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Barbosa C, Rodrigues CF, Lončar N, Martins LO, Todorovic S, Silveira CM. Spectroelectrochemistry for determination of the redox potential in heme enzymes: Dye-decolorizing peroxidases. BBA ADVANCES 2023; 5:100112. [PMID: 38235374 PMCID: PMC10792693 DOI: 10.1016/j.bbadva.2023.100112] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2023] [Revised: 12/19/2023] [Accepted: 12/20/2023] [Indexed: 01/19/2024] Open
Abstract
Dye-decolorizing peroxidases (DyPs) are heme-containing enzymes that are structurally unrelated to other peroxidases. Some DyPs show high potential for applications in biotechnology, which critically depends on the stability and redox potential (E°') of the enzyme. Here we provide a comparative analysis of UV-Vis- and surface-enhanced resonance Raman-based spectroelectrochemical methods for determination of the E°' of DyPs from two different organisms, and their variants generated targeting E°' upshift. We show that substituting the highly conserved Arginine in the distal side of the heme pocket by hydrophobic amino acid residues impacts the heme architecture and redox potential of DyPs from the two organisms in a very distinct manner. We demonstrate the advantages and drawbacks of the used spectroelectrochemical approaches, which is relevant for other heme proteins that contain multiple heme centers or spin populations.
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Affiliation(s)
- Catarina Barbosa
- Instituto de Tecnologia Química e Biológica António Xavier, Universidade NOVA de Lisboa, Av. da República, Oeiras 2780-157, Portugal
| | - Carolina F. Rodrigues
- Instituto de Tecnologia Química e Biológica António Xavier, Universidade NOVA de Lisboa, Av. da República, Oeiras 2780-157, Portugal
| | - Nikola Lončar
- Gecco Biotech, Nijenborgh 4, Groningen 9747AG, the Netherlands
| | - Lígia O. Martins
- Instituto de Tecnologia Química e Biológica António Xavier, Universidade NOVA de Lisboa, Av. da República, Oeiras 2780-157, Portugal
| | - Smilja Todorovic
- Instituto de Tecnologia Química e Biológica António Xavier, Universidade NOVA de Lisboa, Av. da República, Oeiras 2780-157, Portugal
| | - Célia M. Silveira
- Instituto de Tecnologia Química e Biológica António Xavier, Universidade NOVA de Lisboa, Av. da República, Oeiras 2780-157, Portugal
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2
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Sil D, Khan FST, Rath SP. Effect of intermacrocyclic interactions: Modulation of metal spin-state in oxo/hydroxo/fluoro-bridged diiron(III)/dimanganese(III) porphyrin dimers. ADVANCES IN INORGANIC CHEMISTRY 2023. [DOI: 10.1016/bs.adioch.2022.08.002] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
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3
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Antunes JMA, Silva MA, Salgueiro CA, Morgado L. Electron Flow From the Inner Membrane Towards the Cell Exterior in Geobacter sulfurreducens: Biochemical Characterization of Cytochrome CbcL. Front Microbiol 2022; 13:898015. [PMID: 35620088 PMCID: PMC9129911 DOI: 10.3389/fmicb.2022.898015] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2022] [Accepted: 04/04/2022] [Indexed: 11/25/2022] Open
Abstract
Exoelectrogenic microorganisms are in the spotlight due to their unique respiratory mechanisms and potential applications in distinct biotechnological fields, including bioremediation, bioenergy production and microbial electrosynthesis. These applications rely on the capability of these microorganisms to perform extracellular electron transfer, a mechanism that allows the bacteria to transfer electrons to the cell’s exterior by establishing functional interfaces between different multiheme cytochromes at the inner membrane, periplasmic space, and outer membrane. The multiheme cytochrome CbcL from Geobacter sulfurreducens is associated to the inner membrane and plays an essential role in the transfer of electrons to final electron acceptors with a low redox potential, as Fe(III) oxides and electrodes poised at −100 mV. CbcL has a transmembranar di-heme b-type cytochrome domain with six helices, linked to a periplasmic cytochrome domain with nine c-type heme groups. The complementary usage of ultraviolet-visible, circular dichroism and nuclear magnetic resonance permitted the structural and functional characterization of CbcL’s periplasmic domain. The protein was found to have a high percentage of disordered regions and its nine hemes are low-spin and all coordinated by two histidine residues. The apparent midpoint reduction potential of the CbcL periplasmic domain was determined, suggesting a thermodynamically favorable transfer of electrons to the putative redox partner in the periplasm − the triheme cytochrome PpcA. The establishment of a redox complex between the two proteins was confirmed by probing the electron transfer reaction and the molecular interactions between CbcL and PpcA. The results obtained show for the first time how electrons are injected into the periplasm of Geobacter sulfurreducens for subsequent transfer to the cell’s exterior.
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Affiliation(s)
- Jorge M A Antunes
- Associate Laboratory i4HB - Institute for Health and Bioeconomy, NOVA School of Science and Technology, NOVA University Lisbon, Caparica, Portugal.,UCIBIO - Applied Molecular Biosciences Unit, Chemistry Department, NOVA School of Science and Technology, NOVA University Lisbon, Caparica, Portugal
| | - Marta A Silva
- Associate Laboratory i4HB - Institute for Health and Bioeconomy, NOVA School of Science and Technology, NOVA University Lisbon, Caparica, Portugal.,UCIBIO - Applied Molecular Biosciences Unit, Chemistry Department, NOVA School of Science and Technology, NOVA University Lisbon, Caparica, Portugal
| | - Carlos A Salgueiro
- Associate Laboratory i4HB - Institute for Health and Bioeconomy, NOVA School of Science and Technology, NOVA University Lisbon, Caparica, Portugal.,UCIBIO - Applied Molecular Biosciences Unit, Chemistry Department, NOVA School of Science and Technology, NOVA University Lisbon, Caparica, Portugal
| | - Leonor Morgado
- Associate Laboratory i4HB - Institute for Health and Bioeconomy, NOVA School of Science and Technology, NOVA University Lisbon, Caparica, Portugal.,UCIBIO - Applied Molecular Biosciences Unit, Chemistry Department, NOVA School of Science and Technology, NOVA University Lisbon, Caparica, Portugal
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4
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Yan J, Frøkjær EE, Engelbrekt C, Leimkühler S, Ulstrup J, Wollenberger U, Xiao X, Zhang J. Voltammetry and Single‐Molecule In Situ Scanning Tunnelling Microscopy of the Redox Metalloenzyme Human Sulfite Oxidase. ChemElectroChem 2021. [DOI: 10.1002/celc.202001258] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Affiliation(s)
- Jiawei Yan
- Department of Chemistry Technical University of Denmark Building 207, Kemitorvet 2800 Kgs. Lyngby Denmark
- State key Laboratory of Physical Chemistry of Solid Surfaces and College of Chemistry and Chemical Engineering Xiamen University Xiamen 361005 Fujian P.R. China
| | - Emil Egede Frøkjær
- Department of Chemistry Technical University of Denmark Building 207, Kemitorvet 2800 Kgs. Lyngby Denmark
| | - Christian Engelbrekt
- Department of Chemistry Technical University of Denmark Building 207, Kemitorvet 2800 Kgs. Lyngby Denmark
| | - Silke Leimkühler
- Department of Molecular Enzymology University of Potsdam 14476 PotsdamPotsdam-Golm Germany
| | - Jens Ulstrup
- Department of Chemistry Technical University of Denmark Building 207, Kemitorvet 2800 Kgs. Lyngby Denmark
| | - Ulla Wollenberger
- Department of Molecular Enzymology University of Potsdam 14476 PotsdamPotsdam-Golm Germany
| | - Xinxin Xiao
- Department of Chemistry Technical University of Denmark Building 207, Kemitorvet 2800 Kgs. Lyngby Denmark
| | - Jingdong Zhang
- Department of Chemistry Technical University of Denmark Building 207, Kemitorvet 2800 Kgs. Lyngby Denmark
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5
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Cruzeiro VWD, Feliciano GT, Roitberg AE. Exploring Coupled Redox and pH Processes with a Force-Field-Based Approach: Applications to Five Different Systems. J Am Chem Soc 2020; 142:3823-3835. [PMID: 32011132 DOI: 10.1021/jacs.9b11433] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023]
Abstract
Coupled redox and pH-driven processes are at the core of many important biological mechanisms. As the distribution of protonation and redox states in a system is associated with the pH and redox potential of the solution, having efficient computational tools that can simulate under these conditions becomes very important. Such tools have the potential to provide information that complement and drive experiments. In previous publications we have presented the implementation of the constant pH and redox potential molecular dynamics (C(pH,E)MD) method in AMBER and we have shown how multidimensional replica exchange can be used to significantly enhance the convergence efficiency of our simulations. In the current work, after an improvement in our C(pH,E)MD approach that allows a given residue to be simultaneously pH- and redox-active, we have employed our methodologies to study five different systems of interest in the literature. We present results for capped tyrosine dipeptide, two maquette systems containing one pH- and redox-active tyrosine (α3Y and peptide A), and two proteins that contain multiple heme groups (diheme cytochrome c from Rhodobacter sphaeroides and Desulfovibrio vulgaris Hildenborough cytochrome c3). We show that our results can provide new insights into previous theoretical and experimental findings by using a fully force-field-based and GPU-accelerated approach, which allows the simulations to be executed with high computational performance.
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Affiliation(s)
| | - Gustavo Troiano Feliciano
- Departamento de Físico-Química, Instituto de Química , Universidade Estadual Paulista (Unesp) , Araraquara , Brazil
| | - Adrian E Roitberg
- Department of Chemistry , University of Florida , Gainesville , Florida 32611 , United States
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6
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Lai D, Khan FST, Rath SP. Multiheme proteins: effect of heme–heme interactions. Dalton Trans 2018; 47:14388-14401. [DOI: 10.1039/c8dt00518d] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
This Frontier illustrates a brief personal account on the effect of heme–heme interactions in dihemes which thereby discloses some of the evolutionary design principles involved in multiheme proteins for their diverse structures and functions.
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Affiliation(s)
- Dipti Lai
- Department of Chemistry
- Indian Institute of Technology Kanpur
- Kanpur-208016
- India
| | | | - Sankar Prasad Rath
- Department of Chemistry
- Indian Institute of Technology Kanpur
- Kanpur-208016
- India
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7
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Unraveling the electron transfer processes of a nanowire protein from Geobacter sulfurreducens. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2016; 1857:7-13. [DOI: 10.1016/j.bbabio.2015.09.010] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/10/2015] [Revised: 09/04/2015] [Accepted: 09/30/2015] [Indexed: 11/19/2022]
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8
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A Post-Genomic View of the Ecophysiology, Catabolism and Biotechnological Relevance of Sulphate-Reducing Prokaryotes. Adv Microb Physiol 2015. [PMID: 26210106 DOI: 10.1016/bs.ampbs.2015.05.002] [Citation(s) in RCA: 173] [Impact Index Per Article: 19.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
Dissimilatory sulphate reduction is the unifying and defining trait of sulphate-reducing prokaryotes (SRP). In their predominant habitats, sulphate-rich marine sediments, SRP have long been recognized to be major players in the carbon and sulphur cycles. Other, more recently appreciated, ecophysiological roles include activity in the deep biosphere, symbiotic relations, syntrophic associations, human microbiome/health and long-distance electron transfer. SRP include a high diversity of organisms, with large nutritional versatility and broad metabolic capacities, including anaerobic degradation of aromatic compounds and hydrocarbons. Elucidation of novel catabolic capacities as well as progress in the understanding of metabolic and regulatory networks, energy metabolism, evolutionary processes and adaptation to changing environmental conditions has greatly benefited from genomics, functional OMICS approaches and advances in genetic accessibility and biochemical studies. Important biotechnological roles of SRP range from (i) wastewater and off gas treatment, (ii) bioremediation of metals and hydrocarbons and (iii) bioelectrochemistry, to undesired impacts such as (iv) souring in oil reservoirs and other environments, and (v) corrosion of iron and concrete. Here we review recent advances in our understanding of SRPs focusing mainly on works published after 2000. The wealth of publications in this period, covering many diverse areas, is a testimony to the large environmental, biogeochemical and technological relevance of these organisms and how much the field has progressed in these years, although many important questions and applications remain to be explored.
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9
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Sil D, Rath SP. An ethane-bridged porphyrin dimer as a model of di-heme proteins: inorganic and bioinorganic perspectives and consequences of heme–heme interactions. Dalton Trans 2015; 44:16195-211. [DOI: 10.1039/c5dt00947b] [Citation(s) in RCA: 55] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
Abstract
A brief account of our recent efforts on how inter-heme interactions can possibly change the structure and functional properties of the individual heme centers in a highly flexible ethane-bridged porphyrin dimer has been presented.
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Affiliation(s)
- Debangsu Sil
- Department of Chemistry
- Indian Institute of Technology Kanpur
- Kanpur 208016
- India
| | - Sankar Prasad Rath
- Department of Chemistry
- Indian Institute of Technology Kanpur
- Kanpur 208016
- India
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10
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Daidone I, Paltrinieri L, Amadei A, Battistuzzi G, Sola M, Borsari M, Bortolotti CA. Unambiguous Assignment of Reduction Potentials in Diheme Cytochromes. J Phys Chem B 2014; 118:7554-7560. [DOI: 10.1021/jp506017a] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Affiliation(s)
- Isabella Daidone
- Department
of Physical and Chemical Sciences, University of L’Aquila, via
Vetoio (Coppito 1), 67010 L’Aquila, Italy
| | - Licia Paltrinieri
- Department
of Chemical and Geological Sciences, University of Modena and Reggio Emilia, via Campi 183, 41125 Modena, Italy
| | - Andrea Amadei
- Department
of Chemical Sciences and Technologies, University of Rome “Tor Vergata”, via della Ricerca Scientifica 1, 00133 Rome, Italy
| | - Gianantonio Battistuzzi
- Department
of Chemical and Geological Sciences, University of Modena and Reggio Emilia, via Campi 183, 41125 Modena, Italy
| | - Marco Sola
- Department
of Life Sciences, University of Modena and Reggio Emilia, via Campi
183, 41125 Modena, Italy
- CNR-Nano Institute
of Nanoscience, via Campi 213/A, 41125 Modena, Italy
| | - Marco Borsari
- Department
of Chemical and Geological Sciences, University of Modena and Reggio Emilia, via Campi 183, 41125 Modena, Italy
| | - Carlo Augusto Bortolotti
- Department
of Life Sciences, University of Modena and Reggio Emilia, via Campi
183, 41125 Modena, Italy
- CNR-Nano Institute
of Nanoscience, via Campi 213/A, 41125 Modena, Italy
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11
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Paquete CM, Saraiva IH, Louro RO. Redox tuning of the catalytic activity of soluble fumarate reductases from Shewanella. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2014; 1837:717-25. [DOI: 10.1016/j.bbabio.2014.02.006] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/19/2013] [Revised: 02/04/2014] [Accepted: 02/06/2014] [Indexed: 10/25/2022]
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12
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Silva MA, Valente RC, Pokkuluri PR, Turner DL, Salgueiro CA, Catarino T. Thermodynamic and kinetic characterization of two methyl-accepting chemotaxis heme sensors from Geobacter sulfurreducens reveals the structural origin of their functional difference. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2014; 1837:920-8. [DOI: 10.1016/j.bbabio.2014.01.008] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/10/2013] [Revised: 01/08/2014] [Accepted: 01/13/2014] [Indexed: 10/25/2022]
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13
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De March M, Di Rocco G, Hickey N, Geremia S. High-resolution crystal structure of the recombinant diheme cytochrome c fromShewanella baltica(OS155). J Biomol Struct Dyn 2014; 33:395-403. [DOI: 10.1080/07391102.2014.880657] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
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14
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Di Rocco G, Ranieri A, Bortolotti CA, Battistuzzi G, Bonifacio A, Sergo V, Borsari M, Sola M. Axial iron coordination and spin state change in a heme c upon electrostatic protein-SAM interaction. Phys Chem Chem Phys 2014; 15:13499-505. [PMID: 23824165 DOI: 10.1039/c3cp50222h] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
A bacterial di-heme cytochrome c binds electrostatically to a gold electrode surface coated with a negatively charged COOH-terminated SAM adopting a sort of 'perpendicular' orientation. Cyclic voltammetry, Resonance Raman and SERRS spectroscopies indicate that the high-potential C-terminal heme center proximal to the SAM's surface undergoes an adsorption-induced swapping of one axial His ligand with a water molecule, which is probably lost in the reduced form, and a low- to high-spin transition. This coordination change for a bis-His ligated heme center upon an electrostatically-driven molecular recognition is as yet unprecedented, as well as the resulting increase in reduction potential. We discuss it in comparison with the known methionine ligand lability in monoheme cytochromes c occurring upon interaction with charged molecular patches. One possible implication of this finding in biological ET is that mobile redox partners do not behave as rigid and invariant bodies, but in the ET complex are subjected to molecular changes and structural fluctuations that affect in a complex way the thermodynamics and the kinetics of the process.
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Affiliation(s)
- Giulia Di Rocco
- Department of Life Sciences, University of Modena and Reggio Emilia, Via Campi 183, I-41125 Modena, Italy
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15
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Paquete CM, Louro RO. Unveiling the details of electron transfer in multicenter redox proteins. Acc Chem Res 2014; 47:56-65. [PMID: 23984680 DOI: 10.1021/ar4000696] [Citation(s) in RCA: 45] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Metalloproteins modulate the intrinsic properties of transition metals to achieve controlled catalysis, electron transfer, or structural stabilization. Those performing electron transport, redox proteins, are a diverse class of proteins with central roles in numerous metabolic and signaling pathways, including respiration and photosynthesis. Many redox proteins have applications in industry, especially biotechnology, making them the focus of intense research. Redox proteins may contain one or multiple redox centers of the same or a different type. The complexity of proteins with multiple redox centers makes it difficult to establish a detailed molecular mechanism for their activity. Thermodynamic and kinetic information can be interpreted using the molecular structure to elucidate the protein's functional mechanism. This Account reviews experimental strategies developed in recent years to determine the detailed thermodynamic properties of multicenter redox proteins and their kinetic properties during interactions with redox partners. These strategies allow the discrimination of thermodynamic and kinetic properties of each individual redox center. The thermodynamic characterization of the redox transitions results from the combined analysis of data from NMR and UV-visible spectroscopy. Meanwhile, the kinetic characterization of intermolecular electron transfer comes from stopped-flow spectrophotometry. We illustrate an application of these strategies to a particular redox protein, the small tetraheme cytochrome from the periplasmic space of Shewanella oneidensis MR-1. This protein is a convenient prototype for developing methods for the detailed analysis of multicenter electron transfer proteins because hemes have strong UV-visible absorption bands and because heme resonances have exquisite discrimination in NMR spectra. Nonetheless, the methods are fully generalizable. Ultimately, this Account highlights the relevance of detailed characterization of the thermodynamic and kinetic properties of redox proteins. These properties are responsible for the directionality and specificity of the electron transfer process in bioenergetic pathways; a more thorough characterization of these properties should allow better-designed proteins for industrial applications.
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Affiliation(s)
- Catarina M. Paquete
- Instituto de Tecnologia Química e Biológica, Universidade Nova de Lisboa, Av. da República (EAN), 2780-157 Oeiras, Portugal
| | - Ricardo O. Louro
- Instituto de Tecnologia Química e Biológica, Universidade Nova de Lisboa, Av. da República (EAN), 2780-157 Oeiras, Portugal
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16
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Quintas PO, Cepeda AP, Borges N, Catarino T, Turner DL. Relative importance of driving force and electrostatic interactions in the reduction of multihaem cytochromes by small molecules. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2013; 1827:745-50. [DOI: 10.1016/j.bbabio.2013.02.006] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/16/2012] [Revised: 02/08/2013] [Accepted: 02/12/2013] [Indexed: 11/26/2022]
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17
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Nazmutdinov RR, Bronshtein MD, Zinkicheva TT, Chi Q, Zhang J, Ulstrup J. Modeling and computations of the intramolecular electron transfer process in the two-heme protein cytochrome c(4). Phys Chem Chem Phys 2012; 14:5953-65. [PMID: 22430606 DOI: 10.1039/c2cp24084j] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
The di-heme protein Pseudomonas stutzeri cytochrome c(4) (cyt c(4)) has emerged as a useful model for studying long-range protein electron transfer (ET). Recent experimental observations have shown a dramatically different pattern of intramolecular ET between the two heme groups in different local environments. Intramolecular ET in homogeneous solution is too slow (>10 s) to be detected but fast (ms-μs) intramolecular ET in an electrochemical environment has recently been achieved by controlling the molecular orientation of the protein assembled on a gold electrode surface. In this work we have performed computational modeling of the intramolecular ET process by a combination of density functional theory (DFT) and quantum mechanical charge transfer theory to disclose reasons for this difference. We first address the electronic structures of the model heme core with histidine and methionine axial ligands in both low- and high-spin states by structure-optimized DFT. The computations enable estimating the intramolecular reorganization energy of the ET process for different combinations of low- and high-spin heme couples. Environmental reorganization free energies, work terms ("gating") and driving force were determined using dielectric continuum models. We then calculated the electronic transmission coefficient of the intramolecular ET rate using perturbation theory combined with the electronic wave functions determined by the DFT calculations for different heme group orientations and Fe-Fe separations. The reactivity of low- and high-spin heme groups was notably different. The ET rate is exceedingly low for the crystallographic equilibrium orientation but increases by several orders of magnitude for thermally accessible non-equilibrium configurations. Deprotonation of the propionate carboxyl group was also found to enhance the ET rate significantly. The results are discussed in relation to the observed surface immobilization effect and support the notion of conformationally gated ET.
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Affiliation(s)
- Renat R Nazmutdinov
- Kazan National Research Technological University, 420015 Kazan, Republic Tatarstan, Russian Federation
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18
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Interfacial electrochemical electron transfer in biology - towards the level of the single molecule. FEBS Lett 2011; 586:526-35. [PMID: 22024483 DOI: 10.1016/j.febslet.2011.10.023] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2011] [Revised: 10/04/2011] [Accepted: 10/11/2011] [Indexed: 11/21/2022]
Abstract
Physical electrochemistry has undergone a remarkable evolution over the last few decades, integrating advanced techniques and theory from solid state and surface physics. Single-crystal electrode surfaces have been a core notion, opening for scanning tunnelling microscopy directly in aqueous electrolyte (in situ STM). Interfacial electrochemistry of metalloproteins is presently going through a similar transition. Electrochemical surfaces with thiol-based promoter molecular monolayers (SAMs) as biomolecular electrochemical environments and the biomolecules themselves have been mapped with unprecedented resolution, opening a new area of single-molecule bioelectrochemistry. We consider first in situ STM of small redox molecules, followed by in situ STM of thiol-based SAMs as molecular views of bioelectrochemical environments. We then address electron transfer metalloproteins, and multi-centre metalloenzymes including applied single-biomolecular perspectives based on metalloprotein/metallic nanoparticle hybrids.
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19
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Fonseca BM, Paquete CM, Salgueiro CA, Louro RO. The role of intramolecular interactions in the functional control of multiheme cytochromes c. FEBS Lett 2011; 586:504-9. [PMID: 21856299 DOI: 10.1016/j.febslet.2011.08.019] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2011] [Accepted: 08/09/2011] [Indexed: 10/17/2022]
Abstract
Detailed thermodynamic and structural data measured in soluble monomeric multiheme cytochromes c provided the basis to investigate the functional significance of interactions between redox co-factors. The steep decay of intramolecular interactions with distance means that close proximity of the redox centers is necessary to modulate the intrinsic reduction potentials in a significant way. This ensures selection of specific populations during redox activity in addition to maintaining fast intramolecular electron transfer. Therefore, intramolecular interactions between redox co-factors play an important role in establishing the biological function of the protein by controlling how electrons flow through and are distributed among the co-factors.
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Affiliation(s)
- Bruno M Fonseca
- Instituto de Tecnologia Química e Biológica, Universidade Nova de Lisboa, Av. da República, EAN, 2780-157 Oeiras, Portugal
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20
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Homotropic and heterotropic interactions in cytochromes c
3
from sulphate reducing bacteria. FEBS Lett 2011; 586:494-503. [DOI: 10.1016/j.febslet.2011.07.007] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2011] [Accepted: 07/04/2011] [Indexed: 11/23/2022]
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21
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Morgado L, Bruix M, Pessanha M, Londer YY, Salgueiro CA. Thermodynamic characterization of a triheme cytochrome family from Geobacter sulfurreducens reveals mechanistic and functional diversity. Biophys J 2010; 99:293-301. [PMID: 20655858 DOI: 10.1016/j.bpj.2010.04.017] [Citation(s) in RCA: 82] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2010] [Revised: 03/09/2010] [Accepted: 04/05/2010] [Indexed: 10/19/2022] Open
Abstract
A family of five periplasmic triheme cytochromes (PpcA-E) was identified in Geobacter sulfurreducens, where they play a crucial role by driving electron transfer from the cytoplasm to the cell exterior and assisting the reduction of extracellular acceptors. The thermodynamic characterization of PpcA using NMR and visible spectroscopies was previously achieved under experimental conditions identical to those used for the triheme cytochrome c(7) from Desulfuromonas acetoxidans. Under such conditions, attempts to obtain NMR data were complicated by the relatively fast intermolecular electron exchange. This work reports the detailed thermodynamic characterization of PpcB, PpcD, and PpcE under optimal experimental conditions. The thermodynamic characterization of PpcA was redone under these new conditions to allow a proper comparison of the redox properties with those of other members of this family. The heme reduction potentials of the four proteins are negative, differ from each other, and cover different functional ranges. These reduction potentials are strongly modulated by heme-heme interactions and by interactions with protonated groups (the redox-Bohr effect) establishing different cooperative networks for each protein, which indicates that they are designed to perform different functions in the cell. PpcA and PpcD appear to be optimized to interact with specific redox partners involving e(-)/H(+) transfer via different mechanisms. Although no evidence of preferential electron transfer pathway or e(-)/H(+) coupling was found for PpcB and PpcE, the difference in their working potential ranges suggests that they may also have different physiological redox partners. This is the first study, to our knowledge, to characterize homologous cytochromes from the same microorganism and provide evidence of their different mechanistic and functional properties. These findings provide an explanation for the coexistence of five periplasmic triheme cytochromes in G. sulfurreducens.
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Affiliation(s)
- Leonor Morgado
- Requimte-Centro de Química Fina e Biotecnologia, Departamento de Química, Faculdade de Ciências e Tecnologia, Universidade Nova de Lisboa, Caparica, Portugal
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22
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Paixão VB, Vis H, Turner DL. Redox Linked Conformational Changes in Cytochrome c3 from Desulfovibrio desulfuricans ATCC 27774. Biochemistry 2010; 49:9620-9. [DOI: 10.1021/bi101237w] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Vitor B. Paixão
- Instituto de Tecnologia Química e Biológica, Universidade Nova de Lisboa, Rua da Quinta Grande 6, 2780-156 Oeiras, Portugal
| | - Hans Vis
- Instituto de Tecnologia Química e Biológica, Universidade Nova de Lisboa, Rua da Quinta Grande 6, 2780-156 Oeiras, Portugal
| | - David L. Turner
- Instituto de Tecnologia Química e Biológica, Universidade Nova de Lisboa, Rua da Quinta Grande 6, 2780-156 Oeiras, Portugal
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23
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Purification and characterization of OmcZ, an outer-surface, octaheme c-type cytochrome essential for optimal current production by Geobacter sulfurreducens. Appl Environ Microbiol 2010; 76:3999-4007. [PMID: 20400562 DOI: 10.1128/aem.00027-10] [Citation(s) in RCA: 189] [Impact Index Per Article: 13.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
Abstract
Previous studies have demonstrated that Geobacter sulfurreducens requires the c-type cytochrome OmcZ, which is present in large (OmcZ(L); 50-kDa) and small (OmcZ(S); 30-kDa) forms, for optimal current production in microbial fuel cells. This protein was further characterized to aid in understanding its role in current production. Subcellular-localization studies suggested that OmcZ(S) was the predominant extracellular form of OmcZ. N- and C-terminal amino acid sequence analysis of purified OmcZ(S) and molecular weight measurements indicated that OmcZ(S) is a cleaved product of OmcZ(L) retaining all 8 hemes, including 1 heme with the unusual c-type heme-binding motif CX(14)CH. The purified OmcZ(S) was remarkably thermally stable (thermal-denaturing temperature, 94.2 degrees C). Redox titration analysis revealed that the midpoint reduction potential of OmcZ(S) is approximately -220 mV (versus the standard hydrogen electrode [SHE]) with nonequivalent heme groups that cover a large reduction potential range (-420 to -60 mV). OmcZ(S) transferred electrons in vitro to a diversity of potential extracellular electron acceptors, such as Fe(III) citrate, U(VI), Cr(VI), Au(III), Mn(IV) oxide, and the humic substance analogue anthraquinone-2,6-disulfonate, but not Fe(III) oxide. The biochemical properties and extracellular localization of OmcZ suggest that it is well suited for promoting electron transfer in current-producing biofilms of G. sulfurreducens.
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24
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Chi Q, Zhang J, Arslan T, Borg L, Pedersen GW, Christensen HEM, Nazmudtinov RR, Ulstrup J. Approach to Interfacial and Intramolecular Electron Transfer of the Diheme Protein Cytochrome c4 Assembled on Au(111) Surfaces. J Phys Chem B 2010; 114:5617-24. [DOI: 10.1021/jp1007208] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Qijin Chi
- Department of Chemistry and Nano•DTU, Technical University of Denmark, Kemitorvet, Building 207, DK-2800 Kongens Lyngby, Denmark, and Kazan State Technological University, 420015 Kazan, Republic of Tatarstan, Russian Federation
| | - Jingdong Zhang
- Department of Chemistry and Nano•DTU, Technical University of Denmark, Kemitorvet, Building 207, DK-2800 Kongens Lyngby, Denmark, and Kazan State Technological University, 420015 Kazan, Republic of Tatarstan, Russian Federation
| | - Taner Arslan
- Department of Chemistry and Nano•DTU, Technical University of Denmark, Kemitorvet, Building 207, DK-2800 Kongens Lyngby, Denmark, and Kazan State Technological University, 420015 Kazan, Republic of Tatarstan, Russian Federation
| | - Lotte Borg
- Department of Chemistry and Nano•DTU, Technical University of Denmark, Kemitorvet, Building 207, DK-2800 Kongens Lyngby, Denmark, and Kazan State Technological University, 420015 Kazan, Republic of Tatarstan, Russian Federation
| | - Gert W. Pedersen
- Department of Chemistry and Nano•DTU, Technical University of Denmark, Kemitorvet, Building 207, DK-2800 Kongens Lyngby, Denmark, and Kazan State Technological University, 420015 Kazan, Republic of Tatarstan, Russian Federation
| | - Hans E. M. Christensen
- Department of Chemistry and Nano•DTU, Technical University of Denmark, Kemitorvet, Building 207, DK-2800 Kongens Lyngby, Denmark, and Kazan State Technological University, 420015 Kazan, Republic of Tatarstan, Russian Federation
| | - Renat R. Nazmudtinov
- Department of Chemistry and Nano•DTU, Technical University of Denmark, Kemitorvet, Building 207, DK-2800 Kongens Lyngby, Denmark, and Kazan State Technological University, 420015 Kazan, Republic of Tatarstan, Russian Federation
| | - Jens Ulstrup
- Department of Chemistry and Nano•DTU, Technical University of Denmark, Kemitorvet, Building 207, DK-2800 Kongens Lyngby, Denmark, and Kazan State Technological University, 420015 Kazan, Republic of Tatarstan, Russian Federation
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25
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Paquete CM, Saraiva IH, Calçada E, Louro RO. Molecular basis for directional electron transfer. J Biol Chem 2010; 285:10370-5. [PMID: 20089857 DOI: 10.1074/jbc.m109.078337] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Biological macromolecules involved in electron transfer reactions display chains of closely packed redox cofactors when long distances must be bridged. This is a consequence of the need to maintain a rate of transfer compatible with metabolic activity in the framework of the exponential decay of electron tunneling with distance. In this work intermolecular electron transfer was studied in kinetic experiments performed with the small tetraheme cytochrome from Shewanella oneidensis MR-1 and from Shewanella frigidimarina NCIMB400 using non-physiological redox partners. This choice allowed the effect of specific recognition and docking to be eliminated from the measured rates. The results were analyzed with a kinetic model that uses the extensive thermodynamic characterization of these proteins reported in the literature to discriminate the kinetic contribution of each heme to the overall rate of electron transfer. This analysis shows that, in this redox chain that spans 23 A, the kinetic properties of the individual hemes establish a functional specificity for each redox center. This functional specificity combined with the thermodynamic properties of these soluble proteins ensures directional electron flow within the cytochrome even outside of the context of a functioning respiratory chain.
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Affiliation(s)
- Catarina M Paquete
- Instituto de Tecnologia Química e Biológica, Av. da República (EAN), 2780-157 Oeiras, Portugal
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26
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Paquete CM, Louro RO. Molecular details of multielectron transfer: the case of multiheme cytochromes from metal respiring organisms. Dalton Trans 2009; 39:4259-66. [PMID: 20422082 DOI: 10.1039/b917952f] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
Shewanella are facultative anaerobic bacteria of remarkable respiratory versatility that includes the dissimilatory reduction of metal ores. They contain a large number of multiheme c-type cytochromes that play a significant role in various anaerobic respiratory processes. Of all the cytochromes found in Shewanella, only the two most abundant periplasmic cytochromes, the small tetraheme cytochrome (STC) and flavocytochrome c(3) (Fcc(3)) have been structurally characterized. For these two proteins the molecular bases for their redox properties were determined using spectroscopic methods based on paramagnetic NMR, that allow the contribution of specific hemes to be discriminated. In this perspective these results are reviewed in the context of the continuing effort to understand the molecular mechanisms of electron transfer in the respiratory chains of these organisms.
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27
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Monari S, Battistuzzi G, Borsari M, Rocco GD, Martini L, Ranieri A, Sola M. Heterogeneous Electron Transfer of a Two-Centered Heme Protein: Redox and Electrocatalytic Properties of Surface-Immobilized Cytochrome c4. J Phys Chem B 2009; 113:13645-53. [DOI: 10.1021/jp906339u] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Stefano Monari
- Contribution from the Department of Chemistry, University of Modena and Reggio Emilia, Via Campi 183, I-41100 Modena, Italy, and CNR-INFM National Center nanoStructures and bioSystems at Surfaces - S3, Via Campi 213/A, I-41100 Modena, Italy
| | - Gianantonio Battistuzzi
- Contribution from the Department of Chemistry, University of Modena and Reggio Emilia, Via Campi 183, I-41100 Modena, Italy, and CNR-INFM National Center nanoStructures and bioSystems at Surfaces - S3, Via Campi 213/A, I-41100 Modena, Italy
| | - Marco Borsari
- Contribution from the Department of Chemistry, University of Modena and Reggio Emilia, Via Campi 183, I-41100 Modena, Italy, and CNR-INFM National Center nanoStructures and bioSystems at Surfaces - S3, Via Campi 213/A, I-41100 Modena, Italy
| | - Giulia Di Rocco
- Contribution from the Department of Chemistry, University of Modena and Reggio Emilia, Via Campi 183, I-41100 Modena, Italy, and CNR-INFM National Center nanoStructures and bioSystems at Surfaces - S3, Via Campi 213/A, I-41100 Modena, Italy
| | - Laura Martini
- Contribution from the Department of Chemistry, University of Modena and Reggio Emilia, Via Campi 183, I-41100 Modena, Italy, and CNR-INFM National Center nanoStructures and bioSystems at Surfaces - S3, Via Campi 213/A, I-41100 Modena, Italy
| | - Antonio Ranieri
- Contribution from the Department of Chemistry, University of Modena and Reggio Emilia, Via Campi 183, I-41100 Modena, Italy, and CNR-INFM National Center nanoStructures and bioSystems at Surfaces - S3, Via Campi 213/A, I-41100 Modena, Italy
| | - Marco Sola
- Contribution from the Department of Chemistry, University of Modena and Reggio Emilia, Via Campi 183, I-41100 Modena, Italy, and CNR-INFM National Center nanoStructures and bioSystems at Surfaces - S3, Via Campi 213/A, I-41100 Modena, Italy
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28
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Thermodynamic characterization of the redox centres in a representative domain of a novel c-type multihaem cytochrome. Biochem J 2009; 420:485-92. [DOI: 10.1042/bj20082428] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Multihaem cytochromes that could form protein “nanowires” were identified in the Geobacter sulfurreducens genome, and represent a new type of multihaem cytochrome. The sequences of these proteins, two with 12 haems (GSU1996, GSU0592) and one with 27 haems (GSU2210), suggest that they are formed with domains homologous to the trihaem cytochrome c7. Although all three haems have bis-His co-ordination in cytochromes c7, in each domain of the above polymers, the haem equivalent to haem IV has His-Met co-ordination. We previously determined the structure and measured the macroscopic redox potential of one representative domain (domain C) of a dodecahaem cytochrome (GSU1996). In the present study, the microscopic redox properties of the individual haem groups of domain C were determined using NMR and UV–visible spectroscopies. The reduction potentials of the haems for the fully reduced and protonated protein are different from each other (haem I, −106 mV; haem III, −136 mV; and haem IV, −125 mV) and are strongly modulated by redox interactions. This result is rather surprising since the His-Met co-ordinated haem IV does not have the highest potential as was expected. The polypeptide environment of each haem group and the strong haem pairwise redox interactions must play a dominant role in controlling the individual haem potentials. The strong redox interactions between the haems extend the range of their operating potentials at physiological pH (haem I, −71 mV, haem III, −146 mV and haem IV, −110 mV). Such a modulation in haem potentials is likely to have a functional significance in the metabolism of G. sulfurreducens.
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29
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Electron transfer patterns of the di-heme protein cytochrome c4 from Pseudomonas stutzeri. J Inorg Biochem 2009; 103:717-22. [DOI: 10.1016/j.jinorgbio.2009.01.004] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2008] [Revised: 01/08/2009] [Accepted: 01/09/2009] [Indexed: 11/18/2022]
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30
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Pokkuluri PR, Londer YY, Wood SJ, Duke NEC, Morgado L, Salgueiro CA, Schiffer M. Outer membrane cytochrome c, OmcF, from Geobacter sulfurreducens: high structural similarity to an algal cytochrome c6. Proteins 2009; 74:266-70. [PMID: 18837462 DOI: 10.1002/prot.22260] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Affiliation(s)
- P R Pokkuluri
- Biosciences Division, Argonne National Laboratory, Lemont, Illinois 60439, USA.
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31
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The tetraheme cytochrome from Shewanella oneidensis MR-1 shows thermodynamic bias for functional specificity of the hemes. J Biol Inorg Chem 2008; 14:375-85. [DOI: 10.1007/s00775-008-0455-7] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2008] [Accepted: 11/14/2008] [Indexed: 10/21/2022]
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32
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Chi Q, Zhang J, Jensen PS, Nazmudtinov RR, Ulstrup J. Surface-induced intramolecular electron transfer in multi-centre redox metalloproteins: the di-haem protein cytochrome c(4) in homogeneous solution and at electrochemical surfaces. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2008; 20:374124. [PMID: 21694431 DOI: 10.1088/0953-8984/20/37/374124] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
Intramolecular electron transfer (ET) between transition metal centres is a core feature of biological ET and redox enzyme function. The number of microscopic redox potentials and ET rate constants is, however, mostly prohibitive for experimental mapping, but two-centre proteins offer simple enough communication networks for complete mapping to be within reach. At the same time, multi-centre redox proteins operate in a membrane environment where conformational dynamics and ET patterns are quite different from the conditions in a homogeneous solution. The bacterial respiratory di-haem protein Pseudomonas stutzeri cytochrome c(4) offers a prototype target for environmental gating of intra-haem ET. ET between P. stutzeri cyt c(4) and small molecular reaction partners in solution appears completely dominated by intermolecular ET of each haem group/protein domain, with no competing intra-haem ET, for which accompanying propionate-mediated proton transfer is a further barrier. The protein can, however, be immobilized on single-crystal, modified Au(111) electrode surfaces with either the low-potential N terminal or the high-potential C terminal domain facing the surface, clearly with fast intramolecular ET as a key feature in the electrochemical two-ET process. This dual behaviour suggests a pattern for multi-centre redox metalloprotein function. In a homogeneous solution, which is not the natural environment of cyt c(4), the two haem group domains operate largely independently with conformations prohibitive for intramolecular ET. Binding to a membrane or electrochemical surface, however, triggers conformational opening of intramolecular ET channels. The haem group orientation in P. stutzeri cyt c(4) is finally noted to offer a case for orientation dependent electronic rectification between a substrate and a tip in electrochemical in situ scanning tunnelling microscopy or nanoscale electrode configurations.
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Affiliation(s)
- Qijin Chi
- Department of Chemistry, Technical University of Denmark, Building 207, DK-2800 Kongens Lyngby, Denmark
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33
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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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34
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Morgado L, Bruix M, Orshonsky V, Londer YY, Duke NEC, Yang X, Pokkuluri PR, Schiffer M, Salgueiro CA. Structural insights into the modulation of the redox properties of two Geobacter sulfurreducens homologous triheme cytochromes. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2008; 1777:1157-65. [PMID: 18534185 DOI: 10.1016/j.bbabio.2008.04.043] [Citation(s) in RCA: 49] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/22/2008] [Revised: 04/07/2008] [Accepted: 04/28/2008] [Indexed: 11/17/2022]
Abstract
The redox properties of a periplasmic triheme cytochrome, PpcB from Geobacter sulfurreducens, were studied by NMR and visible spectroscopy. The structure of PpcB was determined by X-ray diffraction. PpcB is homologous to PpcA (77% sequence identity), which mediates cytoplasmic electron transfer to extracellular acceptors and is crucial in the bioenergetic metabolism of Geobacter spp. The heme core structure of PpcB in solution, probed by 2D-NMR, was compared to that of PpcA. The results showed that the heme core structures of PpcB and PpcA in solution are similar, in contrast to their crystal structures where the heme cores of the two proteins differ from each other. NMR redox titrations were carried out for both proteins and the order of oxidation of the heme groups was determined. The microscopic properties of PpcB and PpcA redox centers showed important differences: (i) the order in which hemes become oxidized is III-I-IV for PpcB, as opposed to I-IV-III for PpcA; (ii) the redox-Bohr effect is also different in the two proteins. The different redox features observed between PpcB and PpcA suggest that each protein uniquely modulates the properties of their co-factors to assure effectiveness in their respective metabolic pathways. The origins of the observed differences are discussed.
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Affiliation(s)
- Leonor Morgado
- Requimte-CQFB, Departamento de Química, Faculdade de Ciências e Tecnologia, Universidade Nova de Lisboa, Campus Caparica, 2829-516 Caparica, Portugal
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