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Weidenbach K, Gutt M, Cassidy L, Chibani C, Schmitz RA. Small Proteins in Archaea, a Mainly Unexplored World. J Bacteriol 2022; 204:e0031321. [PMID: 34543104 PMCID: PMC8765429 DOI: 10.1128/jb.00313-21] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023] Open
Abstract
In recent years, increasing numbers of small proteins have moved into the focus of science. Small proteins have been identified and characterized in all three domains of life, but the majority remains functionally uncharacterized, lack secondary structure, and exhibit limited evolutionary conservation. While quite a few have already been described for bacteria and eukaryotic organisms, the amount of known and functionally analyzed archaeal small proteins is still very limited. In this review, we compile the current state of research, show strategies for systematic approaches for global identification of small archaeal proteins, and address selected functionally characterized examples. Besides, we document exemplarily for one archaeon the tool development and optimization to identify small proteins using genome-wide approaches.
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Affiliation(s)
- Katrin Weidenbach
- Institute for General Microbiology, Christian Albrechts University, Kiel, Germany
| | - Miriam Gutt
- Institute for General Microbiology, Christian Albrechts University, Kiel, Germany
| | - Liam Cassidy
- AG Proteomics & Bioanalytics, Institute for Experimental Medicine, Christian Albrechts University, Kiel, Germany
| | - Cynthia Chibani
- Institute for General Microbiology, Christian Albrechts University, Kiel, Germany
| | - Ruth A. Schmitz
- Institute for General Microbiology, Christian Albrechts University, Kiel, Germany
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VhuD facilitates electron flow from H2 or formate to heterodisulfide reductase in Methanococcus maripaludis. J Bacteriol 2013; 195:5160-5. [PMID: 24039260 DOI: 10.1128/jb.00895-13] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Flavin-based electron bifurcation has recently been characterized as an essential energy conservation mechanism that is utilized by hydrogenotrophic methanogenic Archaea to generate low-potential electrons in an ATP-independent manner. Electron bifurcation likely takes place at the flavin associated with the α subunit of heterodisulfide reductase (HdrA). In Methanococcus maripaludis the electrons for this reaction come from either formate or H2 via formate dehydrogenase (Fdh) or Hdr-associated hydrogenase (Vhu). However, how these enzymes bind to HdrA to deliver electrons is unknown. Here, we present evidence that the δ subunit of hydrogenase (VhuD) is central to the interaction of both enzymes with HdrA. When M. maripaludis is grown under conditions where both Fdh and Vhu are expressed, these enzymes compete for binding to VhuD, which in turn binds to HdrA. Under these conditions, both enzymes are fully functional and are bound to VhuD in substoichiometric quantities. We also show that Fdh copurifies specifically with VhuD in the absence of other hydrogenase subunits. Surprisingly, in the absence of Vhu, growth on hydrogen still occurs; we show that this involves F420-reducing hydrogenase. The data presented here represent an initial characterization of specific protein interactions centered on Hdr in a hydrogenotrophic methanogen that utilizes multiple electron donors for growth.
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Atomi H, Imanaka T, Fukui T. Overview of the genetic tools in the Archaea. Front Microbiol 2012; 3:337. [PMID: 23060865 PMCID: PMC3462420 DOI: 10.3389/fmicb.2012.00337] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2012] [Accepted: 09/01/2012] [Indexed: 01/17/2023] Open
Abstract
This section provides an overview of the genetic systems developed in the Archaea. Genetic manipulation is possible in many members of the halophiles, methanogens, Sulfolobus, and Thermococcales. We describe the selection/counterselection principles utilized in each of these groups, which consist of antibiotics and their resistance markers, and auxotrophic host strains and complementary markers. The latter strategy utilizes techniques similar to those developed in yeast. However, Archaea are resistant to many of the antibiotics routinely used for selection in the Bacteria, and a number of strategies specific to the Archaea have been developed. In addition, examples utilizing the genetic systems developed for each group will be briefly described.
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Affiliation(s)
- Haruyuki Atomi
- Department of Synthetic Chemistry and Biological Chemistry, Graduate School of Engineering, Kyoto University, Katsura, Nishikyo-ku Kyoto, Japan ; JST, CREST, Sanbancho, Chiyoda-ku Tokyo, Japan
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Protein complexing in a methanogen suggests electron bifurcation and electron delivery from formate to heterodisulfide reductase. Proc Natl Acad Sci U S A 2010; 107:11050-5. [PMID: 20534465 DOI: 10.1073/pnas.1003653107] [Citation(s) in RCA: 134] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
Abstract
In methanogenic Archaea, the final step of methanogenesis generates methane and a heterodisulfide of coenzyme M and coenzyme B (CoM-S-S-CoB). Reduction of this heterodisulfide by heterodisulfide reductase to regenerate HS-CoM and HS-CoB is an exergonic process. Thauer et al. [Thauer, et al. 2008 Nat Rev Microbiol 6:579-591] recently suggested that in hydrogenotrophic methanogens the energy of heterodisulfide reduction powers the most endergonic reaction in the pathway, catalyzed by the formylmethanofuran dehydrogenase, via flavin-based electron bifurcation. Here we present evidence that these two steps in methanogenesis are physically linked. We identify a protein complex from the hydrogenotrophic methanogen, Methanococcus maripaludis, that contains heterodisulfide reductase, formylmethanofuran dehydrogenase, F(420)-nonreducing hydrogenase, and formate dehydrogenase. In addition to establishing a physical basis for the electron-bifurcation model of energy conservation, the composition of the complex also suggests that either H(2) or formate (two alternative electron donors for methanogenesis) can donate electrons to the heterodisulfide-H(2) via F(420)-nonreducing hydrogenase or formate via formate dehydrogenase. Electron flow from formate to the heterodisulfide rather than the use of H(2) as an intermediate represents a previously unknown path of electron flow in methanogenesis. We further tested whether this path occurs by constructing a mutant lacking F(420)-nonreducing hydrogenase. The mutant displayed growth equal to wild-type with formate but markedly slower growth with hydrogen. The results support the model of electron bifurcation and suggest that formate, like H(2), is closely integrated into the methanogenic pathway.
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Stock T, Selzer M, Rother M. In vivo requirement of selenophosphate for selenoprotein synthesis in archaea. Mol Microbiol 2009; 75:149-60. [PMID: 19919669 DOI: 10.1111/j.1365-2958.2009.06970.x] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
Abstract
Biosynthesis of selenocysteine, the 21st proteinogenic amino acid, occurs bound to a dedicated tRNA in all three domains of life, Bacteria, Eukarya and Archaea, but differences exist between the mechanism employed by bacteria and eukaryotes/archaea. The role of selenophosphate and the enzyme providing it, selenophosphate synthetase, in archaeal selenoprotein synthesis was addressed by mutational analysis. Surprisingly, MMP0904, encoding a homologue of eukaryal selenophosphate synthetase in Methanococcus maripaludis S2, could not be deleted unless selD, encoding selenophosphate synthetase of Escherichia coli, was present in trans, demonstrating that the factor is essential for the organism. In contrast, the homologous gene of M. maripaludis JJ could be readily deleted, obviating the strain's ability to synthesize selenoproteins. Complementing with selD restored selenoprotein synthesis, demonstrating that the deleted gene encodes selenophosphate synthetase and that selenophosphate is the in vivo selenium donor for selenoprotein synthesis of this organism. We also showed that this enzyme is a selenoprotein itself and that M. maripaludis contains another, HesB-like selenoprotein previously only predicted from genome analyses. The data highlight the use of genetic methods in archaea for a causal analysis of their physiology and, by comparing two closely related strains of the same species, illustrate the evolution of the selenium-utilizing trait.
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Affiliation(s)
- Tilmann Stock
- Molekulare Mikrobiologie und Bioenergetik, Institut für Molekulare Biowissenschaften, Johann Wolfgang Goethe-Universität, Frankfurt am Main, Germany
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Strittmatter AW, Liesegang H, Rabus R, Decker I, Amann J, Andres S, Henne A, Fricke WF, Martinez-Arias R, Bartels D, Goesmann A, Krause L, Pühler A, Klenk HP, Richter M, Schüler M, Glöckner FO, Meyerdierks A, Gottschalk G, Amann R. Genome sequence of Desulfobacterium autotrophicum HRM2, a marine sulfate reducer oxidizing organic carbon completely to carbon dioxide. Environ Microbiol 2009; 11:1038-55. [PMID: 19187283 PMCID: PMC2702500 DOI: 10.1111/j.1462-2920.2008.01825.x] [Citation(s) in RCA: 91] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2008] [Accepted: 10/25/2008] [Indexed: 01/23/2023]
Abstract
Sulfate-reducing bacteria (SRB) belonging to the metabolically versatile Desulfobacteriaceae are abundant in marine sediments and contribute to the global carbon cycle by complete oxidation of organic compounds. Desulfobacterium autotrophicum HRM2 is the first member of this ecophysiologically important group with a now available genome sequence. With 5.6 megabasepairs (Mbp) the genome of Db. autotrophicum HRM2 is about 2 Mbp larger than the sequenced genomes of other sulfate reducers (SRB). A high number of genome plasticity elements (> 100 transposon-related genes), several regions of GC discontinuity and a high number of repetitive elements (132 paralogous genes Mbp(-1)) point to a different genome evolution when comparing with Desulfovibrio spp. The metabolic versatility of Db. autotrophicum HRM2 is reflected in the presence of genes for the degradation of a variety of organic compounds including long-chain fatty acids and for the Wood-Ljungdahl pathway, which enables the organism to completely oxidize acetyl-CoA to CO(2) but also to grow chemolithoautotrophically. The presence of more than 250 proteins of the sensory/regulatory protein families should enable Db. autotrophicum HRM2 to efficiently adapt to changing environmental conditions. Genes encoding periplasmic or cytoplasmic hydrogenases and formate dehydrogenases have been detected as well as genes for the transmembrane TpII-c(3), Hme and Rnf complexes. Genes for subunits A, B, C and D as well as for the proposed novel subunits L and F of the heterodisulfide reductases are present. This enzyme is involved in energy conservation in methanoarchaea and it is speculated that it exhibits a similar function in the process of dissimilatory sulfate reduction in Db. autotrophicum HRM2.
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Affiliation(s)
- Axel W Strittmatter
- Göttingen Genomics Laboratory, Georg-August-UniversityGrisebachstr. 8, D-37077 Göttingen, Germany
| | - Heiko Liesegang
- Göttingen Genomics Laboratory, Georg-August-UniversityGrisebachstr. 8, D-37077 Göttingen, Germany
| | - Ralf Rabus
- Max Planck Institute for Marine MicrobiologyCelsiusstr. 1, D-28359 Bremen, Germany
- Institute for Chemistry and Biology of the Marine Environment (ICBM), Carl von Ossietzky University OldenburgCarl-von-Ossietzky Str. 9-11, D-26111 Oldenburg, Germany
| | - Iwona Decker
- Göttingen Genomics Laboratory, Georg-August-UniversityGrisebachstr. 8, D-37077 Göttingen, Germany
| | - Judith Amann
- Max Planck Institute for Marine MicrobiologyCelsiusstr. 1, D-28359 Bremen, Germany
| | - Sönke Andres
- Göttingen Genomics Laboratory, Georg-August-UniversityGrisebachstr. 8, D-37077 Göttingen, Germany
| | - Anke Henne
- Göttingen Genomics Laboratory, Georg-August-UniversityGrisebachstr. 8, D-37077 Göttingen, Germany
| | - Wolfgang Florian Fricke
- Göttingen Genomics Laboratory, Georg-August-UniversityGrisebachstr. 8, D-37077 Göttingen, Germany
| | - Rosa Martinez-Arias
- Göttingen Genomics Laboratory, Georg-August-UniversityGrisebachstr. 8, D-37077 Göttingen, Germany
| | - Daniela Bartels
- Center for Biotechnology (CeBiTec), Bielefeld UniversityUniversitätsstr. 37, D-33615 Bielefeld, Germany
| | - Alexander Goesmann
- Center for Biotechnology (CeBiTec), Bielefeld UniversityUniversitätsstr. 37, D-33615 Bielefeld, Germany
| | - Lutz Krause
- Center for Biotechnology (CeBiTec), Bielefeld UniversityUniversitätsstr. 37, D-33615 Bielefeld, Germany
| | - Alfred Pühler
- Lehrstuhl für Genetik, Fakultät für Biologie, Universität BielefeldD-33594 Bielefeld, Germany
| | - Hans-Peter Klenk
- DSMZ – Deutsche Sammlung von Mikroorganismen und Zellkulturen GmbHInhoffenstraße 7 B, D-38124 Braunschweig, Germany
| | - Michael Richter
- Max Planck Institute for Marine MicrobiologyCelsiusstr. 1, D-28359 Bremen, Germany
| | - Margarete Schüler
- Max Planck Institute for Marine MicrobiologyCelsiusstr. 1, D-28359 Bremen, Germany
| | | | - Anke Meyerdierks
- Max Planck Institute for Marine MicrobiologyCelsiusstr. 1, D-28359 Bremen, Germany
| | - Gerhard Gottschalk
- Göttingen Genomics Laboratory, Georg-August-UniversityGrisebachstr. 8, D-37077 Göttingen, Germany
| | - Rudolf Amann
- Max Planck Institute for Marine MicrobiologyCelsiusstr. 1, D-28359 Bremen, Germany
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Guss AM, Mukhopadhyay B, Zhang JK, Metcalf WW. Genetic analysis of mch mutants in two Methanosarcina species demonstrates multiple roles for the methanopterin-dependent C-1 oxidation/reduction pathway and differences in H(2) metabolism between closely related species. Mol Microbiol 2005; 55:1671-80. [PMID: 15752192 DOI: 10.1111/j.1365-2958.2005.04514.x] [Citation(s) in RCA: 54] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
A mutation in the mch gene, encoding the enzyme 5,10-methenyl tetrahydromethanopterin (H(4)MPT) cyclohydrolase, was constructed in vitro and recombined onto the chromosome of the methanogenic archaeon Methanosarcina barkeri. The resulting mutant does not grow in media using H(2)/CO(2), methanol, or acetate as carbon and energy sources, but does grow in media with methanol/H(2)/CO(2), demonstrating its ability to utilize H(2) as a source of electrons for reduction of methyl groups. Cell suspension experiments showed that methanogenesis from methanol or from H(2)/CO(2) is blocked in the mutant, explaining the lack of growth on these substrates. The corresponding mutation in Methanosarcina acetivorans C2A, which cannot grow on H(2)/CO(2), could not be made in wild-type strains, but could be made in strains carrying a second copy of mch, suggesting that M. acetivorans is incapable of methyl group reduction using H(2). M. acetivorans mch mutants could also be constructed in strains carrying the M. barkeri ech hydrogenase operon, suggesting that the block in the methyl reduction pathway is at the level of H(2) oxidation. Interestingly, the ech-dependent methyl reduction pathway of M. acetivorans involves an electron transport chain distinct from that used by M. barkeri, because M. barkeri ech mutants remain capable of H(2)-dependent methyl reduction.
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Affiliation(s)
- Adam M Guss
- Department of Microbiology, University of Illinois at Urbana-Champaign, B103 Chemical and Life Sciences Laboratory, 601 South Goodwin Avenue, Urbana, IL 61801, USA
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9
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Abstract
For decades, archaea were misclassified as bacteria because of their prokaryotic morphology. Molecular phylogeny eventually revealed that archaea, like bacteria and eukaryotes, are a fundamentally distinct domain of life. Genome analyses have confirmed that archaea share many features with eukaryotes, particularly in information processing, and therefore can serve as streamlined models for understanding eukaryotic biology. Biochemists and structural biologists have embraced the study of archaea but geneticists have been more wary, despite the fact that genetic techniques for archaea are quite sophisticated. It is time for geneticists to start asking fundamental questions about our distant relatives.
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Affiliation(s)
- Thorsten Allers
- Institute of Genetics, University of Nottingham, Queen's Medical Centre, Nottingham NG7 2UH, UK.
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Heinicke I, Müller J, Pittelkow M, Klein A. Mutational analysis of genes encoding chromatin proteins in the archaeon Methanococcus voltae indicates their involvement in the regulation of gene expression. Mol Genet Genomics 2004; 272:76-87. [PMID: 15241681 DOI: 10.1007/s00438-004-1033-5] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2004] [Accepted: 06/07/2004] [Indexed: 10/26/2022]
Abstract
Several genes for chromatin proteins are known in Archaea. These include histones and histone-like proteins in Euryarchaeota, and a DNA binding protein, Alba, which was first detected in the crenarchaeote Sulfolobus solfataricus and is thought to be involved in transcriptional regulation. The methanogenic archaeon Methanococcus voltae harbors four genes coding for all these three types of chromatin proteins. Deletion mutants for the two histone genes ( hstAand hstB), the gene encoding the histone-like protein ( hmvA) and the gene for the Alba homologue ( albA) have now been constructed in this organism. Although all single mutants were viable, deletion of hstA resulted in slow growth. Two transcripts were detected for each of the two histone genes. These were expressed in different relative amounts, which were correlated with different growth phases. Cell extracts obtained from the different mutants exhibited altered protein patterns, as revealed by 2D gel electrophoresis, indicating that the chromatin proteins are involved in gene regulation in M. voltae.
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Affiliation(s)
- I Heinicke
- Fachbereich Biologie-Genetik, Philipps-Universität Marburg, Karl-v.-Frisch-Str 8, 35043 Marburg, Germany.
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11
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Niess UM, Klein A. Dimethylselenide demethylation is an adaptive response to selenium deprivation in the archaeon Methanococcus voltae. J Bacteriol 2004; 186:3640-8. [PMID: 15150252 PMCID: PMC415765 DOI: 10.1128/jb.186.11.3640-3648.2004] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The archaeon Methanococcus voltae needs selenium for optimal growth. A gene group most likely involved in the demethylation of dimethylselenide was discovered, the expression of which is induced upon selenium deprivation. The operon comprises open reading frames for a corrinoid protein and two putative methyltransferases. It is shown that the addition of dimethylselenide to selenium-depleted growth medium relieves the lack of selenium, as indicated by the repression of a promoter of a transcription unit encoding selenium-free hydrogenases which is normally active only upon selenium deprivation. Knockout mutants of the corrinoid protein or one of the two methyltransferase genes did not show repression of the hydrogenase promoter in the presence of dimethylselenide. The mutation of the other methyltransferase gene had no effect. Growth rates of the two effective mutants were reduced compared to wild-type cells in selenium-limited medium in the presence of dimethylselenide.
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Affiliation(s)
- Ulf M Niess
- Genetics, Department of Biology, Philipps University of Marburg, D-35032 Marburg, Germany.
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Meuer J, Kuettner HC, Zhang JK, Hedderich R, Metcalf WW. Genetic analysis of the archaeon Methanosarcina barkeri Fusaro reveals a central role for Ech hydrogenase and ferredoxin in methanogenesis and carbon fixation. Proc Natl Acad Sci U S A 2002; 99:5632-7. [PMID: 11929975 PMCID: PMC122822 DOI: 10.1073/pnas.072615499] [Citation(s) in RCA: 147] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Ech hydrogenase (Ech) from the methanogenic archaeon Methanosarcina barkeri catalyzes the reversible reduction of ferredoxin by H(2) and is a member of a distinct group of membrane-bound [NiFe] hydrogenases with sequence similarity to energy-conserving NADH:quinone oxidoreductase (complex I). To elucidate the physiological role(s) of Ech a mutant lacking this enzyme was constructed. The mutant was unable to grow on methanol/H(2)/CO(2), H(2)/CO(2), or acetate as carbon and energy sources but showed wild-type growth rates with methanol as sole substrate. Addition of pyruvate to the growth medium restored growth on methanol/H(2)/CO(2) but not on H(2)/CO(2) or acetate. Results obtained from growth experiments, cell suspension experiments, and enzyme activity measurements in cell extracts provide compelling evidence for essential functions of Ech and a 2[4Fe-4S] ferredoxin in the metabolism of M. barkeri. The following conclusions were made. (i) In acetoclastic methanogenesis, Ech catalyzes H(2) formation from reduced ferredoxin, generated by the oxidation of the carbonyl group of acetate to CO(2). (ii) Under autotrophic growth conditions, the enzyme catalyzes the energetically unfavorable reduction of ferredoxin by H(2), most probably driven by reversed electron transport, and the reduced ferredoxin thus generated functions as low potential electron donor for the synthesis of pyruvate in an anabolic pathway. (iii) Reduced ferredoxin in addition provides the reducing equivalents for the first step of methanogenesis from H(2)/CO(2), the reduction of CO(2) to formylmethanofuran. Thus, in vivo genetic analysis has led to the identification of the electron donor of this key initial step of methanogenesis.
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Affiliation(s)
- Jörn Meuer
- Max-Planck-Institut für Terrestrische Mikrobiologie, 35043 Marburg, Germany
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13
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Bingemann R, Klein A. Conversion of the central [4Fe-4S] cluster into a [3Fe-4S] cluster leads to reduced hydrogen-uptake activity of the F420-reducing hydrogenase of Methanococcus voltae. EUROPEAN JOURNAL OF BIOCHEMISTRY 2000; 267:6612-8. [PMID: 11054113 DOI: 10.1046/j.1432-1327.2000.01755.x] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
As in many other hydrogenases, the small subunit of the F420-reducing hydrogenase of Methanococcus voltae contains three iron-sulfur clusters. The arrangement of the three [4Fe-4S] clusters corresponds to the arrangement of [Fe-S] clusters in the [NiFeSe] hydrogenase of Desulfomicrobium baculatum. Many other hydrogenases contain two [4Fe-4S] clusters and one [3Fe-4S] cluster with a relatively high redox potential, which is located in the central position between a proximal and a distal [4Fe-4S] cluster. We have investigated the role of the central [4Fe-4S] cluster in M. voltae with regard to its effect on the enzyme activity and its spectroscopic properties. Using site-directed mutagenesis, we constructed a strain in which one cysteine ligand of the central [4Fe-4S] cluster was replaced by proline. The mutant protein was purified, and the [4Fe-4S] to [3Fe-4S] cluster conversion was confirmed by EPR spectroscopy. The conversion resulted in an increase in the redox potential of the [3Fe-4S] cluster by about 400 mV. The [NiFe] active site was not affected significantly by the mutation as assessed by the unchanged Ni EPR spectrum. The specific activity of the mutated enzyme did not show any significant differences with the artificial electron acceptor benzyl viologen, but its specific activity with the natural electron acceptor F420 decreased tenfold.
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Affiliation(s)
- R Bingemann
- Genetics, Department of Biology, Philipps-University, Marburg, Germany
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14
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Zhang JK, Pritchett MA, Lampe DJ, Robertson HM, Metcalf WW. In vivo transposon mutagenesis of the methanogenic archaeon Methanosarcina acetivorans C2A using a modified version of the insect mariner-family transposable element Himar1. Proc Natl Acad Sci U S A 2000; 97:9665-70. [PMID: 10920201 PMCID: PMC16922 DOI: 10.1073/pnas.160272597] [Citation(s) in RCA: 78] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
We present here a method for in vivo transposon mutagenesis of a methanogenic archaeon, Methanosarcina acetivorans C2A, which because of its independence from host-specific factors may have broad application among many microorganisms. Because there are no known Methanosarcina transposons we modified the mariner transposable element Himar1, originally found in the insect Hematobia irritans, to allow its use in this organism. This element was chosen because, like other mariner elements, its transposition is independent of host factors, requiring only its cognate transposase. Modified mini-Himar1 elements were constructed that carry selectable markers that are functional in Methanosarcina species and that express the Himar1 transposase from known Methanosarcina promoters. These mini-mariner elements transpose at high frequency in M. acetivorans to random sites in the genome. The presence of an Escherichia coli selectable marker and plasmid origin of replication within the mini-mariner elements allows facile cloning of these transposon insertions to identify the mutated gene. In preliminary experiments, we have isolated numerous mini-mariner-induced M. acetivorans mutants, including ones with insertions that confer resistance to toxic analogs and in genes that encode proteins involved in heat shock, nitrogen fixation, and cell-wall structures.
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Affiliation(s)
- J K Zhang
- Department of Microbiology, University of Illinois, Life Sciences Laboratory, Urbana 61801, USA
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15
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Boccazzi P, Zhang JK, Metcalf WW. Generation of dominant selectable markers for resistance to pseudomonic acid by cloning and mutagenesis of the ileS gene from the archaeon Methanosarcina barkeri fusaro. J Bacteriol 2000; 182:2611-8. [PMID: 10762266 PMCID: PMC111328 DOI: 10.1128/jb.182.9.2611-2618.2000] [Citation(s) in RCA: 66] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Currently, only one selectable marker is available for genetic studies in the archaeal genus Methanosarcina. Here we report the generation of selectable markers that encode resistance to pseudomonic acid (PA(r)) in Methanosarcina species by mutagenesis of the isoleucyl-tRNA synthetase gene (ileS) from Methanosarcina barkeri Fusaro. The M. barkeri ileS gene was obtained by screening of a genomic library for hybridization to a PCR fragment. The complete 3,787-bp DNA sequence surrounding and including the ileS gene was determined. As expected, M. barkeri IleS is phylogenetically related to other archaeal IleS proteins. The ileS gene was cloned into a Methanosarcina-Escherichia coli shuttle vector and mutagenized with hydroxylamine. Nine independent PA(r) clones were isolated after transformation of Methanosarcina acetivorans C2A with the mutagenized plasmids. Seven of these clones carry multiple changes from the wild-type sequence. Most mutations that confer PA(r) were shown to alter amino acid residues near the KMSKS consensus sequence of class I aminoacyl-tRNA synthetases. One particular mutation (G594E) was present in all but one of the PA(r) clones. The MIC of pseudomonic acid for M. acetivorans transformed with a plasmid carrying this single mutation is 70 microgram/ml of medium (for the wild type, the MIC is 12 microgram/ml). The highest MICs (560 microgram/ml) were observed with two triple mutants, A440V/A482T/G594E and A440V/G593D/G594E. Plasmid shuttle vectors and insertion cassettes that encode PA(r) based on the mutant ileS alleles are described. Finally, the implications of the specific mutations we isolated with respect to binding of pseudomonic acid by IleS are discussed.
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Affiliation(s)
- P Boccazzi
- Department of Microbiology, University of Illinois, Urbana, Illinois 61801, USA
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16
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Abstract
Although the genomic sequences of a number of Archaea have been completed in the last three years, genetic systems in the sequenced organisms are absent. In contrast, genetic studies of the mesophiles in the archaeal genus Methanococcus have become commonplace following the recent developments of antibiotic resistance markers, DNA transformation methods, reporter genes, shuttle vectors and expression vectors. These developments have led to investigations of the transcription of the genes for hydrogen metabolism, nitrogen fixation and flagellin assembly. These genetic systems can potentially be used to analyse the genomic sequence of the hyperthermophile Methanococcus jannaschii, addressing questions of its physiology and the function of its many uncharacterized open reading frames. Thus, the sequence of M. jannaschii can serve as a starting point for gene isolation, while in vivo genetics in the mesophilic methanococci can provide the experimental systems to test the predictions from genomics.
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Affiliation(s)
- D L Tumbula
- Department of Molecular Biophysics and Biochemistry, Yale University, New Haven CT 06520-8114, USA
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