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Hilberath T, van Oosten R, Victoria J, Brasselet H, Alcalde M, Woodley JM, Hollmann F. Toward Kilogram-Scale Peroxygenase-Catalyzed Oxyfunctionalization of Cyclohexane. Org Process Res Dev 2023; 27:1384-1389. [PMID: 37496955 PMCID: PMC10367066 DOI: 10.1021/acs.oprd.3c00135] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2023] [Indexed: 07/28/2023]
Abstract
Mol-scale oxyfunctionalization of cyclohexane to cyclohexanol/cyclohexanone (KA-oil) using an unspecific peroxygenase is reported. Using AaeUPO from Agrocybe aegerita and simple H2O2 as an oxidant, cyclohexanol concentrations of more than 300 mM (>60% yield) at attractive productivities (157 mM h-1, approx. 15 g L-1 h-1) were achieved. Current limitations of the proposed biooxidation system have been identified paving the way for future improvements and implementation.
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Affiliation(s)
- Thomas Hilberath
- Department
of Biotechnology, Delft University of Technology, van der Maasweg 9, 2629HZ Delft, The Netherlands
| | - Remco van Oosten
- Department
of Biotechnology, Delft University of Technology, van der Maasweg 9, 2629HZ Delft, The Netherlands
| | - Juliet Victoria
- Department
of Chemical and Biochemical Engineering, Technical University of Denmark, 2800 Kgs. Lyngby, Denmark
| | - Hugo Brasselet
- Atlant.
Innov., Koornmarkt 52, 2611 EH Delft, The Netherlands
| | - Miguel Alcalde
- Department
of Biocatalysis, Institute of Catalysis,
CSIC, 28049 Madrid, Spain
| | - John M. Woodley
- Department
of Chemical and Biochemical Engineering, Technical University of Denmark, 2800 Kgs. Lyngby, Denmark
| | - Frank Hollmann
- Department
of Biotechnology, Delft University of Technology, van der Maasweg 9, 2629HZ Delft, The Netherlands
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Borisov VB, Siletsky SA, Paiardini A, Hoogewijs D, Forte E, Giuffrè A, Poole RK. Bacterial Oxidases of the Cytochrome bd Family: Redox Enzymes of Unique Structure, Function, and Utility As Drug Targets. Antioxid Redox Signal 2021; 34:1280-1318. [PMID: 32924537 PMCID: PMC8112716 DOI: 10.1089/ars.2020.8039] [Citation(s) in RCA: 36] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/20/2020] [Revised: 09/01/2020] [Accepted: 09/02/2020] [Indexed: 12/23/2022]
Abstract
Significance: Cytochrome bd is a ubiquinol:oxygen oxidoreductase of many prokaryotic respiratory chains with a unique structure and functional characteristics. Its primary role is to couple the reduction of molecular oxygen, even at submicromolar concentrations, to water with the generation of a proton motive force used for adenosine triphosphate production. Cytochrome bd is found in many bacterial pathogens and, surprisingly, in bacteria formally denoted as anaerobes. It endows bacteria with resistance to various stressors and is a potential drug target. Recent Advances: We summarize recent advances in the biochemistry, structure, and physiological functions of cytochrome bd in the light of exciting new three-dimensional structures of the oxidase. The newly discovered roles of cytochrome bd in contributing to bacterial protection against hydrogen peroxide, nitric oxide, peroxynitrite, and hydrogen sulfide are assessed. Critical Issues: Fundamental questions remain regarding the precise delineation of electron flow within this multihaem oxidase and how the extraordinarily high affinity for oxygen is accomplished, while endowing bacteria with resistance to other small ligands. Future Directions: It is clear that cytochrome bd is unique in its ability to confer resistance to toxic small molecules, a property that is significant for understanding the propensity of pathogens to possess this oxidase. Since cytochrome bd is a uniquely bacterial enzyme, future research should focus on harnessing fundamental knowledge of its structure and function to the development of novel and effective antibacterial agents.
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Affiliation(s)
- Vitaliy B. Borisov
- Belozersky Institute of Physico-Chemical Biology, Lomonosov Moscow State University, Moscow, Russian Federation
| | - Sergey A. Siletsky
- Belozersky Institute of Physico-Chemical Biology, Lomonosov Moscow State University, Moscow, Russian Federation
| | | | - David Hoogewijs
- Department of Medicine/Physiology, University of Fribourg, Fribourg, Switzerland
| | - Elena Forte
- Department of Biochemical Sciences, Sapienza University of Rome, Rome, Italy
| | | | - Robert K. Poole
- Department of Molecular Biology and Biotechnology, The University of Sheffield, Sheffield, United Kingdom
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The Small Protein CydX Is Required for Cytochrome bd Quinol Oxidase Stability and Function in Salmonella enterica Serovar Typhimurium: a Phenotypic Study. J Bacteriol 2020; 202:JB.00348-19. [PMID: 31659011 DOI: 10.1128/jb.00348-19] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2019] [Accepted: 10/21/2019] [Indexed: 01/12/2023] Open
Abstract
Cytochrome bd quinol oxidases, which have a greater affinity for oxygen than heme-copper cytochrome oxidases (HCOs), promote bacterial respiration and fitness in low-oxygen environments, such as host tissues. Here, we show that, in addition to the CydA and CydB subunits, the small protein CydX is required for the assembly and function of the cytochrome bd complex in the enteric pathogen Salmonella enterica serovar Typhimurium. Mutant S Typhimurium lacking CydX showed a loss of proper heme arrangement and impaired oxidase activity comparable to that of a ΔcydABX mutant lacking all cytochrome bd subunits. Moreover, both the ΔcydX mutant and the ΔcydABX mutant showed increased sensitivity to β-mercaptoethanol and nitric oxide (NO). Cytochrome bd-mediated protection from β-mercaptoethanol was not a result of resistance to reducing damage but, rather, was due to cytochrome bd oxidase managing Salmonella respiration, while β-mercaptoethanol interacted with the copper ions necessary for the HCO activity of the cytochrome bo-type quinol oxidase. Interactions between NO and hemes in cytochrome bd and cytochrome bd-dependent respiration during nitrosative stress indicated a direct role for cytochrome bd in mediating Salmonella resistance to NO. Additionally, CydX was required for S Typhimurium proliferation inside macrophages. Mutants deficient in cytochrome bd, however, showed a significant increase in resistance to antibiotics, including aminoglycosides, d-cycloserine, and ampicillin. The essential role of CydX in cytochrome bd assembly and function suggests that targeting this small protein could be a useful antimicrobial strategy, but potential drug tolerance responses should also be considered.IMPORTANCE Cytochrome bd quinol oxidases, which are found only in bacteria, govern the fitness of many facultative anaerobic pathogens by promoting respiration in low-oxygen environments and by conferring resistance to antimicrobial radicals. Thus, cytochrome bd complex assembly and activity are considered potential therapeutic targets. Here we report that the small protein CydX is required for the assembly and function of the cytochrome bd complex in S Typhimurium under stress conditions, including exposure to β-mercaptoethanol, nitric oxide, or the phagocytic intracellular environment, demonstrating its crucial function for Salmonella fitness. However, cytochrome bd inactivation also leads to increased resistance to some antibiotics, so considerable caution should be taken when developing therapeutic strategies targeting the CydX-dependent cytochrome bd.
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Abstract
Like most bacteria, Escherichia coli has a flexible and branched respiratory chain that enables the prokaryote to live under a variety of environmental conditions, from highly aerobic to completely anaerobic. In general, the bacterial respiratory chain is composed of dehydrogenases, a quinone pool, and reductases. Substrate-specific dehydrogenases transfer reducing equivalents from various donor substrates (NADH, succinate, glycerophosphate, formate, hydrogen, pyruvate, and lactate) to a quinone pool (menaquinone, ubiquinone, and dimethylmenoquinone). Then electrons from reduced quinones (quinols) are transferred by terminal reductases to different electron acceptors. Under aerobic growth conditions, the terminal electron acceptor is molecular oxygen. A transfer of electrons from quinol to O₂ is served by two major oxidoreductases (oxidases), cytochrome bo₃ encoded by cyoABCDE and cytochrome bd encoded by cydABX. Terminal oxidases of aerobic respiratory chains of bacteria, which use O₂ as the final electron acceptor, can oxidize one of two alternative electron donors, either cytochrome c or quinol. This review compares the effects of different inhibitors on the respiratory activities of cytochrome bo₃ and cytochrome bd in E. coli. It also presents a discussion on the genetics and the prosthetic groups of cytochrome bo₃ and cytochrome bd. The E. coli membrane contains three types of quinones that all have an octaprenyl side chain (C₄₀). It has been proposed that the bo₃ oxidase can have two ubiquinone-binding sites with different affinities. "WHAT'S NEW" IN THE REVISED ARTICLE: The revised article comprises additional information about subunit composition of cytochrome bd and its role in bacterial resistance to nitrosative and oxidative stresses. Also, we present the novel data on the electrogenic function of appBCX-encoded cytochrome bd-II, a second bd-type oxidase that had been thought not to contribute to generation of a proton motive force in E. coli, although its spectral properties closely resemble those of cydABX-encoded cytochrome bd.
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Miura H, Mogi T, Ano Y, Migita CT, Matsutani M, Yakushi T, Kita K, Matsushita K. Cyanide-insensitive quinol oxidase (CIO) from Gluconobacter oxydans is a unique terminal oxidase subfamily of cytochrome bd. ACTA ACUST UNITED AC 2013; 153:535-45. [DOI: 10.1093/jb/mvt019] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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Borisov VB, Gennis RB, Hemp J, Verkhovsky MI. The cytochrome bd respiratory oxygen reductases. BIOCHIMICA ET BIOPHYSICA ACTA 2011; 1807:1398-413. [PMID: 21756872 PMCID: PMC3171616 DOI: 10.1016/j.bbabio.2011.06.016] [Citation(s) in RCA: 367] [Impact Index Per Article: 28.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/23/2011] [Revised: 06/23/2011] [Accepted: 06/24/2011] [Indexed: 01/03/2023]
Abstract
Cytochrome bd is a respiratory quinol: O₂ oxidoreductase found in many prokaryotes, including a number of pathogens. The main bioenergetic function of the enzyme is the production of a proton motive force by the vectorial charge transfer of protons. The sequences of cytochromes bd are not homologous to those of the other respiratory oxygen reductases, i.e., the heme-copper oxygen reductases or alternative oxidases (AOX). Generally, cytochromes bd are noteworthy for their high affinity for O₂ and resistance to inhibition by cyanide. In E. coli, for example, cytochrome bd (specifically, cytochrome bd-I) is expressed under O₂-limited conditions. Among the members of the bd-family are the so-called cyanide-insensitive quinol oxidases (CIO) which often have a low content of the eponymous heme d but, instead, have heme b in place of heme d in at least a majority of the enzyme population. However, at this point, no sequence motif has been identified to distinguish cytochrome bd (with a stoichiometric complement of heme d) from an enzyme designated as CIO. Members of the bd-family can be subdivided into those which contain either a long or a short hydrophilic connection between transmembrane helices 6 and 7 in subunit I, designated as the Q-loop. However, it is not clear whether there is a functional consequence of this difference. This review summarizes current knowledge on the physiological functions, genetics, structural and catalytic properties of cytochromes bd. Included in this review are descriptions of the intermediates of the catalytic cycle, the proposed site for the reduction of O₂, evidence for a proton channel connecting this active site to the bacterial cytoplasm, and the molecular mechanism by which a membrane potential is generated.
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Affiliation(s)
- Vitaliy B Borisov
- Belozersky Institute of Physico-Chemical Biology, Lomonosov Moscow State University, Leninskie Gory, Moscow 119991, Russian Federation.
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7
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Borisov VB, Davletshin AI, Konstantinov AA. Peroxidase activity of cytochrome bd from Escherichia coli. BIOCHEMISTRY (MOSCOW) 2010; 75:428-36. [PMID: 20618131 DOI: 10.1134/s000629791004005x] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
Cytochrome bd from Escherichia coli is able to oxidize such substrates as guaiacol, ferrocene, benzohydroquinone, and potassium ferrocyanide through the peroxidase mechanism, while none of these donors is oxidized in the oxidase reaction (i.e. in the reaction that involves molecular oxygen as the electron acceptor). Peroxidation of guaiacol has been studied in detail. The dependence of the rate of the reaction on the concentration of the enzyme and substrates as well as the effect of various inhibitors of the oxidase reaction on the peroxidase activity have been tested. The dependence of the guaiacol-peroxidase activity on the H2O2 concentration is linear up to the concentration of 8 mM. At higher concentrations of H2O2, inactivation of the enzyme is observed. Guaiacol markedly protects the enzyme from inactivation induced by peroxide. The peroxidase activity of cytochrome bd increases with increasing guaiacol concentration, reaching saturation in the range from 0.5 to 2.5 mM, but then starts falling. Such inhibitors of the ubiquinol-oxidase activity of cytochrome bd as cyanide, pentachlorophenol, and 2-n-heptyl 4-hydroxyquinoline-N-oxide also suppress its guaiacol-peroxidase activity; in contrast, zinc ions have no influence on the enzyme-catalyzed peroxidation of guaiacol. These data suggest that guaiacol interacts with the enzyme in the center of ubiquinol binding and donates electrons into the di-heme center of oxygen reduction via heme b(558), and H2O2 is reduced by heme d. Although the peroxidase activity of cytochrome bd from E. coli is low compared to peroxidases, it might be of physiological significance for the bacterium itself and plays a pathophysiological role for humans and animals.
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Affiliation(s)
- V B Borisov
- Belozersky Institute of Physico-Chemical Biology, Lomonosov Moscow State University, Moscow, 119991, Russia.
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8
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Bansal K, Yang K, Nistala GJ, Gennis RB, Bhalerao KD. A positive feedback-based gene circuit to increase the production of a membrane protein. J Biol Eng 2010; 4:6. [PMID: 20500847 PMCID: PMC2885990 DOI: 10.1186/1754-1611-4-6] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2010] [Accepted: 05/25/2010] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Membrane proteins are an important class of proteins, playing a key role in many biological processes, and are a promising target in pharmaceutical development. However, membrane proteins are often difficult to produce in large quantities for the purpose of crystallographic or biochemical analyses. RESULTS In this paper, we demonstrate that synthetic gene circuits designed specifically to overexpress certain genes can be applied to manipulate the expression kinetics of a model membrane protein, cytochrome bd quinol oxidase in E. coli, resulting in increased expression rates. The synthetic circuit involved is an engineered, autoinducer-independent variant of the lux operon activator LuxR from V. fischeri in an autoregulatory, positive feedback configuration. CONCLUSIONS Our proof-of-concept experiments indicate a statistically significant increase in the rate of production of the bd oxidase membrane protein. Synthetic gene networks provide a feasible solution for the problem of membrane protein production.
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Affiliation(s)
- Karan Bansal
- Department of Agricultural and Biological Engineering, University of Illinois at Urbana Champaign, 1304 W, Pennsylvania Ave, Urbana, IL 61801 USA.
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9
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Davies BW, Kohanski MA, Simmons LA, Winkler JA, Collins JJ, Walker GC. Hydroxyurea induces hydroxyl radical-mediated cell death in Escherichia coli. Mol Cell 2010; 36:845-60. [PMID: 20005847 DOI: 10.1016/j.molcel.2009.11.024] [Citation(s) in RCA: 150] [Impact Index Per Article: 10.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2009] [Revised: 07/13/2009] [Accepted: 08/13/2009] [Indexed: 01/18/2023]
Abstract
Hydroxyurea (HU) specifically inhibits class I ribonucleotide reductase (RNR), depleting dNTP pools and leading to replication fork arrest. Although HU inhibition of RNR is well recognized, the mechanism by which it leads to cell death remains unknown. To investigate the mechanism of HU-induced cell death, we used a systems-level approach to determine the genomic and physiological responses of E. coli to HU treatment. Our results suggest a model by which HU treatment rapidly induces a set of protective responses to manage genomic instability. Continued HU stress activates iron uptake and toxins MazF and RelE, whose activity causes the synthesis of incompletely translated proteins and stimulation of envelope stress responses. These effects alter the properties of one of the cell's terminal cytochrome oxidases, causing an increase in superoxide production. The increased superoxide production, together with the increased iron uptake, fuels the formation of hydroxyl radicals that contribute to HU-induced cell death.
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Affiliation(s)
- Bryan W Davies
- Department of Biology, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
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10
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Abstract
Like most bacteria, Escherichia coli has a flexible and branched respiratory chain that enables the prokaryote to live under a variety of environmental conditions, from highly aerobic to completely anaerobic. In general, the bacterial respiratory chain is composed of dehydrogenases, a quinone pool, and reductases. Substrate specific dehydrogenases transfer reducing equivalents from various donor substrates (NADH, succinate, glycerophoshate, formate, hydrogen, pyruvate, and lactate) to a quinone pool (menaquinone, ubiquinone, and demethylmenoquinone). Then electrons from reduced quinones (quinols) are transferred by terminal reductases to different electron acceptors. Under aerobic growth conditions, the terminal electron acceptor is molecular oxygen. A transfer of electrons from quinol to O2 is served by two major oxidoreductases (oxidases), cytochrome bo3 and cytochrome bd. Terminal oxidases of aerobic respiratory chains of bacteria, which use O2 as the final electron acceptor, can oxidize one of two alternative electron donors, either cytochrome c or quinol. This review compares the effects of different inhibitors on the respiratory activities of cytochrome bo3 and cytochrome bd in E. coli. It also presents a discussion on the genetics and the prosthetic groups of cytochrome bo3 and cytochrome bd. The E. coli membrane contains three types of quinones which all have an octaprenyl side chain (C40). It has been proposed that the bo3 oxidase can have two ubiquinone-binding sites with different affinities. The spectral properties of cytochrome bd-II closely resemble those of cydAB-encoded cytochrome bd.
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11
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Kimoto H, Matsuyama H, Yumoto I, Yoshimune K. Heme content of recombinant catalase from Psychrobacter sp. T-3 altered by host Escherichia coli cell growth conditions. Protein Expr Purif 2008; 59:357-9. [PMID: 18424070 DOI: 10.1016/j.pep.2008.03.016] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2008] [Accepted: 03/24/2008] [Indexed: 10/22/2022]
Abstract
The catalase gene of Psychrobacter sp. T-3 was cloned, and the gene product (PktA) was overexpressed in Escherichia coli. The specific activity of the purified PktA was slightly lower than that of the native purified enzyme obtained from Psychrobacter sp. T-3. Spectrophotometric measurements of the purified enzymes suggested that the recombinant PktA contains a mixture of heme b and d, although the native enzyme contains the sole heme b. An addition of the heme precursor 5-aminolevulinic acid (ALA) to the medium increased the heme b content of the recombinant PktA, and the resulting enzyme showed higher specific activity than the native enzyme. This is the first report that shows the heme content of overproduced catalase altered by the host cell growth conditions.
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Affiliation(s)
- Hideyuki Kimoto
- Department of Bioscience and Technology, School of Engineering, Hokkaido Tokai University, Minaminosawa, Minami-ku, Sapporo 005-8601, Japan
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12
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Belevich I, Borisov VB, Bloch DA, Konstantinov AA, Verkhovsky MI. Cytochrome bd from Azotobacter vinelandii: Evidence for High-Affinity Oxygen Binding. Biochemistry 2007; 46:11177-84. [PMID: 17784736 DOI: 10.1021/bi700862u] [Citation(s) in RCA: 56] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Cytochrome bd from Azotobacter vinelandii is a respiratory quinol oxidase that is highly efficient in reducing intracellular oxygen concentration, thus enabling nitrogen fixation under ambient aerobic conditions. Equilibrium measurements of O2 binding to ferrous heme d in the one-electron-reduced form of the A. vinelandii enzyme give Kd(O2) = 0.5 microM, close to the value for the Escherichia coli cytochrome bd (ca. 0.3 microM); thus, both enzymes have similar, high affinity for oxygen. The reaction of the A. vinelandii cytochrome bd in the one-electron-reduced and fully reduced states with O2 is extremely fast approaching the diffusion-controlled limit in water. In the fully reduced state, the rate of O2 binding depends linearly on the oxygen concentration consistently with a simple, single-step process. In contrast, in the one-electron-reduced state the rate of oxygen binding is hyperbolic, implying a more complex binding pattern. Two possible explanations for the saturation kinetics are considered: (A) There is a spectroscopically silent prebinding of oxygen to an unidentified low-affinity saturatable site followed by the oxygen transfer to heme d. (B) Oxygen binding to heme d requires an "activated" state of the enzyme in which an oxygen channel connecting heme d to the bulk is open. This channel is permanently open in the fully reduced enzyme (hence no saturation behavior) but flickers between the open and closed states in the one-electron-reduced enzyme.
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Affiliation(s)
- Ilya Belevich
- Helsinki Bioenergetics Group, Institute of Biotechnology, University of Helsinki, PB 65 (Viikinkaari 1), 00014, Helsinki, Finland
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Belevich I, Borisov VB, Verkhovsky MI. Discovery of the True Peroxy Intermediate in the Catalytic Cycle of Terminal Oxidases by Real-time Measurement. J Biol Chem 2007; 282:28514-28519. [PMID: 17690093 DOI: 10.1074/jbc.m705562200] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The sequence of the catalytic intermediates in the reaction of cytochrome bd terminal oxidases from Escherichia coli and Azotobacter vinelandii with oxygen was monitored in real time by absorption spectroscopy and electrometry. The initial binding of O(2) to the fully reduced enzyme is followed by the fast (5 micros) conversion of the oxy complex to a novel, previously unresolved intermediate. In this transition, low spin heme b(558) remains reduced while high spin heme b(595) is oxidized with formation of a new heme d-oxygen species with an absorption maximum at 635 nm. Reduction of O(2) by two electrons is sufficient to produce (hydro)peroxide bound to ferric heme d. In this case, the O-O bond is left intact and the newly detected intermediate must be a peroxy complex of heme d (Fe (3+)(d)-O-O-(H)) corresponding to compound 0 in peroxidases. The alternative scenario where the O-O bond is broken as in the P(M) intermediate of heme-copper oxidases and compound I of peroxidases is not very likely, because it would require oxidation of a nearby amino acid residue or the porphyrin ring that is energetically unfavorable in the presence of the reduced heme b(558) in the proximity of the catalytic center. The formation of the peroxy intermediate is not coupled to membrane potential generation, indicating that hemes d and b(595) are located at the same depth of the membrane dielectric. The lifetime of the new intermediate is 47 micros; it decays into oxoferryl species due to oxidation of low spin heme b(558) that is linked to significant charge translocation across the membrane.
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Affiliation(s)
- Ilya Belevich
- Helsinki Bioenergetics Group, Institute of Biotechnology, University of Helsinki, Post Office Box 65 (Viikinkaari 1), FI-00014 Helsinki, Finland
| | - Vitaliy B Borisov
- Department of Molecular Energetics of Microorganisms, Belozersky Institute of Physico-Chemical Biology, Lomonosov Moscow State University, Moscow 119991, Russia
| | - Michael I Verkhovsky
- Helsinki Bioenergetics Group, Institute of Biotechnology, University of Helsinki, Post Office Box 65 (Viikinkaari 1), FI-00014 Helsinki, Finland.
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14
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Yang K, Zhang J, Vakkasoglu AS, Hielscher R, Osborne JP, Hemp J, Miyoshi H, Hellwig P, Gennis RB. Glutamate 107 in subunit I of the cytochrome bd quinol oxidase from Escherichia coli is protonated and near the heme d/heme b595 binuclear center. Biochemistry 2007; 46:3270-8. [PMID: 17305364 DOI: 10.1021/bi061946+] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Cytochrome bd is a quinol oxidase from Escherichia coli, which is optimally expressed under microaerophilic growth conditions. The enzyme catalyzes the two-electron oxidation of either ubiquinol or menaquinol in the membrane and scavenges O2 at low concentrations, reducing it to water. Previous work has shown that, although cytochrome bd does not pump protons, turnover is coupled to the generation of a proton motive force. The generation of a proton electrochemical gradient results from the release of protons from the oxidation of quinol to the periplasm and the uptake of protons used to form H2O from the cytoplasm. Because the active site has been shown to be located near the periplasmic side of the membrane, a proton channel must facilitate the delivery of protons from the cytoplasm to the site of water formation. Two conserved glutamic acid residues, E107 and E99, are located in transmembrane helix III in subunit I and have been proposed to form part of this putative proton channel. In the current work, it is shown that mutations in either of these residues results in the loss of quinol oxidase activity and can result in the loss of the two hemes at the active site, hemes d and b595. One mutant, E107Q, while being totally inactive, retains the hemes. Fourier transform infrared (FTIR) redox difference spectroscopy has identified absorption bands from the COOH group of E107. The data show that E107 is protonated at pH 7.6 and that it is perturbed by the reduction of the heme d/heme b595 binuclear center at the active site. In contrast, mutation of an acidic residue known to be at or near the quinol-binding site (E257A) also inactivates the enzyme but has no substantial influence on the FTIR redox difference spectrum. Mutagenesis shows that there are several acidic residues, including E99 and E107 as well as D29 (in CydB), which are important for the assembly or stability of the heme d/heme b595 active site.
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Affiliation(s)
- Ke Yang
- Department of Biochemistry, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, USA
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15
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Matsumoto Y, Muneyuki E, Fujita D, Sakamoto K, Miyoshi H, Yoshida M, Mogi T. Kinetic mechanism of quinol oxidation by cytochrome bd studied with ubiquinone-2 analogs. J Biochem 2006; 139:779-88. [PMID: 16672279 DOI: 10.1093/jb/mvj087] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Cytochrome bd is a heterodimeric terminal ubiquinol oxidase of Escherichia coli under microaerophilic growth conditions. The oxidase activity shows sigmoidal concentration-dependence with low concentrations of ubiquinols, and a marked substrate inhibition with high concentrations of ubiquinol-2 analogs [Sakamoto, K., Miyoshi, H., Takegami, K., Mogi, T., Anraku, Y., and Iwamura H. (1996) J. Biol. Chem. 271, 29897-29902]. Kinetic analysis of the oxidation of the ubiquinol-2 analogs, where the 2- or 3-methoxy group has been substituted with an azido or ethoxy group, suggested that its peculiar enzyme kinetics can be explained by a modified ping-pong bi-bi mechanism with the formation of inactive binary complex FS in the one-electron reduced oxygenated state and inactive ternary complex (E2S)S(n) on the oxidation of the second quinol molecule. Structure-function studies on the ubiquinol-2 analogs suggested that the 6-diprenyl group and the 3-methoxy group on the quinone ring are involved in the substrate inhibition. We also found that oxidized forms of ubiquinone-2 analogs served as weak noncompetitive inhibitors. These results indicate that the mechanism for the substrate oxidation by cytochrome bd is different from that of the heme-copper terminal quinol oxidase and is tightly coupled to dioxygen reduction chemistry.
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Affiliation(s)
- Yushi Matsumoto
- Chemical Resources Laboratory, Tokyo Institute of Technology, Nagatsuta 4259, Midori-ku, Yokohama 226-8503
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16
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Belevich I, Borisov VB, Konstantinov AA, Verkhovsky MI. Oxygenated complex of cytochrome bd from Escherichia coli: stability and photolability. FEBS Lett 2005; 579:4567-70. [PMID: 16087180 DOI: 10.1016/j.febslet.2005.07.011] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2005] [Revised: 07/08/2005] [Accepted: 07/08/2005] [Indexed: 11/26/2022]
Abstract
Cytochrome bd is one of the two terminal ubiquinol oxidases in the respiratory chain of Escherichia coli catalyzing reduction of O2 to H2O. The enzyme is expressed under low oxygen tension; due to high affinity for O2 it is isolated mainly as a stable oxygenated complex. Direct measurement of O2 binding to heme d in the one-electron reduced isolated enzyme gives K(d(O2)) of approximately 280 nM. It is possible to photolyse the heme d oxy-complex by illumination of the enzyme for several minutes under microaerobic conditions; the light-induced difference absorption spectrum is virtually identical to the inverted spectrum of O2 binding to heme d.
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Affiliation(s)
- Ilya Belevich
- Helsinki Bioenergetics Group, Institute of Biotechnology, University of Helsinki, P.O. Box 65 (Viikinkaari 1), FIN-00014 Helsinki, Finland
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Das A, Silaghi-Dumitrescu R, Ljungdahl LG, Kurtz DM. Cytochrome bd oxidase, oxidative stress, and dioxygen tolerance of the strictly anaerobic bacterium Moorella thermoacetica. J Bacteriol 2005; 187:2020-9. [PMID: 15743950 PMCID: PMC1064043 DOI: 10.1128/jb.187.6.2020-2029.2005] [Citation(s) in RCA: 78] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The gram-positive, thermophilic, acetogenic bacterium Moorella thermoacetica can reduce CO2 to acetate via the Wood-Ljungdahl (acetyl coenzyme A synthesis) pathway. This report demonstrates that, despite its classification as a strict anaerobe, M. thermoacetica contains a membrane-bound cytochrome bd oxidase that can catalyze reduction of low levels of dioxygen. Whole-cell suspensions of M. thermoacetica had significant endogenous O2 uptake activity, and this activity was increased in the presence of methanol or CO, which are substrates in the Wood-Ljungdahl pathway. Cyanide and azide strongly (approximately 70%) inhibited both the endogenous and CO/methanol-dependent O2 uptake. UV-visible light absorption and electron paramagnetic resonance spectra of n-dodecyl-beta-maltoside extracts of M. thermoacetica membranes showed the presence of a cytochrome bd oxidase complex containing cytochrome b561, cytochrome b595, and cytochrome d (chlorin). Subunits I and II of the bd oxidase were identified by N-terminal amino acid sequencing. The M. thermoacetica cytochrome bd oxidase exhibited cyanide-sensitive quinol oxidase activity. The M. thermoacetica cytochrome bd (cyd) operon consists of four genes, encoding subunits I and II along with two ABC-type transporter proteins, homologs of which in other bacteria are required for assembly of the bd complex. The level of this cyd operon transcript was significantly increased when M. thermoacetica was grown in the absence of added reducing agent (cysteine + H2S). Expression of a 35-kDa cytosolic protein, identified as a cysteine synthase (CysK), was also induced by the nonreducing growth conditions. The combined evidence indicates that cytochrome bd oxidase and cysteine synthase protect against oxidative stress and contribute to the limited dioxygen tolerance of M. thermoacetica.
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Affiliation(s)
- Amaresh Das
- Department of Chemistry and Molecular Biology, University of Georgia, Athens, GA 30602-2556, USA
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18
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Conradie J, Ghosh A. Do the One-Electron Oxidized Derivatives of Some Six-Coordinate Low-Spin Iron(III) Porphyrins Feature Strong Metal−Ligand Ferromagnetic Coupling? J Phys Chem B 2003. [DOI: 10.1021/jp030354n] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Jeanet Conradie
- Department of Chemistry, Faculty of Science, University of Tromsø, N-9037 Tromsø, Norway, and Department of Chemistry, University of the Free State, 9300 Bloemfontein, Republic of South Africa
| | - Abhik Ghosh
- Department of Chemistry, Faculty of Science, University of Tromsø, N-9037 Tromsø, Norway, and Department of Chemistry, University of the Free State, 9300 Bloemfontein, Republic of South Africa
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19
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Kobeissi M, Simonneaux G. 1H NMR and EPR studies of the electronic structure of low-spin iron(III) phosphonite mesotetraphenylchlorin complexes: a (dxz,dyz)4(dxy)1 configuration from 293 to 4 K. Inorganica Chim Acta 2003. [DOI: 10.1016/s0020-1693(02)01192-1] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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20
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Kinetic study of CO and O2 binding to horse heart myoglobin reconstituted with synthetic iron chlorin green hemes. Inorganica Chim Acta 2000. [DOI: 10.1016/s0020-1693(00)00320-0] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
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21
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Jasaitis A, Borisov VB, Belevich NP, Morgan JE, Konstantinov AA, Verkhovsky MI. Electrogenic reactions of cytochrome bd. Biochemistry 2000; 39:13800-9. [PMID: 11076519 DOI: 10.1021/bi001165n] [Citation(s) in RCA: 67] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Cytochrome bd is one of the two terminal quinol oxidases in the respiratory chain of Escherichia coli. The enzyme catalyzes charge separation across the bacterial membrane during the oxidation of quinols by dioxygen but does not pump protons. In this work, the reaction of cytochrome bd with O(2) and related reactions has been studied by time-resolved spectrophotometric and electrometric methods. Oxidation of the fully reduced enzyme by oxygen is accompanied by rapid generation of membrane potential (delta psi, negative inside the vesicles) that can be described by a two-step sequence of (i) an initial oxygen concentration-dependent, electrically silent, process (lag phase) corresponding to the formation of a ferrous oxy compound of heme d and (ii) a subsequent monoexponential electrogenic phase with a time constant <60 mus that matches the formation of ferryl-oxo heme d, the product of the reaction of O(2) with the 3-electron reduced enzyme. No evidence for generation of an intermediate analogous to the "peroxy" species of heme-copper oxidases could be obtained in either electrometric or spectrophotometric measurements of cytochrome bd oxidation or in a spectrophotometric study of the reaction of H(2)O(2) with the oxidized enzyme. Backflow of electrons upon flash photolysis of the singly reduced CO complex of cytochrome bd leads to transient generation of a delta psi of the opposite polarity (positive inside the vesicles) concurrent with electron flow from heme d to heme b(558) and backward. The amplitude of the delta psi produced by the backflow process, when normalized to the reaction yield, is close to that observed in the direct reaction during the reaction of fully reduced cytochrome bd with O(2) and is apparently associated with full transmembrane translocation of approximately one charge.
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Affiliation(s)
- A Jasaitis
- Department of Medical Chemistry, University of Helsinki, Finland
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22
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Simonneaux G, Schünemann V, Morice C, Carel L, Toupet L, Winkler H, Trautwein AX, Walker FA. Structural, Magnetic, and Dynamic Characterization of the (dxz,dyz)4(dxy)1 Ground-State Low-Spin Iron(III) Tetraphenylporphyrinate Complex [(p-TTP)Fe(2,6-XylylNC)2]CF3SO3. J Am Chem Soc 2000. [DOI: 10.1021/ja994190t] [Citation(s) in RCA: 74] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Gérard Simonneaux
- Contribution from the Laboratoire de Chimie Organométallique et Biologique, UMR CNRS 6509, Université de Rennes 1, Campus de Beaulieu, 35042 Rennes Cedex, France, Institut für Physik, Medizinische Universität zu Lübeck, 160 Ratzeburger Allee, D-23538 Lübeck, Germany, Groupe de Physique Cristalline, UA CNRS 040804, Université de Rennes 1, Campus de Beaulieu, 35042 Rennes Cedex, France, and Department of Chemistry, University of Arizona, Tucson, Arizona 85721-0041
| | - Volker Schünemann
- Contribution from the Laboratoire de Chimie Organométallique et Biologique, UMR CNRS 6509, Université de Rennes 1, Campus de Beaulieu, 35042 Rennes Cedex, France, Institut für Physik, Medizinische Universität zu Lübeck, 160 Ratzeburger Allee, D-23538 Lübeck, Germany, Groupe de Physique Cristalline, UA CNRS 040804, Université de Rennes 1, Campus de Beaulieu, 35042 Rennes Cedex, France, and Department of Chemistry, University of Arizona, Tucson, Arizona 85721-0041
| | - Christophe Morice
- Contribution from the Laboratoire de Chimie Organométallique et Biologique, UMR CNRS 6509, Université de Rennes 1, Campus de Beaulieu, 35042 Rennes Cedex, France, Institut für Physik, Medizinische Universität zu Lübeck, 160 Ratzeburger Allee, D-23538 Lübeck, Germany, Groupe de Physique Cristalline, UA CNRS 040804, Université de Rennes 1, Campus de Beaulieu, 35042 Rennes Cedex, France, and Department of Chemistry, University of Arizona, Tucson, Arizona 85721-0041
| | - Laurence Carel
- Contribution from the Laboratoire de Chimie Organométallique et Biologique, UMR CNRS 6509, Université de Rennes 1, Campus de Beaulieu, 35042 Rennes Cedex, France, Institut für Physik, Medizinische Universität zu Lübeck, 160 Ratzeburger Allee, D-23538 Lübeck, Germany, Groupe de Physique Cristalline, UA CNRS 040804, Université de Rennes 1, Campus de Beaulieu, 35042 Rennes Cedex, France, and Department of Chemistry, University of Arizona, Tucson, Arizona 85721-0041
| | - Loïc Toupet
- Contribution from the Laboratoire de Chimie Organométallique et Biologique, UMR CNRS 6509, Université de Rennes 1, Campus de Beaulieu, 35042 Rennes Cedex, France, Institut für Physik, Medizinische Universität zu Lübeck, 160 Ratzeburger Allee, D-23538 Lübeck, Germany, Groupe de Physique Cristalline, UA CNRS 040804, Université de Rennes 1, Campus de Beaulieu, 35042 Rennes Cedex, France, and Department of Chemistry, University of Arizona, Tucson, Arizona 85721-0041
| | - Heiner Winkler
- Contribution from the Laboratoire de Chimie Organométallique et Biologique, UMR CNRS 6509, Université de Rennes 1, Campus de Beaulieu, 35042 Rennes Cedex, France, Institut für Physik, Medizinische Universität zu Lübeck, 160 Ratzeburger Allee, D-23538 Lübeck, Germany, Groupe de Physique Cristalline, UA CNRS 040804, Université de Rennes 1, Campus de Beaulieu, 35042 Rennes Cedex, France, and Department of Chemistry, University of Arizona, Tucson, Arizona 85721-0041
| | - Alfred X. Trautwein
- Contribution from the Laboratoire de Chimie Organométallique et Biologique, UMR CNRS 6509, Université de Rennes 1, Campus de Beaulieu, 35042 Rennes Cedex, France, Institut für Physik, Medizinische Universität zu Lübeck, 160 Ratzeburger Allee, D-23538 Lübeck, Germany, Groupe de Physique Cristalline, UA CNRS 040804, Université de Rennes 1, Campus de Beaulieu, 35042 Rennes Cedex, France, and Department of Chemistry, University of Arizona, Tucson, Arizona 85721-0041
| | - F. Ann Walker
- Contribution from the Laboratoire de Chimie Organométallique et Biologique, UMR CNRS 6509, Université de Rennes 1, Campus de Beaulieu, 35042 Rennes Cedex, France, Institut für Physik, Medizinische Universität zu Lübeck, 160 Ratzeburger Allee, D-23538 Lübeck, Germany, Groupe de Physique Cristalline, UA CNRS 040804, Université de Rennes 1, Campus de Beaulieu, 35042 Rennes Cedex, France, and Department of Chemistry, University of Arizona, Tucson, Arizona 85721-0041
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Kobayashi K, Tagawa S, Mogi T. Electron transfer process in cytochrome bd-type ubiquinol oxidase from Escherichia coli revealed by pulse radiolysis. Biochemistry 1999; 38:5913-7. [PMID: 10231544 DOI: 10.1021/bi982088n] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Cytochrome bd is a two-subunit ubiquinol oxidase in the aerobic respiratory chain of Escherichia coli and binds hemes b558, b595, and d as the redox metal centers. Taking advantage of spectroscopic properties of three hemes which exhibit distinct absorption peaks, we investigated electron transfer within the enzyme by the technique of pulse radiolysis. Reduction of the hemes in the air-oxidized, resting-state enzyme, where heme d exists in mainly an oxygenated form and partially an oxoferryl and a ferric low-spin forms, occurred in two phases. In the faster phase, radiolytically generated N-methylnicotinamide radicals simultaneously reduced the ferric hemes b558 and b595 with a second-order rate constant of 3 x 10(8) M-1 s-1, suggesting that a rapid equilibrium occurs for electron transfer between two b-type hemes long before 10 micros. In the slower phase, an intramolecular electron transfer from heme b to the oxoferryl and the ferric heme d occurred with the first-order rate constant of 4.2-5.6 x 10(2) s-1. In contrast, the oxygenated heme d did not exhibit significant spectral change. Reactions with the fully oxidized and hydrogen peroxide-treated forms demonstrated that the oxidation and/or ligation states of heme d do not affect the heme b reduction. The following intramolecular electron transfer transformed the ferric and oxoferryl forms of heme d to the ferrous and ferric forms, respectively, with the first-order rate constants of 3.4 x 10(3) and 5.9 x 10(2) s-1, respectively.
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Affiliation(s)
- K Kobayashi
- Institute of Scientific and Industrial Research, Osaka University, Japan
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24
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Ghosh A, Gonzalez E, Vangberg T. Theoretical Studies of Low-Spin Six-Coordinate Iron(III) Porphyrins Relevant to Cytochromes b: Variable Electronic Configurations, Ligand Noninnocence, and Macrocycle Ruffling. J Phys Chem B 1999. [DOI: 10.1021/jp9830124] [Citation(s) in RCA: 44] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Abhik Ghosh
- Institute of Chemistry, Faculty of Science, University of Tromsø, N-9037 Tromsø, Norway
| | - Emmanuel Gonzalez
- Institute of Chemistry, Faculty of Science, University of Tromsø, N-9037 Tromsø, Norway
| | - Torgil Vangberg
- Institute of Chemistry, Faculty of Science, University of Tromsø, N-9037 Tromsø, Norway
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25
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Osborne JP, Gennis RB. Sequence analysis of cytochrome bd oxidase suggests a revised topology for subunit I. BIOCHIMICA ET BIOPHYSICA ACTA 1999; 1410:32-50. [PMID: 10076013 DOI: 10.1016/s0005-2728(98)00171-6] [Citation(s) in RCA: 57] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Numerous sequences of the cytochrome bd quinol oxidase (cytochrome bd) have recently become available for analysis. The analysis has revealed a small number of conserved residues, a new topology for subunit I and a phylogenetic tree involving extensive horizontal gene transfer. There are 20 conserved residues in subunit I and two in subunit II. Algorithms utilizing multiple sequence alignments predicted a revised topology for cytochrome bd, adding two transmembrane helices to subunit I to the seven that were previously indicated by the analysis of the sequence of the oxidase from E. coli. This revised topology has the effect of relocating the N-terminus and C-terminus to the periplasmic and cytoplasmic sides of the membrane, respectively. The new topology repositions I-H19, the putative ligand for heme b595, close to the periplasmic edge of the membrane, which suggests that the heme b595/heme d active site of the oxidase is located near the outer (periplasmic) surface of the membrane. The most highly conserved region of the sequence of subunit I contains the sequence GRQPW and is located in a predicted periplasmic loop connecting the eighth and ninth transmembrane helices. The potential importance of this region of the protein was previously unsuspected, and it may participate in the binding of either quinol or heme d. There are two very highly conserved glutamates in subunit I, E99 and E107, within the third transmembrane helix (E. coli cytochrome bd-I numbering). It is speculated that these glutamates may be part of a proton channel leading from the cytoplasmic side of the membrane to the heme d oxygen-reactive site, now placed near the periplasmic surface. The revised topology and newly revealed conserved residues provide a clear basis for further experimental tests of these hypotheses. Phylogenetic analysis of the new sequences of cytochrome bd reveals considerable deviation from the 16sRNA tree, suggesting that a large amount of horizontal gene transfer has occurred in the evolution of cytochrome bd.
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Affiliation(s)
- J P Osborne
- School of Chemical Sciences, University of Illinois, Urbana, IL 61801, USA
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26
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Affiliation(s)
- S Jünemann
- Glynn Laboratory of Bioenergetics, Department of Biology, University College London, UK.
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27
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Jünemann S, Wrigglesworth JM, Rich PR. Effects of decyl-aurachin D and reversed electron transfer in cytochrome bd. Biochemistry 1997; 36:9323-31. [PMID: 9235974 DOI: 10.1021/bi970055m] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
Decyl-aurachin D is a near-stoichiometric inhibitor of cytochrome bd from Azotobacter vinelandii. Interaction of decyl-aurachin D with the oxidase induces a redshift of the alpha-band and Soret band of a b-type cytochrome, probably b-558, suggesting close proximity of the inhibitor binding site to this haem and hence to the proposed quinol binding domain. The compound does not affect the oxygen binding site directly as judged from unchanged CO recombination kinetics to haem d in dithionite-reduced enzyme. Although in the presence of ubiquinol-1 a decyl-aurachin D containing sample generates levels of haem reduction and catalytic intermediates similar to the control, the approach to this steady state is severely inhibited. In addition to the spectral effect on b-558, decyl-aurachin D raises the midpoint potential of haem b-558, but also lowers that of haem b-595. Consistent with the shift in midpoint potentials, electron backflow from haem d to the b-type haems can be observed in decyl-aurachin D inhibited samples following photolysis of the mixed-valence CO-ligated form of the enzyme. The data show that decyl-aurachin D acts on the donor side of haem b-558 without substantially affecting internal electron transfer rates or the oxygen reduction site.
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Affiliation(s)
- S Jünemann
- Glynn Research Institute, Bodmin, Cornwall PL30 4AU, U.K., and King's College London, Camden Hill Road, London W8 7AH, U.K
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28
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Walker FA, Nasri H, Turowska-Tyrk I, Mohanrao K, Watson CT, Shokhirev NV, Debrunner PG, Scheidt WR. π-Acid Ligands in Iron(III) Porphyrinates. Characterization of Low-Spin Bis(tert-butylisocyanide)(porphyrinato)iron(III) Complexes Having (dxz,dyz)4(dxy)1 Ground States. J Am Chem Soc 1996. [DOI: 10.1021/ja961971a] [Citation(s) in RCA: 127] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- F. Ann Walker
- Contribution from the Department of Chemistry, University of Arizona, Tucson, Arizona 85721, Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, Indiana 46556, and Department of Physics, University of Illinois, Urbana-Champaign, Illinois 61801
| | - Habib Nasri
- Contribution from the Department of Chemistry, University of Arizona, Tucson, Arizona 85721, Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, Indiana 46556, and Department of Physics, University of Illinois, Urbana-Champaign, Illinois 61801
| | - Ilona Turowska-Tyrk
- Contribution from the Department of Chemistry, University of Arizona, Tucson, Arizona 85721, Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, Indiana 46556, and Department of Physics, University of Illinois, Urbana-Champaign, Illinois 61801
| | - K. Mohanrao
- Contribution from the Department of Chemistry, University of Arizona, Tucson, Arizona 85721, Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, Indiana 46556, and Department of Physics, University of Illinois, Urbana-Champaign, Illinois 61801
| | - C. Todd Watson
- Contribution from the Department of Chemistry, University of Arizona, Tucson, Arizona 85721, Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, Indiana 46556, and Department of Physics, University of Illinois, Urbana-Champaign, Illinois 61801
| | - Nikolai V. Shokhirev
- Contribution from the Department of Chemistry, University of Arizona, Tucson, Arizona 85721, Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, Indiana 46556, and Department of Physics, University of Illinois, Urbana-Champaign, Illinois 61801
| | - Peter G. Debrunner
- Contribution from the Department of Chemistry, University of Arizona, Tucson, Arizona 85721, Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, Indiana 46556, and Department of Physics, University of Illinois, Urbana-Champaign, Illinois 61801
| | - W. Robert Scheidt
- Contribution from the Department of Chemistry, University of Arizona, Tucson, Arizona 85721, Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, Indiana 46556, and Department of Physics, University of Illinois, Urbana-Champaign, Illinois 61801
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29
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Sun J, Kahlow MA, Kaysser TM, Osborne JP, Hill JJ, Rohlfs RJ, Hille R, Gennis RB, Loehr TM. Resonance Raman spectroscopic identification of a histidine ligand of b595 and the nature of the ligation of chlorin d in the fully reduced Escherichia coli cytochrome bd oxidase. Biochemistry 1996; 35:2403-12. [PMID: 8652583 DOI: 10.1021/bi9518252] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
Cytochrome bd oxidase is a bacterial terminal oxidase that contains three cofactors: a low-spin heme (b558), a high-spin heme (b595), and a chlorin d. The center of dioxygen reduction has been proposed to be a binuclear b595/d site, whereas b558 is mainly involved in transferring electrons from ubiquinol to the oxidase. Information on the nature of the axial ligands of the three heme centers has come from site-directed mutagenesis and spectroscopy, which have implicated a His/Met coordination for b558 (Spinner, F., Cheesman, M. R., Thomson, A. J., Kaysser, T., Gennis, R. B., Peng, Q., & Peterson, J. (1995) Biochem. J. 308, 641-644; Kaysser, T. M., Ghaim, J. B., Georgiou, C., & Gennis, R. B. (1995) Biochemistry 34, 13491-13501), but the ligands to b595 and d are not known with certainty. In this work, the three heme chromophores of the fully reduced cytochrome bd oxidase are studied individually by selective enhancement of their resonance Raman (rR) spectra at particular excitation wavelengths. The rR spectrum obtained with 413.1-nm excitation is dominated by the bands of the 5cHS b595(2+) cofactor. Excitation close to 560 nm yields a rR spectrum dominated by the 6cLS b558(2+) heme. Wavelengths between these values enhance contributions from both b595(2+) and b558(2+) chromophores. The rR bands of the ferrous chlorin become the major features with red laser excitation (595-650 nm). The rR data indicate that d2+ is a 5cHS system whose axial ligand is either a weakly coordinating protein donor or a water molecule. In the low-frequency region of the 441.6-nm spectrum, we assign a rR band at 225 cm-1 to the (b595)Fe(II)-N(His) stretching vibration, based on its 1.2-cm(-1) upshift in the 54Fe-labeled enzyme. This observation provides the first physical evidence that the proximal ligand of b595 is a histidine. Site-directed mutagenesis had suggested that His 19 is associated with either b595 or d (Fang, H., Lin, R. -J., & Gennis, R. B. (1989) J. Biol. Chem. 264, 8026-8032). On the basis of the present study, we propose that the proximal ligand of b595 is His 19. We have also studied the reaction of cyanide with the fully reduced cytochrome bd oxidase. In approximately 700-fold excess cyanide (approximately 35 mM), the 629-nm UV/vis band of d2+ is blue-shifted to 625 nm and diminished in intensity. However, the rR spectra at each of three different gamma(0) (413.1, 514.5, and 647.1 nm) are identical with or without cyanide, thus indicating that both b595 and d remain as 5cHS species in the presence of CN-. This observation leads to the proposal that a native ligand of ferrous chlorin d is replaced by CN- to form the 5cHS d2+ cyano adduct. These findings corroborate our companion study of the "as-isolated" enzyme in which we proposed a 5cHS d3+ cyano adduct (Sun, J., Osborne, J. P., Kahlow, M. A., Kaysser, T. M., Hill, J. J., Gennis, R. B., & Loehr, T. M. (1995) Biochemistry 34, 12144-12151). To further characterize the unusual and unexpected nature of these proposed high-spin cyanide adducts, we have obtained EPR spectral evidence that binding of cyanide to fully oxidized cytochrome bd oxidase perturbs a spin-state equilibrium in the chlorin d3+ to yield entirely the high-spin form of the cofactor.
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Affiliation(s)
- J Sun
- Department of Chemistry, Biochemistry & Molecular Biology, Oregon Graduate Institute of Science & Technology, Portland 97291-1000, USA
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30
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Coulter ED, Sono M, Chang CK, Lopez O, Dawson JH. Electron paramagnetic resonance spectroscopy as a probe of coordination structure in green heme systems: iron chlorins and iron formylporphyrins reconstituted into myoglobin. Inorganica Chim Acta 1995. [DOI: 10.1016/0020-1693(95)04588-0] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
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31
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Tsubaki M, Hori H, Mogi T, Anraku Y. Cyanide-binding site of bd-type ubiquinol oxidase from Escherichia coli. J Biol Chem 1995; 270:28565-9. [PMID: 7499371 DOI: 10.1074/jbc.270.48.28565] [Citation(s) in RCA: 64] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023] Open
Abstract
We extended our investigation on the structure of the redox centers of bd-type ubiquinol oxidase from Escherichia coli using cyanide as a monitoring probe. We found that addition of cyanide to the air-oxidized O2-bound enzyme caused appearance of an infrared C-N stretching band at 2161 cm-1 and concomitant disappearance of the 647 nm absorption band of the cytochrome d (Fe2+)-O2 species. Addition of cyanide to the air-oxidized CO-bound enzyme also resulted in disappearance of the 635 nm absorption band and the 1983.4 cm-1 C-O infrared band of the cytochrome d (Fe2+)-CO species. The resulting species had a derivative-shaped electron paramagnetic resonance signal at g = 3.15. Upon partial reduction with sodium dithionite, this species was converted partly to a transient heme d (Fe3+)-C = N species having an electron paramagnetic resonance signal at gz = 2.96 and a C-N infrared band at 2138 cm-1. These observations suggest that the active site of the enzyme has a heme-heme binuclear metal center distinct from that of the heme-copper terminal oxidase and that the treatment of the air-oxidized enzyme with cyanide resulted in a cyanide-bridging species with "heme d(Fe3+)-C = N-heme b595(Fe3+)" structure.
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Affiliation(s)
- M Tsubaki
- Department of Life Science, Faculty of Science, Himeji Institute of Technology, Hyogo, Japan
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Sun J, Osborne JP, Kahlow MA, Kaysser TM, Hil JJ, Gennis RB, Loehr TM. Resonance Raman studies of Escherichia coli cytochrome bd oxidase. Selective enhancement of the three heme chromophores of the "as-isolated" enzyme and characterization of the cyanide adduct. Biochemistry 1995; 34:12144-51. [PMID: 7547954 DOI: 10.1021/bi00038a007] [Citation(s) in RCA: 22] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
Cytochrome bd oxidase is a terminal bacterial oxidase containing three cofactors: a low-spin heme (b558), a high-spin heme (b595), and a chlorin d. The center of dioxygen reduction has been proposed to be at a dinuclear b595/d site, whereas b558 is mainly involved in transferring electrons from ubiquinone. One of the unique functional features of this enzyme is its resistance to high concentrations of cyanide (Ki in the millimolar range). With the appropriate selection of laser lines, the ligation and spin states of the b558, b595, and d hemes can be probed selectively by resonance Raman (rR) spectroscopy. Wavelengths between 400 and 500 nm predominantly excite the rR spectra of the b558 and b595 chromophores. Spectra obtained within this interval show a mixed population of spin and ligation states arising from b558 and b595, with the former more strongly enhanced at higher energy. Red excitation wavelengths (590-650 nm) generate rR spectra characteristic of chlorins, indicating the selective enhancement of the d heme. These rR results reveal that cytochrome bd oxidase "as isolated" contains the b558 heme in a six-coordinate low-spin ferric state, the b595 heme in a five-coordinate high-spin (5cHS) ferric state, and the d heme in a mixture of oxygenated (FeIIO2 <--> FeIIIO2-; d650) and ferryl-oxo (FeIV = O; d680) states. However, the rR spectra of these two chlorin species indicate that they are both in the 5cHS state, suggesting that the d heme is lacking a strongly coordinated sixth ligand.(ABSTRACT TRUNCATED AT 250 WORDS)
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Affiliation(s)
- J Sun
- Department of Chemistry, Biochemistry, and Molecular Biology, Oregon Graduate Institute of Science & Technology, Portland 97291-1000, USA
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Jünemann S, Wrigglesworth JM. Cytochrome bd oxidase from Azotobacter vinelandii. Purification and quantitation of ligand binding to the oxygen reduction site. J Biol Chem 1995; 270:16213-20. [PMID: 7608187 DOI: 10.1074/jbc.270.27.16213] [Citation(s) in RCA: 49] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023] Open
Abstract
Cytochrome bd has been purified from Azotobacter vinelandii by a new simplified procedure. The heme and total iron content has been measured, as has the number of high affinity CO and NO binding sites. Spectral changes indicate high affinity binding of CO and NO to heme d only, with a stoichiometry of 1 molecule of gas per 2 molecules of heme b or per 3 atoms of iron. The results clearly define a stoichiometry of one heme d per complex. Low affinity binding of CO and NO to heme b595 also occurs at higher ligand concentrations. EPR heme-nitrosyl signals are seen with NO bound to both hemes b595 and d but with no indication of spin exchange coupling. Exposure of the air-oxidized complex to alkaline pH results in removal of molecular oxygen from heme d and a change in line shape of the high spin region of the EPR spectrum. Cyanide binds to both heme d and heme b595 in the air-oxidized complex, displacing molecular oxygen from heme d. The rate of cyanide binding to heme d as assessed by spectral changes at 650 nm does not correlate with the rate of binding to heme b595 as assessed by the loss of the high spin EPR signal. In addition, the cyanide binding rate in the presence of reductant is only 3 times that of the rate of binding to the air-oxidized enzyme, in contrast to the copper-containing oxidases where strong redox cooperativity makes these two rates differ by a factor of at least 10(6). The results do not support the idea of the presence of two strongly interacting hemes in a binuclear center.
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Affiliation(s)
- S Jünemann
- Metals in Biology and Medicine Centre, King's College London, United Kingdom
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Hill BC, Hill JJ, Gennis RB. The room temperature reaction of carbon monoxide and oxygen with the cytochrome bd quinol oxidase from Escherichia coli. Biochemistry 1994; 33:15110-5. [PMID: 7999770 DOI: 10.1021/bi00254a021] [Citation(s) in RCA: 44] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
When grown under O2-limited conditions, Escherichia coli expresses a cytochrome bd quinol oxidase that has an unusually high affinity for O2. We have studied the reaction of cytochrome bd with CO and O2 by rapid-reaction spectrophotometry. The reduced enzyme forms a photosensitive ferrocytochrome d-CO complex, and following photolysis, CO recombines with the reduced enzyme with a bimolecular rate of 8 x 10(7) M-1 s-1. Reaction of CO-bound enzyme with O2 gives a CO off-rate of 1.6 s-1. The O2 reaction is followed by a flow-flash procedure in which CO-ligated enzyme is mixed with O2, and the reaction commenced by photolysis of cytochrome d-CO. In the presence of O2, two processes are resolved on a time-scale of 300 microseconds. The absorbance at 645 nm first increases at a rate that is dependent on O2 concentration with a value of 2 x 10(9) M-1 s-1. The second phase results in decreased absorbance at 645 nm and increased absorbance at 680 nm. The rate of the second process is independent from O2 concentration above 50 microM O2 and reaches a first-order limit of 1 x 10(4) s-1. A model for the reaction of the cytochrome bd quinol oxidase with O2 is proposed in which an initial ferrocytochrome d-oxy adduct forms, and then decays to a ferryl-oxo species. The oxidation of the low-spin cytochrome b component of the oxidase, monitored at 560 nm, occurs at the same time as the ferryl species forms. We suggest that the suitability of the cytochrome bd quinol oxidase to function at low O2 concentration is conferred by its rapid rate of binding O2.
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Affiliation(s)
- B C Hill
- Department of Biochemistry, Queen's University, Kingston, Ontario, Canada
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D'mello R, Palmer S, Hill S, Poole RK. The cytochromebdterminal oxidase ofAzotobacter vinelandii: Low temperature photodissociation spectrophotometry reveals reactivity of cytochromesb595anddwith both carbon monoxide and oxygen. FEMS Microbiol Lett 1994. [DOI: 10.1111/j.1574-6968.1994.tb07084.x] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
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Poole RK. Oxygen reactions with bacterial oxidases and globins: binding, reduction and regulation. Antonie Van Leeuwenhoek 1994; 65:289-310. [PMID: 7832588 DOI: 10.1007/bf00872215] [Citation(s) in RCA: 67] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
Oxygen is favoured as terminal electron acceptor in aerobic and facultative microorganisms because of its appropriate physical state, satisfactory solubility and its desirable combinations of kinetic and thermodynamic properties. Oxygen is generally reduced by four electrons to yield oxygen, but there are important biological consequences of, and roles for, the partial reduction to superoxide and peroxide. Complex and multiple regulatory networks ensure (i) the utilization of oxygen in preference to other oxidants, (ii) the synthesis of oxygen-consuming enzymes with appropriate properties (particularly affinity for the ligand), and (iii) appropriate cellular protection in the event of oxidative stress. This contribution reviews the terminal respiratory oxidases of selected Gram-negative bacteria and microbial haemoglobin-like proteins. Recent studies of the cytochrome bd-type oxidases of Escherichia coli and Azotobacter vinelandii suggest that, despite probable similarity at the amino acid level, the reactivities of these oxidases with oxygen are strikingly different. The respiratory protection afforded to nitrogenase in the obligately aerobic diazotroph A. vinelandii by the cytochrome bd complex appears to be accompanied by, and may be the result of, a low affinity for oxygen and a high Vmax. The poorly characterized cytochrome o-containing oxidase in this bacterium is not required for respiratory protection. In E. coli, the cytochrome bd-type oxidase has a remarkably high affinity for oxygen, consistent with the view that this is an oxygen-scavenging oxidase utilized under microaerobic conditions. The demonstration of substrate (i.e. oxygen) inhibition in this complex suggests a mechanism whereby wasteful electron flux through a non-proton-pumping oxidase is avoided at higher dissolved oxygen tensions. The demonstration of two ligand-binding sites (haems d and b595) in oxidases of this type suggests plausible mechanisms for this phenomenon. In E. coli, assembly of the cytochrome bd-type oxidase (and of periplasmic cytochromes b and c) requires the presence of an ABC transporter, which may serve to export haem or some "assembly factor" to the periplasm. There is at least one additional oxygen-consuming protein in E. coli-the flavohaemoglobin encoded by the hmp gene. Globin-like proteins are also widely distributed in other bacteria, fungi and protozoa, but most have unknown functions. The function of HMP and the related chimaeric flavohaemoglobins in other bacteria and yeast is unknown; one of several possibilities for HMP is that its relatively low affinity for oxygen during turnover with NADH as substrate could enable it to function as a sensor of failing (or rising) cytoplasmic oxygen concentrations.
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Affiliation(s)
- R K Poole
- Division of Life Sciences, King's College London, U.K
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Tsubaki M, Uno T, Hori H, Mogi T, Nishimura Y, Anraku Y. Cytochrome d axial ligand of the bd-type terminal quinol oxidase from Escherichia coli. FEBS Lett 1993; 335:13-7. [PMID: 8243657 DOI: 10.1016/0014-5793(93)80430-3] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
Using various spectroscopic techniques, we studied the structure of the dioxygen reduction site of the bd-type terminal quinol oxidase in the aerobic respiratory chain of Escherichia coli. Resonance Raman and FT-IR spectroscopies identified the v(Fe(2+)-CO) and v(C-O) stretching frequencies at 471 and 1980.7 cm-1, respectively, at the cytochrome d center of the dithionite-reduced CO-bound enzyme. The CO ligation in the cytochrome bd complex is considerably different from those of the heme-copper terminal oxidases. Anaerobic addition of NO to the air-oxidized enzyme caused an exchange of cytochrome d-bound dioxygen with NO leading to an appearance of cytochrome d-NO EPR signal. But there is no superhyperfine structure originating from the cytochrome d proximal 14N ligand in the central resonance of the NO EPR signal. These results suggest that cytochrome d axial ligand of the cytochrome bd complex is likely a histidine residue in an anomalous condition or other than a histidine residue and, therefore, the molecular structure around the dioxygen-binding site is different from that of the heme-copper terminal oxidases.
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Affiliation(s)
- M Tsubaki
- Department of Life Science, Faculty of Science, Himeji Institute of Technology, Hyogo, Japan
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Dawson JH, Bracete AM, Huff AM, Kadkhodayan S, Zeitler CM, Sono M, Chang CK, Loewen PC. The active site structure of E. coli HPII catalase. Evidence favoring coordination of a tyrosinate proximal ligand to the chlorin iron. FEBS Lett 1991; 295:123-6. [PMID: 1662642 DOI: 10.1016/0014-5793(91)81401-s] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
E. coli produces 2 catalases known as HPI and HPII. While the heme prosthetic group of the HPII catalase has been established to be a dihydroporphyrin or chlorin, the identity of the proximal ligand to the iron has not been addressed. The magnetic circular dichroism (MCD) spectrum of native ferric HPII catalase is very similar to those of a 5-coordinate phenolate-ligated ferric chlorin complex, a model for tyrosinate proximal ligation, as well as of chlorin-reconstituted ferric horseradish peroxidase, a model for 5-coordinate histidine ligation. However, further MCD comparisons of chlorin-reconstituted myoglobin with parallel ligand-bound adducts of the catalase clearly rule out histidine ligation in the latter, leaving tyrosinate as the best candidate for the proximal ligand.
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Affiliation(s)
- J H Dawson
- Department of Chemistry and Biochemistry, University of South Carolina, Columbia 29208
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Oden KL, Gennis RB. Isolation and characterization of a new class of cytochrome d terminal oxidase mutants of Escherichia coli. J Bacteriol 1991; 173:6174-83. [PMID: 1655701 PMCID: PMC208368 DOI: 10.1128/jb.173.19.6174-6183.1991] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022] Open
Abstract
Cytochrome d terminal oxidase mutants were isolated by using hydroxylamine mutagenesis of pNG2, a pBR322-derived plasmid containing the wild-type cyd operon. The mutagenized plasmid was transformed into a cyo cyd recA strain, and the transformants were screened for the inability to confer aerobic growth on nonfermentable carbon sources. Western blot analysis and visible-light spectroscopy were performed to characterize three independent mutants grown both aerobically and anaerobically. The mutational variants of the cytochrome d complex were stabilized under anaerobic growth conditions. All three mutations perturb the b595 and d heme components of the complex. These mutations were mapped and sequenced and are shown to be located in the N-terminal third of subunit II of the cytochrome d complex. It is proposed that the N terminus of subunit II may interact with subunit I to form an interface that binds the b595 and d heme centers.
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Affiliation(s)
- K L Oden
- Department of Chemistry, School of Chemical Sciences, University of Illinois, Urbana 61801
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Dueweke TJ, Gennis RB. Proteolysis of the cytochrome d complex with trypsin and chymotrypsin localizes a quinol oxidase domain. Biochemistry 1991; 30:3401-6. [PMID: 1707310 DOI: 10.1021/bi00228a007] [Citation(s) in RCA: 41] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
The cytochrome d complex is a two-subunit, membrane-bound terminal oxidase in the aerobic respiratory chain of Escherichia coli. The enzyme catalyzes the two-electron oxidation of ubiquinol and the four-electron reduction of oxygen to water. Previous work demonstrated that the site for ubiquinol oxidation was selectively inactivated by limited proteolysis by trypsin, which cleaves at a locus within subunit I. This work is extended to show that a similar phenomenon is observed with limited chymotrypsin proteolysis of the complex. The cleavage patterns are similar whether one uses the purified oxidase in nondenaturing detergent or reconstituted in proteoliposomes or uses spheroplasts of E. coli as the substrate for the proteolysis. Hence, the protease-sensitive locus is periplasmic in the cell. Fragments resulting from proteolysis were characterized by N-terminal sequencing and by immunoblotting with the use of a monoclonal antibody of known epitope within subunit I. The data indicate that inactivation of the ubiquinol oxidase activity results from cleavage at specific residues with a hydrophilic region previously defined as the Q loop. This domain has been already implicated in ubiquinol oxidation by the use of inhibitory monoclonal antibodies. Electrochemical and HPLC analysis of the protease-cleaved oxidase suggests no global changes in either the quaternary or tertiary structure of the enzyme. It is likely that the Q loop is directly involved in forming a portion of the ubiquinol binding site near the periplasmic surface of the membrane.
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Affiliation(s)
- T J Dueweke
- Department of Biochemistry, University of Illinois, Urbana 61801
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