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Di Trani JM, Moe A, Riepl D, Saura P, Kaila VRI, Brzezinski P, Rubinstein JL. Structural basis of mammalian complex IV inhibition by steroids. Proc Natl Acad Sci U S A 2022; 119:e2205228119. [PMID: 35858451 PMCID: PMC9335260 DOI: 10.1073/pnas.2205228119] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2022] [Accepted: 06/18/2022] [Indexed: 01/21/2023] Open
Abstract
The mitochondrial electron transport chain maintains the proton motive force that powers adenosine triphosphate (ATP) synthesis. The energy for this process comes from oxidation of reduced nicotinamide adenine dinucleotide (NADH) and succinate, with the electrons from this oxidation passed via intermediate carriers to oxygen. Complex IV (CIV), the terminal oxidase, transfers electrons from the intermediate electron carrier cytochrome c to oxygen, contributing to the proton motive force in the process. Within CIV, protons move through the K and D pathways during turnover. The former is responsible for transferring two protons to the enzyme's catalytic site upon its reduction, where they eventually combine with oxygen and electrons to form water. CIV is the main site for respiratory regulation, and although previous studies showed that steroid binding can regulate CIV activity, little is known about how this regulation occurs. Here, we characterize the interaction between CIV and steroids using a combination of kinetic experiments, structure determination, and molecular simulations. We show that molecules with a sterol moiety, such as glyco-diosgenin and cholesteryl hemisuccinate, reversibly inhibit CIV. Flash photolysis experiments probing the rapid equilibration of electrons within CIV demonstrate that binding of these molecules inhibits proton uptake through the K pathway. Single particle cryogenic electron microscopy (cryo-EM) of CIV with glyco-diosgenin reveals a previously undescribed steroid binding site adjacent to the K pathway, and molecular simulations suggest that the steroid binding modulates the conformational dynamics of key residues and proton transfer kinetics within this pathway. The binding pose of the sterol group sheds light on possible structural gating mechanisms in the CIV catalytic cycle.
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Affiliation(s)
- Justin M. Di Trani
- Molecular Medicine Program, The Hospital for Sick Children, Toronto, ON, Canada M5G 0A4
| | - Agnes Moe
- Department of Biochemistry and Biophysics, Arrhenius Laboratories for Natural Sciences, Stockholm University, SE-106 91 Stockholm, Sweden
| | - Daniel Riepl
- Department of Biochemistry and Biophysics, Arrhenius Laboratories for Natural Sciences, Stockholm University, SE-106 91 Stockholm, Sweden
| | - Patricia Saura
- Department of Biochemistry and Biophysics, Arrhenius Laboratories for Natural Sciences, Stockholm University, SE-106 91 Stockholm, Sweden
| | - Ville R. I. Kaila
- Department of Biochemistry and Biophysics, Arrhenius Laboratories for Natural Sciences, Stockholm University, SE-106 91 Stockholm, Sweden
| | - Peter Brzezinski
- Department of Biochemistry and Biophysics, Arrhenius Laboratories for Natural Sciences, Stockholm University, SE-106 91 Stockholm, Sweden
| | - John L. Rubinstein
- Molecular Medicine Program, The Hospital for Sick Children, Toronto, ON, Canada M5G 0A4
- Department of Medical Biophysics, University of Toronto, Toronto, ON, Canada M5G 1L7
- Department of Biochemistry, University of Toronto, Toronto, ON, Canada M5S 1A8
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Lee CQE, Kerouanton B, Chothani S, Zhang S, Chen Y, Mantri CK, Hock DH, Lim R, Nadkarni R, Huynh VT, Lim D, Chew WL, Zhong FL, Stroud DA, Schafer S, Tergaonkar V, St John AL, Rackham OJL, Ho L. Coding and non-coding roles of MOCCI (C15ORF48) coordinate to regulate host inflammation and immunity. Nat Commun 2021; 12:2130. [PMID: 33837217 PMCID: PMC8035321 DOI: 10.1038/s41467-021-22397-5] [Citation(s) in RCA: 45] [Impact Index Per Article: 15.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2020] [Accepted: 03/10/2021] [Indexed: 02/01/2023] Open
Abstract
Mito-SEPs are small open reading frame-encoded peptides that localize to the mitochondria to regulate metabolism. Motivated by an intriguing negative association between mito-SEPs and inflammation, here we screen for mito-SEPs that modify inflammatory outcomes and report a mito-SEP named "Modulator of cytochrome C oxidase during Inflammation" (MOCCI) that is upregulated during inflammation and infection to promote host-protective resolution. MOCCI, a paralog of the NDUFA4 subunit of cytochrome C oxidase (Complex IV), replaces NDUFA4 in Complex IV during inflammation to lower mitochondrial membrane potential and reduce ROS production, leading to cyto-protection and dampened immune response. The MOCCI transcript also generates miR-147b, which targets the NDUFA4 mRNA with similar immune dampening effects as MOCCI, but simultaneously enhances RIG-I/MDA-5-mediated viral immunity. Our work uncovers a dual-component pleiotropic regulation of host inflammation and immunity by MOCCI (C15ORF48) for safeguarding the host during infection and inflammation.
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Affiliation(s)
- Cheryl Q. E. Lee
- grid.414735.00000 0004 0367 4692Institute of Medical Biology, A*STAR, Singapore, Singapore
| | - Baptiste Kerouanton
- grid.428397.30000 0004 0385 0924Duke-NUS Medical School, Program in Cardiovascular and Metabolic Disorders, Singapore, Singapore
| | - Sonia Chothani
- grid.428397.30000 0004 0385 0924Duke-NUS Medical School, Program in Cardiovascular and Metabolic Disorders, Singapore, Singapore
| | - Shan Zhang
- grid.428397.30000 0004 0385 0924Duke-NUS Medical School, Program in Cardiovascular and Metabolic Disorders, Singapore, Singapore
| | - Ying Chen
- grid.418812.60000 0004 0620 9243Institute of Molecular and Cell Biology, A*STAR, Singapore, Singapore
| | - Chinmay Kumar Mantri
- grid.428397.30000 0004 0385 0924Duke-NUS Medical School, Program in Emerging Infectious Diseases, Singapore, Singapore
| | - Daniella Helena Hock
- grid.1008.90000 0001 2179 088XDepartment of Biochemistry and Molecular Biology, The Bio21 Molecular Science & Biotechnology Institute, University of Melbourne, Melbourne, VIC Australia
| | - Radiance Lim
- grid.428397.30000 0004 0385 0924Duke-NUS Medical School, Program in Cardiovascular and Metabolic Disorders, Singapore, Singapore
| | - Rhea Nadkarni
- grid.428397.30000 0004 0385 0924Duke-NUS Medical School, Program in Cardiovascular and Metabolic Disorders, Singapore, Singapore
| | - Vinh Thang Huynh
- grid.418812.60000 0004 0620 9243Institute of Molecular and Cell Biology, A*STAR, Singapore, Singapore ,grid.59025.3b0000 0001 2224 0361Lee Kong Chian School of Medicine, Nanyang Technological University Singapore, Singapore, Singapore
| | - Daryl Lim
- grid.418377.e0000 0004 0620 715XGenome Institute Singapore, A*STAR, Singapore, Singapore
| | - Wei Leong Chew
- grid.418377.e0000 0004 0620 715XGenome Institute Singapore, A*STAR, Singapore, Singapore
| | - Franklin L. Zhong
- grid.59025.3b0000 0001 2224 0361Nanyang Technological University, Skin Diseases and Wound Repair Program, Singapore, Singapore ,grid.185448.40000 0004 0637 0221Skin Research Institute of Singapore, A*STAR, Singapore, Singapore
| | - David Arthur Stroud
- grid.1008.90000 0001 2179 088XDepartment of Biochemistry and Molecular Biology, The Bio21 Molecular Science & Biotechnology Institute, University of Melbourne, Melbourne, VIC Australia
| | - Sebastian Schafer
- grid.428397.30000 0004 0385 0924Duke-NUS Medical School, Program in Cardiovascular and Metabolic Disorders, Singapore, Singapore ,grid.419385.20000 0004 0620 9905National Heart Research Institute Singapore, National Heart Centre Singapore, Singapore, Singapore
| | - Vinay Tergaonkar
- grid.418812.60000 0004 0620 9243Institute of Molecular and Cell Biology, A*STAR, Singapore, Singapore ,grid.4280.e0000 0001 2180 6431Department of Pathology, Yong Loo Lin School of Medicine, National University of Singapore, Singapore, Singapore
| | - Ashley L. St John
- grid.428397.30000 0004 0385 0924Duke-NUS Medical School, Program in Emerging Infectious Diseases, Singapore, Singapore ,grid.4280.e0000 0001 2180 6431Department of Microbiology and Immunology, Yong Loo Lin School of Medicine, National University of Singapore, Singapore, Singapore ,grid.189509.c0000000100241216Department of Pathology, Duke University Medical Center, Durham, NC USA
| | - Owen J. L. Rackham
- grid.428397.30000 0004 0385 0924Duke-NUS Medical School, Program in Cardiovascular and Metabolic Disorders, Singapore, Singapore
| | - Lena Ho
- grid.414735.00000 0004 0367 4692Institute of Medical Biology, A*STAR, Singapore, Singapore ,grid.428397.30000 0004 0385 0924Duke-NUS Medical School, Program in Cardiovascular and Metabolic Disorders, Singapore, Singapore ,grid.418812.60000 0004 0620 9243Institute of Molecular and Cell Biology, A*STAR, Singapore, Singapore
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The Interplay among Subunit Composition, Cardiolipin Content, and Aggregation State of Bovine Heart Cytochrome c Oxidase. Cells 2020; 9:cells9122588. [PMID: 33287231 PMCID: PMC7761698 DOI: 10.3390/cells9122588] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2020] [Revised: 11/24/2020] [Accepted: 12/01/2020] [Indexed: 02/07/2023] Open
Abstract
Mitochondrial cytochrome c oxidase (CcO) is a multisubunit integral membrane complex consisting of 13 dissimilar subunits, as well as three to four tightly bound molecules of cardiolipin (CL). The monomeric unit of CcO is able to form a dimer and participate in the formation of supercomplexes in the inner mitochondrial membrane. The structural and functional integrity of the enzyme is crucially dependent on the full subunit complement and the presence of unperturbed bound CL. A direct consequence of subunit loss, CL removal, or its oxidative modification is the destabilization of the quaternary structure, loss of the activity, and the inability to dimerize. Thus, the intimate interplay between individual components of the complex is imperative for regulation of the CcO aggregation state. While it appears that the aggregation state of CcO might affect its conformational stability, the functional role of the aggregation remains unclear as both monomeric and dimeric forms of CcO seem to be fully active. Here, we review the current status of our knowledge with regard to the role of dimerization in the function and stability of CcO and factors, such as subunit composition, amphiphilic environment represented by phospholipids/detergents, and posttranslational modifications that play a role in the regulation of the CcO aggregation state.
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Individual biochemical behaviour versus biological robustness: spotlight on the regulation of cytochrome c oxidase. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2012; 748:265-81. [PMID: 22729862 DOI: 10.1007/978-1-4614-3573-0_11] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
During evolution from prokaryotes to eukaryotes, the main function of cytochrome c oxidase (COX), i.e., the coupling of oxygen reduction to proton translocation without the production of ROS (reactive oxygen species) remained unchanged demonstrating its robustness. A new regulation of respiration by the ATP/ADP ratio was introduced in eukaryotes based on nucleotide interaction with the added COX subunit IV. This allosteric ATP-inhibition was proposed to keep the mitochondrial membrane potential (ΔΨ(m)) at low healthy values and thus prevents the formation of ROS at complexes I and III. ROS have been implicated in various degenerative diseases. The allosteric ATP-inhibition of COX is reversibly switched on and off by phosphorylation of COX at a serine or threonine. In more than 100 individual preparations of rat heart and liver mitochondria, prepared under identical conditions, the extent of allosteric ATP-inhibition varied. This variability correlates with the variable inhibition of uncoupled respiration in intact isolated mitochondria by ATP. It is concluded that in higher organisms the allosteric ATP-inhibition is continually switched on and off by neuronal signalling in order to change oxidative phosphorylation from optimal efficiency with lower rate of ATP synthesis under resting conditions (low ΔΨ(m) and ROS production) to maximal rate of ATP synthesis under active (working, stress) conditions (elevated ΔΨ(m) and ROS production).
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Martin LJ, Brambrink AM, Price AC, Kaiser A, Agnew DM, Ichord RN, Traystman RJ. Neuronal death in newborn striatum after hypoxia-ischemia is necrosis and evolves with oxidative stress. Neurobiol Dis 2000; 7:169-91. [PMID: 10860783 DOI: 10.1006/nbdi.2000.0282] [Citation(s) in RCA: 115] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The mechanisms for neurodegeneration after hypoxia-ischemia (HI) in newborns are not understood. We tested the hypothesis that striatal neuron death is necrosis and evolves with oxidative stress and selective organelle damage. Piglets ( approximately 1 week old) were used in a model of hypoxia-asphyxia and survived for 3, 6, 12, or 24 h. Neuronal death was progressive over 3-24 h recovery, with approximately 80% of putaminal neurons dead at 24 h. Striatal DNA was digested randomly at 6-12 h. Ultrastructurally, dying neurons were necrotic. Damage to the Golgi apparatus and rough endoplasmic reticulum occurred at 3-12 h, while most mitochondria appeared intact until 12 h. Mitochondria showed early suppression of activity, then a transient burst of activity at 6 h, followed by mitochondrial failure (determined by cytochrome c oxidase assay). Cytochrome c was depleted at 6 h after HI and thereafter. Damage to lysosomes occurred within 3-6 h. By 3 h recovery, glutathione levels were reduced, and peroxynitrite-mediated oxidative damage to membrane proteins, determined by immunoblots for nitrotyrosine, occurred at 3-12 h. The Golgi apparatus and cytoskeleton were early targets for extensive tyrosine nitration. Striatal neurons also sustained hydroxyl radical damage to DNA and RNA within 6 h after HI. We conclude that early glutathione depletion and oxidative stress between 3 and 6 h reperfusion promote damage to membrane and cytoskeletal proteins, DNA and RNA, as well as damage to most organelles, thereby causing neuronal necrosis in the striatum of newborns after HI.
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Affiliation(s)
- L J Martin
- Department of Pathology, Division of Neuropathy, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA.
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Kadenbach B, Napiwotzki J, Frank V, Arnold S, Exner S, Hüttemann M. Regulation of energy transduction and electron transfer in cytochrome c oxidase by adenine nucleotides. J Bioenerg Biomembr 1998; 30:25-33. [PMID: 9623802 DOI: 10.1023/a:1020599209468] [Citation(s) in RCA: 23] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Cytochrome c oxidase from bovine heart contains seven high-affinity binding sites for ATP or ADP and three additional only for ADP. One binding site for ATP or ADP, located at the matrix-oriented domain of the heart-type subunit VIaH, increases the H+/e- stoichiometry of the enzyme from heart or skeletal muscle from 0.5 to 1.0 when bound ATP is exchanged by ADP. Two further binding sites for ATP or ADP, located at the cytosolic and the matrix domain of subunit IV, increases the K(M) for cytochrome c and inhibit the respiratory activity at high ATP/ADP ratios, respectively. We propose that thermogenesis in mammals is related to subunit VIaL of cytochrome c oxidase with a H+/e- stoichiometry of 0.5 compared to 1.0 in the enzyme from bacteria or ectotherm animals. This hypothesis is supported by the lack of subunit VIa isoforms in cytochrome c oxidase from fish.
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Affiliation(s)
- B Kadenbach
- Fachbereich Chemie, Philipps-Universität, Marburg, Germany
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Arnold S, Kadenbach B. Cell respiration is controlled by ATP, an allosteric inhibitor of cytochrome-c oxidase. EUROPEAN JOURNAL OF BIOCHEMISTRY 1997; 249:350-4. [PMID: 9363790 DOI: 10.1111/j.1432-1033.1997.t01-1-00350.x] [Citation(s) in RCA: 185] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
The activity of cytochrome-c oxidase, the terminal enzyme of the mitochondrial respiratory chain, is known to be regulated by the substrate pressure, i.e. the ferro-/ferricytochrome c ratio, by the oxygen concentration, and by the electrochemical proton gradient delta muH+ across the inner mitochondrial membrane. Here we describe a further mechanism of 'respiratory control' via allosteric inhibition of cytochrome-c oxidase by ATP, which binds to the matrix domain, of subunit IV. The cooperativity between cytochrome-c-binding sites in the dimeric enzyme complex is mediated by cardiolipin, which is essential for cooperativity of the enzyme within the lipid membrane.
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Affiliation(s)
- S Arnold
- Fachbereich Chemie, Philipps-Universität, Marburg, Germany
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Napiwotzki J, Shinzawa-Itoh K, Yoshikawa S, Kadenbach B. ATP and ADP bind to cytochrome c oxidase and regulate its activity. Biol Chem 1997; 378:1013-21. [PMID: 9348111 DOI: 10.1515/bchm.1997.378.9.1013] [Citation(s) in RCA: 84] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
By equilibrium dialysis of cytochrome c oxidase from bovine heart with [35S]ATPalphaS and [35S]ADPalphaS, seven binding sites for ATP and ten for ADP were determined per monomer of the isolated enzyme. The binding of ATP occurs in a time-dependent manner, as shown by a filtration method, which is apparently due to slow exchange of bound cholate. In the crystallized enzyme 10 mol of cholate were determined and partly identified in the high resolution crystal structure. Binding of ADP leads to conformational changes of the Tween 20-solubilized enzyme, as shown by a 12% decrease of the gamma-band. The conformational change is specific for ADP, since CDP, GDP and UDP showed no effects. The spectral changes are not obtained with the dodecylmaltoside solubilized enzyme. The polarographically measured activity of cytochrome c oxidase is lower after preincubation with high ATP/ADP-ratios than with low, in the presence of Tween 20. This effect of nucleotides is due to interaction with subunit IV, because preincubation of the enzyme with a monoclonal antibody to subunit IV released the inhibition by ATP. In the presence of dodecylmaltoside the enzyme had a 2 to 3-fold higher total activity, but this activity was not influenced by preincubation with ATP or ADP.
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Affiliation(s)
- J Napiwotzki
- Fachbereich Chemie, Philipps-Universität, Marburg, Germany
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Freedman JA, Dyer B, Tattrie B, Nicholls P. The effect of antibodies to subunit V of cytochrome oxidase on cyanide inhibition of electron transfer. BIOCHIMICA ET BIOPHYSICA ACTA 1993; 1164:138-42. [PMID: 8392373 DOI: 10.1016/0167-4838(93)90240-r] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
Binding of antibodies raised against subunit V of mammalian cytochrome oxidase to the intact membranous enzyme is redox-sensitive, suggesting the existence of 'open' and 'closed' protein conformers (Freedman, J.A., Cooper, C.E., Leece, B., Nicholls, P. and Chan, S.H.P. (1988) Biochem. Cell Biol. 66, 1210-1217). Similar open and closed states for the oxygen-reacting site have been proposed to explain cyanide binding kinetics (Jensen, P., Wilson, M.T., Aasa, R. and Malmström, B.G. (1984) Biochem. J. 224, 829-837). We therefore examined cyanide inhibition of oxidase activity polarographically and spectrophotometrically using soluble oxidase preincubated with and without anti-subunit V or non-immune rabbit gamma-globulin. The subunit-specific antibody decreased the cyanide 'on' rate and essentially eliminated the rapid phase of cyanide binding. We conclude that (i), bound antibody blocks HCN binding; (ii), antibody and HCN probably bind to the same conformation of the oxidase and (iii), the 'open'-'closed' conformation change that modulates binding of HCN may be similar to that which modulates antibody binding. The results are consistent with some reciprocating models of electron transfer and energy transduction by the oxidase (cf., Wikström, M.K.F., Krab, K. and Saraste, M. (1981) Cytochrome Oxidase: A Synthesis).
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Supramolecular membrane protein assemblies in photosynthesis and respiration. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 1993. [DOI: 10.1016/0005-2728(93)90039-i] [Citation(s) in RCA: 23] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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Chervin C, Thibaud MC. Inhibition of plant and animal cytochrome oxidases by nitrous oxide as a function of cytochrome c concentration. Biochimie 1992; 74:1125-7. [PMID: 1337983 DOI: 10.1016/0300-9084(92)90012-4] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
Cytochrome oxidase from both pea leaves and bovine heart shows lower activity under a mixture of 79% N2O/21% O2 than under ambient air. This inhibition is not detectable below 5 microM cytochrome c but appears with increasing concentrations of cytochrome c. These results suggest that the N2O-induced inhibition of cytochrome c oxidase is modulated by cytochrome c concentration. This seems to concern only the lowest affinity site of the oxidase. Apparently, N2O and cytochrome c do not share the same site of fixation on the oxidase.
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Affiliation(s)
- C Chervin
- Département de Physiologie Végétale et Ecosystèmes, Centre d'Etudes de Cadarache, Saint-Paul-lez-Durance, France
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Long RC, Hawkridge FM, Chlebowski JF, Hartzell CR. The temperature dependence and thermal denaturation of the cytochrome c/cytochrome c oxidase/dioxygen system: an electrochemical investigation. ACTA ACUST UNITED AC 1988. [DOI: 10.1016/0022-0728(88)85011-3] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
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13
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Site-directed cross-linking. Establishing the dimeric structure of the aspartate receptor of bacterial chemotaxis. J Biol Chem 1988. [DOI: 10.1016/s0021-9258(18)68781-2] [Citation(s) in RCA: 182] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
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Hakvoort TB, Moolenaar K, Lankvelt AH, Sinjorgo KM, Dekker HL, Muijsers AO. Separation, stability and kinetics of monomeric and dimeric bovine heart cytochrome c oxidase. BIOCHIMICA ET BIOPHYSICA ACTA 1987; 894:347-54. [PMID: 2825776 DOI: 10.1016/0005-2728(87)90112-5] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
The stability of monomeric and dimeric bovine heart cytochrome c oxidase in laurylmaltoside-containing buffers of high ionic strength allowed separation of the two forms by gel-filtration high-performance liquid chromatography (HPLC). A solution of the dimeric oxidase could be diluted without monomerisation. Both monomeric and dimeric cytochrome c oxidase showed biphasic steady-state kinetics when assayed spectrophotometrically at low ionic strength. Thus, the biphasic kinetics did not result from negative cooperativity between the two adjacent cytochrome c binding sites of the monomers constituting the dimeric oxidase. On polyacrylamide gels in the presence of sodium dodecyl sulphate (SDS) a fraction of subunit III of the dimeric enzyme migrated as a dimer, a phenomenon not seen with the monomeric enzyme. This might suggest that in the dimeric oxidase subunit III lies on the contact surface between the protomers. If so, the presumably hydrophobic interaction between the two subunits III resisted dissociation by SDS to some extent. Addition of sufficient ascorbate and cytochrome c to the monomeric oxidase to allow a few turnovers induced slow dimerisation (on a time-scale of hours). This probably indicates that one of the transient forms arising upon reoxidation of the reduced enzyme is more easily converted to the dimeric state than the resting enzyme. Gel-filtration HPLC proved to be a useful step in small-scale purification of cytochrome c oxidase. In the presence of laurylmaltoside the monomeric oxidase eluted after the usual trace contaminants, the dimeric Complex III and the much larger Complex I. The procedure is fast and non-denaturing, although limited by the capacity of available columns.
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Affiliation(s)
- T B Hakvoort
- Laboratory of Biochemistry, University of Amsterdam, The Netherlands
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15
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Structure of Cytochrome-c Oxidase. CURRENT TOPICS IN BIOENERGETICS - STRUCTURE, BIOGENESIS, AND ASSEMBLY OF ENERGY TRANSDUCING ENZYME SYSTEMS 1987. [DOI: 10.1016/b978-0-12-152515-6.50008-4] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
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Bolli R, Nałecz KA, Azzi A. Cytochrome c oxidase from Paracoccus denitrificans in Triton X-100: aggregation state and kinetics. J Bioenerg Biomembr 1986; 18:277-84. [PMID: 3017928 DOI: 10.1007/bf00743048] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
Cytochrome c oxidase from Paracoccus denitrificans was homogeneously dispersed in Triton X-100. Using gel exclusion chromatography and sucrose gradient centrifugation analysis a molecular weight of the detergent-protein complex of 155,000 was determined. After subtraction of the bound detergent (111 mol/mol heme aa3) a molecular weight of 85,000 resulted, which agreed well with the model of a monomer containing two subunits. This monomer showed high cytochrome c oxidase activity when measured spectrophotometrically in the presence of Triton X-100 (Vmax = 85 s-1). The molecular activity, plotted according to Eadie-Hofstee, was monophasic as a function of the cytochrome c concentration. A Km of 3.6 X 10(-6) M was evaluated, similar to the Km observed in the presence of dodecyl maltoside [Nałecz et al. (1985).
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