapidly; in particular, NO can coordinate to either the ferric or ferrous iron of the heme. Remarkably, in the ferrous form, NO binds preferentially to the proximal side of the heme and thus behaves in a way similar to cytochrome c'-type proteins and to guanylate cyclase. The implications of NO binding to the proapoptotic cytochrome c/cardiolipin complex are discussed in terms of modulating the apoptotic response and buffering NO concentrations. Insights into the structure of the complex are provided by comparison with cytochrome c' for which X-ray structures are available.
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Affiliation(s)
- Michael A Hough
- School of Biological Sciences, University of Essex, Colchester, United Kingdom
| | - Gary Silkstone
- School of Biological Sciences, University of Essex, Colchester, United Kingdom
| | - J A R Worrall
- School of Biological Sciences, University of Essex, Colchester, United Kingdom
| | - Michael T Wilson
- School of Biological Sciences, University of Essex, Colchester, United Kingdom.
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