1
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Zhao F, Niman CM, Ostovar G, Chavez MS, Atkinson JT, Bonis BM, Gralnick JA, El-Naggar MY, Boedicker JQ. Red-Light-Induced Genetic System for Control of Extracellular Electron Transfer. ACS Synth Biol 2024; 13:1467-1476. [PMID: 38696739 DOI: 10.1021/acssynbio.3c00684] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/04/2024]
Abstract
Optogenetics is a powerful tool for spatiotemporal control of gene expression. Several light-inducible gene regulators have been developed to function in bacteria, and these regulatory circuits have been ported to new host strains. Here, we developed and adapted a red-light-inducible transcription factor for Shewanella oneidensis. This regulatory circuit is based on the iLight optogenetic system, which controls gene expression using red light. A thermodynamic model and promoter engineering were used to adapt this system to achieve differential gene expression in light and dark conditions within a S. oneidensis host strain. We further improved the iLight optogenetic system by adding a repressor to invert the genetic circuit and activate gene expression under red light illumination. The inverted iLight genetic circuit was used to control extracellular electron transfer within S. oneidensis. The ability to use both red- and blue-light-induced optogenetic circuits simultaneously was also demonstrated. Our work expands the synthetic biology capabilities in S. oneidensis, which could facilitate future advances in applications with electrogenic bacteria.
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Affiliation(s)
- Fengjie Zhao
- Department of Physics and Astronomy, University of Southern California, Los Angeles, California 90089, United States
| | - Christina M Niman
- Department of Physics and Astronomy, University of Southern California, Los Angeles, California 90089, United States
| | - Ghazaleh Ostovar
- Department of Physics and Astronomy, University of Southern California, Los Angeles, California 90089, United States
| | - Marko S Chavez
- Department of Physics and Astronomy, University of Southern California, Los Angeles, California 90089, United States
| | - Joshua T Atkinson
- Department of Physics and Astronomy, University of Southern California, Los Angeles, California 90089, United States
- Department of Civil and Environmental Engineering, Princeton University, Princeton, New Jersey 08540, United States
- Omenn-Darling Bioengineering Institute, Princeton University, Princeton, New Jersey 08540, United States
| | - Benjamin M Bonis
- BioTechnology Institute and Department of Plant and Microbial Biology, University of Minnesota─Twin Cities, St. Paul, Minnesota 55108, United States
| | - Jeffrey A Gralnick
- BioTechnology Institute and Department of Plant and Microbial Biology, University of Minnesota─Twin Cities, St. Paul, Minnesota 55108, United States
| | - Mohamed Y El-Naggar
- Department of Physics and Astronomy, University of Southern California, Los Angeles, California 90089, United States
- Department of Biological Sciences, University of Southern California, Los Angeles, California 90089, United States
- Department of Chemistry, University of Southern California, Los Angeles, California 90089, United States
| | - James Q Boedicker
- Department of Physics and Astronomy, University of Southern California, Los Angeles, California 90089, United States
- Department of Biological Sciences, University of Southern California, Los Angeles, California 90089, United States
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2
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Molinas M, Meibom KL, Faizova R, Mazzanti M, Bernier-Latmani R. Mechanism of Reduction of Aqueous U(V)-dpaea and Solid-Phase U(VI)-dpaea Complexes: The Role of Multiheme c-Type Cytochromes. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2023; 57:7537-7546. [PMID: 37133831 DOI: 10.1021/acs.est.3c00666] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/04/2023]
Abstract
The biological reduction of soluble U(VI) complexes to form immobile U(IV) species has been proposed to remediate contaminated sites. It is well established that multiheme c-type cytochromes (MHCs) are key mediators of electron transfer to aqueous phase U(VI) complexes for bacteria such as Shewanella oneidensis MR-1. Recent studies have confirmed that the reduction proceeds via a first electron transfer forming pentavalent U(V) species that readily disproportionate. However, in the presence of the stabilizing aminocarboxylate ligand, dpaea2- (dpaeaH2═bis(pyridyl-6-methyl-2-carboxylate)-ethylamine), biologically produced U(V) persisted in aqueous solution at pH 7. We aim to pinpoint the role of MHC in the reduction of U(V)-dpaea and to establish the mechanism of solid-phase U(VI)-dpaea reduction. To that end, we investigated U-dpaea reduction by two deletion mutants of S. oneidensis MR-1-one lacking outer membrane MHCs and the other lacking all outer membrane MHCs and a transmembrane MHC-and by the purified outer membrane MHC, MtrC. Our results suggest that solid-phase U(VI)-dpaea is reduced primarily by outer membrane MHCs. Additionally, MtrC can directly transfer electrons to U(V)-dpaea to form U(IV) species but is not strictly necessary, underscoring the primary involvement of outer membrane MHCs in the reduction of this pentavalent U species but not excluding that of periplasmic MHCs.
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Affiliation(s)
- Margaux Molinas
- Environmental Microbiology Laboratory, Ecole Polytechnique Fédérale de Lausanne (EPFL), Lausanne 1015, Switzerland
| | - Karin Lederballe Meibom
- Environmental Microbiology Laboratory, Ecole Polytechnique Fédérale de Lausanne (EPFL), Lausanne 1015, Switzerland
| | - Radmila Faizova
- Group of Coordination Chemistry, Ecole Polytechnique Fédérale de Lausanne (EPFL), Lausanne 1015, Switzerland
| | - Marinella Mazzanti
- Group of Coordination Chemistry, Ecole Polytechnique Fédérale de Lausanne (EPFL), Lausanne 1015, Switzerland
| | - Rizlan Bernier-Latmani
- Environmental Microbiology Laboratory, Ecole Polytechnique Fédérale de Lausanne (EPFL), Lausanne 1015, Switzerland
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3
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Wang F, Chan CH, Suciu V, Mustafa K, Ammend M, Si D, Hochbaum AI, Egelman EH, Bond DR. Structure of Geobacter OmcZ filaments suggests extracellular cytochrome polymers evolved independently multiple times. eLife 2022; 11:81551. [PMID: 36062910 PMCID: PMC9473688 DOI: 10.7554/elife.81551] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2022] [Accepted: 09/03/2022] [Indexed: 11/26/2022] Open
Abstract
While early genetic and low-resolution structural observations suggested that extracellular conductive filaments on metal-reducing organisms such as Geobacter were composed of type IV pili, it has now been established that bacterial c-type cytochromes can polymerize to form extracellular filaments capable of long-range electron transport. Atomic structures exist for two such cytochrome filaments, formed from the hexaheme cytochrome OmcS and the tetraheme cytochrome OmcE. Due to the highly conserved heme packing within the central OmcS and OmcE cores, and shared pattern of heme coordination between subunits, it has been suggested that these polymers have a common origin. We have now used cryo-electron microscopy (cryo-EM) to determine the structure of a third extracellular filament, formed from the Geobacter sulfurreducens octaheme cytochrome, OmcZ. In contrast to the linear heme chains in OmcS and OmcE from the same organism, the packing of hemes, heme:heme angles, and between-subunit heme coordination is quite different in OmcZ. A branched heme arrangement within OmcZ leads to a highly surface exposed heme in every subunit, which may account for the formation of conductive biofilm networks, and explain the higher measured conductivity of OmcZ filaments. This new structural evidence suggests that conductive cytochrome polymers arose independently on more than one occasion from different ancestral multiheme proteins.
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Affiliation(s)
- Fengbin Wang
- Department of Biochemistry and Molecular Genetics, University of Virginia, Charlottesville, United States
| | - Chi Ho Chan
- Department of Plant and MIcrobial Biology, University of Minnesota, St. Paul, United States
| | - Victor Suciu
- Division of Computing and Software Systems, University of Washington Bothell, Bothell, United States
| | - Khawla Mustafa
- Department of Chemistry, University of California, Irvine, Irvine, United States
| | - Madeline Ammend
- Department of Plant and Microbial Biology, University of Minnesota, Saint Paul, United States
| | - Dong Si
- Division of Computing and Software Systems, University of Washington Bothell, Bothell, United States
| | - Allon I Hochbaum
- Department of Chemistry, University of California, Irvine, Irvine, United States
| | - Edward H Egelman
- Department of Biochemistry and Molecular Genetics, University of Virginia, Charlottesville, United States
| | - Daniel R Bond
- Department of Plant and Microbial Biology, University of Minnesota, Saint Paul, United States
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4
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van Wonderen JH, Li D, Piper SEH, Lau CY, Jenner LP, Hall CR, Clarke TA, Watmough NJ, Butt JN. Photosensitised Multiheme Cytochromes as Light-Driven Molecular Wires and Resistors. Chembiochem 2018; 19:2206-2215. [DOI: 10.1002/cbic.201800313] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2018] [Indexed: 01/12/2023]
Affiliation(s)
- Jessica H. van Wonderen
- School of Chemistry and School of Biology; University of East Anglia; Norwich Research Park Norfolk NR4 7TJ UK
| | - Daobo Li
- School of Chemistry and School of Biology; University of East Anglia; Norwich Research Park Norfolk NR4 7TJ UK
- Present address: Department of Chemistry; University of Science and Technology of China; Hefei 230026 China
- Present address: Collaborative Innovation Center of Suzhou Nano Science and Technology; Suzhou 215123 China
| | - Samuel E. H. Piper
- School of Chemistry and School of Biology; University of East Anglia; Norwich Research Park Norfolk NR4 7TJ UK
| | - Cheuk Y. Lau
- School of Chemistry and School of Biology; University of East Anglia; Norwich Research Park Norfolk NR4 7TJ UK
| | - Leon P. Jenner
- School of Chemistry and School of Biology; University of East Anglia; Norwich Research Park Norfolk NR4 7TJ UK
| | - Christopher R. Hall
- School of Chemistry and School of Biology; University of East Anglia; Norwich Research Park Norfolk NR4 7TJ UK
- Present address: ARC Centre of Excellence in Exciton Science; School of Chemistry; The University of Melbourne; Parkville Victoria 3010 Australia
| | - Thomas A. Clarke
- School of Chemistry and School of Biology; University of East Anglia; Norwich Research Park Norfolk NR4 7TJ UK
| | - Nicholas J. Watmough
- School of Chemistry and School of Biology; University of East Anglia; Norwich Research Park Norfolk NR4 7TJ UK
| | - Julea N. Butt
- School of Chemistry and School of Biology; University of East Anglia; Norwich Research Park Norfolk NR4 7TJ UK
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5
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Modulation of the reactivity of multiheme cytochromes by site-directed mutagenesis: moving towards the optimization of microbial electrochemical technologies. J Biol Inorg Chem 2016; 22:87-97. [DOI: 10.1007/s00775-016-1409-0] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2016] [Accepted: 10/21/2016] [Indexed: 01/06/2023]
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6
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Breuer M, Rosso KM, Blumberger J, Butt JN. Multi-haem cytochromes in Shewanella oneidensis MR-1: structures, functions and opportunities. J R Soc Interface 2015; 12:20141117. [PMID: 25411412 DOI: 10.1098/rsif.2014.1117] [Citation(s) in RCA: 129] [Impact Index Per Article: 14.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
Multi-haem cytochromes are employed by a range of microorganisms to transport electrons over distances of up to tens of nanometres. Perhaps the most spectacular utilization of these proteins is in the reduction of extracellular solid substrates, including electrodes and insoluble mineral oxides of Fe(III) and Mn(III/IV), by species of Shewanella and Geobacter. However, multi-haem cytochromes are found in numerous and phylogenetically diverse prokaryotes where they participate in electron transfer and redox catalysis that contributes to biogeochemical cycling of N, S and Fe on the global scale. These properties of multi-haem cytochromes have attracted much interest and contributed to advances in bioenergy applications and bioremediation of contaminated soils. Looking forward, there are opportunities to engage multi-haem cytochromes for biological photovoltaic cells, microbial electrosynthesis and developing bespoke molecular devices. As a consequence, it is timely to review our present understanding of these proteins and we do this here with a focus on the multitude of functionally diverse multi-haem cytochromes in Shewanella oneidensis MR-1. We draw on findings from experimental and computational approaches which ideally complement each other in the study of these systems: computational methods can interpret experimentally determined properties in terms of molecular structure to cast light on the relation between structure and function. We show how this synergy has contributed to our understanding of multi-haem cytochromes and can be expected to continue to do so for greater insight into natural processes and their informed exploitation in biotechnologies.
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Affiliation(s)
- Marian Breuer
- Department of Physics and Astronomy, University College London, London WC1E 6BT, UK
| | - Kevin M Rosso
- Pacific Northwest National Laboratory, Richland, WA, USA
| | - Jochen Blumberger
- Department of Physics and Astronomy, University College London, London WC1E 6BT, UK
| | - Julea N Butt
- School of Biological Sciences and School of Chemistry, University of East Anglia, Norwich NR4 7TJ, UK
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7
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Sturm-Richter K, Golitsch F, Sturm G, Kipf E, Dittrich A, Beblawy S, Kerzenmacher S, Gescher J. Unbalanced fermentation of glycerol in Escherichia coli via heterologous production of an electron transport chain and electrode interaction in microbial electrochemical cells. BIORESOURCE TECHNOLOGY 2015; 186:89-96. [PMID: 25812811 DOI: 10.1016/j.biortech.2015.02.116] [Citation(s) in RCA: 65] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/16/2015] [Revised: 02/27/2015] [Accepted: 02/28/2015] [Indexed: 05/28/2023]
Abstract
Microbial electrochemical cells are an emerging technology for achieving unbalanced fermentations. However, organisms that can serve as potential biocatalysts for this application are limited by their narrow substrate spectrum. This study describes the reprogramming of Escherichia coli for the efficient use of anodes as electron acceptors. Electron transfer into the periplasm was accelerated by 183% via heterologous expression of the c-type cytochromes CymA, MtrA and STC from Shewanella oneidensis. STC was identified as a target for heterologous expression via a two-stage screening approach. First, mass spectroscopic analysis revealed natively expressed cytochromes in S. oneidensis. Thereafter, the corresponding genes were cloned and expressed in E. coli to quantify periplasmic electron transfer activity using methylene blue. This redox dye was further used to expand electron transfer to carbon electrode surfaces. The results demonstrate that E. coli can be reprogrammed from glycerol fermentation to respiration upon production of the new electron transport chain.
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Affiliation(s)
- Katrin Sturm-Richter
- Institute for Applied Biosciences, Department of Applied Biology, Karlsruhe Institute of Technology, Fritz-Haber-Weg 2, 76131 Karlsruhe, Germany
| | - Frederik Golitsch
- Institute for Applied Biosciences, Department of Applied Biology, Karlsruhe Institute of Technology, Fritz-Haber-Weg 2, 76131 Karlsruhe, Germany
| | - Gunnar Sturm
- Institute for Applied Biosciences, Department of Applied Biology, Karlsruhe Institute of Technology, Fritz-Haber-Weg 2, 76131 Karlsruhe, Germany
| | - Elena Kipf
- Laboratory for MEMS Applications, IMTEK - Department of Microsystems Engineering, University of Freiburg, Georges-Koehler-Allee 103, D-79110 Freiburg, Germany
| | - André Dittrich
- Institute of Photogrammetry and Remote Sensing, Englerstraße 7, D-76131 Karlsruhe, Germany
| | - Sebastian Beblawy
- Institute for Applied Biosciences, Department of Applied Biology, Karlsruhe Institute of Technology, Fritz-Haber-Weg 2, 76131 Karlsruhe, Germany
| | - Sven Kerzenmacher
- Laboratory for MEMS Applications, IMTEK - Department of Microsystems Engineering, University of Freiburg, Georges-Koehler-Allee 103, D-79110 Freiburg, Germany
| | - Johannes Gescher
- Institute for Applied Biosciences, Department of Applied Biology, Karlsruhe Institute of Technology, Fritz-Haber-Weg 2, 76131 Karlsruhe, Germany.
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8
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9
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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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10
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Neto SE, Fonseca BM, Maycock C, Louro RO. Analysis of the residual alignment of a paramagnetic multiheme cytochrome by NMR. Chem Commun (Camb) 2014; 50:4561-3. [DOI: 10.1039/c3cc49135h] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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11
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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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12
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Bücking C, Piepenbrock A, Kappler A, Gescher J. Outer-membrane cytochrome-independent reduction of extracellular electron acceptors in Shewanella oneidensis. Microbiology (Reading) 2012; 158:2144-2157. [DOI: 10.1099/mic.0.058404-0] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Affiliation(s)
- Clemens Bücking
- Institut für angewandte Biowissenschaften, Angewandte Biologie, Karlsruher Institut für Technologie, Fritz-Haber-Weg 2, D-76131 Karlsruhe, Germany
| | - Annette Piepenbrock
- Geomicrobiology, Center for Applied Geosciences, University of Tübingen, Sigwartstrasse 10, D-72076 Tübingen, Germany
| | - Andreas Kappler
- Geomicrobiology, Center for Applied Geosciences, University of Tübingen, Sigwartstrasse 10, D-72076 Tübingen, Germany
| | - Johannes Gescher
- Institut für angewandte Biowissenschaften, Angewandte Biologie, Karlsruher Institut für Technologie, Fritz-Haber-Weg 2, D-76131 Karlsruhe, Germany
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13
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Fonseca BM, Tien M, Rivera M, Shi L, Louro RO. Efficient and selective isotopic labeling of hemes to facilitate the study of multiheme proteins. Biotechniques 2012; 52:000113859. [PMID: 26307249 DOI: 10.2144/000113859] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2012] [Accepted: 04/02/2012] [Indexed: 11/23/2022] Open
Abstract
Specific isotopic labeling of hemes provides a unique opportunity to characterize the structure and function of heme-proteins. Unfortunately, current methods do not allow efficient labeling in high yields of multiheme cytochromes c, which are of great biotechnological interest. Here, a method for production of recombinant multiheme cytochromes c in Escherichia coli with isotopically labeled hemes is reported. A small tetraheme cytochrome of 12 kDa from Shewanella oneidensis MR-1 was used to demonstrate the method, achieving a production of 4 mg pure protein per liter. This method achieves, in a single step, efficient expression and incorporation of hemes isotopically labeled in specific atom positions adequate for spectroscopic characterization of these complex heme proteins. It is, furthermore, of general application to heme proteins, opening new possibilities for the characterization of this important class of proteins.
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Affiliation(s)
- Bruno M Fonseca
- Instituto de Tecnologia Química e Biológica, Universidade Nova de Lisboa, Oeiras, Portugal
| | - Ming Tien
- Department of Biochemistry and Molecular Biology, Pennsylvania State University, University Park, PA, USA
| | - Mario Rivera
- Department of Chemistry, University of Kansas, Lawrence, KS, USA
| | - Liang Shi
- Microbiology Group, Pacific Northwest National Laboratory, Richland, WA, USA
| | - Ricardo O Louro
- Instituto de Tecnologia Química e Biológica, Universidade Nova de Lisboa, Oeiras, Portugal
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14
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McMillan DGG, Marritt SJ, Butt JN, Jeuken LJC. Menaquinone-7 is specific cofactor in tetraheme quinol dehydrogenase CymA. J Biol Chem 2012; 287:14215-25. [PMID: 22393052 PMCID: PMC3340143 DOI: 10.1074/jbc.m112.348813] [Citation(s) in RCA: 69] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022] Open
Abstract
Little is known about enzymatic quinone-quinol interconversions in the lipid membrane when compared with our knowledge of substrate transformations by globular enzymes. Here, the smallest example of a quinol dehydrogenase in nature, CymA, has been studied. CymA is a monotopic membrane tetraheme c-type cytochrome belonging to the NapC/NirT family and central to anaerobic respiration in Shewanella sp. Using protein-film electrochemistry, it is shown that vesicle-bound menaquinone-7 is not only a substrate for this enzyme but is also required as a cofactor when converting other quinones. Here, we propose that the high concentration of quinones in the membrane negates the evolutionary pressure to create a high affinity active site. However, the instability and reactivity of reaction intermediate, semiquinone, might require a cofactor that functions to minimize damaging side reactions.
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Affiliation(s)
- Duncan G G McMillan
- Institute of Membrane and Systems Biology, University of Leeds, Leeds LS2 9JT, United Kingdom
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15
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Qian Y, Shi L, Tien M. SO2907, a putative TonB-dependent receptor, is involved in dissimilatory iron reduction by Shewanella oneidensis strain MR-1. J Biol Chem 2011; 286:33973-80. [PMID: 21813652 DOI: 10.1074/jbc.m111.262113] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Shewanella oneidensis strain MR-1 utilizes soluble and insoluble ferric ions as terminal electron acceptors during anaerobic respiration. The components of respiratory metabolism are localized in the membrane fractions which include the outer membrane and cytoplasmic membrane. Many of the biological components that interact with the various iron forms are proposed to be localized in these membrane fractions. To identify the iron-binding proteins acting either as an iron transporter or as a terminal iron reductase, we used metal-catalyzed oxidation reactions. This system catalyzed the oxidation of amino acids in close proximity to the iron binding site. The carbonyl groups formed from this oxidation can then be labeled with fluoresceinamine (FLNH(2)). The peptide harboring the FLNH(2) can then be proteolytically digested, purified by HPLC and then identified by MALDI-TOF tandem MS. A predominant peptide was identified to be part of SO2907 that encodes a putative TonB-dependent receptor. Compared with wild type (wt), the so2907 gene deletion (ΔSO2907) mutant has impaired ability to reduce soluble Fe(III), but retains the same ability to respire oxygen or fumarate as the wt. The ΔSO2907 mutant was also impacted in reduction of insoluble iron. Iron binding assays using isothermal titration calorimetry and fluorescence tryptophan quenching demonstrated that a truncated form of heterologous-expressed SO2907 that contains the Fe(III) binding site, is capable of binding soluble Fe(III) forms with K(d) of approximate 50 μm. To the best of our knowledge, this is the first report of the physiological role of SO2907 in Fe(III) reduction by MR-1.
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Affiliation(s)
- Yufeng Qian
- Department of Biochemistry and Molecular Biology, the Pennsylvania State University, University Park, Pennsylvania 16802, USA
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