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Murray DT, Walia N, Weiss KL, Stanley CB, Nagy G, Stroupe ME. Neutron scattering maps the higher-order assembly of NADPH-dependent assimilatory sulfite reductase. Biophys J 2022; 121:1799-1812. [PMID: 35443926 DOI: 10.1016/j.bpj.2022.04.021] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2021] [Revised: 03/09/2022] [Accepted: 04/15/2022] [Indexed: 11/30/2022] Open
Abstract
Precursor molecules for biomass incorporation must be imported into cells and made available to the molecular machines that build the cell. Sulfur-containing macromolecules require that sulfur be in its S2- oxidation state before assimilation into amino acids, cofactors, and vitamins that are essential to organisms throughout the biosphere. In α-proteobacteria, NADPH-dependent assimilatory sulfite reductase (SiR) performs the final six-electron reduction of sulfur. SiR is a dodecameric oxidoreductase composed of an octameric flavoprotein reductase (SiRFP) and four hemoprotein metalloenzyme oxidases (SiRHP). SiR performs the electron transfer reduction reaction to produce sulfide from sulfite through coordinated domain movements and subunit interactions without release of partially reduced intermediates. Efforts to understand the electron transfer mechanism responsible for SiR's efficiency are confounded by structural heterogeneity arising from intrinsically disordered regions throughout its complex, including the flexible linker joining SiRFP's flavin-binding domains. As a result, high-resolution structures of SiR dodecamer and its subcomplexes are unknown, leaving a gap in the fundamental understanding of how SiR performs this uniquely large-volume electron transfer reaction. Here, we use deuterium labeling, in vitro reconstitution, analytical ultracentrifugation (AUC), small-angle neutron scattering (SANS), and neutron contrast variation (NCV) to observe the relative subunit positions within SiR's higher-order assembly. AUC and SANS reveal SiR to be a flexible dodecamer and confirm the mismatched SiRFP and SiRHP subunit stoichiometry. NCV shows that the complex is asymmetric, with SiRHP on the periphery of the complex and the centers of mass between SiRFP and SiRHP components over 100 Å apart. SiRFP undergoes compaction upon assembly into SiR's dodecamer and SiRHP adopts multiple positions in the complex. The resulting map of SiR's higher-order structure supports a cis/trans mechanism for electron transfer between domains of reductase subunits as well as between tightly-bound or transiently-interacting reductase and oxidase subunits.
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Affiliation(s)
- Daniel T Murray
- Department of Biological Science and Institute of Molecular Biophysics, Florida State University, Tallahassee, FL 32306, USA
| | - Nidhi Walia
- Department of Biological Science and Institute of Molecular Biophysics, Florida State University, Tallahassee, FL 32306, USA
| | - Kevin L Weiss
- Neutron Scattering Division, Oak Ridge National Laboratory, Oak Ridge, TN 37830, USA
| | - Christopher B Stanley
- Neutron Scattering Division, Oak Ridge National Laboratory, Oak Ridge, TN 37830, USA; Computational Sciences and Engineering Division, Oak Ridge National Laboratory, Oak Ridge, TN 37830, USA
| | - Gergely Nagy
- Neutron Scattering Division, Oak Ridge National Laboratory, Oak Ridge, TN 37830, USA
| | - M Elizabeth Stroupe
- Department of Biological Science and Institute of Molecular Biophysics, Florida State University, Tallahassee, FL 32306, USA.
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Zhang B, Kang C, Davydov DR. Conformational Rearrangements in the Redox Cycling of NADPH-Cytochrome P450 Reductase from Sorghum bicolor Explored with FRET and Pressure-Perturbation Spectroscopy. BIOLOGY 2022; 11:biology11040510. [PMID: 35453709 PMCID: PMC9030436 DOI: 10.3390/biology11040510] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/04/2022] [Revised: 03/21/2022] [Accepted: 03/23/2022] [Indexed: 12/01/2022]
Abstract
Simple Summary NADPH-cytochrome P450 reductase (CPR) enzymes are known to undergo an ample conformational transition between the closed and open states in the process of their redox cycling. To explore the conformational landscape of CPR from the potential biofuel crop Sorghum bicolor (SbCPR), we incorporated a FRET donor/acceptor pair into the enzyme and employed rapid scanning stop-flow and pressure perturbation spectroscopy to characterize the equilibrium between its open and closed states at different stages of the redox cycle. Our results suggest the presence of several open conformational sub-states differing in the system volume change associated with the opening transition (ΔV0). Although the closed conformation always predominates in the conformational landscape, the population of the open conformations increases by order of magnitude upon the two-electron reduction and the formation of the disemiquinone state of the enzyme. In addition to elucidating the functional choreography of plant CPRs, our study demonstrates the high exploratory potential of a combination of the pressure-perturbation approach with the FRET-based monitoring of protein conformational transitions. Abstract NADPH-cytochrome P450 reductase (CPR) from Sorghum bicolor (SbCPR) serves as an electron donor for cytochrome P450 essential for monolignol and lignin production in this biofuel crop. The CPR enzymes undergo an ample conformational transition between the closed and open states in their functioning. This transition is triggered by electron transfer between the FAD and FMN and provides access of the partner protein to the electron-donating FMN domain. To characterize the electron transfer mechanisms in the monolignol biosynthetic pathway better, we explore the conformational transitions in SbCPR with rapid scanning stop-flow and pressure-perturbation spectroscopy. We used FRET between a pair of donor and acceptor probes incorporated into the FAD and FMN domains of SbCPR, respectively, to characterize the equilibrium between the open and closed states and explore its modulation in connection with the redox state of the enzyme. We demonstrate that, although the closed conformation always predominates in the conformational landscape, the population of open state increases by order of magnitude upon the formation of the disemiquinone state. Our results are consistent with several open conformation sub-states differing in the volume change (ΔV0) of the opening transition. While the ΔV0 characteristic of the oxidized enzyme is as large as −88 mL/mol, the interaction of the enzyme with the nucleotide cofactor and the formation of the double-semiquinone state of CPR decrease this value to −34 and −18 mL/mol, respectively. This observation suggests that the interdomain electron transfer in CPR increases protein hydration, while promoting more open conformation. In addition to elucidating the functional choreography of plant CPRs, our study demonstrates the high exploratory potential of a combination of the pressure-perturbation approach with the FRET-based monitoring of protein conformational transitions.
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3
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Schröder GC, Meilleur F. Metalloprotein catalysis: structural and mechanistic insights into oxidoreductases from neutron protein crystallography. Acta Crystallogr D Struct Biol 2021; 77:1251-1269. [PMID: 34605429 PMCID: PMC8489226 DOI: 10.1107/s2059798321009025] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2021] [Accepted: 08/31/2021] [Indexed: 11/11/2022] Open
Abstract
Metalloproteins catalyze a range of reactions, with enhanced chemical functionality due to their metal cofactor. The reaction mechanisms of metalloproteins have been experimentally characterized by spectroscopy, macromolecular crystallography and cryo-electron microscopy. An important caveat in structural studies of metalloproteins remains the artefacts that can be introduced by radiation damage. Photoreduction, radiolysis and ionization deriving from the electromagnetic beam used to probe the structure complicate structural and mechanistic interpretation. Neutron protein diffraction remains the only structural probe that leaves protein samples devoid of radiation damage, even when data are collected at room temperature. Additionally, neutron protein crystallography provides information on the positions of light atoms such as hydrogen and deuterium, allowing the characterization of protonation states and hydrogen-bonding networks. Neutron protein crystallography has further been used in conjunction with experimental and computational techniques to gain insight into the structures and reaction mechanisms of several transition-state metal oxidoreductases with iron, copper and manganese cofactors. Here, the contribution of neutron protein crystallography towards elucidating the reaction mechanism of metalloproteins is reviewed.
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Affiliation(s)
- Gabriela C. Schröder
- Department of Molecular and Structural Biochemistry, North Carolina State University, Raleigh, NC 27695, USA
- Neutron Scattering Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA
| | - Flora Meilleur
- Department of Molecular and Structural Biochemistry, North Carolina State University, Raleigh, NC 27695, USA
- Neutron Scattering Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA
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4
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Krishnarjuna B, Yamazaki T, Anantharamaiah GM, Ramamoorthy A. Nanodisc reconstitution of flavin mononucleotide binding domain of cytochrome-P450-reductase enables high-resolution NMR probing. Chem Commun (Camb) 2021; 57:4819-4822. [PMID: 33982687 PMCID: PMC8136615 DOI: 10.1039/d1cc01018b] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
Cytochrome-P450-reductase transfers electrons to cytochrome-P450 through its flavin mononucleotide binding domain (FBD). Despite the importance of membrane-anchoring for FBD function, studies have focused on its soluble domain lacking the transmembrane-domain. Here we demonstrate that the reconstitution of FBD in nanodiscs enables high-resolution NMR measurements and renders a stable conformation.
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Affiliation(s)
- Bankala Krishnarjuna
- Biophysics Program, Department of Chemistry, Biomedical Engineering, Macromolecular Science and Engineering, University of Michigan, Arbor, MI 48109, USA.
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5
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Small-angle neutron scattering solution structures of NADPH-dependent sulfite reductase. J Struct Biol 2021; 213:107724. [PMID: 33722582 DOI: 10.1016/j.jsb.2021.107724] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2021] [Revised: 03/04/2021] [Accepted: 03/08/2021] [Indexed: 11/23/2022]
Abstract
Sulfite reductase (SiR), a dodecameric complex of flavoprotein reductase subunits (SiRFP) and hemoprotein oxidase subunits (SiRHP), reduces sulfur for biomass incorporation. Electron transfer within SiR requires intra- and inter-subunit interactions that are mediated by the relative position of each protein, governed by flexible domain movements. Using small-angle neutron scattering, we report the first solution structures of SiR heterodimers containing a single copy of each subunit. These structures show how the subunits bind and how both subunit binding and oxidation state impact SiRFP's conformation. Neutron contrast matching experiments on selectively deuterated heterodimers allow us to define the contribution of each subunit to the solution scattering. SiRHP binding induces a change in the position of SiRFP's flavodoxin-like domain relative to its ferredoxin-NADP+ reductase domain while compacting SiRHP's N-terminus. Reduction of SiRFP leads to a more open structure relative to its oxidized state, re-positioning SiRFP's N-terminal flavodoxin-like domain towards the SiRHP binding position. These structures show, for the first time, how both SiRHP binding to, and reduction of, SiRFP positions SiRFP for electron transfer between the subunits.
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6
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Sellner M, Fischer A, Don CG, Smieško M. Conformational Landscape of Cytochrome P450 Reductase Interactions. Int J Mol Sci 2021; 22:1023. [PMID: 33498551 PMCID: PMC7864194 DOI: 10.3390/ijms22031023] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2020] [Revised: 01/15/2021] [Accepted: 01/18/2021] [Indexed: 01/05/2023] Open
Abstract
Oxidative reactions catalyzed by Cytochrome P450 enzymes (CYPs), which constitute the most relevant group of drug-metabolizing enzymes, are enabled by their redox partner Cytochrome P450 reductase (CPR). Both proteins are anchored to the membrane of the endoplasmic reticulum and the CPR undergoes a conformational change in order to interact with the respective CYP and transfer electrons. Here, we conducted over 22 microseconds of molecular dynamics (MD) simulations in combination with protein-protein docking to investigate the conformational changes necessary for the formation of the CPR-CYP complex. While some structural features of the CPR and the CPR-CYP2D6 complex that we highlighted confirmed previous observations, our simulations revealed additional mechanisms for the conformational transition of the CPR. Unbiased simulations exposed a movement of the whole protein relative to the membrane, potentially to facilitate interactions with its diverse set of redox partners. Further, we present a structural mechanism for the susceptibility of the CPR to different redox states based on the flip of a glycine residue disrupting the local interaction network that maintains inter-domain proximity. Simulations of the CPR-CYP2D6 complex pointed toward an additional interaction surface of the FAD domain and the proximal side of CYP2D6. Altogether, this study provides novel structural insight into the mechanism of CPR-CYP interactions and underlying conformational changes, improving our understanding of this complex machinery Cytochrome P450 reductase; CPR; conformational; dynamicsrelevant for drug metabolism.
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Affiliation(s)
| | | | | | - Martin Smieško
- Computational Pharmacy, Departement of Pharmaceutical Sciences, University of Basel, 4056 Basel, Switzerland; (M.S.); (A.F.); (C.G.D.)
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7
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Biochemical and structural insights into the cytochrome P450 reductase from Candida tropicalis. Sci Rep 2019; 9:20088. [PMID: 31882753 PMCID: PMC6934812 DOI: 10.1038/s41598-019-56516-6] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2019] [Accepted: 12/04/2019] [Indexed: 12/15/2022] Open
Abstract
Cytochrome P450 reductases (CPRs) are diflavin oxidoreductases that supply electrons to type II cytochrome P450 monooxygenases (CYPs). In addition, it can also reduce other proteins and molecules, including cytochrome c, ferricyanide, and different drugs. Although various CPRs have been functionally and structurally characterized, the overall mechanism and its interaction with different redox acceptors remain elusive. One of the main problems regarding electron transfer between CPRs and CYPs is the so-called “uncoupling”, whereby NAD(P)H derived electrons are lost due to the reduced intermediates’ (FAD and FMN of CPR) interaction with molecular oxygen. Additionally, the decay of the iron-oxygen complex of the CYP can also contribute to loss of reducing equivalents during an unproductive reaction cycle. This phenomenon generates reactive oxygen species (ROS), leading to an inefficient reaction. Here, we present the study of the CPR from Candida tropicalis (CtCPR) lacking the hydrophobic N-terminal part (Δ2–22). The enzyme supports the reduction of cytochrome c and ferricyanide, with an estimated 30% uncoupling during the reactions with cytochrome c. The ROS produced was not influenced by different physicochemical conditions (ionic strength, pH, temperature). The X-ray structures of the enzyme were solved with and without its cofactor, NADPH. Both CtCPR structures exhibited the closed conformation. Comparison with the different solved structures revealed an intricate ionic network responsible for the regulation of the open/closed movement of CtCPR.
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8
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Ebrecht AC, van der Bergh N, Harrison STL, Smit MS, Sewell BT, Opperman DJ. Biochemical and structural insights into the cytochrome P450 reductase from Candida tropicalis. Sci Rep 2019; 9:20088. [PMID: 31882753 DOI: 10.1101/711317] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2019] [Accepted: 12/04/2019] [Indexed: 05/28/2023] Open
Abstract
Cytochrome P450 reductases (CPRs) are diflavin oxidoreductases that supply electrons to type II cytochrome P450 monooxygenases (CYPs). In addition, it can also reduce other proteins and molecules, including cytochrome c, ferricyanide, and different drugs. Although various CPRs have been functionally and structurally characterized, the overall mechanism and its interaction with different redox acceptors remain elusive. One of the main problems regarding electron transfer between CPRs and CYPs is the so-called "uncoupling", whereby NAD(P)H derived electrons are lost due to the reduced intermediates' (FAD and FMN of CPR) interaction with molecular oxygen. Additionally, the decay of the iron-oxygen complex of the CYP can also contribute to loss of reducing equivalents during an unproductive reaction cycle. This phenomenon generates reactive oxygen species (ROS), leading to an inefficient reaction. Here, we present the study of the CPR from Candida tropicalis (CtCPR) lacking the hydrophobic N-terminal part (Δ2-22). The enzyme supports the reduction of cytochrome c and ferricyanide, with an estimated 30% uncoupling during the reactions with cytochrome c. The ROS produced was not influenced by different physicochemical conditions (ionic strength, pH, temperature). The X-ray structures of the enzyme were solved with and without its cofactor, NADPH. Both CtCPR structures exhibited the closed conformation. Comparison with the different solved structures revealed an intricate ionic network responsible for the regulation of the open/closed movement of CtCPR.
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Affiliation(s)
- Ana C Ebrecht
- Department of Microbial, Biochemical, and Food Biotechnology, University of the Free State, Bloemfontein, 9301, South Africa
- South African DST-NRF Centre of Excellence in Catalysis (c*Change), University of Cape Town, Private Bag, Rondebosch, Cape Town, 7701, South Africa
| | - Naadia van der Bergh
- Centre for Bioprocess Engineering Research (CeBER), Department of Chemical Engineering, University of Cape Town, Rondebosch, Cape Town, 7701, South Africa
- South African DST-NRF Centre of Excellence in Catalysis (c*Change), University of Cape Town, Private Bag, Rondebosch, Cape Town, 7701, South Africa
| | - Susan T L Harrison
- Centre for Bioprocess Engineering Research (CeBER), Department of Chemical Engineering, University of Cape Town, Rondebosch, Cape Town, 7701, South Africa
- South African DST-NRF Centre of Excellence in Catalysis (c*Change), University of Cape Town, Private Bag, Rondebosch, Cape Town, 7701, South Africa
| | - Martha S Smit
- Department of Microbial, Biochemical, and Food Biotechnology, University of the Free State, Bloemfontein, 9301, South Africa
- South African DST-NRF Centre of Excellence in Catalysis (c*Change), University of Cape Town, Private Bag, Rondebosch, Cape Town, 7701, South Africa
| | - B Trevor Sewell
- Structural Biology Research Unit, Department of Integrative Biomedical Sciences, Institute for Infectious Diseases and Molecular Medicine, University of Cape Town, Cape Town, 7700, South Africa.
| | - Diederik J Opperman
- Department of Microbial, Biochemical, and Food Biotechnology, University of the Free State, Bloemfontein, 9301, South Africa.
- South African DST-NRF Centre of Excellence in Catalysis (c*Change), University of Cape Town, Private Bag, Rondebosch, Cape Town, 7701, South Africa.
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9
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A large-scale comparative analysis of affinity, thermodynamics and functional characteristics of interactions of twelve cytochrome P450 isoforms and their redox partners. Biochimie 2019; 162:156-166. [DOI: 10.1016/j.biochi.2019.04.020] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2019] [Accepted: 04/24/2019] [Indexed: 12/16/2022]
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10
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Li J, Zheng H, Feng C. Effect of Macromolecular Crowding on the FMN-Heme Intraprotein Electron Transfer in Inducible NO Synthase. Biochemistry 2019; 58:3087-3096. [PMID: 31251033 DOI: 10.1021/acs.biochem.9b00193] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
Previous biochemical studies of nitric oxide synthase enzymes (NOSs) were conducted in diluted solutions. However, the intracellular milieu where the proteins perform their biological functions is crowded with macromolecules. The effect of crowding on the electron transfer kinetics of multidomain proteins is much less understood. Herein, we investigated the effect of macromolecular crowding on the FMN-heme intraprotein interdomain electron transfer (IET), an obligatory step in NOS catalysis. A noticeable increase in the IET rate in the bidomain oxygenase/FMN (oxyFMN) and the holoprotein of human inducible NOS (iNOS) was observed upon addition of Ficoll 70 in a nonsaturable manner. Additionally, the magnitude of IET enhancement for the holoenzyme is much higher than that that of the oxyFMN construct. The crowding effect is also evident at different ionic strengths. Importantly, the enhancing extent is similar for the iNOS oxyFMN protein with added Ficoll 70 and Dextran 70 that give the same solution viscosity, showing that specific interactions do not exist between the NOS protein and the crowder. Moreover, the population of the docked FMN-heme state is significantly increased upon addition of Ficoll 70 and the fluorescence lifetime values do not correspond to those in the absence of Ficoll 70. The steady-state cytochrome c reduction by the holoenzyme is noticeably enhanced by the crowder, while the ferricyanide reduction is unchanged. The NO production activity of the iNOS holoenzyme is stimulated by Ficoll 70. The effect of macromolecular crowding on the kinetics can be rationalized on the basis of the excluded volume effect, with an entropic origin. The intraprotein electron transfer kinetics, fluorescence lifetime, and steady-state enzymatic activity results indicate that macromolecular crowding modulates the NOS electron transfer through multiple pathways. Such a mechanism should be applicable to electron transfer in other multidomain redox proteins.
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Affiliation(s)
- Jinghui Li
- College of Pharmacy , University of New Mexico , Albuquerque , New Mexico 87131 , United States
| | - Huayu Zheng
- College of Pharmacy , University of New Mexico , Albuquerque , New Mexico 87131 , United States.,Department of Chemistry and Chemical Biology , University of New Mexico , Albuquerque , New Mexico 87131 , United States
| | - Changjian Feng
- College of Pharmacy , University of New Mexico , Albuquerque , New Mexico 87131 , United States.,Department of Chemistry and Chemical Biology , University of New Mexico , Albuquerque , New Mexico 87131 , United States
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11
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Coupling of Redox and Structural States in Cytochrome P450 Reductase Studied by Molecular Dynamics Simulation. Sci Rep 2019; 9:9341. [PMID: 31249341 PMCID: PMC6597723 DOI: 10.1038/s41598-019-45690-2] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2019] [Accepted: 06/10/2019] [Indexed: 01/09/2023] Open
Abstract
Cytochrome P450 reductase (CPR) is the key protein that regulates the electron transfer from NADPH to various heme-containing monooxygenases. CPR has two flavin-containing domains: one with flavin adenine dinucleotide (FAD), called FAD domain, and the other with flavin mononucleotide (FMN), called FMN domain. It is considered that the electron transfer occurs via FAD and FMN (NADPH → FAD → FMN → monooxygenase) and is regulated by an interdomain open-close motion. It is generally thought that the structural state is coupled with the redox state, which, however, has not yet been firmly established. In this report, we studied the coupling of the redox and the structural states by full-scale molecular dynamics (MD) simulation of CPR (total 86.4 μs). Our MD result showed that while CPR predominantly adopts the closed state both in the oxidized and reduced states, it exhibits a tendency to open in the reduced state. We also found a correlation between the FAD-FMN distance and the predicted FMN-monooxygenase distance, which is embedded in the equilibrium thermal fluctuation of CPR. Based on these results, a physical mechanism for the electron transfer by CPR is discussed.
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12
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Tavolieri AM, Murray DT, Askenasy I, Pennington JM, McGarry L, Stanley CB, Stroupe ME. NADPH-dependent sulfite reductase flavoprotein adopts an extended conformation unique to this diflavin reductase. J Struct Biol 2019; 205:170-179. [DOI: 10.1016/j.jsb.2019.01.001] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2018] [Revised: 12/30/2018] [Accepted: 01/03/2019] [Indexed: 11/17/2022]
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13
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Hedison TM, Scrutton NS. Tripping the light fantastic in membrane redox biology: linking dynamic structures to function in ER electron transfer chains. FEBS J 2019; 286:2004-2017. [PMID: 30657259 PMCID: PMC6563164 DOI: 10.1111/febs.14757] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2018] [Revised: 12/16/2018] [Accepted: 01/15/2019] [Indexed: 12/19/2022]
Abstract
How the dynamics of proteins assist catalysis is a contemporary issue in enzymology. In particular, this holds true for membrane‐bound enzymes, where multiple structural, spectroscopic and biochemical approaches are needed to build up a comprehensive picture of how dynamics influence enzyme reaction cycles. Of note are the recent studies of cytochrome P450 reductases (CPR)–P450 (CYP) endoplasmic reticulum redox chains, showing the relationship between dynamics and electron flow through flavin and haem redox centres and the impact this has on monooxygenation chemistry. These studies have led to deeper understanding of mechanisms of electron flow, including the timing and control of electron delivery to protein‐bound cofactors needed to facilitate CYP‐catalysed reactions. Individual and multiple component systems have been used to capture biochemical behaviour and these have led to the emergence of more integrated models of catalysis. Crucially, the effects of membrane environment and composition on reaction cycle chemistry have also been probed, including effects on coenzyme binding/release, thermodynamic control of electron transfer, conformational coupling between partner proteins and vectorial versus ‘off pathway’ electron flow. Here, we review these studies and discuss evidence for the emergence of dynamic structural models of electron flow along human microsomal CPR–P450 redox chains.
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Affiliation(s)
- Tobias M Hedison
- Manchester Institute of Biotechnology and School of Chemistry, University of Manchester, UK
| | - Nigel S Scrutton
- Manchester Institute of Biotechnology and School of Chemistry, University of Manchester, UK
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14
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Molecular mechanism of metabolic NAD(P)H-dependent electron-transfer systems: The role of redox cofactors. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2018; 1860:233-258. [PMID: 30419202 DOI: 10.1016/j.bbabio.2018.11.014] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/16/2018] [Revised: 10/30/2018] [Accepted: 11/07/2018] [Indexed: 12/14/2022]
Abstract
NAD(P)H-dependent electron-transfer (ET) systems require three functional components: a flavin-containing NAD(P)H-dehydrogenase, one-electron carrier and metal-containing redox center. In principle, these ET systems consist of one-, two- and three-components, and the electron flux from pyridine nucleotide cofactors, NADPH or NADH to final electron acceptor follows a linear pathway: NAD(P)H → flavin → one-electron carrier → metal containing redox center. In each step ET is primarily controlled by one- and two-electron midpoint reduction potentials of protein-bound redox cofactors in which the redox-linked conformational changes during the catalytic cycle are required for the domain-domain interactions. These interactions play an effective ET reactions in the multi-component ET systems. The microsomal and mitochondrial cytochrome P450 (cyt P450) ET systems, nitric oxide synthase (NOS) isozymes, cytochrome b5 (cyt b5) ET systems and methionine synthase (MS) ET system include a combination of multi-domain, and their organizations display similarities as well as differences in their components. However, these ET systems are sharing of a similar mechanism. More recent structural information obtained by X-ray and cryo-electron microscopy (cryo-EM) analysis provides more detail for the mechanisms associated with multi-domain ET systems. Therefore, this review summarizes the roles of redox cofactors in the metabolic ET systems on the basis of one-electron redox potentials. In final Section, evolutionary aspects of NAD(P)H-dependent multi-domain ET systems will be discussed.
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