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Payne N, Kpebe A, Guendon C, Baffert C, Ros J, Lebrun R, Denis Y, Shintu L, Brugna M. The electron-bifurcating FeFe-hydrogenase Hnd is involved in ethanol metabolism in Desulfovibrio fructosovorans grown on pyruvate. Mol Microbiol 2022; 117:907-920. [PMID: 35066935 DOI: 10.1111/mmi.14881] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2021] [Revised: 01/19/2022] [Accepted: 01/19/2022] [Indexed: 11/28/2022]
Abstract
Desulfovibrio fructosovorans, a sulfate-reducing bacterium, possesses six gene clusters encoding six hydrogenases catalyzing the reversible oxidation of H2 into protons and electrons. Among them, Hnd is an electron-bifurcating hydrogenase, coupling the exergonic reduction of NAD+ to the endergonic reduction of a ferredoxin with electrons derived from H2 . It was previously hypothesized that its biological function involves the production of NADPH necessary for biosynthetic purposes. However, it was subsequently demonstrated that Hnd is instead a NAD+ -reducing enzyme, thus its specific function has yet to be established. To understand the physiological role of Hnd in D. fructosovorans, we compared the hnd deletion mutant with the wild-type strain grown on pyruvate. Growth, metabolites production and comsumption, and gene expression were compared under three different growth conditions. Our results indicate that hnd is strongly regulated at the transcriptional level and that its deletion has a drastic effect on the expression of genes for two enzymes, an aldehyde ferredoxin oxidoreductase and an alcohol dehydrogenase. We demonstrated here that Hnd is involved in ethanol metabolism when bacteria grow fermentatively and proposed that Hnd might oxidize part of the H2 produced during fermentation generating both NADH and reduced ferredoxin for ethanol production via its electron bifurcation mechanism.
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Affiliation(s)
| | | | | | | | - Julien Ros
- CNRS, Aix Marseille Univ, BIP, Marseille, France
| | - Régine Lebrun
- CNRS, Aix Marseille Univ, Plate-forme Protéomique de l'IMM, FR 3479, Marseille Protéomique (MaP), Marseille, France
| | - Yann Denis
- CNRS, Aix Marseille Univ, Plate-forme Transcriptomique, Marseille, France
| | - Laetitia Shintu
- CNRS, Aix Marseille Univ, Centrale Marseille, ISM2, Marseille, France
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Chongdar N, Pawlak K, Rüdiger O, Reijerse EJ, Rodríguez-Maciá P, Lubitz W, Birrell JA, Ogata H. Spectroscopic and biochemical insight into an electron-bifurcating [FeFe] hydrogenase. J Biol Inorg Chem 2019; 25:135-149. [PMID: 31823008 PMCID: PMC7064455 DOI: 10.1007/s00775-019-01747-1] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2019] [Accepted: 11/21/2019] [Indexed: 01/28/2023]
Abstract
Abstract The heterotrimeric electron-bifurcating [FeFe] hydrogenase (HydABC) from Thermotoga maritima (Tm) couples the endergonic reduction of protons (H+) by dihydronicotinamide adenine dinucleotide (NADH) (∆G0 ≈ 18 kJ mol−1) to the exergonic reduction of H+ by reduced ferredoxin (Fdred) (∆G0 ≈ − 16 kJ mol−1). The specific mechanism by which HydABC functions is not understood. In the current study, we describe the biochemical and spectroscopic characterization of TmHydABC recombinantly produced in Escherichia coli and artificially maturated with a synthetic diiron cofactor. We found that TmHydABC catalyzed the hydrogen (H2)-dependent reduction of nicotinamide adenine dinucleotide (NAD+) in the presence of oxidized ferredoxin (Fdox) at a rate of ≈17 μmol NADH min−1 mg−1. Our data suggest that only one flavin is present in the enzyme and is not likely to be the site of electron bifurcation. FTIR and EPR spectroscopy, as well as FTIR spectroelectrochemistry, demonstrated that the active site for H2 conversion, the H-cluster, in TmHydABC behaves essentially the same as in prototypical [FeFe] hydrogenases, and is most likely also not the site of electron bifurcation. The implications of these results are discussed with respect to the current hypotheses on the electron bifurcation mechanism of [FeFe] hydrogenases. Overall, the results provide insight into the electron-bifurcating mechanism and present a well-defined system for further investigations of this fascinating class of [FeFe] hydrogenases. Graphic abstract ![]()
Electronic supplementary material The online version of this article (10.1007/s00775-019-01747-1) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Nipa Chongdar
- Max Planck Institute for Chemical Energy Conversion, Stiftstrasse 34-36, 45470, Mülheim an der Ruhr, Germany.
| | - Krzysztof Pawlak
- Max Planck Institute for Chemical Energy Conversion, Stiftstrasse 34-36, 45470, Mülheim an der Ruhr, Germany
| | - Olaf Rüdiger
- Max Planck Institute for Chemical Energy Conversion, Stiftstrasse 34-36, 45470, Mülheim an der Ruhr, Germany
| | - Edward J Reijerse
- Max Planck Institute for Chemical Energy Conversion, Stiftstrasse 34-36, 45470, Mülheim an der Ruhr, Germany
| | - Patricia Rodríguez-Maciá
- Max Planck Institute for Chemical Energy Conversion, Stiftstrasse 34-36, 45470, Mülheim an der Ruhr, Germany
| | - Wolfgang Lubitz
- Max Planck Institute for Chemical Energy Conversion, Stiftstrasse 34-36, 45470, Mülheim an der Ruhr, Germany
| | - James A Birrell
- Max Planck Institute for Chemical Energy Conversion, Stiftstrasse 34-36, 45470, Mülheim an der Ruhr, Germany.
| | - Hideaki Ogata
- Max Planck Institute for Chemical Energy Conversion, Stiftstrasse 34-36, 45470, Mülheim an der Ruhr, Germany. .,Institute of Low Temperature Science, Hokkaido University, Kita-19, Nishi-8, Kita-ku, Sapporo, 060-0819, Japan.
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Baffert C, Kpebe A, Avilan L, Brugna M. Hydrogenases and H 2 metabolism in sulfate-reducing bacteria of the Desulfovibrio genus. Adv Microb Physiol 2019; 74:143-189. [PMID: 31126530 DOI: 10.1016/bs.ampbs.2019.03.001] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
Hydrogen metabolism plays a central role in sulfate-reducing bacteria of the Desulfovibrio genus and is based on hydrogenases that catalyze the reversible conversion of protons into dihydrogen. These metabolically versatile microorganisms possess a complex hydrogenase system composed of several enzymes of both [FeFe]- and [NiFe]-type that can vary considerably from one Desulfovibrio species to another. This review covers the molecular and physiological aspects of hydrogenases and H2 metabolism in Desulfovibrio but focuses particularly on our model bacterium Desulfovibrio fructosovorans. The search of hydrogenase genes in more than 30 sequenced genomes provides an overview of the distribution of these enzymes in Desulfovibrio. Our discussion will consider the significance of the involvement of electron-bifurcation in H2 metabolism.
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Affiliation(s)
- Carole Baffert
- Aix-Marseille University, CNRS, BIP, 31 Chemin Joseph Aiguier, 13402 Marseille, France
| | - Arlette Kpebe
- Aix-Marseille University, CNRS, BIP, 31 Chemin Joseph Aiguier, 13402 Marseille, France
| | - Luisana Avilan
- Aix-Marseille University, CNRS, BIP, 31 Chemin Joseph Aiguier, 13402 Marseille, France
| | - Myriam Brugna
- Aix-Marseille University, CNRS, BIP, 31 Chemin Joseph Aiguier, 13402 Marseille, France
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Chongdar N, Birrell JA, Pawlak K, Sommer C, Reijerse EJ, Rüdiger O, Lubitz W, Ogata H. Unique Spectroscopic Properties of the H-Cluster in a Putative Sensory [FeFe] Hydrogenase. J Am Chem Soc 2018; 140:1057-1068. [PMID: 29251926 DOI: 10.1021/jacs.7b11287] [Citation(s) in RCA: 44] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Sensory type [FeFe] hydrogenases are predicted to play a role in transcriptional regulation by detecting the H2 level of the cellular environment. These hydrogenases contain the hydrogenase domain with distinct modifications in the active site pocket, followed by a Per-Arnt-Sim (PAS) domain. As yet, neither the physiological function nor the biochemical or spectroscopic properties of these enzymes have been explored. Here, we present the characterization of an artificially maturated, putative sensory [FeFe] hydrogenase from Thermotoga maritima (HydS). This enzyme shows lower hydrogen conversion activity than prototypical [FeFe] hydrogenases and a reduced inhibition by CO. Using FTIR spectroelectrochemistry and EPR spectroscopy, three redox states of the active site were identified. The spectroscopic signatures of the most oxidized state closely resemble those of the Hox state from the prototypical [FeFe] hydrogenases, while the FTIR spectra of both singly and doubly reduced states show large differences. The FTIR bands of both the reduced states are strongly red-shifted relative to the Hox state, indicating reduction at the diiron site, but with retention of the bridging CO ligand. The unique functional and spectroscopic features of HydS are discussed with regard to the possible role of altered amino acid residues influencing the electronic properties of the H-cluster.
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Affiliation(s)
- Nipa Chongdar
- Max Planck Institute for Chemical Energy Conversion , Stiftstrasse 34-36, D45470 Mülheim an der Ruhr, Germany
| | - James A Birrell
- Max Planck Institute for Chemical Energy Conversion , Stiftstrasse 34-36, D45470 Mülheim an der Ruhr, Germany
| | - Krzysztof Pawlak
- Max Planck Institute for Chemical Energy Conversion , Stiftstrasse 34-36, D45470 Mülheim an der Ruhr, Germany
| | - Constanze Sommer
- Max Planck Institute for Chemical Energy Conversion , Stiftstrasse 34-36, D45470 Mülheim an der Ruhr, Germany
| | - Edward J Reijerse
- Max Planck Institute for Chemical Energy Conversion , Stiftstrasse 34-36, D45470 Mülheim an der Ruhr, Germany
| | - Olaf Rüdiger
- Max Planck Institute for Chemical Energy Conversion , Stiftstrasse 34-36, D45470 Mülheim an der Ruhr, Germany
| | - Wolfgang Lubitz
- Max Planck Institute for Chemical Energy Conversion , Stiftstrasse 34-36, D45470 Mülheim an der Ruhr, Germany
| | - Hideaki Ogata
- Max Planck Institute for Chemical Energy Conversion , Stiftstrasse 34-36, D45470 Mülheim an der Ruhr, Germany.,Institute of Low Temperature Science, Hokkaido University , Kita19 Nishi8, Kita-ku, 060-0819 Sapporo, Japan
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Türker L. A Model Study on the Possible Effects of an External Electrical Field on Enzymes Having Dinuclear Iron Cluster [2Fe-2S]. ScientificWorldJournal 2012; 2012:985958. [PMID: 22629229 PMCID: PMC3353660 DOI: 10.1100/2012/985958] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2011] [Accepted: 12/01/2011] [Indexed: 11/17/2022] Open
Abstract
Hydrogenases which catalyze the H2↔ 2H+ + 2e− reaction are metalloenzymes that can be divided into two classes, the NiFe and Fe enzymes, on the basis of their metal content. Iron-sulfur clusters [2Fe-2S] and [4Fe-4S] are common in ironhydrogenases. In the present model study, [2Fe-2S] cluster has been considered to visualize the effect of external electric field on various quantum chemical properties of it. In the model, all the cysteinyl residues are in the amide form. The PM3 type semiempirical calculations have been performed for the geometry optimization of the model structure in the absence and presence of the external field. Then, single point DFT calculations (B3LYP/6-31+G(d)) have been carried out. Depending on the direction of the field, the chemical reactivity of the model enzyme varies which suggests that an external electric field could, under proper conditions, improve the enzymatic hydrogen production.
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Affiliation(s)
- Lemi Türker
- Department of Chemistry, Middle East Technical University, 06531 Ankara, Turkey
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Chou CJ, Jenney FE, Adams MW, Kelly RM. Hydrogenesis in hyperthermophilic microorganisms: Implications for biofuels. Metab Eng 2008; 10:394-404. [DOI: 10.1016/j.ymben.2008.06.007] [Citation(s) in RCA: 69] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2007] [Accepted: 06/20/2008] [Indexed: 11/25/2022]
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Fontecilla-Camps JC, Volbeda A, Cavazza C, Nicolet Y. Structure/function relationships of [NiFe]- and [FeFe]-hydrogenases. Chem Rev 2007; 107:4273-303. [PMID: 17850165 DOI: 10.1021/cr050195z] [Citation(s) in RCA: 998] [Impact Index Per Article: 58.7] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Affiliation(s)
- Juan C Fontecilla-Camps
- Laboratoire de Cristallographie et Cristallogenèse des Proteines, Institut de Biologie Structurale J. P. Ebel, CEA, CNRS, Universitè Joseph Fourier, 41 rue J. Horowitz, 38027 Grenoble Cedex 1, France.
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9
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Conners SB, Mongodin EF, Johnson MR, Montero CI, Nelson KE, Kelly RM. Microbial biochemistry, physiology, and biotechnology of hyperthermophilic Thermotoga species. FEMS Microbiol Rev 2006; 30:872-905. [PMID: 17064285 DOI: 10.1111/j.1574-6976.2006.00039.x] [Citation(s) in RCA: 90] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023] Open
Abstract
High-throughput sequencing of microbial genomes has allowed the application of functional genomics methods to species lacking well-developed genetic systems. For the model hyperthermophile Thermotoga maritima, microarrays have been used in comparative genomic hybridization studies to investigate diversity among Thermotoga species. Transcriptional data have assisted in prediction of pathways for carbohydrate utilization, iron-sulfur cluster synthesis and repair, expolysaccharide formation, and quorum sensing. Structural genomics efforts aimed at the T. maritima proteome have yielded hundreds of high-resolution datasets and predicted functions for uncharacterized proteins. The information gained from genomics studies will be particularly useful for developing new biotechnology applications for T. maritima enzymes.
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Affiliation(s)
- Shannon B Conners
- Department of Chemical and Biomolecular Engineering, North Carolina State University, Raleigh, NC 27695-7905, USA
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Abstract
Enzymes possessing the capacity to oxidize molecular hydrogen have developed convergently three class of enzymes leading to: [FeFe]-, [NiFe]-, and [FeS]-cluster-free hydrogenases. They differ in the composition and the structure of the active site metal centre and the sequence of the constituent structural polypeptides but they show one unifying feature, namely the existence of CN and/or CO ligands at the active site Fe. Recent developments in the analysis of the maturation of [FeFe]- and [NiFe]- hydrogenases have revealed a remarkably complex pattern of mostly novel biochemical reactions. Maturation of [FeFe]-hydrogenases requires a minimum of three auxiliary proteins, two of which belong to the class of Radical-SAM enzymes and other to the family of GTPases. They are sufficient to generate active enzyme when their genes are co-expressed with the structural genes in a heterologous host, otherwise deficient in [FeFe]-hydrogenase expression. Maturation of the large subunit of [NiFe]-hydrogenases depends on the activity of at least seven core proteins that catalyse the synthesis of the CN ligand, have a function in the coordination of the active site iron, the insertion of nickel and the proteolytic maturation of the large subunit. Whereas this core maturation machinery is sufficient to generate active hydrogenase in the cytoplasm, like that of hydrogenase 3 from Escherichia coli, additional proteins are involved in the export of the ready-assembled heterodimeric enzyme to the periplasm via the twin-arginine translocation system in the case of membrane-bound hydrogenases. A series of other gene products with intriguing putative functions indicate that the minimal pathway established for E. coli [NiFe]-hydrogenase maturation may possess even higher complexity in other organisms.
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Affiliation(s)
- August Böck
- Department Biology I, University of Munich, 80638 Munich, Germany
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11
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Wu X, Alexander PB, He Y, Kikkawa M, Vogel PD, McKnight SL. Mammalian sprouty proteins assemble into large monodisperse particles having the properties of intracellular nanobatteries. Proc Natl Acad Sci U S A 2005; 102:14058-62. [PMID: 16172380 PMCID: PMC1216833 DOI: 10.1073/pnas.0506714102] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Sprouty proteins act as intracellular inhibitors of receptor tyrosine kinase signaling. Here we show that the mammalian Sprouty2 protein contains an iron-sulfur complex that can exist in an oxidized, reduced, or nitrosylated state. Purified Sprouty2 assembles into large monodisperse spheres containing approximately 24 polypeptides per particle. Biochemical experiments indicate that the charge state of the iron within Sprouty2 particles may be insulated from ambient intracellular redox. These features offer the possibility that Sprouty2 particles are capable of receiving, maintaining, and dissipating electrical charge in a manner formally equivalent to a battery.
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Affiliation(s)
- Xinle Wu
- Department of Biochemistry and Cell Biology, University of Texas Southwestern Medical Center, 5323 Harry Hines Boulevard, Dallas, TX 75390, USA
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Pysz MA, Conners SB, Montero CI, Shockley KR, Johnson MR, Ward DE, Kelly RM. Transcriptional analysis of biofilm formation processes in the anaerobic, hyperthermophilic bacterium Thermotoga maritima. Appl Environ Microbiol 2004; 70:6098-112. [PMID: 15466556 PMCID: PMC522082 DOI: 10.1128/aem.70.10.6098-6112.2004] [Citation(s) in RCA: 71] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023] Open
Abstract
Thermotoga maritima, a fermentative, anaerobic, hyperthermophilic bacterium, was found to attach to bioreactor glass walls, nylon mesh, and polycarbonate filters during chemostat cultivation on maltose-based media at 80 degrees C. A whole-genome cDNA microarray was used to examine differential expression patterns between biofilm and planktonic populations. Mixed-model statistical analysis revealed differential expression (twofold or more) of 114 open reading frames in sessile cells (6% of the genome), over a third of which were initially annotated as hypothetical proteins in the T. maritima genome. Among the previously annotated genes in the T. maritima genome, which showed expression changes during biofilm growth, were several that corresponded to biofilm formation genes identified in mesophilic bacteria (i.e., Pseudomonas species, Escherichia coli, and Staphylococcus epidermidis). Most notably, T. maritima biofilm-bound cells exhibited increased transcription of genes involved in iron and sulfur transport, as well as in biosynthesis of cysteine, thiamine, NAD, and isoprenoid side chains of quinones. These findings were all consistent with the up-regulation of iron-sulfur cluster assembly and repair functions in biofilm cells. Significant up-regulation of several beta-specific glycosidases was also noted in biofilm cells, despite the fact that maltose was the primary carbon source fed to the chemostat. The reasons for increased beta-glycosidase levels are unclear but are likely related to the processing of biofilm-based polysaccharides. In addition to revealing insights into the phenotype of sessile T. maritima communities, the methodology developed here can be extended to study other anaerobic biofilm formation processes as well as to examine aspects of microbial ecology in hydrothermal environments.
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Affiliation(s)
- Marybeth A Pysz
- Department of Chemical Engineering, North Carolina State University, Raleigh, NC 27695-7905, USA
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Soboh B, Linder D, Hedderich R. A multisubunit membrane-bound [NiFe] hydrogenase and an NADH-dependent Fe-only hydrogenase in the fermenting bacterium Thermoanaerobacter tengcongensis. MICROBIOLOGY-SGM 2004; 150:2451-2463. [PMID: 15256587 DOI: 10.1099/mic.0.27159-0] [Citation(s) in RCA: 100] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Thermoanaerobacter tengcongensis is a thermophilic Gram-positive bacterium able to dispose of the reducing equivalents generated during the fermentation of glucose to acetate and CO(2) by reducing H(+) to H(2). A unique combination of hydrogenases, a ferredoxin-dependent [NiFe] hydrogenase and an NADH-dependent Fe-only hydrogenase, were found to be responsible for H(2) formation in this organism. Both enzymes were purified and characterized. The tightly membrane-bound [NiFe] hydrogenase belongs to a small group of complex-I-related [NiFe] hydrogenases and has highest sequence similarity to energy-converting [NiFe] hydrogenase (Ech) from Methanosarcina barkeri. A ferredoxin isolated from Ta. tengcongensis was identified as the physiological substrate of this enzyme. The heterotetrameric Fe-only hydrogenase was isolated from the soluble fraction. It contained FMN and multiple iron-sulfur clusters, and exhibited a typical H-cluster EPR signal after autooxidation. Sequence analysis predicted and kinetic studies confirmed that the enzyme is an NAD(H)-dependent Fe-only hydrogenase. When H(2) was allowed to accumulate in the culture, the fermentation was partially shifted to ethanol production. In cells grown at high hydrogen partial pressure [p(H(2))] the NADH-dependent hydrogenase activity was fourfold lower than in cells grown at low p(H(2)), whereas aldehyde dehydrogenase and alcohol dehydrogenase activities were higher in cells grown at elevated p(H(2)). These results indicate a regulation in response to the p(H(2)).
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Affiliation(s)
- Basem Soboh
- Max-Planck-Institut für terrestrische Mikrobiologie, Karl-von-Frisch-Straße, D-35043 Marburg, Germany
| | - Dietmar Linder
- Biochemisches Institut, Fachbereich Humanmedizin, Justus-Liebig-Universität Giessen, Germany
| | - Reiner Hedderich
- Max-Planck-Institut für terrestrische Mikrobiologie, Karl-von-Frisch-Straße, D-35043 Marburg, Germany
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Posewitz MC, King PW, Smolinski SL, Zhang L, Seibert M, Ghirardi ML. Discovery of two novel radical S-adenosylmethionine proteins required for the assembly of an active [Fe] hydrogenase. J Biol Chem 2004; 279:25711-20. [PMID: 15082711 DOI: 10.1074/jbc.m403206200] [Citation(s) in RCA: 265] [Impact Index Per Article: 13.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
To identify genes necessary for the photoproduction of H(2) in Chlamydomonas reinhardtii, random insertional mutants were screened for clones unable to produce H(2). One of the identified mutants, denoted hydEF-1, is incapable of assembling an active [Fe] hydrogenase. Although the hydEF-1 mutant transcribes both hydrogenase genes and accumulates full-length hydrogenase protein, H(2) production activity is not observed. The HydEF protein contains two unique domains that are homologous to two distinct prokaryotic proteins, HydE and HydF, which are found exclusively in organisms containing [Fe] hydrogenase. In the C. reinhardtii genome, the HydEF gene is adjacent to another hydrogenase-related gene, HydG. All organisms with [Fe] hydrogenase and sequenced genomes contain homologues of HydE, HydF, and HydG, which, prior to this study, were of unknown function. Within several prokaryotic genomes HydE, HydF, and HydG are found in putative operons with [Fe] hydrogenase structural genes. Both HydE and HydG belong to the emerging radical S-adenosylmethionine (commonly designated "Radical SAM") superfamily of proteins. We demonstrate here that HydEF and HydG function in the assembly of [Fe] hydrogenase. Northern blot analysis indicates that mRNA transcripts for both the HydEF gene and the HydG gene are anaerobically induced concomitantly with the two C. reinhardtii [Fe] hydrogenase genes, HydA1 and HydA2. Complementation of the bx;1C. reinhardtii hydEF-1 mutant with genomic DNA corresponding to a functional copy of the HydEF gene restores hydrogenase activity. Moreover, co-expression of the C. reinhardtii HydEF, HydG, and HydA1 genes in Escherichia coli results in the formation of an active HydA1 enzyme. This represents the first report on the nature of the accessory genes required for the maturation of an active [Fe] hydrogenase.
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Affiliation(s)
- Matthew C Posewitz
- National Renewable Energy Laboratory, Colorado School of Mines, Golden, CO 80401, USA
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