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Sarti P, Forte E, Mastronicola D, Giuffrè A, Arese M. Cytochrome c oxidase and nitric oxide in action: molecular mechanisms and pathophysiological implications. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2011; 1817:610-9. [PMID: 21939634 DOI: 10.1016/j.bbabio.2011.09.002] [Citation(s) in RCA: 340] [Impact Index Per Article: 26.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/28/2011] [Revised: 09/06/2011] [Accepted: 09/07/2011] [Indexed: 11/18/2022]
Abstract
BACKGROUND The reactions between Complex IV (cytochrome c oxidase, CcOX) and nitric oxide (NO) were described in the early 60's. The perception, however, that NO could be responsible for physiological or pathological effects, including those on mitochondria, lags behind the 80's, when the identity of the endothelial derived relaxing factor (EDRF) and NO synthesis by the NO synthases were discovered. NO controls mitochondrial respiration, and cytotoxic as well as cytoprotective effects have been described. The depression of OXPHOS ATP synthesis has been observed, attributed to the inhibition of mitochondrial Complex I and IV particularly, found responsible of major effects. SCOPE OF REVIEW The review is focused on CcOX and NO with some hints about pathophysiological implications. The reactions of interest are reviewed, with special attention to the molecular mechanisms underlying the effects of NO observed on cytochrome c oxidase, particularly during turnover with oxygen and reductants. MAJOR CONCLUSIONS AND GENERAL SIGNIFICANCE The NO inhibition of CcOX is rapid and reversible and may occur in competition with oxygen. Inhibition takes place following two pathways leading to formation of either a relatively stable nitrosyl-derivative (CcOX-NO) of the enzyme reduced, or a more labile nitrite-derivative (CcOX-NO(2)(-)) of the enzyme oxidized, and during turnover. The pathway that prevails depends on the turnover conditions and concentration of NO and physiological substrates, cytochrome c and O(2). All evidence suggests that these parameters are crucial in determining the CcOX vs NO reaction pathway prevailing in vivo, with interesting physiological and pathological consequences for cells.
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Affiliation(s)
- Paolo Sarti
- Department of Biochemical Sciences, Sapienza University of Rome, Italy.
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Zhang J, Guan P, Wang T, Chang D, Jiang T, Wang S. Freeze-dried liposomes as potential carriers for ocular administration of cytochrome c against selenite cataract formation. J Pharm Pharmacol 2010. [DOI: 10.1211/jpp.61.09.0006] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/31/2022]
Abstract
Abstract
Objectives
In this study, the preparation, stability and anti-cataract effect of cationic freeze-dried liposomes containing cytochrome c, along with nicotinamide and adenosine, are described.
Methods
Cytochrome c-loaded cationic liposomes (CC-L) were prepared by the thin-layer evaporation technique and lyophilized to obtain freeze-dried cytochrome c liposomes (CC-F). The influence of the preparation components on the liposomal encapsulation efficiency and the stability were studied. The anti-cataract effect of the CC-F was demonstrated through attenuating lens opacity development with slit lamp examination in rats with selenite-induced cataract.
Key findings
Our study indicates that: (1) the liposomal encapsulation efficiency increased with increasing phosphatidylcholine content and reduced in the presence of stearylamine. Moreover, optimal encapsulation efficiency was obtained at an appropriate ratio of phosphatidylcholine to cholesterol; (2) CC-F was stable for at least 12 months at 4°C; (3) satisfactory improvements in lens opacity were shown in the cytochrome c-treated groups, especially for the CC-F-treated group with the decreased percentage of lens opacity at about 28% at the final examination.
Conclusions
CC-F were shown to be stable superior ophthalmic carriers and were able to markedly retard the onset of cataract development.
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Affiliation(s)
- Jing Zhang
- School of Pharmacy, Shenyang Pharmaceutical University, Shenyang, People's Republic of China
| | - Peipei Guan
- School of Pharmacy, Shenyang Pharmaceutical University, Shenyang, People's Republic of China
| | - Tianyi Wang
- School of Life Sciences & Biopharmaceutical Sciences, Shenyang Pharmaceutical University, Shenyang, People's Republic of China
| | - Di Chang
- School of Pharmacy, Shenyang Pharmaceutical University, Shenyang, People's Republic of China
| | - Tongying Jiang
- School of Pharmacy, Shenyang Pharmaceutical University, Shenyang, People's Republic of China
| | - Siling Wang
- School of Pharmacy, Shenyang Pharmaceutical University, Shenyang, People's Republic of China
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Bicuculline-induced seizures: a challenge for optical and biochemical modeling of the cytochrome oxidase CuA NIRS signal. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2009. [PMID: 19227461 DOI: 10.1007/978-0-387-85998-9_20] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register]
Abstract
The effect of seizures on brain blood flow and metabolism has been extensively studied. However, few studies have focused on mitochondria. We used near infrared spectroscopy (NIRS) to study hemoglobin and cytochrome oxidase changes during seizures, induced by the GABA antagonist bicuculline, in the adult rat. A broadband spectroscopy system was used with the optodes placed across the rat head. We focused on the initial seizures post-bicuculline addition during which oxyhemoglobin (HbO2) increased, deoxyhemoglobin (HHb) decreased and total hemoglobin (Hbtot) increased. The NIRS signal associated with the oxidised CuA centre of mitochondrial cytochrome c oxidase (oxCCO) decreased. At the highest bicuculline doses (0.25 mg/animal) the maximum values recorded were: delta HbO2 = +19 +/- 7 microM; delta HHb = -12 +/- 4 microM; delta Hbtot = +7 +/- 4 microM, delta oxCCO = - 1.7 +/- 0.3 microM. These results are broadly in line with other NIRS studies. However, previous measurements of NADH fluorescence indicate oxidation of the mitochondrial redox chain under these conditions. The changes induced by bicuculline provide an interesting challenge to the physics and biochemistry of using NIRS to study mitochondrial redox states in vivo and we explore the possible spectroscopic and/or biochemical meaning of these apparent anomalies.
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Richter OMH, Ludwig B. Electron transfer and energy transduction in the terminal part of the respiratory chain - lessons from bacterial model systems. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2009; 1787:626-34. [PMID: 19268423 DOI: 10.1016/j.bbabio.2009.02.020] [Citation(s) in RCA: 56] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/27/2008] [Revised: 02/13/2009] [Accepted: 02/16/2009] [Indexed: 11/18/2022]
Abstract
This review focuses on the terminal part of the respiratory chain where, macroscopically speaking, electron transfer (ET) switches from the two-electron donor, ubiquinol, to the single-electron carrier, cytochrome c, to finally reduce the four-electron acceptor dioxygen. With 3-D structures of prominent representatives of such multi-subunit membrane complexes known for some time, this section of the ET chain still leaves a number of key questions unanswered. The two relevant enzymes, ubiquinol:cytochrome c oxidoreductase and cytochrome c oxidase, appear as rather diverse modules, differing largely in their design for substrate interaction, internal ET, and moreover, in their mechanisms of energy transduction. While the canonical mitochondrial complexes have been investigated for almost five decades, the corresponding bacterial enzymes have been established only recently as attractive model systems to address basic reactions in ET and energy transduction. Lacking the intricate coding background and mitochondrial assembly pathways, bacterial respiratory enzymes typically offer a much simpler subunit composition, while maintaining all fundamental functions established for their complex "relatives". Moreover, related issues ranging from primary steps in cofactor insertion to supramolecular architecture of ET complexes, can also be favourably addressed in prokaryotic systems to hone our views on prototypic structures and mechanisms common to all family members.
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Affiliation(s)
- Oliver-Matthias H Richter
- Institute of Biochemistry, Molecular Genetics, Biozentrum Goethe University, Max-von-Laue-Str. 9, D 60438 Frankfurt, Germany
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Hwang HJ, Nagraj N, Lu Y. Spectroscopic characterizations of bridging cysteine ligand variants of an engineered Cu2(Scys)2 CuA azurin. Inorg Chem 2006; 45:102-7. [PMID: 16390045 DOI: 10.1021/ic051375u] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Bridging cysteine ligands of the Cu(A) center in an engineered Cu(A) azurin were replaced with serine, and the variants (Cys116Ser and Cys112Ser Cu(A) azurin) were characterized by mass spectrometry, as well as UV-vis and electron paramagnetic resonance (EPR) spectroscopic techniques. The replacements resulted in dramatically perturbed spectroscopic properties, indicating that the cysteines play a critical role in maintaining the structural integrity of the Cu center. The replacements at different cysteine residues resulted in different perturbations, even though the two cysteines are geometrically symmetrical in the primary coordination sphere with respect to the two copper ions. The Cys112Ser variant contains two distinct type 2 copper centers, while the Cys116Ser variant has one type 1 copper center with slight tetragonal distortion. Both the UV-vis and EPR spectra of the Cys116Ser variant change with pH, and the pK(a) of the transition is 6.0. A type 1 copper EPR spectrum with A(||) = 26 G was obtained at pH 7.0, while a type 2 copper EPR spectrum with A(||) = 140 G was found at pH 5.0. Interestingly, lowering the temperature from 290 to 85 K resulted in conversion of the Cys116Ser variant from a type 1 copper center to a type 2 copper center, suggesting rearrangement of the ligand around the copper or binding of an exogenous ligand at low temperature. This difference in mutation effects at different cysteines may be due to different constraints exerted on the two cysteines by hydrogen-bonding patterns in the ligand loop.
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Affiliation(s)
- Hee Jung Hwang
- Department of Chemistry, University of Illinois at Urbana-Champaign, 61801, USA
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Paumann M, Regelsberger G, Obinger C, Peschek GA. The bioenergetic role of dioxygen and the terminal oxidase(s) in cyanobacteria. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2005; 1707:231-53. [PMID: 15863101 DOI: 10.1016/j.bbabio.2004.12.007] [Citation(s) in RCA: 55] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/23/2004] [Revised: 12/15/2004] [Accepted: 12/16/2004] [Indexed: 01/21/2023]
Abstract
Owing to the release of 13 largely or totally sequenced cyanobacterial genomes (see and ), it is now possible to critically assess and compare the most neglected aspect of cyanobacterial physiology, i.e., cyanobacterial respiration, also on the grounds of pure molecular biology (gene sequences). While there is little doubt that cyanobacteria (blue-green algae) do form the largest, most diversified and in both evolutionary and ecological respects most significant group of (micro)organisms on our earth, and that what renders our blue planet earth to what it is, viz. the O(2)-containing atmosphere, dates back to the oxygenic photosynthetic activity of primordial cyanobacteria about 3.2x10(9) years ago, there is still an amazing lack of knowledge on the second half of bioenergetic oxygen metabolism in cyanobacteria, on (aerobic) respiration. Thus, the purpose of this review is threefold: (1) to point out the unprecedented role of the cyanobacteria for maintaining the delicate steady state of our terrestrial biosphere and atmosphere through a major contribution to the poising of oxygenic photosynthesis against aerobic respiration ("the global biological oxygen cycle"); (2) to briefly highlight the membrane-bound electron-transport assemblies of respiration and photosynthesis in the unique two-membrane system of cyanobacteria (comprising cytoplasmic membrane and intracytoplasmic or thylakoid membranes, without obvious anastomoses between them); and (3) to critically compare the (deduced) amino acid sequences of the multitude of hypothetical terminal oxidases in the nine fully sequenced cyanobacterial species plus four additional species where at least the terminal oxidases were sequenced. These will then be compared with sequences of other proton-pumping haem-copper oxidases, with special emphasis on possible mechanisms of electron and proton transfer.
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Affiliation(s)
- Martina Paumann
- Molecular Bioenergetics Group, Institute of Physical Chemistry, University of Vienna, Austria
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Heering HA, de Vries S. NO reductase from Bacillus azotoformans is a bifunctional enzyme accepting electrons from menaquinol and a specific endogenous membrane-bound cytochrome c551. Biochemistry 2004; 43:13487-95. [PMID: 15491156 DOI: 10.1021/bi0488101] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Bacillus azotoformans is a Gram-positive denitrifying soil bacterium, which is capable of respiring nitrate, nitrite, nitric oxide, and nitrous oxide under anaerobic conditions. It contains a unique menaquinol-dependent nitric oxide reductase (qCu(A)NOR) with a Cu(A) center in its small subunit. The qCu(A)NOR exhibits menaquinol-dependent NO reductase activity, whereas reduced horse heart cytochrome c was inactive. Here we describe the purification of three membrane-bound c cytochromes from B. azotoformans. Their apparent molecular masses on SDS-PAGE are approximately 11 kDa. At neutral pH, these c cytochromes are negatively charged and the E(m) for all is close to 150 mV. Only one of these c cytochromes, which exhibits an alpha-band maximum at 551 nm, acts as a direct electron donor to qCu(A)NOR. Further investigation demonstrated that this cytochrome c(551) possesses two lipoyl moieties, which presumably function to anchor it to the membrane. Steady-state kinetic studies reveal that cytochrome c(551) is a noncompetitive inhibitor of NO reduction when menaquinol is used as an electron donor. This finding points to the presence of two different electron donation pathways in qCu(A)NOR. The ability of qCu(A)NOR to accept electrons from both menaquinol and cytochrome c(551) might be related to the regulation of the rate of NO reduction especially as a defense mechanism of B. azotoformans against the toxicity of NO. Growth experiments in batch culture indeed show that B. azotoformans is highly NO tolerant, in contrast to, for example, Paracoccus denitrificans that has a monofunctional cytochrome c-dependent NOR. We propose that the menaquinol pathway, which has a 4-fold greater maximal activity than the pathway via cytochrome c(551), is used for NO detoxification, whereas electron donation via the endogenous cytochrome c involves the cytochrome b(6)f complex serving the bioenergetic needs of the organism.
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Affiliation(s)
- Eunsuk Kim
- Department of Chemistry, Johns Hopkins University, Charles and 34th Streets, Baltimore, Maryland 21218, USA
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9
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Paumann M, Lubura B, Regelsberger G, Feichtinger M, Köllensberger G, Jakopitsch C, Furtmüller PG, Peschek GA, Obinger C. Soluble CuA Domain of Cyanobacterial Cytochrome c Oxidase. J Biol Chem 2004; 279:10293-303. [PMID: 14672950 DOI: 10.1074/jbc.m308903200] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The genomes of several cyanobacteria show the existence of gene clusters encoding subunits I, II, and III of aa(3)-type cytochrome c oxidase. The enzyme occurs on both plasma and thylakoid membranes of these oxygenic phototrophic prokaryotes. Here we report the expression and purification of a truncated subunit II copper A (Cu(A)) domain (i.e. the electron entry and donor binding site) of cytochrome c oxidase from the cyanobacterium Synechocystis PCC 6803 in high yield. The water-soluble purple redox-active bimetallic center displays a relatively low standard reduction potential of 216 mV. Its absorption spectrum at pH 7 is similar to that of other soluble fragments from aa(3)-type oxidases, but the insensitivity of both absorbance and circular dichroism spectra to pH suggests that it is less exposed to the aqueous milieu compared with other Cu(A) domains. Oxidation of horse heart cytochrome c by the bimetallic center follows monophasic kinetics. At pH 7 and low ionic strength the bimolecular rate constant is (2.1 +/- 0.3) x 10(4) m-1 s(-1), and the rates decrease upon the increase of ionic strength. Sequence alignment and modeling of cyanobacterial Cu(A) domains show several peculiarities such as: (i) a large insertion located between the second transmembrane region and the putative hydrophobic cytochrome c docking site, (ii) the lack of acidic residues shown to be important in the interaction between cytochrome c and Paracoccus Cu(A) domain, and (iii) an extended C terminus similar to Escherichia coli ubiquinol oxidase.
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Affiliation(s)
- Martina Paumann
- Institute of Physical Chemistry, Molecular Bioenergetics Group, University of Vienna, Austria
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Richter OMH, Ludwig B. Cytochrome c oxidase--structure, function, and physiology of a redox-driven molecular machine. Rev Physiol Biochem Pharmacol 2003; 147:47-74. [PMID: 12783267 DOI: 10.1007/s10254-003-0006-0] [Citation(s) in RCA: 133] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
Cytochome c oxidase is the terminal member of the electron transport chains of mitochondria and many bacteria. Providing an efficient mechanism for dioxygen reduction on the one hand, it also acts as a redox-linked proton pump, coupling the free energy of water formation to the generation of a transmembrane electrochemical gradient to eventually drive ATP synthesis. The overall complexity of the mitochondrial enzyme is also reflected by its subunit structure and assembly pathway, whereas the diversity of the bacterial enzymes has fostered the notion of a large family of heme-copper terminal oxidases. Moreover, the successful elucidation of 3-D structures for both the mitochondrial and several bacterial oxidases has greatly helped in designing mutagenesis approaches to study functional aspects in these enzymes.
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Affiliation(s)
- O-M H Richter
- Institute of Biochemistry, Biocenter, J.W. Goethe-Universität, Marie-Curie-Str. 9, 60439 Frankfurt, Germany.
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Abstract
Life of higher organisms is essentially dependent on the efficient synthesis of ATP by oxidative phosphorylation in mitochondria. An important and as yet unsolved question of energy metabolism is how are the variable rates of ATP synthesis at maximal work load during exercise or mental work and at rest or during sleep regulated. This article reviews our present knowledge on the structure of bacterial and eukaryotic cytochrome c oxidases and correlates it with recent results on the regulatory functions of nuclear-coded subunits of the eukaryotic enzyme, which are absent from the bacterial enzyme. A new molecular hypothesis on the physiological regulation of oxidative phosphorylation is proposed, assuming a hormonally controlled dynamic equilibrium in vivo between two states of energy metabolism, a relaxed state with low ROS (reactive oxygen species) formation, and an excited state with elevated formation of ROS, which are known to accelerate aging and to cause degenerative diseases and cancer. The hypothesis is based on the allosteric ATP inhibition of cytochrome c oxidase at high intramitochondrial ATP/ADP ratios ("second mechanism of respiratory control"), which is switched on by cAMP-dependent phosphorylation and switched off by calcium-induced dephosphorylation of the enzyme.
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Affiliation(s)
- B Ludwig
- Biozentrum, Molekulare Genetik, Johann-Wolfgang-Goethe-Universität Frankfurt, Marie-Curie-Strasse 9, 60439 Frankfurt, Germany
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12
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Fedurco M. Redox reactions of heme-containing metalloproteins: dynamic effects of self-assembled monolayers on thermodynamics and kinetics of cytochrome c electron-transfer reactions. Coord Chem Rev 2000. [DOI: 10.1016/s0010-8545(00)00292-7] [Citation(s) in RCA: 200] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
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Zhen Y, Hoganson CW, Babcock GT, Ferguson-Miller S. Definition of the interaction domain for cytochrome c on cytochrome c oxidase. I. Biochemical, spectral, and kinetic characterization of surface mutants in subunit ii of Rhodobacter sphaeroides cytochrome aa(3). J Biol Chem 1999; 274:38032-41. [PMID: 10608872 DOI: 10.1074/jbc.274.53.38032] [Citation(s) in RCA: 92] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
To determine the interaction site for cytochrome c (Cc) on cytochrome c oxidase (CcO), a number of conserved carboxyl residues in subunit II of Rhodobacter sphaeroides CcO were mutated to neutral forms. A highly conserved tryptophan, Trp(143), was also mutated to phenylalanine and alanine. Spectroscopic and metal analyses of the surface carboxyl mutants revealed no overall structural changes. The double mutants D188Q/E189N and D151Q/E152N exhibit similar steady-state kinetic behavior as wild-type oxidase with horse Cc and R. sphaeroides Cc(2), showing that these residues are not involved in Cc binding. The single mutants E148Q, E157Q, D195N, and D214N have decreased activities and increased K(m) values, indicating they contribute to the Cc:CcO interface. However, their reactions with horse and R. sphaeroides Cc are different, as expected from the different distribution of surface lysines on these cytochromes c. Mutations at Trp(143) severely inhibit activity without changing the K(m) for Cc or disturbing the adjacent Cu(A) center. From these data, we identify a Cc binding area on CcO with Trp(143) and Asp(214) close to the site of electron transfer and Glu(148), Glu(157), and Asp(195) providing electrostatic guidance. The results are completely consistent with time-resolved kinetic measurements (Wang, K., Zhen, Y., Sadoski, R., Grinnell, S., Geren, L., Ferguson-Miller, S., Durham, B., and Millett, F. (1999) J. Biol. Chem. 274, 38042-38050) and computational docking analysis (Roberts, V. A., and Pique, M. E. (1999) J. Biol. Chem. 274, 38051-38060).
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Affiliation(s)
- Y Zhen
- Department of Biochemistry, Michigan State University, East Lansing, Michigan 48824, USA
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Roberts VA, Pique ME. Definition of the interaction domain for cytochrome c on cytochrome c oxidase. III. Prediction of the docked complex by a complete, systematic search. J Biol Chem 1999; 274:38051-60. [PMID: 10608874 DOI: 10.1074/jbc.274.53.38051] [Citation(s) in RCA: 116] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023] Open
Abstract
The electron transfer complex between bovine cytochrome c oxidase and horse cytochrome c has been predicted with the docking program DOT, which performs a complete, systematic search over all six rotational and translational degrees of freedom. Energies for over 36 billion configurations were calculated, providing a free-energy landscape showing guidance of positively charged cytochrome c to the negative region on the cytochrome c oxidase surface formed by subunit II. In a representative configuration, the solvent-exposed cytochrome c heme edge is within 4 A of the indole ring of subunit II residue Trp(104), indicating a likely electron transfer path. These two groups are surrounded by a small, hydrophobic contact region, which is surrounded by electrostatically complementary hydrophilic interactions. Cytochrome c/cytochrome c oxidase interactions of Lys(13) with Asp(119) and Lys(72) with Gln(103) and Asp(158) are the most critical polar interactions due to their proximity to the hydrophobic region and exclusion from bulk solvent. The predicted complex matches previous mutagenesis, binding, and time-resolved kinetics studies that implicate Trp(104) in electron transfer and show the importance of specific charged residues to protein affinity. Electrostatic forces not only enhance long range protein/protein association; they also predominate in short range alignment, creating the transient interaction needed for rapid turnover.
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Affiliation(s)
- V A Roberts
- Department of Molecular Biology, The Scripps Research Institute, La Jolla, California 92037, USA.
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Das TK, Gomes CM, Teixeira M, Rousseau DL. Redox-linked transient deprotonation at the binuclear site in the aa(3)-type quinol oxidase from Acidianus ambivalens: implications for proton translocation. Proc Natl Acad Sci U S A 1999; 96:9591-6. [PMID: 10449737 PMCID: PMC22253 DOI: 10.1073/pnas.96.17.9591] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The hyperthermophilic archaeon Acidianus ambivalens expresses a membrane-bound aa(3)-type quinol oxidase, when grown aerobically, that we have studied by resonance Raman spectroscopy. The purified aa(3) oxidase, which does not contain bound quinol, undergoes a reversible slow conformational change at heme a(3) upon reduction, as indicated by a change in the frequency of its heme formyl stretching mode, from 1,660 cm(-1) to 1,667 cm(-1). In contrast, upon reduction of the integral membrane enzyme or the purified enzyme preincubated with decylubiquinol, this mode appears at 1,667 cm(-1) much more rapidly, suggesting a role of the bound quinol in controlling the redox-linked conformational changes. The shift of the formyl mode to higher frequency is attributed to a loss of hydrogen bonding that is associated with a group having a pKa of approximately 3.8. Based on these observations, a crucial element for proton translocation involving a redox-linked conformational change near the heme a(3) formyl group is postulated.
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Affiliation(s)
- T K Das
- Department of Physiology and Biophysics, Albert Einstein College of Medicine, 1300 Morris Park Avenue, Bronx, NY 10461, USA
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