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Król S, Fedotovskaya O, Högbom M, Ädelroth P, Brzezinski P. Electron and proton transfer in the M. smegmatis III 2IV 2 supercomplex. BIOCHIMICA ET BIOPHYSICA ACTA. BIOENERGETICS 2022; 1863:148585. [PMID: 35753381 DOI: 10.1016/j.bbabio.2022.148585] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/12/2022] [Revised: 05/25/2022] [Accepted: 06/17/2022] [Indexed: 06/15/2023]
Abstract
The M. smegmatis respiratory III2IV2 supercomplex consists of a complex III (CIII) dimer flanked on each side by a complex IV (CIV) monomer, electronically connected by a di-heme cyt. cc subunit of CIII. The supercomplex displays a quinol oxidation‑oxygen reduction activity of ~90 e-/s. In the current work we have investigated the kinetics of electron and proton transfer upon reaction of the reduced supercomplex with molecular oxygen. The data show that, as with canonical CIV, oxidation of reduced CIV at pH 7 occurs in three resolved components with time constants ~30 μs, 100 μs and 4 ms, associated with the formation of the so-called peroxy (P), ferryl (F) and oxidized (O) intermediates, respectively. Electron transfer from cyt. cc to the primary electron acceptor of CIV, CuA, displays a time constant of ≤100 μs, while re-reduction of cyt. cc by heme b occurs with a time constant of ~4 ms. In contrast to canonical CIV, neither the P → F nor the F → O reactions are pH dependent, but the P → F reaction displays a H/D kinetic isotope effect of ~3. Proton uptake through the D pathway in CIV displays a single time constant of ~4 ms, i.e. a factor of ~40 slower than with canonical CIV. The slowed proton uptake kinetics and absence of pH dependence are attributed to binding of a loop from the QcrB subunit of CIII at the D proton pathway of CIV. Hence, the data suggest that function of CIV is modulated by way of supramolecular interactions with CIII.
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Affiliation(s)
- Sylwia Król
- Department of Biochemistry and Biophysics, The Arrhenius Laboratories for Natural Sciences, Stockholm University, SE-106 91 Stockholm, Sweden
| | - Olga Fedotovskaya
- Department of Biochemistry and Biophysics, The Arrhenius Laboratories for Natural Sciences, Stockholm University, SE-106 91 Stockholm, Sweden
| | - Martin Högbom
- Department of Biochemistry and Biophysics, The Arrhenius Laboratories for Natural Sciences, Stockholm University, SE-106 91 Stockholm, Sweden
| | - Pia Ädelroth
- Department of Biochemistry and Biophysics, The Arrhenius Laboratories for Natural Sciences, Stockholm University, SE-106 91 Stockholm, Sweden.
| | - Peter Brzezinski
- Department of Biochemistry and Biophysics, The Arrhenius Laboratories for Natural Sciences, Stockholm University, SE-106 91 Stockholm, Sweden.
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Sarewicz M, Pintscher S, Pietras R, Borek A, Bujnowicz Ł, Hanke G, Cramer WA, Finazzi G, Osyczka A. Catalytic Reactions and Energy Conservation in the Cytochrome bc1 and b6f Complexes of Energy-Transducing Membranes. Chem Rev 2021; 121:2020-2108. [PMID: 33464892 PMCID: PMC7908018 DOI: 10.1021/acs.chemrev.0c00712] [Citation(s) in RCA: 61] [Impact Index Per Article: 20.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2020] [Indexed: 12/16/2022]
Abstract
This review focuses on key components of respiratory and photosynthetic energy-transduction systems: the cytochrome bc1 and b6f (Cytbc1/b6f) membranous multisubunit homodimeric complexes. These remarkable molecular machines catalyze electron transfer from membranous quinones to water-soluble electron carriers (such as cytochromes c or plastocyanin), coupling electron flow to proton translocation across the energy-transducing membrane and contributing to the generation of a transmembrane electrochemical potential gradient, which powers cellular metabolism in the majority of living organisms. Cytsbc1/b6f share many similarities but also have significant differences. While decades of research have provided extensive knowledge on these enzymes, several important aspects of their molecular mechanisms remain to be elucidated. We summarize a broad range of structural, mechanistic, and physiological aspects required for function of Cytbc1/b6f, combining textbook fundamentals with new intriguing concepts that have emerged from more recent studies. The discussion covers but is not limited to (i) mechanisms of energy-conserving bifurcation of electron pathway and energy-wasting superoxide generation at the quinol oxidation site, (ii) the mechanism by which semiquinone is stabilized at the quinone reduction site, (iii) interactions with substrates and specific inhibitors, (iv) intermonomer electron transfer and the role of a dimeric complex, and (v) higher levels of organization and regulation that involve Cytsbc1/b6f. In addressing these topics, we point out existing uncertainties and controversies, which, as suggested, will drive further research in this field.
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Affiliation(s)
- Marcin Sarewicz
- Department
of Molecular Biophysics, Faculty of Biochemistry, Biophysics and Biotechnology, Jagiellonian University, 30-387 Kraków, Poland
| | - Sebastian Pintscher
- Department
of Molecular Biophysics, Faculty of Biochemistry, Biophysics and Biotechnology, Jagiellonian University, 30-387 Kraków, Poland
| | - Rafał Pietras
- Department
of Molecular Biophysics, Faculty of Biochemistry, Biophysics and Biotechnology, Jagiellonian University, 30-387 Kraków, Poland
| | - Arkadiusz Borek
- Department
of Molecular Biophysics, Faculty of Biochemistry, Biophysics and Biotechnology, Jagiellonian University, 30-387 Kraków, Poland
| | - Łukasz Bujnowicz
- Department
of Molecular Biophysics, Faculty of Biochemistry, Biophysics and Biotechnology, Jagiellonian University, 30-387 Kraków, Poland
| | - Guy Hanke
- School
of Biological and Chemical Sciences, Queen
Mary University of London, London E1 4NS, U.K.
| | - William A. Cramer
- Department
of Biological Sciences, Purdue University, West Lafayette, Indiana 47907 United States
| | - Giovanni Finazzi
- Laboratoire
de Physiologie Cellulaire et Végétale, Université Grenoble Alpes, Centre National Recherche Scientifique,
Commissariat Energie Atomique et Energies Alternatives, Institut National
Recherche l’agriculture, l’alimentation et l’environnement, 38054 Grenoble Cedex 9, France
| | - Artur Osyczka
- Department
of Molecular Biophysics, Faculty of Biochemistry, Biophysics and Biotechnology, Jagiellonian University, 30-387 Kraków, Poland
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Pérez-Mejías G, Olloqui-Sariego JL, Guerra-Castellano A, Díaz-Quintana A, Calvente JJ, Andreu R, De la Rosa MA, Díaz-Moreno I. Physical contact between cytochrome c1 and cytochrome c increases the driving force for electron transfer. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2020; 1861:148277. [DOI: 10.1016/j.bbabio.2020.148277] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/30/2020] [Revised: 06/29/2020] [Accepted: 07/09/2020] [Indexed: 01/09/2023]
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Melin F, Hellwig P. Redox Properties of the Membrane Proteins from the Respiratory Chain. Chem Rev 2020; 120:10244-10297. [DOI: 10.1021/acs.chemrev.0c00249] [Citation(s) in RCA: 22] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Affiliation(s)
- Frederic Melin
- Chimie de la Matière Complexe UMR 7140, Laboratoire de Bioelectrochimie et Spectroscopie, CNRS-Université de Strasbourg, 1 rue Blaise Pascal, 67070 Strasbourg, France
| | - Petra Hellwig
- Chimie de la Matière Complexe UMR 7140, Laboratoire de Bioelectrochimie et Spectroscopie, CNRS-Université de Strasbourg, 1 rue Blaise Pascal, 67070 Strasbourg, France
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Borek A, Ekiert R, Osyczka A. Functional flexibility of electron flow between quinol oxidation Q o site of cytochrome bc 1 and cytochrome c revealed by combinatory effects of mutations in cytochrome b, iron-sulfur protein and cytochrome c 1. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2018; 1859:754-761. [PMID: 29705394 DOI: 10.1016/j.bbabio.2018.04.010] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/17/2018] [Revised: 04/16/2018] [Accepted: 04/24/2018] [Indexed: 01/07/2023]
Abstract
Transfer of electron from quinol to cytochrome c is an integral part of catalytic cycle of cytochrome bc1. It is a multi-step reaction involving: i) electron transfer from quinol bound at the catalytic Qo site to the Rieske iron-sulfur ([2Fe-2S]) cluster, ii) large-scale movement of a domain containing [2Fe-2S] cluster (ISP-HD) towards cytochrome c1, iii) reduction of cytochrome c1 by reduced [2Fe-2S] cluster, iv) reduction of cytochrome c by cytochrome c1. In this work, to examine this multi-step reaction we introduced various types of barriers for electron transfer within the chain of [2Fe-2S] cluster, cytochrome c1 and cytochrome c. The barriers included: impediment in the motion of ISP-HD, uphill electron transfer from [2Fe-2S] cluster to heme c1 of cytochrome c1, and impediment in the catalytic quinol oxidation. The barriers were introduced separately or in various combinations and their effects on enzymatic activity of cytochrome bc1 were compared. This analysis revealed significant degree of functional flexibility allowing the cofactor chains to accommodate certain structural and/or redox potential changes without losing overall electron and proton transfers capabilities. In some cases inhibitory effects compensated one another to improve/restore the function. The results support an equilibrium model in which a random oscillation of ISP-HD between the Qo site and cytochrome c1 helps maintaining redox equilibrium between all cofactors of the chain. We propose a new concept in which independence of the dynamics of the Qo site substrate and the motion of ISP-HD is one of the elements supporting this equilibrium and also is a potential factor limiting the overall catalytic rate.
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Affiliation(s)
- Arkadiusz Borek
- Department of Molecular Biophysics, Faculty of Biochemistry, Biophysics and Biotechnology, Jagiellonian University, 30-387 Kraków, Poland
| | - Robert Ekiert
- Department of Molecular Biophysics, Faculty of Biochemistry, Biophysics and Biotechnology, Jagiellonian University, 30-387 Kraków, Poland
| | - Artur Osyczka
- Department of Molecular Biophysics, Faculty of Biochemistry, Biophysics and Biotechnology, Jagiellonian University, 30-387 Kraków, Poland.
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Vos MH, Reeder BJ, Daldal F, Liebl U. Ultrafast photochemistry of the bc 1 complex. Phys Chem Chem Phys 2018; 19:6807-6813. [PMID: 28218331 DOI: 10.1039/c7cp00193b] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
We present a full investigation of ultrafast light-induced events in the membraneous cytochrome bc1 complex by transient absorption spectroscopy. This energy-transducing complex harbors four redox-active components per monomer: heme c1, two 6-coordinate b-hemes and a [2Fe-2S] cluster. Using excitation of these components in different ratios under various excitation conditions, probing in the full visible range and under three well-defined redox conditions, we demonstrate that for all ferrous hemes of the complex photodissociation of axial ligands takes place and that they rebind in 5-7 ps, as in other 6-coordinate heme proteins, including cytoglobin, which is included as a reference in this study. By contrast, the signals are not consistent with photooxidation of the b hemes. This conclusion contrasts with a recent assessment based on a more limited data set. The binding kinetics of internal and external ligands are indicative of a rigid heme environment, consistent with the electron transfer function. We also report, for the first time, photoactivity of the very weakly absorbing iron-sulfur center. This yields the unexpected perspective of studying photochemistry, initiated by excitation of iron-sulfur clusters, in a range of protein complexes.
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Affiliation(s)
- Marten H Vos
- LOB, Ecole Polytechnique, CNRS, INSERM, 91128 Palaiseau Cedex, France.
| | | | - Fevzi Daldal
- Department of Biology, University of Pennsylvania, Philadelphia, PA 19104, USA
| | - Ursula Liebl
- LOB, Ecole Polytechnique, CNRS, INSERM, 91128 Palaiseau Cedex, France.
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Cerda JF, Guzman CX, Zhang H, Amendola EJ, Castorino JD, Millet N, Fritz AL, Houchins DN, Roeder MH. Spectroelectrochemical measurements of redox proteins by using a simple UV/visible cell. Electrochem commun 2013. [DOI: 10.1016/j.elecom.2013.05.004] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022] Open
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Kokhan O, Shinkarev VP, Wraight CA. Binding of imidazole to the heme of cytochrome c1 and inhibition of the bc1 complex from Rhodobacter sphaeroides: II. Kinetics and mechanism of binding. J Biol Chem 2010; 285:22522-31. [PMID: 20448037 PMCID: PMC2903381 DOI: 10.1074/jbc.m110.128082] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2010] [Revised: 04/30/2010] [Indexed: 11/06/2022] Open
Abstract
The kinetics of imidazole (Im) and N-methylimidazole (MeIm) binding to oxidized cytochrome (cyt) c(1) of detergent-solubilized bc(1) complex from Rhodobacter sphaeroides are described. The rate of formation of the cyt c(1)-Im complex exhibited three separated regions of dependence on the concentration of imidazole: (i) below 8 mM Im, the rate increased with concentration in a parabolic manner; (ii) above 20 mM, the rate leveled off, indicating a rate-limiting conformational step with lifetime approximately 1 s; and (iii) at Im concentrations above 100 mM, the rate substantially increased again, also parabolically. In contrast, binding of MeIm followed a simple hyperbolic concentration dependence. The temperature dependences of the binding and release kinetics of Im and MeIm were also measured and revealed very large activation parameters for all reactions. The complex concentration dependence of the Im binding rate is not consistent with the popular model for soluble c-type cytochromes in which exogenous ligand binding is preceded by spontaneous opening of the heme cleft, which becomes rate-limiting at high ligand concentrations. Instead, binding of ligand to the heme is explained by a model in which an initial and superficial binding facilitates access to the heme by disruption of hydrogen-bonded structures in the heme domain. For imidazole, two separate pathways of heme access are indicated by the distinct kinetics at low and high concentration. The structural basis for ligand entry to the heme cleft is discussed.
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Affiliation(s)
| | | | - Colin A. Wraight
- From the Center for Biophysics and Computational Biology and
- the Department of Biochemistry, University of Illinois, Urbana, Illinois 61801
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Kokhan O, Shinkarev VP, Wraight CA. Binding of imidazole to the heme of cytochrome c1 and inhibition of the bc1 complex from Rhodobacter sphaeroides: I. Equilibrium and modeling studies. J Biol Chem 2010; 285:22513-21. [PMID: 20448035 DOI: 10.1074/jbc.m110.128058] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
We have used imidazole (Im) and N-methylimidazole (MeIm) as probes of the heme-binding cavity of membrane-bound cytochrome (cyt) c(1) in detergent-solubilized bc(1) complex from Rhodobacter sphaeroides. Imidazole binding to cyt c(1) substantially lowers the midpoint potential of the heme and fully inhibits bc(1) complex activity. Temperature dependences showed that binding of Im (K(d) approximately 330 microM, 25 degrees C, pH 8) is enthalpically driven (DeltaH(0) = -56 kJ/mol, DeltaS(0) = -121 J/mol/K), whereas binding of MeIm is 30 times weaker (K(d) approximately 9.3 mM) and is entropically driven (DeltaH(0) = 47 kJ/mol, DeltaS(0)(o) = 197 J/mol/K). The large enthalpic and entropic contributions suggest significant structural and solvation changes in cyt c(1) triggered by ligand binding. Comparison of these results with those obtained previously for soluble cyts c and c(2) suggested that Im binding to cyt c(1) is assisted by formation of hydrogen bonds within the heme cleft. This was strongly supported by molecular dynamics simulations of Im adducts of cyts c, c(2), and c(1), which showed hydrogen bonds formed between the N(delta)H of Im and the cyt c(1) protein, or with a water molecule sequestered with the ligand in the heme cleft.
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Affiliation(s)
- Oleksandr Kokhan
- Center for Biophysics and Computational Biology, University of Illinois, Urbana, Illinois 61801, USA
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Cieluch E, Pietryga K, Sarewicz M, Osyczka A. Visualizing changes in electron distribution in coupled chains of cytochrome bc(1) by modifying barrier for electron transfer between the FeS cluster and heme c(1). BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2009; 1797:296-303. [PMID: 19917265 PMCID: PMC2807467 DOI: 10.1016/j.bbabio.2009.11.003] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 09/22/2009] [Revised: 11/09/2009] [Accepted: 11/10/2009] [Indexed: 11/24/2022]
Abstract
Cytochrome c1 of Rhodobacter (Rba.) species provides a series of mutants which change barriers for electron transfer through the cofactor chains of cytochrome bc1 by modifying heme c1 redox midpoint potential. Analysis of post-flash electron distribution in such systems can provide useful information about the contribution of individual reactions to the overall electron flow. In Rba. capsulatus, the non-functional low-potential forms of cytochrome c1 which are devoid of the disulfide bond naturally present in this protein revert spontaneously by introducing a second-site suppression (mutation A181T) that brings the potential of heme c1 back to the functionally high levels, yet maintains it some 100 mV lower from the native value. Here we report that the disulfide and the mutation A181T can coexist in one protein but the mutation exerts a dominant effect on the redox properties of heme c1 and the potential remains at the same lower value as in the disulfide-free form. This establishes effective means to modify a barrier for electron transfer between the FeS cluster and heme c1 without breaking disulfide. A comparison of the flash-induced electron transfers in native and mutated cytochrome bc1 revealed significant differences in the post-flash equilibrium distribution of electrons only when the connection of the chains with the quinone pool was interrupted at the level of either of the catalytic sites by the use of specific inhibitors, antimycin or myxothiazol. In the non-inhibited system no such differences were observed. We explain the results using a kinetic model in which a shift in the equilibrium of one reaction influences the equilibrium of all remaining reactions in the cofactor chains. It follows a rather simple description in which the direction of electron flow through the coupled chains of cytochrome bc1 exclusively depends on the rates of all reversible partial reactions, including the Q/QH2 exchange rate to/from the catalytic sites.
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Affiliation(s)
- Ewelina Cieluch
- Department of Biophysics, Faculty of Biochemistry, Biophysics and Biotechnology, Jagiellonian University, ul. Gronostajowa 7, 30-307 Kraków, Poland
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Quinone and non-quinone redox couples in Complex III. J Bioenerg Biomembr 2008; 40:493-9. [PMID: 18975063 DOI: 10.1007/s10863-008-9174-6] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2008] [Accepted: 07/17/2008] [Indexed: 10/21/2022]
Abstract
The Q cycle mechanism proposed by Peter Mitchell in the 1970's explicitly considered the modification of ubiquinone two-electron redox properties upon binding to Complex III to match the thermodynamics of the other single-electron redox cofactors in the complex, and guide electron transfer to support the generation of a proton electro-chemical gradient across native membranes. A better understanding of the engineering of Complex III is coming from a now moderately well defined thermodynamic description of the redox components as a function of pH, including the Qi/heme b(H) cluster. The redox properties of the most obscure component, Qo, is finally beginning to be resolved.
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