1
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Islam Z, Kumar P. Inhibitors of riboflavin biosynthetic pathway enzymes as potential antibacterial drugs. Front Mol Biosci 2023; 10:1228763. [PMID: 37496776 PMCID: PMC10366380 DOI: 10.3389/fmolb.2023.1228763] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2023] [Accepted: 07/03/2023] [Indexed: 07/28/2023] Open
Abstract
Multiple drug resistance is the main obstacle in the treatment of bacterial diseases. Resistance against antibiotics demands the exploration of new antimicrobial drug targets. A variety of in silico and genetic approaches show that the enzymes of the riboflavin biosynthetic pathway are crucial for the survival of bacteria. This pathway is absent in humans thus enzymes of the riboflavin biosynthetic pathway are emerging drug targets for resistant pathogenic bacterial strains. Exploring the structural details, their mechanism of action, intermediate elucidation, and interaction analysis would help in designing suitable inhibitors of these enzymes. The riboflavin biosynthetic pathway consists of seven distinct enzymes, namely, 3,4-dihydroxy-2-butanone 4-phosphate synthase, GTP cyclohydrolase II, pyrimidine deaminase/reductase, phosphatase, lumazine synthase, and riboflavin synthase. The present review summarizes the research work that has been carried out on these enzymes in terms of their structures, active site architectures, and molecular mechanism of catalysis. This review also walks through small molecule inhibitors that have been developed against several of these enzymes.
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Affiliation(s)
- Zeyaul Islam
- Qatar Biomedical Research Institute (QBRI), Qatar Foundation, Hamad Bin Khalifa University, Doha, Qatar
| | - Pankaj Kumar
- Department of Biochemistry, Jamia Hamdard, New Delhi, India
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2
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Iverson TM, Singh PK, Cecchini G. An evolving view of Complex II - non-canonical complexes, megacomplexes, respiration, signaling, and beyond. J Biol Chem 2023; 299:104761. [PMID: 37119852 DOI: 10.1016/j.jbc.2023.104761] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2023] [Revised: 04/20/2023] [Accepted: 04/22/2023] [Indexed: 05/01/2023] Open
Abstract
Mitochondrial Complex II is traditionally studied for its participation in two key respiratory processes: the electron transport chain and the Krebs cycle. There is now a rich body of literature explaining how Complex II contributes to respiration. However, more recent research shows that not all of the pathologies associated with altered Complex II activity clearly correlate with this respiratory role. Complex II activity has now been shown to be necessary for a range of biological processes peripherally-related to respiration, including metabolic control, inflammation, and cell fate. Integration of findings from multiple types of studies suggests that Complex II both participates in respiration and controls multiple succinate-dependent signal transduction pathways. Thus, the emerging view is that the true biological function of Complex II is well beyond respiration. This review uses a semi-chronological approach to highlight major paradigm shifts that occurred over time. Special emphasis is given to the more recently identified functions of Complex II and its subunits because these findings have infused new directions into an established field.
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Affiliation(s)
- T M Iverson
- Departments of Pharmacology, Vanderbilt University, Nashville, TN 37232; Departments of Biochemistry, Vanderbilt University, Nashville, TN 37232; Departments of Center for Structural Biology, Vanderbilt University, Nashville, TN 37232; Vanderbilt Institute of Chemical Biology, Vanderbilt University, Nashville, TN 37232.
| | - Prashant K Singh
- Departments of Pharmacology, Vanderbilt University, Nashville, TN 37232; Departments of Center for Structural Biology, Vanderbilt University, Nashville, TN 37232
| | - Gary Cecchini
- Molecular Biology Division, San Francisco VA Health Care System, San Francisco, CA 94121; Department of Biochemistry & Biophysics, University of California, San Francisco, CA 94158.
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3
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Abstract
The theory of electron transfer reactions establishes the conceptual foundation for redox solution chemistry, electrochemistry, and bioenergetics. Electron and proton transfer across the cellular membrane provide all energy of life gained through natural photosynthesis and mitochondrial respiration. Rates of biological charge transfer set kinetic bottlenecks for biological energy storage. The main system-specific parameter determining the activation barrier for a single electron-transfer hop is the reorganization energy of the medium. Both harvesting of light energy in natural and artificial photosynthesis and efficient electron transport in biological energy chains require reduction of the reorganization energy to allow fast transitions. This review article discusses mechanisms by which small values of the reorganization energy are achieved in protein electron transfer and how similar mechanisms can operate in other media, such as nonpolar and ionic liquids. One of the major mechanisms of reorganization energy reduction is through non-Gibbsian (nonergodic) sampling of the medium configurations on the reaction time. A number of alternative mechanisms, such as electrowetting of active sites of proteins, give rise to non-parabolic free energy surfaces of electron transfer. These mechanisms, and nonequilibrium population of donor-acceptor vibrations, lead to a universal phenomenology of separation between the Stokes shift and variance reorganization energies of electron transfer.
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Affiliation(s)
- Dmitry V Matyushov
- School of Molecular Sciences and Department of Physics, Arizona State University, PO Box 871504, Tempe, Arizona 85287-1504, USA.
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4
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Hessin C, Schleinitz J, Le Breton N, Choua S, Grimaud L, Fourmond V, Desage-El Murr M, Léger C. Assessing the Extent of Potential Inversion by Cyclic Voltammetry: Theory, Pitfalls, and Application to a Nickel Complex with Redox-Active Iminosemiquinone Ligands. Inorg Chem 2023; 62:3321-3332. [PMID: 36780646 DOI: 10.1021/acs.inorgchem.2c04365] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/15/2023]
Abstract
Potential inversion refers to the situation where a protein cofactor or a synthetic molecule can be oxidized or reduced twice in a cooperative manner; that is, the second electron transfer is easier than the first. This property is very important regarding the catalytic mechanism of enzymes that bifurcate electrons and the properties of bidirectional redox molecular catalysts that function in either direction of the reaction with no overpotential. Cyclic voltammetry is the most common technique for characterizing the thermodynamics and kinetics of electron transfer to or from these molecules. However, a gap in the literature is the absence of analytical predictions to help interpret the values of the voltammetric peak potentials when potential inversion occurs; the cyclic voltammograms are therefore often analyzed by simulating the data, with no discussion of the possibility of overfitting and often no estimation of the error on the determined parameters. Here we formulate the theory for the voltammetry of freely diffusing or surface-confined two-electron redox species in the experimentally relevant irreversible limit where the peak separation depends on the scan rate. We explain why the model is intrinsically underdetermined, and we illustrate this conclusion by analysis of the voltammetry of a nickel complex with redox-active iminosemiquinone ligands. Being able to characterize the thermodynamics of two-electron electron-transfer reactions will be crucial for designing more efficient catalysts.
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Affiliation(s)
- Cheriehan Hessin
- Institut de Chimie, Université de Strasbourg, UMR CNRS 7177, Strasbourg 67000, France
| | - Jules Schleinitz
- Laboratoire des Biomolécules, Département de Chimie, Sorbonne Université, École Normale Supérieure, PSL University, CNRS, Paris 75005, France
| | - Nolwenn Le Breton
- Institut de Chimie, Université de Strasbourg, UMR CNRS 7177, Strasbourg 67000, France
| | - Sylvie Choua
- Institut de Chimie, Université de Strasbourg, UMR CNRS 7177, Strasbourg 67000, France
| | - Laurence Grimaud
- Laboratoire des Biomolécules, Département de Chimie, Sorbonne Université, École Normale Supérieure, PSL University, CNRS, Paris 75005, France
| | - Vincent Fourmond
- Laboratoire de Bioénergétique et Ingénierie des Protéines, CNRS, Aix Marseille Université, Marseille 13009, France
| | - Marine Desage-El Murr
- Institut de Chimie, Université de Strasbourg, UMR CNRS 7177, Strasbourg 67000, France
| | - Christophe Léger
- Laboratoire de Bioénergétique et Ingénierie des Protéines, CNRS, Aix Marseille Université, Marseille 13009, France
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5
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How an assembly factor enhances covalent FAD attachment to the flavoprotein subunit of complex II. J Biol Chem 2022; 298:102472. [PMID: 36089066 PMCID: PMC9557727 DOI: 10.1016/j.jbc.2022.102472] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2022] [Revised: 08/31/2022] [Accepted: 09/02/2022] [Indexed: 01/25/2023] Open
Abstract
The membrane-bound complex II family of proteins is composed of enzymes that catalyze succinate and fumarate interconversion coupled with reduction or oxidation of quinones within the membrane domain. The majority of complex II enzymes are protein heterotetramers with the different subunits harboring a variety of redox centers. These redox centers are used to transfer electrons between the site of succinate-fumarate oxidation/reduction and the membrane domain harboring the quinone. A covalently bound FAD cofactor is present in the flavoprotein subunit, and the covalent flavin linkage is absolutely required to enable the enzyme to oxidize succinate. Assembly of the covalent flavin linkage in eukaryotic cells and many bacteria requires additional protein assembly factors. Here, we provide mechanistic details for how the assembly factors work to enhance covalent flavinylation. Both prokaryotic SdhE and mammalian SDHAF2 enhance FAD binding to their respective apoprotein of complex II. These assembly factors also increase the affinity for dicarboxylates to the apoprotein-noncovalent FAD complex and stabilize the preassembly complex. These findings are corroborated by previous investigations of the roles of SdhE in enhancing covalent flavinylation in both bacterial succinate dehydrogenase and fumarate reductase flavoprotein subunits and of SDHAF2 in performing the same function for the human mitochondrial succinate dehydrogenase flavoprotein. In conclusion, we provide further insight into assembly factor involvement in building complex II flavoprotein subunit active site required for succinate oxidation.
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6
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Obi CD, Bhuiyan T, Dailey HA, Medlock AE. Ferrochelatase: Mapping the Intersection of Iron and Porphyrin Metabolism in the Mitochondria. Front Cell Dev Biol 2022; 10:894591. [PMID: 35646904 PMCID: PMC9133952 DOI: 10.3389/fcell.2022.894591] [Citation(s) in RCA: 10] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2022] [Accepted: 04/14/2022] [Indexed: 12/29/2022] Open
Abstract
Porphyrin and iron are ubiquitous and essential for sustaining life in virtually all living organisms. Unlike iron, which exists in many forms, porphyrin macrocycles are mostly functional as metal complexes. The iron-containing porphyrin, heme, serves as a prosthetic group in a wide array of metabolic pathways; including respiratory cytochromes, hemoglobin, cytochrome P450s, catalases, and other hemoproteins. Despite playing crucial roles in many biological processes, heme, iron, and porphyrin intermediates are potentially cytotoxic. Thus, the intersection of porphyrin and iron metabolism at heme synthesis, and intracellular trafficking of heme and its porphyrin precursors are tightly regulated processes. In this review, we discuss recent advances in understanding the physiological dynamics of eukaryotic ferrochelatase, a mitochondrially localized metalloenzyme. Ferrochelatase catalyzes the terminal step of heme biosynthesis, the insertion of ferrous iron into protoporphyrin IX to produce heme. In most eukaryotes, except plants, ferrochelatase is localized to the mitochondrial matrix, where substrates are delivered and heme is synthesized for trafficking to multiple cellular locales. Herein, we delve into the structural and functional features of ferrochelatase, as well as its metabolic regulation in the mitochondria. We discuss the regulation of ferrochelatase via post-translational modifications, transportation of substrates and product across the mitochondrial membrane, protein-protein interactions, inhibition by small-molecule inhibitors, and ferrochelatase in protozoal parasites. Overall, this review presents insight on mitochondrial heme homeostasis from the perspective of ferrochelatase.
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Affiliation(s)
- Chibuike David Obi
- Department of Biochemistry and Molecular Biology, University of Georgia, Athens, GA, United States
| | - Tawhid Bhuiyan
- Department of Biochemistry and Molecular Biology, University of Georgia, Athens, GA, United States
| | - Harry A. Dailey
- Department of Biochemistry and Molecular Biology, University of Georgia, Athens, GA, United States
- Department of Microbiology, University of Georgia, Athens, GA, United States
| | - Amy E. Medlock
- Department of Biochemistry and Molecular Biology, University of Georgia, Athens, GA, United States
- Augusta University/University of Georgia Medical Partnership, University of Georgia, Athens, GA, United States
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7
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Wang Y, Kang Z, Zhang L, Zhu Z. Elucidating the Interactions between a [NiFe]-hydrogenase and Carbon Electrodes for Enhanced Bioelectrocatalysis. ACS Catal 2022. [DOI: 10.1021/acscatal.1c05306] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Yuanming Wang
- Tianjin Institute of Industrial Biotechnology, Chinese Academy of Sciences, 32 West Seventh Avenue, Tianjin Airport Economic Area, Tianjin 300308, People’s Republic of China
- University of Chinese Academy of Sciences, 19A Yuquan Road, Shijingshan District, Beijing 100049, People’s Republic of China
| | - Zepeng Kang
- Tianjin Institute of Industrial Biotechnology, Chinese Academy of Sciences, 32 West Seventh Avenue, Tianjin Airport Economic Area, Tianjin 300308, People’s Republic of China
| | - Lingling Zhang
- Tianjin Institute of Industrial Biotechnology, Chinese Academy of Sciences, 32 West Seventh Avenue, Tianjin Airport Economic Area, Tianjin 300308, People’s Republic of China
- University of Chinese Academy of Sciences, 19A Yuquan Road, Shijingshan District, Beijing 100049, People’s Republic of China
- National Technology Innovation Center of Synthetic Biology, Tianjin 300308, People’s Republic of China
| | - Zhiguang Zhu
- Tianjin Institute of Industrial Biotechnology, Chinese Academy of Sciences, 32 West Seventh Avenue, Tianjin Airport Economic Area, Tianjin 300308, People’s Republic of China
- University of Chinese Academy of Sciences, 19A Yuquan Road, Shijingshan District, Beijing 100049, People’s Republic of China
- National Technology Innovation Center of Synthetic Biology, Tianjin 300308, People’s Republic of China
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8
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Saroha M, Sindhu J, Kumar S, Bhasin KK, Khurana JM, Varma RS, Tomar D. Transition Metal‐Free Sulfenylation of C−H Bonds for C−S Bond Formation in Recent Years: Mechanistic Approach and Promising Future. ChemistrySelect 2021. [DOI: 10.1002/slct.202102042] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
Affiliation(s)
- Mohit Saroha
- Department of Chemistry University of Delhi Delhi 110007 India
| | - Jayant Sindhu
- Department of Chemistry, COBS&H, CCSHAU Hisar Haryana 125004 India
| | - Sudhir Kumar
- Department of Chemistry, COBS&H, CCSHAU Hisar Haryana 125004 India
| | - Kuldip K. Bhasin
- Department of Chemistry & Centre of Advanced Studies in Chemistry Panjab University Chandigarh 160014 India
| | | | - Rajender S. Varma
- Regional Centre of Advanced Technologies and Materials Palacký University in Olomouc Šlechtitelů 27 783 71 Olomouc Czech Republic
| | - Deepak Tomar
- Department of Chemistry R. K. P. G. College Shamli Uttar Pradesh 247776 India
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9
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Oliveira F, Rohde H, Vilanova M, Cerca N. Fighting Staphylococcus epidermidis Biofilm-Associated Infections: Can Iron Be the Key to Success? Front Cell Infect Microbiol 2021; 11:798563. [PMID: 34917520 PMCID: PMC8670311 DOI: 10.3389/fcimb.2021.798563] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2021] [Accepted: 11/11/2021] [Indexed: 12/29/2022] Open
Abstract
Staphylococcus epidermidis is one of the most important commensal microorganisms of human skin and mucosae. However, this bacterial species is also the cause of severe infections in immunocompromised patients, specially associated with the utilization of indwelling medical devices, that often serve as a scaffold for biofilm formation. S. epidermidis strains are often multidrug resistant and its association with biofilm formation makes these infections hard to treat. Their remarkable ability to form biofilms is widely regarded as its major pathogenic determinant. Although a significant amount of knowledge on its biofilm formation mechanisms has been achieved, we still do not understand how the species survives when exposed to the host harsh environment during invasion. A previous RNA-seq study highlighted that iron-metabolism associated genes were the most up-regulated bacterial genes upon contact with human blood, which suggested that iron acquisition plays an important role in S. epidermidis biofilm development and escape from the host innate immune system. In this perspective article, we review the available literature on the role of iron metabolism on S. epidermidis pathogenesis and propose that exploiting its dependence on iron could be pursued as a viable therapeutic alternative.
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Affiliation(s)
- Fernando Oliveira
- Centre of Biological Engineering, Laboratory of Research in Biofilms Rosário Oliveira (LIBRO), University of Minho, Braga, Portugal
| | - Holger Rohde
- Institut für Medizinische Mikrobiologie, Virologie und Hygiene, Universitätsklinikum Hamburg-Eppendorf, Hamburg, Germany
| | - Manuel Vilanova
- Instituto de Investigação e Inovação em Saúde (i3S), Universidade do Porto, Porto, Portugal
- Instituto de Biologia Molecular e Celular (IBMC), Universidade do Porto, Porto, Portugal
- Instituto de Ciências Biomédicas de Abel Salazar, Universidade do Porto (ICBAS-UP), Porto, Portugal
| | - Nuno Cerca
- Centre of Biological Engineering, Laboratory of Research in Biofilms Rosário Oliveira (LIBRO), University of Minho, Braga, Portugal
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10
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Dobrautz W, Weser O, Bogdanov NA, Alavi A, Li Manni G. Spin-Pure Stochastic-CASSCF via GUGA-FCIQMC Applied to Iron-Sulfur Clusters. J Chem Theory Comput 2021; 17:5684-5703. [PMID: 34469685 PMCID: PMC8444347 DOI: 10.1021/acs.jctc.1c00589] [Citation(s) in RCA: 24] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2021] [Indexed: 11/28/2022]
Abstract
In this work, we demonstrate how to efficiently compute the one- and two-body reduced density matrices within the spin-adapted full configuration interaction quantum Monte Carlo (FCIQMC) method, which is based on the graphical unitary group approach (GUGA). This allows us to use GUGA-FCIQMC as a spin-pure configuration interaction (CI) eigensolver within the complete active space self-consistent field (CASSCF) procedure and hence to stochastically treat active spaces far larger than conventional CI solvers while variationally relaxing orbitals for specific spin-pure states. We apply the method to investigate the spin ladder in iron-sulfur dimer and tetramer model systems. We demonstrate the importance of the orbital relaxation by comparing the Heisenberg model magnetic coupling parameters from the CASSCF procedure to those from a CI-only (CASCI) procedure based on restricted open-shell Hartree-Fock orbitals. We show that the orbital relaxation differentially stabilizes the lower-spin states, thus enlarging the coupling parameters with respect to the values predicted by ignoring orbital relaxation effects. Moreover, we find that, while CASCI results are well fit by a simple bilinear Heisenberg Hamiltonian, the CASSCF eigenvalues exhibit deviations that necessitate the inclusion of biquadratic terms in the model Hamiltonian.
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Affiliation(s)
- Werner Dobrautz
- Max
Planck Institute for Solid State Research, Heisenbergstr. 1, 70569 Stuttgart, Germany
| | - Oskar Weser
- Max
Planck Institute for Solid State Research, Heisenbergstr. 1, 70569 Stuttgart, Germany
| | - Nikolay A. Bogdanov
- Max
Planck Institute for Solid State Research, Heisenbergstr. 1, 70569 Stuttgart, Germany
| | - Ali Alavi
- Max
Planck Institute for Solid State Research, Heisenbergstr. 1, 70569 Stuttgart, Germany
- Yusuf
Hamied Department of Chemistry, University
of Cambridge, Lensfield
Road, Cambridge CB2 1EW, United Kingdom
| | - Giovanni Li Manni
- Max
Planck Institute for Solid State Research, Heisenbergstr. 1, 70569 Stuttgart, Germany
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11
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Bocanegra-Rodríguez S, Molins-Legua C, Campíns-Falcó P, Giroud F, Gross AJ, Cosnier S. Monofunctional pyrenes at carbon nanotube electrodes for direct electron transfer H 2O 2 reduction with HRP and HRP-bacterial nanocellulose. Biosens Bioelectron 2021; 187:113304. [PMID: 34020225 DOI: 10.1016/j.bios.2021.113304] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2021] [Revised: 04/29/2021] [Accepted: 05/02/2021] [Indexed: 12/16/2022]
Abstract
The non-covalent modification of carbon nanotube electrodes with pyrene derivatives is a versatile approach to enhance the electrical wiring of enzymes for biosensors and biofuel cells. We report here a comparative study of five pyrene derivatives adsorbed at multi-walled carbon nanotube electrodes to shed light on their ability to promote direct electron transfer with horseradish peroxidase (HRP) for H2O2 reduction. In all cases, pyrene-modified electrodes enhanced catalytic reduction compared to the unmodified electrodes. The pyrene N-hydroxysuccinimide (NHS) ester derivative provided access to the highest catalytic current of 1.4 mA cm-2 at 6 mmol L-1 H2O2, high onset potential of 0.61 V vs. Ag/AgCl, insensitivity to parasitic H2O2 oxidation, and a large linear dynamic range that benefits from insensitivity to HRP "suicide inactivation" at 4-6 mmol L-1 H2O2. Pyrene-aliphatic carboxylic acid groups offer better sensor sensitivity and higher catalytic currents at ≤ 1 mmol L-1 H2O2 concentrations. The butyric acid and NHS ester derivatives gave high analytical sensitivities of 5.63 A M-1 cm-2 and 2.96 A M-1 cm-2, respectively, over a wide range (0.25-4 mmol-1) compared to existing carbon-based HRP biosensor electrodes. A bacterial nanocellulose pyrene-NHS HRP bioelectrode was subsequently elaborated via "one-pot" and "layer-by-layer" strategies. The optimised bioelectrode exhibited slightly weaker voltage output, further enhanced catalytic currents, and a major enhancement in 1-week stability with 67% activity remaining compared to 39% at the equivalent electrode without nanocellulose, thus offering excellent prospects for biosensing and biofuel cell applications.
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Affiliation(s)
- Sara Bocanegra-Rodríguez
- Departamento de Química Analítica, Facultat de Química, Universitat de València, Dr. Moliner 50, 46100, Burjassot, Valencia, Spain
| | - Carmen Molins-Legua
- Departamento de Química Analítica, Facultat de Química, Universitat de València, Dr. Moliner 50, 46100, Burjassot, Valencia, Spain
| | - Pilar Campíns-Falcó
- Departamento de Química Analítica, Facultat de Química, Universitat de València, Dr. Moliner 50, 46100, Burjassot, Valencia, Spain
| | - Fabien Giroud
- Département de Chimie Moléculaire (DCM), Univ. Grenoble Alpes - CNRS, 570 Rue de La Chimie, 38041, Grenoble, France
| | - Andrew J Gross
- Département de Chimie Moléculaire (DCM), Univ. Grenoble Alpes - CNRS, 570 Rue de La Chimie, 38041, Grenoble, France.
| | - Serge Cosnier
- Département de Chimie Moléculaire (DCM), Univ. Grenoble Alpes - CNRS, 570 Rue de La Chimie, 38041, Grenoble, France.
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12
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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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13
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Maklashina E, Cecchini G. Determination of Flavin Potential in Proteins by Xanthine/Xanthine Oxidase Method. Bio Protoc 2020; 10:e3571. [PMID: 33659541 DOI: 10.21769/bioprotoc.3571] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2019] [Revised: 02/25/2020] [Accepted: 02/26/2020] [Indexed: 11/02/2022] Open
Abstract
This protocol describes a simple xanthine/xanthine oxidase enzymatic equilibration method for determination of the redox potential of a flavin. As an example of the use of this method, we determine the reduction potential of the covalently bound FAD cofactor ( Em = -55 mV) in the SdhA flavoprotein subunit of succinate dehydrogenase from Escherichia coli. In principle, this method can be used routinely to determine the redox potential of flavin cofactors in any simple flavoprotein from equilibrium concentrations with an appropriate reference dye of known Em without the use of sophisticated electrochemical equipment.
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Affiliation(s)
- Elena Maklashina
- Molecular Biology Division, San Francisco VA Health Care System, San Francisco, CA 94121, USA.,Department of Biochemistry & Biophysics, University of California, San Francisco, Ca 95158, USA
| | - Gary Cecchini
- Molecular Biology Division, San Francisco VA Health Care System, San Francisco, CA 94121, USA.,Department of Biochemistry & Biophysics, University of California, San Francisco, Ca 95158, USA
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14
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Joseph R. Selective Detection of Fe 3+, F -, and Cysteine by a Novel Triazole-Linked Decaamine Derivative of Pillar[5]arene and Its Metal Ion Complex in Water. ACS OMEGA 2020; 5:6215-6220. [PMID: 32226907 PMCID: PMC7098014 DOI: 10.1021/acsomega.0c00595] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 02/10/2020] [Accepted: 02/28/2020] [Indexed: 06/10/2023]
Abstract
Appropriately functionalized pillar[n]arenes are elegant supramolecular hosts for ion and molecule sensing. A water-soluble decaamine derivative of pillar[5]arene (APA) bearing triazole and amide moieties is synthesized. The ion and molecular recognition properties of APA are studied by fluorescence, UV-visible, and 1H nuclear magnetic resonance (NMR) spectroscopy. The APA selectively detects Fe3+ among 11 studied ions, which are important in several biological processes. Moreover, the in situ prepared Fe3+ complex of APA (FeAPA) exhibits the highest responsiveness toward F- (∼12-fold) among 11 anions and cysteine (∼120-fold) among the 20 naturally occurring amino acids by a fluorescence turn-on mechanism.
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15
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Hassan A, Macedo LJA, Souza JCPD, Lima FCDA, Crespilho FN. A combined Far-FTIR, FTIR Spectromicroscopy, and DFT Study of the Effect of DNA Binding on the [4Fe4S] Cluster Site in EndoIII. Sci Rep 2020; 10:1931. [PMID: 32029762 PMCID: PMC7005299 DOI: 10.1038/s41598-020-58531-4] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2019] [Accepted: 11/04/2019] [Indexed: 11/28/2022] Open
Abstract
Endonuclease III (EndoIII) is a DNA glycosylase that contains the [4Fe4S] cluster, which is essential for the protein to bind to damaged DNA in a process called base excision repair (BER). Here we propose that the change in the covalency of Fe–S bonds of the [4Fe4S] cluster caused by double-stranded (ds)-DNA binding is accompanied by a change in their strength, which is due to alterations of the electronic structure of the cluster. Micro-FTIR spectroscopy in the mid-IR region and FTIR spectroscopy in the far IR (450 and 300 cm−1) were used independently to study the structural changes in EndoIII and the behavior of the [4Fe4S] cluster it contains, in the native form and upon its binding to ds-DNA. Structural changes in the DNA itself were also examined. The characteristics vibrational modes, corresponding to Fe–S (sulfide) and Fe–S (thiolate) bonds were identified in the cluster through far IR spectroscopy as well through quantum chemistry calculations. Based on the experimental results, these vibrational modes shift in their spectral positions caused by negatively charged DNA in the vicinity of the cluster. Modifications of the Fe–S bond lengths upon DNA binding, both of the Fe–S (sulfide) and Fe–S (thiolate) bonds in the [4Fe4S] cluster of EndoIII are responsible for the stabilization of the cluster towards higher oxidation state (3+), and hence its redox communication along the ds-DNA helix.
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Affiliation(s)
- Ayaz Hassan
- São Carlos Institute of Chemistry, University of São Paulo, 13560-970, São Paulo, Brazil.
| | - Lucyano J A Macedo
- São Carlos Institute of Chemistry, University of São Paulo, 13560-970, São Paulo, Brazil
| | - João C P de Souza
- Goiano Federal Institute of Education, Science and Technology, Campus Rio Verde, 75901-970, Goiás, Brazil
| | - Filipe C D A Lima
- Federal Institute of Education, Science, and Technology of São Paulo, Campus Matão, 15991-502, São Paulo, Brazil
| | - Frank N Crespilho
- São Carlos Institute of Chemistry, University of São Paulo, 13560-970, São Paulo, Brazil.
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16
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Koganitsky A, Tworowski D, Dadosh T, Cecchini G, Eisenbach M. A Mechanism of Modulating the Direction of Flagellar Rotation in Bacteria by Fumarate and Fumarate Reductase. J Mol Biol 2019; 431:3662-3676. [PMID: 31412261 DOI: 10.1016/j.jmb.2019.08.001] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2019] [Revised: 07/31/2019] [Accepted: 08/01/2019] [Indexed: 02/04/2023]
Abstract
Fumarate, an electron acceptor in anaerobic respiration of Escherichia coli, has an additional function of assisting the flagellar motor to shift from counterclockwise to clockwise rotation, with a consequent modulation of the bacterial swimming behavior. Fumarate transmits its effect to the motor via the fumarate reductase complex (FrdABCD), shown to bind to FliG-one of the motor's switch proteins. How binding of the FrdABCD respiratory enzyme to FliG enhances clockwise rotation and how fumarate is involved in this activity have remained puzzling. Here we show that the FrdA subunit in the presence of fumarate is sufficient for binding to FliG and for clockwise enhancement. We further demonstrate by in vitro binding assays and super-resolution microscopy in vivo that the mechanism by which fumarate-occupied FrdA enhances clockwise rotation involves its preferential binding to the clockwise state of FliG (FliGcw). Continuum electrostatics combined with docking analysis and conformational sampling endorsed the experimental conclusions and suggested that the FrdA-FliGcw interaction is driven by the positive electrostatic potential generated by FrdA and the negatively charged areas of FliG. They further demonstrated that fumarate changes FrdA's conformation to one that can bind to FliGcw. These findings also show that the reason for the failure of the succinate dehydrogenase flavoprotein SdhA (an almost-identical analog of FrdA shown to bind to FliG equally well) to enhance clockwise rotation is that it has no binding preference for FliGcw. We suggest that this mechanism is physiologically important as it can modulate the magnitude of ΔG0 between the clockwise and counterclockwise states of the motor to tune the motor to the growth conditions of the bacteria.
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Affiliation(s)
- Anna Koganitsky
- Department of Biomolecular Sciences, The Weizmann Institute of Science, 7610001 Rehovot, Israel
| | - Dmitry Tworowski
- Department of Structural Biology, The Weizmann Institute of Science, 7610001 Rehovot, Israel
| | - Tali Dadosh
- Department of Chemical Research Support, The Weizmann Institute of Science, 7610001 Rehovot, Israel
| | - Gary Cecchini
- Molecular Biology Division, San Francisco VA Health Care System, San Francisco, CA 94121, USA; Department of Biochemistry & Biophysics, University of California, San Francisco, CA 94158, USA
| | - Michael Eisenbach
- Department of Biomolecular Sciences, The Weizmann Institute of Science, 7610001 Rehovot, Israel.
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17
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Evans RM, Siritanaratkul B, Megarity CF, Pandey K, Esterle TF, Badiani S, Armstrong FA. The value of enzymes in solar fuels research – efficient electrocatalysts through evolution. Chem Soc Rev 2019; 48:2039-2052. [DOI: 10.1039/c8cs00546j] [Citation(s) in RCA: 47] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Enzymes which evolved more than 2 billion years ago set exceptional standards for electrocatalysts being sought today.
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Affiliation(s)
- Rhiannon M. Evans
- Department of Chemistry
- Inorganic Chemistry Laboratory
- University of Oxford
- Oxford
- UK
| | | | - Clare F. Megarity
- Department of Chemistry
- Inorganic Chemistry Laboratory
- University of Oxford
- Oxford
- UK
| | - Kavita Pandey
- Department of Chemistry
- Inorganic Chemistry Laboratory
- University of Oxford
- Oxford
- UK
| | - Thomas F. Esterle
- Department of Chemistry
- Inorganic Chemistry Laboratory
- University of Oxford
- Oxford
- UK
| | - Selina Badiani
- Department of Chemistry
- Inorganic Chemistry Laboratory
- University of Oxford
- Oxford
- UK
| | - Fraser A. Armstrong
- Department of Chemistry
- Inorganic Chemistry Laboratory
- University of Oxford
- Oxford
- UK
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18
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Structure and electrochemistry of proteins harboring iron-sulfur clusters of different nuclearities. Part III. [4Fe-4S], [3Fe-4S] and [2Fe-2S] iron-sulfur proteins. J Struct Biol 2018; 202:264-274. [DOI: 10.1016/j.jsb.2018.03.008] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2018] [Accepted: 03/16/2018] [Indexed: 11/18/2022]
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19
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Dai Y, Wang P, Fu J, Yao K, Xu K, Pang X. A quinoline-based Cu 2+ ion complex fluorescence probe for selective detection of inorganic phosphate anion in aqueous solution and its application to living cells. SPECTROCHIMICA ACTA. PART A, MOLECULAR AND BIOMOLECULAR SPECTROSCOPY 2017; 183:30-36. [PMID: 28432918 DOI: 10.1016/j.saa.2017.04.015] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/29/2016] [Revised: 04/04/2017] [Accepted: 04/14/2017] [Indexed: 06/07/2023]
Abstract
A quinaldine functionalized probe QP has been designed and synthesized. It exhibited selective turn-off fluorescence response toward Cu2+ ion over most of the biologically important ions at physiological pH. The binding ratio of the probe QP and Cu2+ ion was determined to be 1:1 through fluorescence titration, Job's plot and ESI-MS. The binding constant (K) of Cu2+ to probe QP was found to be 2.12×104M-1. Further, the Cu2+ ensemble of probe QP was found to respond H2PO4- and HPO42- among other important biological anions via fluorescence turn-on response at physiological pH. Fluorescence microscopy imaging using living Hela cells showed that probe QP could be used as an effective fluorescent probe for detecting Cu2+ cation and H2PO4- and HPO42- anions in living cells.
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Affiliation(s)
- Yanpeng Dai
- Engineering Laboratory for Flame Retardant and Functional Materials of Hennan Province, College of Chemistry and Chemical Engineering, Henan University, Kaifeng 475004, China
| | - Peng Wang
- Engineering Laboratory for Flame Retardant and Functional Materials of Hennan Province, College of Chemistry and Chemical Engineering, Henan University, Kaifeng 475004, China
| | - Jiaxin Fu
- Engineering Laboratory for Flame Retardant and Functional Materials of Hennan Province, College of Chemistry and Chemical Engineering, Henan University, Kaifeng 475004, China
| | - Kun Yao
- Engineering Laboratory for Flame Retardant and Functional Materials of Hennan Province, College of Chemistry and Chemical Engineering, Henan University, Kaifeng 475004, China
| | - Kuoxi Xu
- Engineering Laboratory for Flame Retardant and Functional Materials of Hennan Province, College of Chemistry and Chemical Engineering, Henan University, Kaifeng 475004, China; Institute of Environmental and Analytical Sciences, Henan University, Kaifeng, Henan 475004, China.
| | - Xiaobin Pang
- Institute of Pharmacy, Henan University, Kaifeng, Henan 475004, China
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20
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The Fumarate Reductase of Bacteroides thetaiotaomicron, unlike That of Escherichia coli, Is Configured so that It Does Not Generate Reactive Oxygen Species. mBio 2017; 8:mBio.01873-16. [PMID: 28049145 PMCID: PMC5210497 DOI: 10.1128/mbio.01873-16] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
The impact of oxidative stress upon organismal fitness is most apparent in the phenomenon of obligate anaerobiosis. The root cause may be multifaceted, but the intracellular generation of reactive oxygen species (ROS) likely plays a key role. ROS are formed when redox enzymes accidentally transfer electrons to oxygen rather than to their physiological substrates. In this study, we confirm that the predominant intestinal anaerobe Bacteroides thetaiotaomicron generates intracellular ROS at a very high rate when it is aerated. Fumarate reductase (Frd) is a prominent enzyme in the anaerobic metabolism of many bacteria, including B. thetaiotaomicron, and prior studies of Escherichia coli Frd showed that the enzyme is unusually prone to ROS generation. Surprisingly, in this study biochemical analysis demonstrated that the B. thetaiotaomicron Frd does not react with oxygen at all: neither superoxide nor hydrogen peroxide is formed. Subunit-swapping experiments indicated that this difference does not derive from the flavoprotein subunit at which ROS normally arise. Experiments with the related enzyme succinate dehydrogenase discouraged the hypothesis that heme moieties are responsible. Thus, resistance to oxidation may reflect a shift of electron density away from the flavin moiety toward the iron-sulfur clusters. This study shows that the autoxidizability of a redox enzyme can be suppressed by subtle modifications that do not compromise its physiological function. One implication is that selective pressures might enhance the oxygen tolerance of an organism by manipulating the electronic properties of its redox enzymes so they do not generate ROS. IMPORTANCE Whether in sediments or pathogenic biofilms, the structures of microbial communities are configured around the sensitivities of their members to oxygen. Oxygen triggers the intracellular formation of reactive oxygen species (ROS), and the sensitivity of a microbe to oxygen likely depends upon the rates at which ROS are formed inside it. This study supports that idea, as an obligate anaerobe was confirmed to generate ROS very rapidly upon aeration. However, the suspected source of the ROS was disproven, as the fumarate reductase of the anaerobe did not display the high oxidation rate of its E. coli homologue. Evidently, adjustments in its electronic structure can suppress the tendency of an enzyme to generate ROS. Importantly, this outcome suggests that evolutionary pressure may succeed in modifying redox enzymes and thereby diminishing the stress that an organism experiences in oxic environments. The actual source of ROS in the anaerobe remains to be discovered.
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21
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Protein Electrochemistry: Questions and Answers. ADVANCES IN BIOCHEMICAL ENGINEERING/BIOTECHNOLOGY 2016; 158:1-41. [DOI: 10.1007/10_2015_5016] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
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22
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Design of a single protein that spans the entire 2-V range of physiological redox potentials. Proc Natl Acad Sci U S A 2015; 113:262-7. [PMID: 26631748 DOI: 10.1073/pnas.1515897112] [Citation(s) in RCA: 73] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The reduction potential (E°') is a critical parameter in determining the efficiency of most biological and chemical reactions. Biology employs three classes of metalloproteins to cover the majority of the 2-V range of physiological E°'s. An ultimate test of our understanding of E°' is to find out the minimal number of proteins and their variants that can cover this entire range and the structural features responsible for the extreme E°'. We report herein the design of the protein azurin to cover a range from +970 mV to -954 mV vs. standard hydrogen electrode (SHE) by mutating only five residues and using two metal ions. Spectroscopic methods have revealed geometric parameters important for the high E°'. The knowledge gained and the resulting water-soluble redox agents with predictable E°'s, in the same scaffold with the same surface properties, will find wide applications in chemical, biochemical, biophysical, and biotechnological fields.
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23
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Electrochemical evidence that pyranopterin redox chemistry controls the catalysis of YedY, a mononuclear Mo enzyme. Proc Natl Acad Sci U S A 2015; 112:14506-11. [PMID: 26561582 DOI: 10.1073/pnas.1516869112] [Citation(s) in RCA: 39] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
A long-standing contradiction in the field of mononuclear Mo enzyme research is that small-molecule chemistry on active-site mimic compounds predicts ligand participation in the electron transfer reactions, but biochemical measurements only suggest metal-centered catalytic electron transfer. With the simultaneous measurement of substrate turnover and reversible electron transfer that is provided by Fourier-transformed alternating-current voltammetry, we show that Escherichia coli YedY is a mononuclear Mo enzyme that reconciles this conflict. In YedY, addition of three protons and three electrons to the well-characterized "as-isolated" Mo(V) oxidation state is needed to initiate the catalytic reduction of either dimethyl sulfoxide or trimethylamine N-oxide. Based on comparison with earlier studies and our UV-vis redox titration data, we assign the reversible one-proton and one-electron reduction process centered around +174 mV vs. standard hydrogen electrode at pH 7 to a Mo(V)-to-Mo(IV) conversion but ascribe the two-proton and two-electron transition occurring at negative potential to the organic pyranopterin ligand system. We predict that a dihydro-to-tetrahydro transition is needed to generate the catalytically active state of the enzyme. This is a previously unidentified mechanism, suggested by the structural simplicity of YedY, a protein in which Mo is the only metal site.
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24
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Fuss JO, Tsai CL, Ishida JP, Tainer JA. Emerging critical roles of Fe-S clusters in DNA replication and repair. BIOCHIMICA ET BIOPHYSICA ACTA 2015; 1853:1253-71. [PMID: 25655665 PMCID: PMC4576882 DOI: 10.1016/j.bbamcr.2015.01.018] [Citation(s) in RCA: 130] [Impact Index Per Article: 14.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/23/2014] [Revised: 01/13/2015] [Accepted: 01/26/2015] [Indexed: 10/24/2022]
Abstract
Fe-S clusters are partners in the origin of life that predate cells, acetyl-CoA metabolism, DNA, and the RNA world. The double helix solved the mystery of DNA replication by base pairing for accurate copying. Yet, for genome stability necessary to life, the double helix has equally important implications for damage repair. Here we examine striking advances that uncover Fe-S cluster roles both in copying the genetic sequence by DNA polymerases and in crucial repair processes for genome maintenance, as mutational defects cause cancer and degenerative disease. Moreover, we examine an exciting, controversial role for Fe-S clusters in a third element required for life - the long-range coordination and regulation of replication and repair events. By their ability to delocalize electrons over both Fe and S centers, Fe-S clusters have unbeatable features for protein conformational control and charge transfer via double-stranded DNA that may fundamentally transform our understanding of life, replication, and repair. This article is part of a Special Issue entitled: Fe/S proteins: Analysis, structure, function, biogenesis and diseases.
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Affiliation(s)
- Jill O Fuss
- Life Sciences Division, Lawrence Berkeley National Laboratory, 1 Cyclotron Road, Berkeley, CA 94720, USA.
| | - Chi-Lin Tsai
- Life Sciences Division, Lawrence Berkeley National Laboratory, 1 Cyclotron Road, Berkeley, CA 94720, USA
| | - Justin P Ishida
- Life Sciences Division, Lawrence Berkeley National Laboratory, 1 Cyclotron Road, Berkeley, CA 94720, USA
| | - John A Tainer
- Life Sciences Division, Lawrence Berkeley National Laboratory, 1 Cyclotron Road, Berkeley, CA 94720, USA; Department of Molecular and Cellular Oncology, The University of Texas M. D. Anderson Cancer Center, 1515 Holcombe Blvd., Houston, TX 77030, USA.
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25
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Khanna N, Lindblad P. Cyanobacterial hydrogenases and hydrogen metabolism revisited: recent progress and future prospects. Int J Mol Sci 2015; 16:10537-61. [PMID: 26006225 PMCID: PMC4463661 DOI: 10.3390/ijms160510537] [Citation(s) in RCA: 39] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2015] [Revised: 04/29/2015] [Accepted: 04/30/2015] [Indexed: 11/25/2022] Open
Abstract
Cyanobacteria have garnered interest as potential cell factories for hydrogen production. In conjunction with photosynthesis, these organisms can utilize inexpensive inorganic substrates and solar energy for simultaneous biosynthesis and hydrogen evolution. However, the hydrogen yield associated with these organisms remains far too low to compete with the existing chemical processes. Our limited understanding of the cellular hydrogen production pathway is a primary setback in the potential scale-up of this process. In this regard, the present review discusses the recent insight around ferredoxin/flavodoxin as the likely electron donor to the bidirectional Hox hydrogenase instead of the generally accepted NAD(P)H. This may have far reaching implications in powering solar driven hydrogen production. However, it is evident that a successful hydrogen-producing candidate would likely integrate enzymatic traits from different species. Engineering the [NiFe] hydrogenases for optimal catalytic efficiency or expression of a high turnover [FeFe] hydrogenase in these photo-autotrophs may facilitate the development of strains to reach target levels of biohydrogen production in cyanobacteria. The fundamental advancements achieved in these fields are also summarized in this review.
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Affiliation(s)
- Namita Khanna
- Microbial Chemistry, Department of Chemistry-Ångström Laboratory, Uppsala University, Box 523, Uppsala SE-75120, Sweden.
| | - Peter Lindblad
- Microbial Chemistry, Department of Chemistry-Ångström Laboratory, Uppsala University, Box 523, Uppsala SE-75120, Sweden.
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26
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Farver O, Hosseinzadeh P, Marshall NM, Wherland S, Lu Y, Pecht I. Long-Range Electron Transfer in Engineered Azurins Exhibits Marcus Inverted Region Behavior. J Phys Chem Lett 2015; 6:100-105. [PMID: 26263097 DOI: 10.1021/jz5022685] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
The Marcus theory of electron transfer (ET) predicts that while the ET rate constants increase with rising driving force until it equals a reaction's reorganization energy, at higher driving force the ET rate decreases, having reached the Marcus inverted region. While experimental evidence of the inverted region has been reported for organic and inorganic ET reactions as well as for proteins conjugated with ancillary redox moieties, evidence of the inverted region in a "protein-only" system has remained elusive. We herein provide such evidence in a series of nonderivatized proteins. These results may facilitate the design of ET centers for future applications such as advanced energy conversions.
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Affiliation(s)
- Ole Farver
- †Department of Analytical and Bioinorganic Chemistry, University of Copenhagen, Universitetsparken 5, Copenhagen 2100, Denmark
| | | | | | - Scot Wherland
- ∥Department of Chemistry, Washington State University, PO Box 644630, Pullman, Washington 99164, United States
| | | | - Israel Pecht
- §Department of Immunology, Weizmann Institute of Science, Wolfson Building, Rehovot 76100, Israel
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27
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Fapyane D, Kartashov A, von Wachenfeldt C, Ferapontova EE. Gated electron transfer reactions of truncated hemoglobin from Bacillus subtilis differently orientated on SAM-modified electrodes. Phys Chem Chem Phys 2015; 17:15365-74. [DOI: 10.1039/c5cp00960j] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
Electron transfer in truncated hemoglobin depends on the SAMs it is attached to demonstrating a new type of electronic responsivity.
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Affiliation(s)
- Deby Fapyane
- Interdisciplinary Nanoscience Center (iNANO)
- Science and Technology
- Aarhus University
- DK-8000 Aarhus C
- Denmark
| | - Andrey Kartashov
- Interdisciplinary Nanoscience Center (iNANO)
- Science and Technology
- Aarhus University
- DK-8000 Aarhus C
- Denmark
| | | | - Elena E. Ferapontova
- Interdisciplinary Nanoscience Center (iNANO)
- Science and Technology
- Aarhus University
- DK-8000 Aarhus C
- Denmark
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28
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Zanello P. The competition between chemistry and biology in assembling iron–sulfur derivatives. Molecular structures and electrochemistry. Part II. {[Fe2S2](SγCys)4} proteins. Coord Chem Rev 2014. [DOI: 10.1016/j.ccr.2014.08.003] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
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29
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Melin F, Noor MR, Pardieu E, Boulmedais F, Banhart F, Cecchini G, Soulimane T, Hellwig P. Investigating the thermostability of succinate: quinone oxidoreductase enzymes by direct electrochemistry at SWNTs-modified electrodes and FTIR spectroscopy. Chemphyschem 2014; 15:3572-9. [PMID: 25139263 DOI: 10.1002/cphc.201402354] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2014] [Revised: 06/27/2014] [Indexed: 11/07/2022]
Abstract
Succinate: quinone reductases (SQRs) are the enzymes that couple the oxidation of succinate and the reduction of quinones in the respiratory chain of prokaryotes and eukaryotes. Herein, we compare the temperature-dependent activity and structural stability of two SQRs, the first from the mesophilic bacterium Escherichia coli and the second from the thermophilic bacterium Thermus thermophilus, using a combined electrochemical and infrared spectroscopy approach. Direct electron transfer was achieved with full membrane protein complexes at single-walled carbon nanotube (SWNT)-modified electrodes. The possible structural factors that contribute to the temperature-dependent activity of the enzymes and, in particular, to the thermostability of the Thermus thermophilus SQR are discussed.
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Affiliation(s)
- Frederic Melin
- Laboratoire de Bioélectrochimie et Spectroscopie, Chimie de la Matière Complexe (UMR 7140), Université de Strasbourg, 1 Rue Blaise Pascal, 67000 Strasbourg (France)
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30
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Defining a direction: electron transfer and catalysis in Escherichia coli complex II enzymes. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2013; 1827:668-78. [PMID: 23396003 DOI: 10.1016/j.bbabio.2013.01.010] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/19/2012] [Revised: 01/23/2013] [Accepted: 01/23/2013] [Indexed: 11/24/2022]
Abstract
There are two homologous membrane-bound enzymes in Escherichia coli that catalyze reversible conversion between succinate/fumarate and quinone/quinol. Succinate:ubiquinone reductase (SQR) is a component of aerobic respiratory chains, whereas quinol:fumarate reductase (QFR) utilizes menaquinol to reduce fumarate in a final step of anaerobic respiration. Although, both protein complexes are capable of supporting bacterial growth on either minimal succinate or fumarate media, the enzymes are more proficient in their physiological directions. Here we evaluate factors that may underlie this catalytic bias. This article is part of a Special Issue entitled: Respiratory complex II: Role in cellular physiology and disease.
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31
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Healy AJ, Reeve HA, Parkin A, Vincent KA. Electrically conducting particle networks in polymer electrolyte as three-dimensional electrodes for hydrogenase electrocatalysis. Electrochim Acta 2011. [DOI: 10.1016/j.electacta.2011.01.051] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
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32
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Joseph R, Chinta JP, Rao CP. Calix[4]arene-Based 1,3-Diconjugate of Salicylyl Imine Having Dibenzyl Amine Moiety (L): Synthesis, Characterization, Receptor Properties toward Fe2+, Cu2+, and Zn2+, Crystal Structures of Its Zn2+and Cu2+Complexes, and Selective Phosphate Sensing by the [ZnL]. Inorg Chem 2011; 50:7050-8. [DOI: 10.1021/ic200544a] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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33
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Magalon A, Fedor JG, Walburger A, Weiner JH. Molybdenum enzymes in bacteria and their maturation. Coord Chem Rev 2011. [DOI: 10.1016/j.ccr.2010.12.031] [Citation(s) in RCA: 87] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
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Majtan T, Frerman FE, Kraus JP. Effect of cobalt on Escherichia coli metabolism and metalloporphyrin formation. Biometals 2010; 24:335-47. [PMID: 21184140 DOI: 10.1007/s10534-010-9400-7] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2010] [Accepted: 12/14/2010] [Indexed: 02/01/2023]
Abstract
Toxicity in Escherichia coli resulting from high concentrations of cobalt has been explained by competition of cobalt with iron in various metabolic processes including Fe-S cluster assembly, sulfur assimilation, production of free radicals and reduction of free thiol pool. Here we present another aspect of increased cobalt concentrations in the culture medium resulting in the production of cobalt protoporphyrin IX (CoPPIX), which was incorporated into heme proteins including membrane-bound cytochromes and an expressed human cystathionine beta-synthase (CBS). The presence of CoPPIX in cytochromes inhibited their electron transport capacity and resulted in a substantially decreased respiration. Bacterial cells adapted to the increased cobalt concentration by inducing a modified mixed acid fermentative pathway under aerobiosis. We capitalized on the ability of E. coli to insert cobalt into PPIX to carry out an expression of CoPPIX-substituted heme proteins. The level of CoPPIX-substitution increased with the number of passages of cells in a cobalt-containing medium. This approach is an inexpensive method to prepare cobalt-substituted heme proteins compared to in vitro enzyme reconstitution or in vivo replacement using metalloporphyrin heme analogs and seems to be especially suitable for complex heme proteins with an additional coenzyme, such as human CBS.
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Affiliation(s)
- Tomas Majtan
- Department of Pediatrics and the Colorado Intellectual and Developmental Disabilities Research Center (IDDRC), University of Colorado at Denver, 12800 E 19th Ave, Aurora, CO 80045, USA
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Hoke KR, Crane BR. The solution electrochemistry of tetrahydrobiopterin revisited. Nitric Oxide 2009; 20:79-87. [PMID: 19059356 DOI: 10.1016/j.niox.2008.11.002] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2008] [Revised: 10/28/2008] [Accepted: 11/16/2008] [Indexed: 10/21/2022]
Abstract
Re-investigation of the electrochemical behavior of the nitric oxide synthase (NOS) cofactor tetrahydrobiopterin on graphite electrodes has revealed drastic differences in reversibility of electron transfer (ET) depending on the type of electrode surface employed. In particular, slow electron transfer kinetics and quasireversibility on an unpolished glassy carbon electrode can mask underlying concerted two-electron transfer chemistry and cause the appearance of an apparent one-electron couple. Nonetheless, the thermodynamic instability of the radical intermediate prevents any detectable build-up of this intermediate under any conditions tested. Scan rate and pH-dependencies of the concerted two-electron couple indicate a kinetic barrier to formation of the radical that depends on proton availability. These observations resolve previous conflicting interpretations of tetrahydrobiopterin solution electrochemistry and comment on how NOS may stabilize the one-electron oxidized radical state that participates in enzymatic production of nitric oxide.
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Affiliation(s)
- Kevin R Hoke
- Department of Chemistry and Chemical Biology, Cornell University, Ithaca, NY 14853, USA.
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ZHANG HN, GUO ZY, GAI PP. Research Progress in Protein Film Voltammetry. CHINESE JOURNAL OF ANALYTICAL CHEMISTRY 2009. [DOI: 10.1016/s1872-2040(08)60093-6] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
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Gawryluk RMR, Gray MW. A split and rearranged nuclear gene encoding the iron-sulfur subunit of mitochondrial succinate dehydrogenase in Euglenozoa. BMC Res Notes 2009; 2:16. [PMID: 19192292 PMCID: PMC2663770 DOI: 10.1186/1756-0500-2-16] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2008] [Accepted: 02/03/2009] [Indexed: 11/10/2022] Open
Abstract
Background Analyses based on phylogenetic and ultrastructural data have suggested that euglenids (such as Euglena gracilis), trypanosomatids and diplonemids are members of a monophyletic lineage termed Euglenozoa. However, many uncertainties are associated with phylogenetic reconstructions for ancient and rapidly evolving groups; thus, rare genomic characters become increasingly important in reinforcing inferred phylogenetic relationships. Findings We discovered that the iron-sulfur subunit (SdhB) of mitochondrial succinate dehydrogenase is encoded by a split and rearranged nuclear gene in Euglena gracilis and trypanosomatids, an example of a rare genomic character. The two subgenic modules are transcribed independently and the resulting mRNAs appear to be independently translated, with the two protein products imported into mitochondria, based on the presence of predicted mitochondrial targeting peptides. Although the inferred protein sequences are in general very divergent from those of other organisms, all of the required iron-sulfur cluster-coordinating residues are present. Moreover, the discontinuity in the euglenozoan SdhB sequence occurs between the two domains of a typical, covalently continuous SdhB, consistent with the inference that the euglenozoan 'half' proteins are functional. Conclusion The discovery of this unique molecular marker provides evidence for the monophyly of Euglenozoa that is independent of evolutionary models. Our results pose questions about the origin and timing of this novel gene arrangement and the structure and function of euglenozoan SdhB.
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Affiliation(s)
- Ryan M R Gawryluk
- Department of Biochemistry and Molecular Biology, Dalhousie University, Halifax, Nova Scotia B3H 1X5, Canada.
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Pessanha M, Rothery EL, Miles CS, Reid GA, Chapman SK, Louro RO, Turner DL, Salgueiro CA, Xavier AV. Tuning of functional heme reduction potentials in Shewanella fumarate reductases. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2009; 1787:113-20. [DOI: 10.1016/j.bbabio.2008.11.007] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/19/2008] [Revised: 11/06/2008] [Accepted: 11/07/2008] [Indexed: 11/15/2022]
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Giese B, Graber M, Cordes M. Electron transfer in peptides and proteins. Curr Opin Chem Biol 2008; 12:755-9. [PMID: 18804174 DOI: 10.1016/j.cbpa.2008.08.026] [Citation(s) in RCA: 84] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2008] [Accepted: 08/18/2008] [Indexed: 11/15/2022]
Abstract
Proteins and peptides use their amino acids as medium for electron-transfer reactions that occur either in single-step superexchange or in multistep hopping processes. Whereas the rate of the single-step electron transfer dramatically decreases with the distance, a hopping process is less distance dependent. Electron hopping is possible if amino acids carry oxidizable side chains, like the phenol group in tyrosine. These side chains become intermediate charge carriers. Because of the weak distance dependency of hopping processes, fast electron transfer over very long distances occurs in multistep reactions, as in the enzyme ribonucleotide reductase.
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Affiliation(s)
- Bernd Giese
- Department of Chemistry, University of Basel, St. Johanns Ring 19, CH-4056 Basel, Switzerland.
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41
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Rothery RA, Workun GJ, Weiner JH. The prokaryotic complex iron–sulfur molybdoenzyme family. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2008; 1778:1897-929. [DOI: 10.1016/j.bbamem.2007.09.002] [Citation(s) in RCA: 144] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/20/2007] [Revised: 08/17/2007] [Accepted: 09/02/2007] [Indexed: 10/22/2022]
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Zhang J, Kuznetsov AM, Medvedev IG, Chi Q, Albrecht T, Jensen PS, Ulstrup J. Single-Molecule Electron Transfer in Electrochemical Environments. Chem Rev 2008; 108:2737-91. [PMID: 18620372 DOI: 10.1021/cr068073+] [Citation(s) in RCA: 252] [Impact Index Per Article: 15.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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Léger C, Bertrand P. Direct Electrochemistry of Redox Enzymes as a Tool for Mechanistic Studies. Chem Rev 2008; 108:2379-438. [DOI: 10.1021/cr0680742] [Citation(s) in RCA: 594] [Impact Index Per Article: 37.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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Cohen-Ben-Lulu GN, Francis NR, Shimoni E, Noy D, Davidov Y, Prasad K, Sagi Y, Cecchini G, Johnstone RM, Eisenbach M. The bacterial flagellar switch complex is getting more complex. EMBO J 2008; 27:1134-44. [PMID: 18337747 DOI: 10.1038/emboj.2008.48] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2007] [Accepted: 02/25/2008] [Indexed: 11/09/2022] Open
Abstract
The mechanism of function of the bacterial flagellar switch, which determines the direction of flagellar rotation and is essential for chemotaxis, has remained an enigma for many years. Here we show that the switch complex associates with the membrane-bound respiratory protein fumarate reductase (FRD). We provide evidence that FRD binds to preparations of isolated switch complexes, forms a 1:1 complex with the switch protein FliG, and that this interaction is required for both flagellar assembly and switching the direction of flagellar rotation. We further show that fumarate, known to be a clockwise/switch factor, affects the direction of flagellar rotation through FRD. These results not only uncover a new component important for switching and flagellar assembly, but they also reveal that FRD, an enzyme known to be primarily expressed and functional under anaerobic conditions in Escherichia coli, nonetheless, has important, unexpected functions under aerobic conditions.
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Fischer M, Bacher A. Biosynthesis of vitamin B2: Structure and mechanism of riboflavin synthase. Arch Biochem Biophys 2008; 474:252-65. [PMID: 18298940 DOI: 10.1016/j.abb.2008.02.008] [Citation(s) in RCA: 62] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2007] [Revised: 02/05/2008] [Accepted: 02/06/2008] [Indexed: 11/30/2022]
Abstract
The biosynthesis of one riboflavin molecule requires one molecule of GTP and two molecules of ribulose 5-phosphate as substrates. GTP is hydrolytically opened, converted into 5-amino-6-ribitylamino-2,4(1H,3H)-pyrimidinedione by a sequence of deamination, side chain reduction and dephosphorylation. Condensation with 3,4-dihydroxy-2-butanone 4-phosphate obtained from ribulose 5-phosphate leads to 6,7-dimethyl-8-ribityllumazine. The final step in the biosynthesis of the vitamin involves the dismutation of 6,7-dimethyl-8-ribityllumazine catalyzed by riboflavin synthase. The mechanistically unusual reaction involves the transfer of a four-carbon fragment between two identical substrate molecules. The second product, 5-amino-6-ribitylamino-2,4(1H,3H)-pyrimidinedione, is recycled in the biosynthetic pathway by 6,7-dimethyl-8-ribityllumazine synthase. This article will review structures and reaction mechanisms of riboflavin synthases and related proteins up to 2007 and 122 references are cited.
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Affiliation(s)
- Markus Fischer
- Institute of Food Chemistry, University of Hamburg, Grindelallee 117, D-20146 Hamburg, Germany.
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Cottevieille M, Larquet E, Jonic S, Petoukhov MV, Caprini G, Paravisi S, Svergun DI, Vanoni MA, Boisset N. The subnanometer resolution structure of the glutamate synthase 1.2-MDa hexamer by cryoelectron microscopy and its oligomerization behavior in solution: functional implications. J Biol Chem 2008; 283:8237-49. [PMID: 18199747 DOI: 10.1074/jbc.m708529200] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The three-dimensional structure of the hexameric (alphabeta)(6) 1.2-MDa complex formed by glutamate synthase has been determined at subnanometric resolution by combining cryoelectron microscopy, small angle x-ray scattering, and molecular modeling, providing for the first time a molecular model of this complex iron-sulfur flavoprotein. In the hexameric species, interprotomeric alpha-alpha and alpha-beta contacts are mediated by the C-terminal domain of the alpha subunit, which is based on a beta helical fold so far unique to glutamate synthases. The alphabeta protomer extracted from the hexameric model is fully consistent with it being the minimal catalytically active form of the enzyme. The structure clarifies the electron transfer pathway from the FAD cofactor on the beta subunit, to the FMN on the alpha subunit, through the low potential [4Fe-4S](1+/2+) centers on the beta subunit and the [3Fe-4S](0/1+) cluster on the alpha subunit. The (alphabeta)(6) hexamer exhibits a concentration-dependent equilibrium with alphabeta monomers and (alphabeta)(2) dimers, in solution, the hexamer being destabilized by high ionic strength and, to a lower extent, by the reaction product NADP(+). Hexamerization seems to decrease the catalytic efficiency of the alphabeta protomer only 3-fold by increasing the K(m) values measured for l-Gln and 2-OG. However, it cannot be ruled out that the (alphabeta)(6) hexamer acts as a scaffold for the assembly of multienzymatic complexes of nitrogen metabolism or that it provides a means to regulate the activity of the enzyme through an as yet unknown ligand.
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Affiliation(s)
- Magali Cottevieille
- Département de Biologie Structurale, IMPMC-UMR 7590, CNRS, Universités Paris 6 et Paris 7, IPGP, Paris, France
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Vincent KA, Li X, Blanford CF, Belsey NA, Weiner JH, Armstrong FA. Enzymatic catalysis on conducting graphite particles. Nat Chem Biol 2007; 3:761-2. [DOI: 10.1038/nchembio.2007.47] [Citation(s) in RCA: 59] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2007] [Accepted: 09/14/2007] [Indexed: 11/10/2022]
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Vincent KA, Parkin A, Armstrong FA. Investigating and Exploiting the Electrocatalytic Properties of Hydrogenases. Chem Rev 2007; 107:4366-413. [PMID: 17845060 DOI: 10.1021/cr050191u] [Citation(s) in RCA: 554] [Impact Index Per Article: 32.6] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Kylie A Vincent
- Inorganic Chemistry Laboratory, Department of Chemistry, University of Oxford, South Parks Road, Oxford OX1 3QR, United Kingdom
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Bertrand P, Frangioni B, Dementin S, Sabaty M, Arnoux P, Guigliarelli B, Pignol D, Léger C. Effects of Slow Substrate Binding and Release in Redox Enzymes: Theory and Application to Periplasmic Nitrate Reductase. J Phys Chem B 2007; 111:10300-11. [PMID: 17676894 DOI: 10.1021/jp074340j] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
For redox enzymes, the technique called protein film voltammetry makes it possible to determine the entire profile of activity against driving force by having the enzyme exchanging directly electrons with the rotating-disc electrode onto which it is adsorbed. Both the potential location of the catalytic response and its detailed shape report on the sequence of catalytic events, electron transfers and chemical steps, but the models that have been used so far to decipher this signal lack generality. For example, it was often proposed that substrate binding to multiple redox states of the active site may explain that turnover is greater in a certain window of electrode potential, but no fully analytical treatment has been given. Here, we derive (i) the general current equation for the case of reversible substrate binding to any redox states of a two-electron active site (as exemplified by flavins and Mo cofactors), (ii) the quantitative conditions for an extremum in activity to occur, and (iii) the expressions from which the substrate-concentration dependence of the catalytic potential can be interpreted to learn about the kinetics of substrate binding and how this affects the reduction potential of the active site. Not only does slow substrate binding and release make the catalytic wave shape highly complex, but we also show that it can have important consequences which will escape detection in traditional experiments: the position of the wave (this is the driving force that is required to elicit catalysis) departs from the reduction potential of the active site even at the lowest substrate concentration, and this deviation may be large if substrate binding is irreversible. This occurs in the reductive half-cycle of periplasmic nitrate reductase where irreversibility lowers the driving force required to reduce the active site under turnover conditions and favors intramolecular electron transfer from the proximal [4Fe4S]+ cluster to the active site Mo(V).
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Affiliation(s)
- Patrick Bertrand
- Laboratoire de Bioénergétique et Ingénierie des Protéines, CNRS UPR 9036, IBSM, France
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50
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Fleming BD, Barlow NL, Zhang J, Bond AM, Armstrong FA. Application of power spectra patterns in Fourier transform square wave voltammetry to evaluate electrode kinetics of surface-confined proteins. Anal Chem 2007; 78:2948-56. [PMID: 16642980 DOI: 10.1021/ac051823f] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
This paper describes an application of Fourier transform (FT) voltammetry that provides a quantitative evaluation of the electron-transfer kinetics of protein molecules attached to electrode surfaces. The potential waveform applied in these experiments consists of a large-amplitude square wave of frequency f superimposed onto the traditional triangular voltage used in dc cyclic voltammetry. The resultant current-time response, when Fourier transformed into the frequency domain, provides patterns of data at the even harmonic frequencies that arise from nonlinearity in the Faradaic response. These even harmonic contributions are ideally suited for kinetic evaluation of electron-transfer processes because they are highly selective to quasi-reversible behavior (insensitive to reversible or irreversible processes) and almost devoid of background charging current. Inverse FT methods can then be used to provide the wave shapes of the dc as well as the ac voltammetric components and other characteristics employed to detect the level of nonideality present relative to theoretical models based upon noninteracting surface-confined molecules. The new form of data evaluation has been applied to the electron-transfer properties of a typical biological electron carrier, the blue copper protein azurin, immobilized on polycrystalline gold electrodes modified with self-assembled monolayers of different length alkanethiols. Details of the electrode kinetics (rates of electron transfer, dispersion, and charge-transfer coefficients) as a function of alkanethiol, apparent surface coverage, and capacitance are all deduced from the square wave (FT-inverse FT) protocol, and the implications of these findings are considered.
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Affiliation(s)
- Barry D Fleming
- School of Chemistry, Monash University, Victoria 3800, Australia
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