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Nasreen M, Ellis D, Hosmer J, Essilfie AT, Fantino E, Sly P, McEwan AG, Kappler U. The DmsABC S-oxide reductase is an essential component of a novel, hypochlorite-inducible system of extracellular stress defense in Haemophilus influenzae. Front Microbiol 2024; 15:1359513. [PMID: 38638903 PMCID: PMC11024254 DOI: 10.3389/fmicb.2024.1359513] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2023] [Accepted: 03/11/2024] [Indexed: 04/20/2024] Open
Abstract
Defenses against oxidative damage to cell components are essential for survival of bacterial pathogens during infection, and here we have uncovered that the DmsABC S-/N-oxide reductase is essential for virulence and in-host survival of the human-adapted pathogen, Haemophilus influenzae. In several different infection models, H. influenzae ΔdmsA strains showed reduced immunogenicity as well as lower levels of survival in contact with host cells. Expression of DmsABC was induced in the presence of hypochlorite and paraquat, closely linking this enzyme to defense against host-produced antimicrobials. In addition to methionine sulfoxide, DmsABC converted nicotinamide- and pyrimidine-N-oxide, precursors of NAD and pyrimidine for which H. influenzae is an auxotroph, at physiologically relevant concentrations, suggesting that these compounds could be natural substrates for DmsABC. Our data show that DmsABC forms part of a novel, periplasmic system for defense against host-induced S- and N-oxide stress that also comprises the functionally related MtsZ S-oxide reductase and the MsrAB peptide methionine sulfoxide reductase. All three enzymes are induced following exposure of the bacteria to hypochlorite. MsrAB is required for physical resistance to HOCl and protein repair. In contrast, DmsABC was required for intracellular colonization of host cells and, together with MtsZ, contributed to resistance to N-Chlorotaurine. Our work expands and redefines the physiological role of DmsABC and highlights the importance of different types of S-oxide reductases for bacterial virulence.
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Affiliation(s)
- Marufa Nasreen
- School of Chemistry and Molecular Biosciences, Australian Infectious Diseases Research Centre, The University of Queensland, St. Lucia, QLD, Australia
| | - Daniel Ellis
- School of Chemistry and Molecular Biosciences, Australian Infectious Diseases Research Centre, The University of Queensland, St. Lucia, QLD, Australia
| | - Jennifer Hosmer
- School of Chemistry and Molecular Biosciences, Australian Infectious Diseases Research Centre, The University of Queensland, St. Lucia, QLD, Australia
| | | | | | - Peter Sly
- Child Health Research Centre, South Brisbane, QLD, Australia
| | - Alastair G. McEwan
- School of Chemistry and Molecular Biosciences, Australian Infectious Diseases Research Centre, The University of Queensland, St. Lucia, QLD, Australia
| | - Ulrike Kappler
- School of Chemistry and Molecular Biosciences, Australian Infectious Diseases Research Centre, The University of Queensland, St. Lucia, QLD, Australia
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Hasnat MA, Zupok A, Gorka M, Iobbi-Nivol C, Skirycz A, Jourlin-Castelli C, Bier F, Agarwal S, Irefo E, Leimkühler S. Iron limitation indirectly reduces the Escherichia coli torCAD operon expression by a reduction of molybdenum cofactor availability. Microbiol Spectr 2024; 12:e0348023. [PMID: 38193660 PMCID: PMC10845959 DOI: 10.1128/spectrum.03480-23] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2023] [Accepted: 11/29/2023] [Indexed: 01/10/2024] Open
Abstract
The expression of most molybdoenzymes in Escherichia coli has so far been revealed to be regulated by anaerobiosis and requires the presence of iron, based on the necessity of the transcription factor FNR to bind one [4Fe-4S] cluster. One exception is trimethylamine-N-oxide reductase encoded by the torCAD operon, which has been described to be expressed independently from FNR. In contrast to other alternative anaerobic respiratory systems, the expression of the torCAD operon was shown not to be completely repressed by the presence of dioxygen. To date, the basis for the O2-dependent expression of the torCAD operon has been related to the abundance of the transcriptional regulator IscR, which represses the transcription of torS and torT, and is more abundant under aerobic conditions than under anaerobic conditions. In this study, we reinvestigated the regulation of the torCAD operon and its dependence on the presence of iron and identified a novel regulation that depends on the presence of the bis-molybdopterin guanine dinucleotide (bis-MGD) molybdenum cofactor . We confirmed that the torCAD operon is directly regulated by the heme-containing protein TorC and is indirectly regulated by ArcA and by the availability of iron via active FNR and Fur, both regulatory proteins that influence the synthesis of the molybdenum cofactor. Furthermore, we identified a novel regulation mode of torCAD expression that is dependent on cellular levels of bis-MGD and is not used by other bis-MGD-containing enzymes like nitrate reductase.IMPORTANCEIn bacteria, molybdoenzymes are crucial for anaerobic respiration using alternative electron acceptors. FNR is a very important transcription factor that represents the master switch for the expression of target genes in response to anaerobiosis. Only Escherichia coli trimethylamine-N-oxide (TMAO) reductase escapes this regulation by FNR. We identified that the expression of TMAO reductase is regulated by the amount of bis-molybdopterin guanine dinucleotide (bis-MGD) cofactor synthesized by the cell itself, representing a novel regulation pathway for the expression of an operon coding for a molybdoenzyme. Furthermore, TMAO reductase gene expression is indirectly regulated by the presence of iron, which is required for the production of the bis-MGD cofactor in the cell.
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Affiliation(s)
- Muhammad Abrar Hasnat
- Department of Molecular Enzymology, Institute of Biochemistry and Biology, University of Potsdam, Potsdam, Germany
| | - Arkadiusz Zupok
- Department of Molecular Enzymology, Institute of Biochemistry and Biology, University of Potsdam, Potsdam, Germany
| | - Michal Gorka
- Max-Planck-Institute of Molecular Plant Physiology, Potsdam, Germany
| | - Chantal Iobbi-Nivol
- Laboratoire de Bioénergétique et Ingénierie des Protéines, Institut de Microbiologie de la Méditerranée, Centre National de la Recherche Scientifique, Aix-Marseille Université, Marseille, France
| | | | - Cécile Jourlin-Castelli
- Laboratoire de Bioénergétique et Ingénierie des Protéines, Institut de Microbiologie de la Méditerranée, Centre National de la Recherche Scientifique, Aix-Marseille Université, Marseille, France
| | - Frank Bier
- Department of Molecular Bioanalytics and Bioelectronics, Institute of Biochemistry and Biology, University of Potsdam, Potsdam, Germany
| | - Saloni Agarwal
- Department of Molecular Bioanalytics and Bioelectronics, Institute of Biochemistry and Biology, University of Potsdam, Potsdam, Germany
| | - Ehizode Irefo
- Department of Molecular Enzymology, Institute of Biochemistry and Biology, University of Potsdam, Potsdam, Germany
| | - Silke Leimkühler
- Department of Molecular Enzymology, Institute of Biochemistry and Biology, University of Potsdam, Potsdam, Germany
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3
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Nitrate-responsive suppression of DMSO respiration in a facultative anaerobic haloarchaeon Haloferax volcanii. J Bacteriol 2021; 203:e0065520. [PMID: 33820797 DOI: 10.1128/jb.00655-20] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
Haloferax volcanii is a facultative anaerobic haloarchaeon that can grow using nitrate or dimethyl sulfoxide (DMSO) as respiratory substrates in an anaerobic condition. Comparative transcriptome analysis of denitrifying and aerobic cells of H. volcanii indicated extensive changes in the gene expression involving activation of denitrification, suppression of DMSO respiration, and conversion of the heme biosynthetic pathway under denitrifying condition. Anaerobic growth of H. volcanii by DMSO respiration was inhibited at nitrate concentrations lower than 1 mM, whereas the nitrate-responsive growth inhibition was not observed in the ΔnarO mutant. A reporter assay experiment demonstrated that transcription of the dms operon was suppressed by nitrate. In contrast, anaerobic growth of the ΔdmsR mutant by denitrification was little affected by addition of DMSO. NarO has been identified as an activator of the denitrification-related genes in response to anaerobic conditions, and here we found that NarO is also involved in nitrate-responsive suppression of the dms operon. Nitrate-responsive suppression of DMSO respiration is known in several bacteria, such as Escherichia coli and photosynthetic Rhodobacter sp. This is the first report to show that a regulatory mechanism that suppresses DMSO respiration in response to nitrate exists not only in bacteria but also in the haloarchaea.IMPORTANCE Haloferax volcanii can grow anaerobically by denitrification (nitrate respiration) or DMSO respiration. In the facultative anaerobic bacteria that can grow by both nitrate respiration and DMSO respiration, nitrate respiration is preferentially induced when both nitrate and DMSO are available as respiratory substrates. The results of transcriptome analysis, growth phenotyping, and reporter assay indicated that DMSO respiration is suppressed in response to nitrate in H. volcanii The haloarchaea-specific regulator NarO, which activates denitrification under anaerobic conditions, is suggested to be involved in the nitrate-responsive suppression of DMSO respiration.
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Chen YW, Yeh WH, Tang HJ, Chen JW, Shu HY, Su YC, Wang ST, Kuo CJ, Chuang YC, Chen CC, Ko WC, Chen CS, Chen PL. UvrY is required for the full virulence of Aeromonas dhakensis. Virulence 2021; 11:502-520. [PMID: 32434424 PMCID: PMC7250320 DOI: 10.1080/21505594.2020.1768339] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
Aeromonas dhakensis is an emerging human pathogen which causes fast and severe infections worldwide. Under the gradual pressure of lacking useful antibiotics, finding a new strategy against A. dhakensis infection is urgent. To understand its pathogenesis, we created an A. dhakensis AAK1 mini-Tn10 transposon library to study the mechanism of A. dhakensis infection. By using a Caenorhabditis elegans model, we established a screening platform for the purpose of identifying attenuated mutants. The uvrY mutant, which conferred the most attenuated toxicity toward C. elegans, was identified. The uvrY mutant was also less virulent in C2C12 fibroblast and mice models, in line with in vitro results. To further elucidate the mechanism of UvrY in controlling the toxicity in A. dhakensis, we conducted a transcriptomic analysis. The RNAseq results showed that the expression of a unique hemolysin ahh1 and other virulence factors were regulated by UvrY. Complementation of Ahh1, one of the most important virulence factors, rescued the pore-formation phenotype of uvrY mutant in C. elegans; however, complementation of ahh1 endogenous promoter-driven ahh1 could not produce Ahh1 and rescue the virulence in the uvrY mutant. These findings suggest that UvrY is required for the expression of Ahh1 in A. dhakensis. Taken together, our results suggested that UvrY controls several different virulence factors and is required for the full virulence of A. dhakensis. The two-component regulator UvrY therefore a potential therapeutic target which is worthy of further study.
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Affiliation(s)
- Yi-Wei Chen
- Department of Biochemistry and Molecular Biology, College of Medicine, National Cheng Kung University, Tainan, Taiwan.,Institute of Basic Medical Sciences, College of Medicine, National Cheng Kung University, Tainan, Taiwan.,Division of Oral Biology and Medicine, School of Dentistry, University of California, Los Angeles, CA, USA
| | - Wen-Hsuan Yeh
- Department of Biochemistry and Molecular Biology, College of Medicine, National Cheng Kung University, Tainan, Taiwan
| | - Hung-Jen Tang
- Department of Medicine, Chi Mei Medical Center, Tainan, Taiwan
| | - Jenn-Wei Chen
- Department of Microbiology and Immunology, College of Medicine, National Cheng Kung University, Tainan, Taiwan
| | - Hung-Yu Shu
- Department of Bioscience Technology, Chang Jung Christian University, Tainan, Taiwan
| | - Yu-Chen Su
- Department of Microbiology and Immunology, College of Medicine, National Cheng Kung University, Tainan, Taiwan
| | - Sin-Tian Wang
- Department of Biochemistry and Molecular Biology, College of Medicine, National Cheng Kung University, Tainan, Taiwan.,Institute of Basic Medical Sciences, College of Medicine, National Cheng Kung University, Tainan, Taiwan
| | - Cheng-Ju Kuo
- Department of Biochemistry and Molecular Biology, College of Medicine, National Cheng Kung University, Tainan, Taiwan.,Institute of Basic Medical Sciences, College of Medicine, National Cheng Kung University, Tainan, Taiwan
| | - Yin-Ching Chuang
- Department of Medicine, Chi Mei Medical Center, Tainan, Taiwan.,Department of Medical Research, Chi Mei Medical Center, Tainan, Taiwan
| | - Chi-Chung Chen
- Department of Medical Research, Chi Mei Medical Center, Tainan, Taiwan.,Department of Food Science, National Chiayi University, Chiayi, Taiwan
| | - Wen-Chien Ko
- Department of Internal Medicine, National Cheng Kung University Hospital, College of Medicine, National Cheng Kung University, Tainan, Taiwan
| | - Chang-Shi Chen
- Department of Biochemistry and Molecular Biology, College of Medicine, National Cheng Kung University, Tainan, Taiwan.,Institute of Basic Medical Sciences, College of Medicine, National Cheng Kung University, Tainan, Taiwan
| | - Po-Lin Chen
- Department of Microbiology and Immunology, College of Medicine, National Cheng Kung University, Tainan, Taiwan.,Department of Internal Medicine, National Cheng Kung University Hospital, College of Medicine, National Cheng Kung University, Tainan, Taiwan
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5
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The coordinated action of RNase III and RNase G controls enolase expression in response to oxygen availability in Escherichia coli. Sci Rep 2019; 9:17257. [PMID: 31754158 PMCID: PMC6872547 DOI: 10.1038/s41598-019-53883-y] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2019] [Accepted: 10/09/2019] [Indexed: 01/25/2023] Open
Abstract
Rapid modulation of RNA function by endoribonucleases during physiological responses to environmental changes is known to be an effective bacterial biochemical adaptation. We report a molecular mechanism underlying the regulation of enolase (eno) expression by two endoribonucleases, RNase G and RNase III, the expression levels of which are modulated by oxygen availability in Escherichia coli. Analyses of transcriptional eno-cat fusion constructs strongly suggested the existence of cis-acting elements in the eno 5' untranslated region that respond to RNase III and RNase G cellular concentrations. Primer extension and S1 nuclease mapping analyses of eno mRNA in vivo identified three eno mRNA transcripts that are generated in a manner dependent on RNase III expression, one of which was found to accumulate in rng-deleted cells. Moreover, our data suggested that RNase III-mediated cleavage of primary eno mRNA transcripts enhanced Eno protein production, a process that involved putative cis-antisense RNA. We found that decreased RNase G protein abundance coincided with enhanced RNase III expression in E. coli grown anaerobically, leading to enhanced eno expression. Thereby, this posttranscriptional up-regulation of eno expression helps E. coli cells adjust their physiological reactions to oxygen-deficient metabolic modes. Our results revealed a molecular network of coordinated endoribonuclease activity that post-transcriptionally modulates the expression of Eno, a key enzyme in glycolysis.
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6
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Zhang Q, Huang Q, Fang Q, Li H, Tang H, Zou G, Wang D, Li S, Bei W, Chen H, Li L, Zhou R. Identification of genes regulated by the two-component system response regulator NarP of Actinobacillus pleuropneumoniae via DNA-affinity-purified sequencing. Microbiol Res 2019; 230:126343. [PMID: 31539852 DOI: 10.1016/j.micres.2019.126343] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2019] [Revised: 09/08/2019] [Accepted: 09/09/2019] [Indexed: 01/21/2023]
Abstract
Identifying the direct target genes of response regulators (RRs) of a bacterial two-component system (TCS) is critical to understand the roles of TCS in bacterial environmental adaption and pathogenesis. Actinobacillus pleuropneumoniae is an important respiratory bacterial pathogen that causes considerable economic losses to swine industry worldwide. The targets of A. pleuropneumoniae NarP (nitrate/nitrite RR), which is the cognate RR of the nitrate/nitrite sensor histidine kinase NarQ, are still unknown. In the present study, a DNA-affinity-purified sequencing (DAP-Seq) approach was established. The upstream regions of a total of 131 candidate genes from the genome of A. pleuropneumoniae were co-purified with the activated NarP protein. Electrophoretic mobility shift assay (EMSA) results confirmed the interactions of NarP with the promoter regions of five selected target genes, including dmsA, pgaA, ftpA, cstA and ushA. The EMSA-confirmed target genes were significantly up-regulated in the narP-deleted mutant in the presence of additional nitrate, whilst the transcriptional changes were restored in the complemented strain. The NarP binding motif in the upstream regions of the target genes dmsA and ftpA were further identified and confirmed by EMSA using the truncated binding motif. The NarP binding sites were present in a total of 25.2% of the DNA fragments captured by DAP-Seq. These results demonstrated that the established DAP-Seq method is effective for exploring the direct targets of RRs of bacterial TCSs and that the A. pleuropneumoniae NarP could be a repressor in response to nitrate.
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Affiliation(s)
- Qiuhong Zhang
- State Key Laboratory of Agricultural Microbiology, College of Veterinary Medicine, Huazhong Agricultural University, Wuhan, Hubei, 430070, China; Key Laboratory of Preventive Veterinary Medicine in Hubei Province, The Cooperative Innovation Center for Sustainable Pig Production, Wuhan, Hubei, 430070, China
| | - Qi Huang
- State Key Laboratory of Agricultural Microbiology, College of Veterinary Medicine, Huazhong Agricultural University, Wuhan, Hubei, 430070, China; Key Laboratory of Preventive Veterinary Medicine in Hubei Province, The Cooperative Innovation Center for Sustainable Pig Production, Wuhan, Hubei, 430070, China
| | - Qiong Fang
- State Key Laboratory of Agricultural Microbiology, College of Veterinary Medicine, Huazhong Agricultural University, Wuhan, Hubei, 430070, China; Key Laboratory of Preventive Veterinary Medicine in Hubei Province, The Cooperative Innovation Center for Sustainable Pig Production, Wuhan, Hubei, 430070, China
| | - Haotian Li
- State Key Laboratory of Agricultural Microbiology, College of Veterinary Medicine, Huazhong Agricultural University, Wuhan, Hubei, 430070, China; Key Laboratory of Preventive Veterinary Medicine in Hubei Province, The Cooperative Innovation Center for Sustainable Pig Production, Wuhan, Hubei, 430070, China
| | - Hao Tang
- State Key Laboratory of Agricultural Microbiology, College of Veterinary Medicine, Huazhong Agricultural University, Wuhan, Hubei, 430070, China; Key Laboratory of Preventive Veterinary Medicine in Hubei Province, The Cooperative Innovation Center for Sustainable Pig Production, Wuhan, Hubei, 430070, China
| | - Geng Zou
- State Key Laboratory of Agricultural Microbiology, College of Veterinary Medicine, Huazhong Agricultural University, Wuhan, Hubei, 430070, China; Key Laboratory of Preventive Veterinary Medicine in Hubei Province, The Cooperative Innovation Center for Sustainable Pig Production, Wuhan, Hubei, 430070, China
| | - Dong Wang
- State Key Laboratory of Agricultural Microbiology, College of Veterinary Medicine, Huazhong Agricultural University, Wuhan, Hubei, 430070, China; Key Laboratory of Preventive Veterinary Medicine in Hubei Province, The Cooperative Innovation Center for Sustainable Pig Production, Wuhan, Hubei, 430070, China
| | - Siqi Li
- State Key Laboratory of Agricultural Microbiology, College of Veterinary Medicine, Huazhong Agricultural University, Wuhan, Hubei, 430070, China; Key Laboratory of Preventive Veterinary Medicine in Hubei Province, The Cooperative Innovation Center for Sustainable Pig Production, Wuhan, Hubei, 430070, China
| | - Weicheng Bei
- State Key Laboratory of Agricultural Microbiology, College of Veterinary Medicine, Huazhong Agricultural University, Wuhan, Hubei, 430070, China; Key Laboratory of Preventive Veterinary Medicine in Hubei Province, The Cooperative Innovation Center for Sustainable Pig Production, Wuhan, Hubei, 430070, China; Key Laboratory of Development of Veterinary Diagnostic Products, Ministry of Agriculture and Rural Affairs of the People's Republic of China, Wuhan, Hubei, 430070, China; International Research Center for Animal Disease, Ministry of Science and Technology of the People's Republic of China, Wuhan, Hubei, 430070, China
| | - Huanchun Chen
- State Key Laboratory of Agricultural Microbiology, College of Veterinary Medicine, Huazhong Agricultural University, Wuhan, Hubei, 430070, China; Key Laboratory of Preventive Veterinary Medicine in Hubei Province, The Cooperative Innovation Center for Sustainable Pig Production, Wuhan, Hubei, 430070, China; Key Laboratory of Development of Veterinary Diagnostic Products, Ministry of Agriculture and Rural Affairs of the People's Republic of China, Wuhan, Hubei, 430070, China; International Research Center for Animal Disease, Ministry of Science and Technology of the People's Republic of China, Wuhan, Hubei, 430070, China
| | - Lu Li
- State Key Laboratory of Agricultural Microbiology, College of Veterinary Medicine, Huazhong Agricultural University, Wuhan, Hubei, 430070, China; Key Laboratory of Preventive Veterinary Medicine in Hubei Province, The Cooperative Innovation Center for Sustainable Pig Production, Wuhan, Hubei, 430070, China; Key Laboratory of Development of Veterinary Diagnostic Products, Ministry of Agriculture and Rural Affairs of the People's Republic of China, Wuhan, Hubei, 430070, China; International Research Center for Animal Disease, Ministry of Science and Technology of the People's Republic of China, Wuhan, Hubei, 430070, China.
| | - Rui Zhou
- State Key Laboratory of Agricultural Microbiology, College of Veterinary Medicine, Huazhong Agricultural University, Wuhan, Hubei, 430070, China; Key Laboratory of Preventive Veterinary Medicine in Hubei Province, The Cooperative Innovation Center for Sustainable Pig Production, Wuhan, Hubei, 430070, China; Key Laboratory of Development of Veterinary Diagnostic Products, Ministry of Agriculture and Rural Affairs of the People's Republic of China, Wuhan, Hubei, 430070, China; International Research Center for Animal Disease, Ministry of Science and Technology of the People's Republic of China, Wuhan, Hubei, 430070, China.
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Iron-Dependent Regulation of Molybdenum Cofactor Biosynthesis Genes in Escherichia coli. J Bacteriol 2019; 201:JB.00382-19. [PMID: 31235512 DOI: 10.1128/jb.00382-19] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2019] [Accepted: 06/15/2019] [Indexed: 01/15/2023] Open
Abstract
Molybdenum cofactor (Moco) biosynthesis is a complex process that involves the coordinated function of several proteins. In recent years it has become obvious that the availability of iron plays an important role in the biosynthesis of Moco. First, the MoaA protein binds two [4Fe-4S] clusters per monomer. Second, the expression of the moaABCDE and moeAB operons is regulated by FNR, which senses the availability of oxygen via a functional [4Fe-4S] cluster. Finally, the conversion of cyclic pyranopterin monophosphate to molybdopterin requires the availability of the l-cysteine desulfurase IscS, which is a shared protein with a main role in the assembly of Fe-S clusters. In this report, we investigated the transcriptional regulation of the moaABCDE operon by focusing on its dependence on cellular iron availability. While the abundance of selected molybdoenzymes is largely decreased under iron-limiting conditions, our data show that the regulation of the moaABCDE operon at the level of transcription is only marginally influenced by the availability of iron. Nevertheless, intracellular levels of Moco were decreased under iron-limiting conditions, likely based on an inactive MoaA protein in addition to lower levels of the l-cysteine desulfurase IscS, which simultaneously reduces the sulfur availability for Moco production.IMPORTANCE FNR is a very important transcriptional factor that represents the master switch for the expression of target genes in response to anaerobiosis. Among the FNR-regulated operons in Escherichia coli is the moaABCDE operon, involved in Moco biosynthesis. Molybdoenzymes have essential roles in eukaryotic and prokaryotic organisms. In bacteria, molybdoenzymes are crucial for anaerobic respiration using alternative electron acceptors. This work investigates the connection of iron availability to the biosynthesis of Moco and the production of active molybdoenzymes.
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8
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Wang Z, Sun J, Tian M, Xu Z, Liu Y, Fu J, Yan A, Liu X. Proteomic Analysis of FNR-Regulated Anaerobiosis in Salmonella Typhimurium. JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY 2019; 30:1001-1012. [PMID: 30903387 DOI: 10.1007/s13361-019-02145-2] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/02/2018] [Revised: 01/23/2019] [Accepted: 01/24/2019] [Indexed: 06/09/2023]
Abstract
Bacterial pathogens such as Salmonella enterica serovar Typhimurium (S. Typhimurium) have to cope with fluctuating oxygen levels during infection within host gastrointestinal tracts. The global transcription factor FNR (fumarate nitrate reduction) plays a vital role in the adaptation of enteric bacteria to the low oxygen environment. Nevertheless, a comprehensive profile of the FNR regulon on the proteome level is still lacking in S. Typhimurium. Herein, we quantitatively profiled S. Typhimurium proteome of an fnr-deletion mutant during anaerobiosis in comparison to its parental strain. Notably, we found that FNR represses the expression of virulence genes of Salmonella pathogenicity island 1 (SPI-1) and negatively regulates propanediol utilization by directly binding to the promoter region of the pdu operon. Importantly, we provided evidence that S. Typhimurium lacking fnr exhibited increased antibiotics susceptibility and membrane permeability as well. Furthermore, genetic deletion of fnr leads to decreased bacterial survival in a Caenorhabditis elegans infection model, highlighting an important role of this regulator in mediating host-pathogen interactions.
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Affiliation(s)
- Zhen Wang
- Institute of Analytical Chemistry and Synthetic and Functional Biomolecules Center, College of Chemistry and Molecular Engineering, Peking University, Beijing, China
| | - Jingjing Sun
- School of Biological Sciences, The University of Hong Kong, Pok Fu Lam Rd, Hong Kong SAR, China
| | - Mengdan Tian
- School of Biological Sciences, The University of Hong Kong, Pok Fu Lam Rd, Hong Kong SAR, China
| | - Zeling Xu
- School of Biological Sciences, The University of Hong Kong, Pok Fu Lam Rd, Hong Kong SAR, China
| | - Yanhua Liu
- Institute of Analytical Chemistry and Synthetic and Functional Biomolecules Center, College of Chemistry and Molecular Engineering, Peking University, Beijing, China
| | - Jiaqi Fu
- Institute of Analytical Chemistry and Synthetic and Functional Biomolecules Center, College of Chemistry and Molecular Engineering, Peking University, Beijing, China
| | - Aixin Yan
- School of Biological Sciences, The University of Hong Kong, Pok Fu Lam Rd, Hong Kong SAR, China.
| | - Xiaoyun Liu
- Institute of Analytical Chemistry and Synthetic and Functional Biomolecules Center, College of Chemistry and Molecular Engineering, Peking University, Beijing, China.
- Department of Microbiology, School of Basic Medical Sciences, Peking University Health Science Center, 38 Xueyuan Rd, Haidian District, Beijing, China.
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9
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Zupok A, Iobbi-Nivol C, Méjean V, Leimkühler S. The regulation of Moco biosynthesis and molybdoenzyme gene expression by molybdenum and iron in bacteria. Metallomics 2019; 11:1602-1624. [DOI: 10.1039/c9mt00186g] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
The regulation of the operons involved in Moco biosynthesis is dependent on the availability of Fe–S clusters in the cell.
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Affiliation(s)
- Arkadiusz Zupok
- University of Potsdam
- Institute of Biochemistry and Biology
- Molecular Enzymology
- Potsdam-Golm
- Germany
| | - Chantal Iobbi-Nivol
- Aix-Marseille Université
- Institut de Microbiologie de la Méditerranée
- Laboratoire de Bioénergétique et Ingénierie des Protéines
- Centre National de la Recherche Scientifique
- Marseille
| | - Vincent Méjean
- Aix-Marseille Université
- Institut de Microbiologie de la Méditerranée
- Laboratoire de Bioénergétique et Ingénierie des Protéines
- Centre National de la Recherche Scientifique
- Marseille
| | - Silke Leimkühler
- University of Potsdam
- Institute of Biochemistry and Biology
- Molecular Enzymology
- Potsdam-Golm
- Germany
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10
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Chan CS, Turner RJ. Biogenesis of Escherichia coli DMSO Reductase: A Network of Participants for Protein Folding and Complex Enzyme Maturation. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2015; 883:215-34. [PMID: 26621470 DOI: 10.1007/978-3-319-23603-2_12] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/17/2023]
Abstract
Protein folding and structure have been of interest since the dawn of protein chemistry. Following translation from the ribosome, a protein must go through various steps to become a functional member of the cellular society. Every protein has a unique function in the cell and is classified on this basis. Proteins that are involved in cellular respiration are the bioenergetic workhorses of the cell. Bacteria are resilient organisms that can survive in diverse environments by fine tuning these workhorses. One class of proteins that allow survival under anoxic conditions are anaerobic respiratory oxidoreductases, which utilize many different compounds other than oxygen as its final electron acceptor. Dimethyl sulfoxide (DMSO) is one such compound. Respiration using DMSO as a final electron acceptor is performed by DMSO reductase, converting it to dimethyl sulfide in the process. Microbial respiration using DMSO is reviewed in detail by McCrindle et al. (Adv Microb Physiol 50:147-198, 2005). In this chapter, we discuss the biogenesis of DMSO reductase as an example of the participant network for complex iron-sulfur molybdoenzyme maturation pathways.
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Affiliation(s)
- Catherine S Chan
- Department of Biological Sciences, University of Calgary, BI156 Biological Sciences Bldg, 2500 University Dr NW, Calgary, AB, T2N 1N4, Canada.
| | - Raymond J Turner
- Department of Biological Sciences, University of Calgary, BI156 Biological Sciences Bldg, 2500 University Dr NW, Calgary, AB, T2N 1N4, Canada.
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Qi Q, Ito Y, Yoshimatsu K, Fujiwara T. Transcriptional regulation of dimethyl sulfoxide respiration in a haloarchaeon, Haloferax volcanii. Extremophiles 2015; 20:27-36. [PMID: 26507955 DOI: 10.1007/s00792-015-0794-6] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2015] [Accepted: 10/08/2015] [Indexed: 11/27/2022]
Abstract
The halophilic euryarchaeon Haloferax volcanii can grow anaerobically by DMSO respiration. DMSO reductase was induced by DMSO respiration not only under anaerobic growth conditions but also in denitrifying cells of H. volcanii. Deletion of the dmsR gene, encoding a putative regulator for the DMSO reductase, resulted in the loss of anaerobic growth by DMSO respiration. Reporter experiments revealed that only the anaerobic condition was essential for transcription of the dmsEABCD genes encoding DMSO reductase and that transcription was enhanced threefold by supplementation of DMSO. In the ∆dmsR mutant, transcription of the dmsEABCD genes induced by the anaerobic condition was not enhanced by DMSO, suggesting that DmsR is a DMSO-responsive regulator. Transcriptions of the dmsR and mgd genes for Mo-bisMGD biosynthesis were regulated in the same manner as the dmsEABCD genes. These results suggest that the genetic regulation of DMSO respiration in H. volcanii is controlled by at least two systems: one is the DMSO-responsive DmsR, and the other is an unknown anaerobic regulator.
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Affiliation(s)
- Qiuzi Qi
- Department of Environment and Energy Systems, Graduate School of Science and Technology, Shizuoka University, 836 Oh-ya, Suruga-ku, Shizuoka, 422-8529, Japan
| | - Yoshiyasu Ito
- Department of Biological Science, Faculty of Science, Shizuoka University, 836 Oh-ya, Suruga-ku, Shizuoka, 422-8529, Japan
| | - Katsuhiko Yoshimatsu
- Research Institute of Green Science and Technology, Shizuoka University, 836 Oh-ya, Suruga-ku, Shizuoka, 422-8529, Japan
| | - Taketomo Fujiwara
- Department of Environment and Energy Systems, Graduate School of Science and Technology, Shizuoka University, 836 Oh-ya, Suruga-ku, Shizuoka, 422-8529, Japan. .,Department of Biological Science, Faculty of Science, Shizuoka University, 836 Oh-ya, Suruga-ku, Shizuoka, 422-8529, Japan.
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12
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Abstract
Escherichia coli is a versatile facultative anaerobe that can respire on a number of terminal electron acceptors, including oxygen, fumarate, nitrate, and S- and N-oxides. Anaerobic respiration using S- and N-oxides is accomplished by enzymatic reduction of these substrates by dimethyl sulfoxide reductase (DmsABC) and trimethylamine N-oxide reductase (TorCA). Both DmsABC and TorCA are membrane-associated redox enzymes that couple the oxidation of menaquinol to the reduction of S- and N-oxides in the periplasm. DmsABC is membrane bound and is composed of a membrane-extrinsic dimer with a 90.4-kDa catalytic subunit (DmsA) and a 23.1-kDa electron transfer subunit (DmsB). These subunits face the periplasm and are held to the membrane by a 30.8-kDa membrane anchor subunit (DmsC). The enzyme provides the scaffold for an electron transfer relay composed of a quinol binding site, five [4Fe-4S] clusters, and a molybdo-bis(molybdopterin guanine dinucleotide) (present nomenclature: Mo-bis-pyranopterin) (Mo-bisMGD) cofactor. TorCA is composed of a soluble periplasmic subunit (TorA, 92.5 kDa) containing a Mo-bis-MGD. TorA is coupled to the quinone pool via a pentaheme c subunit (TorC, 40.4 kDa) in the membrane. Both DmsABC and TorCA require system-specific chaperones (DmsD or TorD) for assembly, cofactor insertion, and/or targeting to the Tat translocon. In this chapter, we discuss the complex regulation of the dmsABC and torCAD operons, the poorly understood paralogues, and what is known about the assembly and translocation to the periplasmic space by the Tat translocon.
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13
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Katsir G, Jarvis M, Phillips M, Ma Z, Gunsalus RP. The Escherichia coli NarL receiver domain regulates transcription through promoter specific functions. BMC Microbiol 2015; 15:174. [PMID: 26307095 PMCID: PMC4549865 DOI: 10.1186/s12866-015-0502-9] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2015] [Accepted: 08/06/2015] [Indexed: 12/20/2022] Open
Abstract
Background The Escherichia coli response regulator NarL controls transcription of genes involved in nitrate respiration during anaerobiosis. NarL consists of two domains joined by a linker that wraps around the interdomain interface. Phosphorylation of the NarL N-terminal receiver domain (RD) releases the, otherwise sequestered, C-terminal output domain (OD) that subsequently binds specific DNA promoter sites to repress or activate gene expression. The aim of this study is to investigate the extent to which the NarL OD and RD function independently to regulate transcription, and the affect of the linker on OD function. Results NarL OD constructs containing different linker segments were examined for their ability to repress frdA-lacZ or activate narG-lacZ reporter fusion genes. These in vivo expression assays revealed that the NarL OD, in the absence or presence of linker helix α6, constitutively repressed frdA-lacZ expression regardless of nitrate availability. However, the presence of the linker loop α5-α6 reversed this repression and also showed impaired DNA binding in vitro. The OD alone could not activate narG-lacZ expression; this activity required the presence of the NarL RD. A footprint assay demonstrated that the NarL OD only partially bound recognition sites at the narG promoter, and the binding affinity was increased by the presence of the phosphorylated RD. Analytical ultracentrifugation used to examine domain oligomerization showed that the NarL RD forms dimers in solution while the OD is monomeric. Conclusions The NarL RD operates as an on-off switch to occlude or release the OD in a nitrate-responsive manner, but has additional roles to directly stimulate transcription at promoters for which the OD lacks independent function. One such role of the RD is to enhance the DNA binding affinity of the OD to target promoter sites. The data also imply that NarL phosphorylation results in RD dimerization and in the separation of the entire linker region from the OD. Electronic supplementary material The online version of this article (doi:10.1186/s12866-015-0502-9) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Galit Katsir
- Department of Chemistry and Biochemistry, University of California, Los Angeles, USA.,Molecular Biology Institute, University of California, Los Angeles, USA.,Present address: San Jose City College, San Jose, CA, USA
| | - Michael Jarvis
- Department of Microbiology, Immunology, and Molecular Genetics, University of California, Los Angeles, USA.,Present address: Ambry Genetics, Aliso Viejo, CA, USA
| | - Martin Phillips
- Department of Chemistry and Biochemistry, University of California, Los Angeles, USA
| | - Zhongcai Ma
- Department of Microbiology, Immunology, and Molecular Genetics, University of California, Los Angeles, USA.,Present address: NeuroInDx, Inc, Signal Hill, CA, USA
| | - Robert P Gunsalus
- Department of Microbiology, Immunology, and Molecular Genetics, University of California, Los Angeles, USA. .,Molecular Biology Institute, University of California, Los Angeles, USA.
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14
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Myers KS, Yan H, Ong IM, Chung D, Liang K, Tran F, Keleş S, Landick R, Kiley PJ. Genome-scale analysis of escherichia coli FNR reveals complex features of transcription factor binding. PLoS Genet 2013; 9:e1003565. [PMID: 23818864 PMCID: PMC3688515 DOI: 10.1371/journal.pgen.1003565] [Citation(s) in RCA: 132] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2013] [Accepted: 04/29/2013] [Indexed: 01/05/2023] Open
Abstract
FNR is a well-studied global regulator of anaerobiosis, which is widely conserved across bacteria. Despite the importance of FNR and anaerobiosis in microbial lifestyles, the factors that influence its function on a genome-wide scale are poorly understood. Here, we report a functional genomic analysis of FNR action. We find that FNR occupancy at many target sites is strongly influenced by nucleoid-associated proteins (NAPs) that restrict access to many FNR binding sites. At a genome-wide level, only a subset of predicted FNR binding sites were bound under anaerobic fermentative conditions and many appeared to be masked by the NAPs H-NS, IHF and Fis. Similar assays in cells lacking H-NS and its paralog StpA showed increased FNR occupancy at sites bound by H-NS in WT strains, indicating that large regions of the genome are not readily accessible for FNR binding. Genome accessibility may also explain our finding that genome-wide FNR occupancy did not correlate with the match to consensus at binding sites, suggesting that significant variation in ChIP signal was attributable to cross-linking or immunoprecipitation efficiency rather than differences in binding affinities for FNR sites. Correlation of FNR ChIP-seq peaks with transcriptomic data showed that less than half of the FNR-regulated operons could be attributed to direct FNR binding. Conversely, FNR bound some promoters without regulating expression presumably requiring changes in activity of condition-specific transcription factors. Such combinatorial regulation may allow Escherichia coli to respond rapidly to environmental changes and confer an ecological advantage in the anaerobic but nutrient-fluctuating environment of the mammalian gut. Regulation of gene expression by transcription factors (TFs) is key to adaptation to environmental changes. Our comprehensive, genome-scale analysis of a prototypical global TF, the anaerobic regulator FNR from Escherichia coli, leads to several novel and unanticipated insights into the influences on FNR binding genome-wide and the complex structure of bacterial regulons. We found that binding of NAPs restricts FNR binding at a subset of sites, suggesting that the bacterial genome is not freely accessible for FNR binding. Our finding that less than half of the predicted FNR binding sites were occupied in vivo further challenges the utility of using bioinformatic searches alone to predict regulon structure, reinforcing the need for experimental determination of TF binding. By correlating the occupancy data with transcriptomic data, we confirm that FNR serves as a global signal of anaerobiosis but expression of some operons in the FNR regulon require other regulators sensitive to alternative environmental stimuli. Thus, FNR binding and regulation appear to depend on both the nucleoprotein structure of the chromosome and on combinatorial binding of FNR with other regulators. Both of these phenomena are typical of TF binding in eukaryotes; our results establish that they are also features of bacterial TF binding.
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Affiliation(s)
- Kevin S. Myers
- Microbiology Doctoral Training Program, University of Wisconsin-Madison, Madison, Wisconsin, United States of America
- Department of Biomolecular Chemistry, University of Wisconsin-Madison, Madison, Wisconsin, United States of America
| | - Huihuang Yan
- Great Lakes Bioenergy Research Center, University of Wisconsin-Madison, Madison, Wisconsin, United States of America
| | - Irene M. Ong
- Great Lakes Bioenergy Research Center, University of Wisconsin-Madison, Madison, Wisconsin, United States of America
| | - Dongjun Chung
- Department of Statistics, University of Wisconsin-Madison, Madison, Wisconsin, United States of America
| | - Kun Liang
- Department of Statistics, University of Wisconsin-Madison, Madison, Wisconsin, United States of America
- Department of Biostatistics and Medical Informatics, University of Wisconsin-Madison, Madison, Wisconsin, United States of America
| | - Frances Tran
- Department of Biochemistry, University of Wisconsin-Madison, Madison, Wisconsin, United States of America
| | - Sündüz Keleş
- Department of Statistics, University of Wisconsin-Madison, Madison, Wisconsin, United States of America
- Department of Biostatistics and Medical Informatics, University of Wisconsin-Madison, Madison, Wisconsin, United States of America
| | - Robert Landick
- Great Lakes Bioenergy Research Center, University of Wisconsin-Madison, Madison, Wisconsin, United States of America
- Department of Biochemistry, University of Wisconsin-Madison, Madison, Wisconsin, United States of America
- Department of Bacteriology, University of Wisconsin-Madison, Madison, Wisconsin, United States of America
- * E-mail: (RL); (PJK)
| | - Patricia J. Kiley
- Department of Biomolecular Chemistry, University of Wisconsin-Madison, Madison, Wisconsin, United States of America
- Great Lakes Bioenergy Research Center, University of Wisconsin-Madison, Madison, Wisconsin, United States of America
- * E-mail: (RL); (PJK)
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15
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Magalon A, Fedor JG, Walburger A, Weiner JH. Molybdenum enzymes in bacteria and their maturation. Coord Chem Rev 2011. [DOI: 10.1016/j.ccr.2010.12.031] [Citation(s) in RCA: 87] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
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16
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Marijuán PC, Navarro J, del Moral R. On prokaryotic intelligence: strategies for sensing the environment. Biosystems 2009; 99:94-103. [PMID: 19781596 DOI: 10.1016/j.biosystems.2009.09.004] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2009] [Revised: 09/14/2009] [Accepted: 09/17/2009] [Indexed: 10/20/2022]
Abstract
The adaptive relationship with the environment is a sine qua non condition for any intelligent system. Discussions on the nature of cellular intelligence, however, have not systematically pursued yet the question of whether there is a fundamental way of sensing the environment, which may characterize prokaryotic cells, or not. The molecular systems found in bacterial signaling are extremely diverse, ranging from very simple transcription regulators (single proteins comprising just two domains) to the multi-component, multi-pathway signaling cascades that regulate crucial stages of the cell cycle, such as sporulation, biofilm formation, dormancy, pathogenesis or flagellar biosynthesis. The combined complexity of the environment and of the cellular way of life is reflected as a whole in the aggregate of signaling elements: an interesting power-law relationship emerges in that regard. In a basic taxonomy of bacterial signaling systems, the first level of complexity corresponds to the simplest regulators, the "one-component systems" (OCSs), which are defined as proteins that contain known or predicted input and output domains but lack histidine kinase and receiver domains. They are evolutionary precursors of the "two-component systems" (TCSs), which include histidine protein-kinase receptors and an independent response regulator, and are considered as the central signaling paradigm within prokaryotic organisms. The addition of independent receptors begets further functional complexity: thus, "three-component systems" (ThCSs) should be applied to those two-component systems that incorporate an extra non-kinase receptor to activate the protein-kinase. Further, the combined information processing functions (cross-talk) and integrative dynamics that OCS, TCS and ThCS may achieve together in the prokaryotic cell have to be depicted, as well as the relationship of these informational functions with the life cycle organization and its checkpoints. Finally, the extent to which formal models would capture the ongoing relationship of the living cell with its medium has to be gauged, in the light of both the complexity of molecular recognition events and the impredicative nature of living systems.
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Affiliation(s)
- Pedro C Marijuán
- Grupo de Bioinformación y Biología de Sistemas, Instituto Aragonés de Ciencias de la Salud (I+CS), Zaragoza, Spain.
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Abstract
Induction of the Escherichia coli K-12 ynfEFGHI operon in response to anaerobiosis is repressed by nitrate ions. In this study, we show that the global transcription factor FNR is a class II activator at the ynfEFGHI promoter and that NarL represses activation by binding to a single target that overlaps the promoter -10 element. Electromobility shift assays show that NarL does not prevent RNA polymerase binding and suggest that repression may involve a quaternary NarL-FNR-RNA polymerase-promoter complex.
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Gábor K, Hailesellasse Sene K, Smidt H, de Vos WM, van der Oost J. Divergent roles of CprK paralogues from Desulfitobacterium hafniense in activating gene expression. MICROBIOLOGY-SGM 2009; 154:3686-3696. [PMID: 19047736 DOI: 10.1099/mic.0.2008/021584-0] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Gene duplication and horizontal gene transfer play an important role in the evolution of prokaryotic genomes. We have investigated the role of three CprK paralogues from the cAMP receptor protein-fumarate and nitrate reduction regulator (CRP-FNR) family of transcriptional regulators that are encoded in the genome of Desulfitobacterium hafniense DCB-2 and possibly regulate expression of genes involved in the energy-conserving terminal reduction of organohalides (halorespiration). The results from in vivo and in vitro promoter probe assays show that two regulators (CprK1 and CprK2) have an at least partially overlapping effector specificity, with preference for ortho-chlorophenols, while meta-chlorophenols proved to be effectors for CprK4. The presence of a potential transposase-encoding gene in the vicinity of the cprK genes indicates that their redundancy is probably caused by mobile genetic elements. The CprK paralogues activated transcription from promoters containing a 14 bp inverted repeat (dehalobox) that closely resembles the FNR-box. We found a strong negative correlation between the rate of transcriptional activation and the number of nucleotide changes from the optimal dehalobox sequence (TTAAT-N4-ATTAA). Transcription was initiated by CprK4 from a promoter that is situated upstream of a gene encoding a methyl-accepting chemotaxis protein. This might be the first indication of taxis of an anaerobic bacterium to halogenated aromatic compounds.
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Affiliation(s)
- Krisztina Gábor
- Wageningen University and Research Centre, Laboratory of Microbiology, Dreijenplein 10, Wageningen 6703-HB, The Netherlands
| | - Kagnew Hailesellasse Sene
- Wageningen University and Research Centre, Laboratory of Microbiology, Dreijenplein 10, Wageningen 6703-HB, The Netherlands
| | - Hauke Smidt
- Wageningen University and Research Centre, Laboratory of Microbiology, Dreijenplein 10, Wageningen 6703-HB, The Netherlands
| | - Willem M de Vos
- Wageningen University and Research Centre, Laboratory of Microbiology, Dreijenplein 10, Wageningen 6703-HB, The Netherlands
| | - John van der Oost
- Wageningen University and Research Centre, Laboratory of Microbiology, Dreijenplein 10, Wageningen 6703-HB, The Netherlands
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19
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Genetic analysis of trimethylamine N-oxide reductases in the light organ symbiont Vibrio fischeri ES114. J Bacteriol 2008; 190:5814-23. [PMID: 18606737 DOI: 10.1128/jb.00227-08] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Trimethylamine N-oxide (TMAO) reductases are widespread in bacteria and often function in anaerobic respiration. The regulation and expression of TMAO reductase operons have been well studied in model genera such as Escherichia, Shewanella, and Rhodobacter, although TMAO reductases are present in many other bacteria, including the marine Vibrio species. The genome sequence of Vibrio fischeri revealed three putative TMAO reductase operons, and a previous report identified TMAO reductase activity in symbiotic V. fischeri isolates associated with the light organs of adult Hawaiian bobtail squid, Euprymna scolopes. We examined the roles and regulation of these three operons using mutational analyses and promoter-reporter fusions. We found that the torECA promoter, and to a lesser extent the torYZ and dmsABC promoters, were active during symbiotic colonization of juvenile E. scolopes; however, a V. fischeri strain lacking TMAO reductase activity displays no discernible colonization defect over the first 48 h. Our studies also revealed that torECA has the most active promoter of the putative TMAO reductase operons, and TorECA is the major contributor to TMAO-dependent growth in V. fischeri under the conditions tested. Interestingly, the transcriptional regulation of TMAO reductase operons in V. fischeri appears to differ from that in previously studied organisms, such as Escherichia coli, which may reflect differences in gene arrangement and bacterial habitat. This study lays the foundation for using V. fischeri as a model system for studying TMAO reductases in the Vibrionaceae.
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20
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Partridge JD, Browning DF, Xu M, Newnham LJ, Scott C, Roberts RE, Poole RK, Green J. Characterization of the Escherichia coli K-12 ydhYVWXUT operon: regulation by FNR, NarL and NarP. MICROBIOLOGY-SGM 2008; 154:608-618. [PMID: 18227264 DOI: 10.1099/mic.0.2007/012146-0] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
In Escherichia coli K-12 the expression of many genes is controlled by the oxygen-responsive transcription factor FNR and the nitrate- and nitrite-responsive two-component systems NarXL and NarPQ. Here, the ydhY gene is shown to be the first gene of a six-gene operon (ydhYVWXUT) that encodes proteins predicted to be components of an oxidoreductase. Mapping the ydhY-T transcript start and site-directed mutagenesis confirmed that the ydhY-T genes are transcribed from an FNR-dependent class II promoter and showed that the FNR site is centred at -42.5. In the presence of nitrate or nitrite, NarXL and NarPQ repressed ydhY-T expression. Analysis of the DNA sequence of the ydhY promoter region (PydhY) revealed the presence of four heptameric sequences similar to NarL/P binding sites centred at -42, -16, +6 and +15. The latter heptamers are arranged as a 7-2-7 inverted repeat, which is required for recognition by NarP. Accordingly, NarP protected the 7-2-7 region in DNase I footprints, and mutation of either heptamer +6 or heptamer +15 impaired nitrite-mediated repression, whereas mutation of heptamer -42 and heptamer -16 did not affect the response to nitrite. The NarL protein also protected the 7-2-7 region, but in contrast to NarP, the NarL footprint extended further upstream to encompass the -16 heptamer. The extended NarL footprint was consistent with the presence of multiple NarL-PydhY complexes in gel retardation assays. Mutation of heptamer -42, which is located within the FNR binding site, or heptamer +6 (but not heptamers -16 or +15) impaired nitrate-mediated repression. Thus, although the region of the ydhY-T promoter containing the -16 and +15 heptamers was recognized by NarL in vitro, mutation of these heptamers did not affect NarL-mediated repression in vivo.
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Affiliation(s)
- Jonathan D Partridge
- Department of Molecular Biology and Biotechnology, The University of Sheffield, Sheffield S10 2TN, UK
| | - Douglas F Browning
- The School of Biosciences, The University of Birmingham, Birmingham B15 2TT, UK
| | - Meng Xu
- The School of Biosciences, The University of Birmingham, Birmingham B15 2TT, UK
| | - Louise J Newnham
- Department of Molecular Biology and Biotechnology, The University of Sheffield, Sheffield S10 2TN, UK
| | - Colin Scott
- Department of Molecular Biology and Biotechnology, The University of Sheffield, Sheffield S10 2TN, UK
| | - Ruth E Roberts
- Department of Molecular Biology and Biotechnology, The University of Sheffield, Sheffield S10 2TN, UK
| | - Robert K Poole
- Department of Molecular Biology and Biotechnology, The University of Sheffield, Sheffield S10 2TN, UK
| | - Jeffrey Green
- Department of Molecular Biology and Biotechnology, The University of Sheffield, Sheffield S10 2TN, UK
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21
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Cho BK, Knight EM, Barrett CL, Palsson BØ. Genome-wide analysis of Fis binding in Escherichia coli indicates a causative role for A-/AT-tracts. Genome Res 2008; 18:900-10. [PMID: 18340041 DOI: 10.1101/gr.070276.107] [Citation(s) in RCA: 139] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
Abstract
We determined the genome-wide distribution of the nucleoid-associated protein Fis in Escherichia coli using chromatin immunoprecipitation coupled with high-resolution whole genome-tiling microarrays. We identified 894 Fis-associated regions across the E. coli genome. A significant number of these binding sites were found within open reading frames (33%) and between divergently transcribed transcripts (5%). Analysis indicates that A-tracts and AT-tracts are an important signal for preferred Fis-binding sites, and that A(6)-tracts in particular constitute a high-affinity signal that dictates Fis phasing in stretches of DNA containing multiple and variably spaced A-tracts and AT-tracts. Furthermore, we find evidence for an average of two Fis-binding regions per supercoiling domain in the chromosome of exponentially growing cells. Transcriptome analysis shows that approximately 21% of genes are affected by the deletion of fis; however, the changes in magnitude are small. To address the differential Fis bindings under growth environment perturbation, ChIP-chip analysis was performed using cells grown under aerobic and anaerobic growth conditions. Interestingly, the Fis-binding regions are almost identical in aerobic and anaerobic growth conditions-indicating that the E. coli genome topology mediated by Fis is superficially identical in the two conditions. These novel results provide new insight into how Fis modulates DNA topology at a genome scale and thus advance our understanding of the architectural bases of the E. coli nucleoid.
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Affiliation(s)
- Byung-Kwan Cho
- Department of Bioengineering, University of California-San Diego, La Jolla, California 92093-0412, USA
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22
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Makarova KS, Omelchenko MV, Gaidamakova EK, Matrosova VY, Vasilenko A, Zhai M, Lapidus A, Copeland A, Kim E, Land M, Mavromatis K, Pitluck S, Richardson PM, Detter C, Brettin T, Saunders E, Lai B, Ravel B, Kemner KM, Wolf YI, Sorokin A, Gerasimova AV, Gelfand MS, Fredrickson JK, Koonin EV, Daly MJ. Deinococcus geothermalis: the pool of extreme radiation resistance genes shrinks. PLoS One 2007; 2:e955. [PMID: 17895995 PMCID: PMC1978522 DOI: 10.1371/journal.pone.0000955] [Citation(s) in RCA: 185] [Impact Index Per Article: 10.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2007] [Accepted: 09/04/2007] [Indexed: 11/19/2022] Open
Abstract
Bacteria of the genus Deinococcus are extremely resistant to ionizing radiation (IR), ultraviolet light (UV) and desiccation. The mesophile Deinococcus radiodurans was the first member of this group whose genome was completely sequenced. Analysis of the genome sequence of D. radiodurans, however, failed to identify unique DNA repair systems. To further delineate the genes underlying the resistance phenotypes, we report the whole-genome sequence of a second Deinococcus species, the thermophile Deinococcus geothermalis, which at its optimal growth temperature is as resistant to IR, UV and desiccation as D. radiodurans, and a comparative analysis of the two Deinococcus genomes. Many D. radiodurans genes previously implicated in resistance, but for which no sensitive phenotype was observed upon disruption, are absent in D. geothermalis. In contrast, most D. radiodurans genes whose mutants displayed a radiation-sensitive phenotype in D. radiodurans are conserved in D. geothermalis. Supporting the existence of a Deinococcus radiation response regulon, a common palindromic DNA motif was identified in a conserved set of genes associated with resistance, and a dedicated transcriptional regulator was predicted. We present the case that these two species evolved essentially the same diverse set of gene families, and that the extreme stress-resistance phenotypes of the Deinococcus lineage emerged progressively by amassing cell-cleaning systems from different sources, but not by acquisition of novel DNA repair systems. Our reconstruction of the genomic evolution of the Deinococcus-Thermus phylum indicates that the corresponding set of enzymes proliferated mainly in the common ancestor of Deinococcus. Results of the comparative analysis weaken the arguments for a role of higher-order chromosome alignment structures in resistance; more clearly define and substantially revise downward the number of uncharacterized genes that might participate in DNA repair and contribute to resistance; and strengthen the case for a role in survival of systems involved in manganese and iron homeostasis.
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Affiliation(s)
- Kira S. Makarova
- National Center for Biotechnology Information, National Library of Medicine, National Institutes of Health, Bethesda, Maryland, United States of America
- * To whom correspondence should be addressed. E-mail: (KM); (MD)
| | - Marina V. Omelchenko
- National Center for Biotechnology Information, National Library of Medicine, National Institutes of Health, Bethesda, Maryland, United States of America
| | - Elena K. Gaidamakova
- Department of Pathology, Uniformed Services University of the Health Sciences (USUHS), Bethesda, Maryland, United States of America
| | - Vera Y. Matrosova
- Department of Pathology, Uniformed Services University of the Health Sciences (USUHS), Bethesda, Maryland, United States of America
| | - Alexander Vasilenko
- Department of Pathology, Uniformed Services University of the Health Sciences (USUHS), Bethesda, Maryland, United States of America
| | - Min Zhai
- Department of Pathology, Uniformed Services University of the Health Sciences (USUHS), Bethesda, Maryland, United States of America
| | - Alla Lapidus
- US Department of Energy, Joint Genome Institute, Walnut Creek, California, United States of America
| | - Alex Copeland
- US Department of Energy, Joint Genome Institute, Walnut Creek, California, United States of America
| | - Edwin Kim
- US Department of Energy, Joint Genome Institute, Walnut Creek, California, United States of America
| | - Miriam Land
- US Department of Energy, Joint Genome Institute, Walnut Creek, California, United States of America
| | - Konstantinos Mavromatis
- US Department of Energy, Joint Genome Institute, Walnut Creek, California, United States of America
| | - Samuel Pitluck
- US Department of Energy, Joint Genome Institute, Walnut Creek, California, United States of America
| | - Paul M. Richardson
- US Department of Energy, Joint Genome Institute, Walnut Creek, California, United States of America
| | - Chris Detter
- US Department of Energy, Joint Genome Institute, Los Alamos National Laboratory, Los Alamos, New Mexico, United States of America
| | - Thomas Brettin
- US Department of Energy, Joint Genome Institute, Los Alamos National Laboratory, Los Alamos, New Mexico, United States of America
| | - Elizabeth Saunders
- US Department of Energy, Joint Genome Institute, Los Alamos National Laboratory, Los Alamos, New Mexico, United States of America
| | - Barry Lai
- Environmental Research Division and Advanced Photon Source, Argonne National Laboratory, Argonne, Illinois, United States of America
| | - Bruce Ravel
- Environmental Research Division and Advanced Photon Source, Argonne National Laboratory, Argonne, Illinois, United States of America
| | - Kenneth M. Kemner
- Environmental Research Division and Advanced Photon Source, Argonne National Laboratory, Argonne, Illinois, United States of America
| | - Yuri I. Wolf
- National Center for Biotechnology Information, National Library of Medicine, National Institutes of Health, Bethesda, Maryland, United States of America
| | - Alexander Sorokin
- National Center for Biotechnology Information, National Library of Medicine, National Institutes of Health, Bethesda, Maryland, United States of America
| | - Anna V. Gerasimova
- Research Institute of Genetics and Selection of Industrial Microorganisms, Moscow, Russia
| | - Mikhail S. Gelfand
- Institute for Information Transmission Problems of RAS, Moscow, Russia
- Faculty of Bioengineering and Bioinformatics, M. V. Lomonosov Moscow State University, Moscow, Russia
| | - James K. Fredrickson
- Biological Sciences Division, Pacific Northwest National Laboratory, Richland, Washington, United States of America
| | - Eugene V. Koonin
- National Center for Biotechnology Information, National Library of Medicine, National Institutes of Health, Bethesda, Maryland, United States of America
| | - Michael J. Daly
- Department of Pathology, Uniformed Services University of the Health Sciences (USUHS), Bethesda, Maryland, United States of America
- * To whom correspondence should be addressed. E-mail: (KM); (MD)
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23
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Cho BK, Knight EM, Palsson BO. PCR-based tandem epitope tagging system for Escherichia coli genome engineering. Biotechniques 2006; 40:67-72. [PMID: 16454042 DOI: 10.2144/000112039] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022] Open
Abstract
Biological discovery in the postgenomic era requires a systematic and high-throughput experimental approach. To this end, a versatile PCR-based tandem epitope tagging system is described, which inserts a tandem epitope coding sequence into any desired position of the Escherichia coli chromosome. Template plasmids were constructed that carry tandem copies of the epitope encoding sequence, Flp recombinase target (FRT) sites, and antibiotic resistance genes. The linear DNA fragment, amplified from the template plasmid with extensions homologous to the end of the target gene and part of its downstream region, was transformed into E. coli K-12 MG1655 harboring the bacteriophage gamma Red recombination system. The antibiotic resistance gene was then removed from the inserted heterologous PCR fragment using Flp recombinase. This epitope tagging system was applied to global transcription factors of E. coli to obtain proteins fused with tandem c-myc epitope tags. The tandem myc epitope-fused transcription factors were successfully detected by Western blot analysis and chromatin immunoprecipitation with increased detection sensitivity and higher yield. Higher copy numbers of the epitope molecule allowed the use of more stringent experimental conditions to increase the signal-to-noise ratio in subsequent experimental applications. Furthermore, judging from the measurement of gene expression using reverse transcription PCR (RT-PCR), the epitope-fused transcription factors retained their normal function for gene regulation in vivo.
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Affiliation(s)
- Byung-Kwan Cho
- University of California at San Diego, La Jolla, CA 92093, USA
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24
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Stewart V, Bledsoe PJ. Fnr-, NarP- and NarL-dependent regulation of transcription initiation from the Haemophilus influenzae Rd napF (periplasmic nitrate reductase) promoter in Escherichia coli K-12. J Bacteriol 2005; 187:6928-35. [PMID: 16199562 PMCID: PMC1251606 DOI: 10.1128/jb.187.20.6928-6935.2005] [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: 11/20/2022] Open
Abstract
Periplasmic nitrate reductase (napFDAGHBC operon product) functions in anaerobic respiration. Transcription initiation from the Escherichia coli napF operon control region is activated by the Fnr protein in response to anaerobiosis and by the NarQ-NarP two-component regulatory system in response to nitrate or nitrite. The binding sites for the Fnr and phospho-NarP proteins are centered at positions -64.5 and -44.5, respectively, with respect to the major transcription initiation point. The E. coli napF operon is a rare example of a class I Fnr-activated transcriptional control region, in which the Fnr protein binding site is located upstream of position -60. To broaden our understanding of napF operon transcriptional control, we studied the Haemophilus influenzae Rd napF operon control region, expressed as a napF-lacZ operon fusion in the surrogate host E. coli. Mutational analysis demonstrated that expression required binding sites for the Fnr and phospho-NarP proteins centered at positions -81.5 and -42.5, respectively. Transcription from the E. coli napF operon control region is activated by phospho-NarP but antagonized by the orthologous protein, phospho-NarL. By contrast, expression from the H. influenzae napF-lacZ operon fusion in E. coli was stimulated equally well by nitrate in both narP and narL null mutants, indicating that phospho-NarL and -NarP are equally effective regulators of this promoter. Overall, the H. influenzae napF operon control region provides a relatively simple model for studying synergistic transcription by the Fnr and phospho-NarP proteins acting from class I and class II locations, respectively.
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Affiliation(s)
- Valley Stewart
- Section of Microbiology, University of California, One Shields Avenue, Davis, CA 95616-8665, USA.
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25
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Regulation of Nitrate and Nitrite Respiration in γ-Proteobacteria: A Comparative Genomics Study. Mol Biol 2005. [DOI: 10.1007/s11008-005-0088-7] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
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26
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Mesa S, Ucurum Z, Hennecke H, Fischer HM. Transcription activation in vitro by the Bradyrhizobium japonicum regulatory protein FixK2. J Bacteriol 2005; 187:3329-38. [PMID: 15866917 PMCID: PMC1112000 DOI: 10.1128/jb.187.10.3329-3338.2005] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
In Bradyrhizobium japonicum, the N2-fixing root nodule endosymbiont of soybean, a group of genes required for microaerobic, anaerobic, or symbiotic growth is controlled by FixK2, a key regulator that is part of the FixLJ-FixK2 cascade. FixK2 belongs to the family of cyclic AMP receptor protein/fumarate and nitrate reductase (CRP/FNR) transcription factors that recognize a palindromic DNA motif (CRP/FNR box) associated with the regulated promoters. Here, we report on a biochemical analysis of FixK2 and its transcription activation activity in vitro. FixK2 was expressed in Escherichia coli and purified as a soluble N-terminally histidine-tagged protein. Gel filtration experiments revealed that increasing the protein concentration shifts the monomer-dimer equilibrium toward the dimer. Purified FixK2 productively interacted with the B. japonicum sigma80-RNA polymerase holoenzyme, but not with E. coli sigma70-RNA polymerase holoenzyme, to activate transcription from the B. japonicum fixNOQP, fixGHIS, and hemN2 promoters in vitro. Furthermore, FixK2 activated transcription from the E. coli FF(-41.5) model promoter, again only in concert with B. japonicum RNA polymerase. All of these promoters are so-called class II CRP/FNR-type promoters. We showed by specific mutagenesis that the FixK2 box at nucleotide position -40.5 in the hemN2 promoter, but not that at -78.5, is crucial for activation both in vivo and in vitro, which argues against recognition of a potential class III promoter. Given the lack of any evidence for the presence of a cofactor in purified FixK2, we surmise that FixK2 alone is sufficient to activate in vitro transcription to at least a basal level. This contrasts with all well-studied CRP/FNR-type proteins, which do require coregulators.
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Affiliation(s)
- Socorro Mesa
- Institute of Microbiology, Eidgenössische Technische Hochschule, CH-8093 Zürich, Switzerland.
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27
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Zhou L, Lei XH, Bochner BR, Wanner BL. Phenotype microarray analysis of Escherichia coli K-12 mutants with deletions of all two-component systems. J Bacteriol 2003; 185:4956-72. [PMID: 12897016 PMCID: PMC166450 DOI: 10.1128/jb.185.16.4956-4972.2003] [Citation(s) in RCA: 235] [Impact Index Per Article: 11.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Two-component systems are the most common mechanism of transmembrane signal transduction in bacteria. A typical system consists of a histidine kinase and a partner response regulator. The histidine kinase senses an environmental signal, which it transmits to its partner response regulator via a series of autophosphorylation, phosphotransfer, and dephosphorylation reactions. Much work has been done on particular systems, including several systems with regulatory roles in cellular physiology, communication, development, and, in the case of bacterial pathogens, the expression of genes important for virulence. We used two methods to investigate two-component regulatory systems in Escherichia coli K-12. First, we systematically constructed mutants with deletions of all two-component systems by using a now-standard technique of gene disruption (K. A. Datsenko and B. L. Wanner, Proc. Natl. Acad. Sci. USA 97:6640-6645, 2000). We then analyzed these deletion mutants with a new technology called Phenotype MicroArrays, which permits assays of nearly 2,000 growth phenotypes simultaneously. In this study we tested 100 mutants, including mutants with individual deletions of all two-component systems and several related genes, including creBC-regulated genes (cbrA and cbrBC), phoBR-regulated genes (phoA, phoH, phnCDEFGHIJKLMNOP, psiE, and ugpBAECQ), csgD, luxS, and rpoS. The results of this battery of nearly 200,000 tests provided a wealth of new information concerning many of these systems. Of 37 different two-component mutants, 22 showed altered phenotypes. Many phenotypes were expected, and several new phenotypes were also revealed. The results are discussed in terms of the biological roles and other information concerning these systems, including DNA microarray data for a large number of the same mutants. Other mutational effects are also discussed.
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Affiliation(s)
- Lu Zhou
- Department of Biological Sciences, Purdue University, West Lafayette, Indiana 47907, USA
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28
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Stewart V, Bledsoe PJ. Synthetic lac operator substitutions for studying the nitrate- and nitrite-responsive NarX-NarL and NarQ-NarP two-component regulatory systems of Escherichia coli K-12. J Bacteriol 2003; 185:2104-11. [PMID: 12644479 PMCID: PMC151514 DOI: 10.1128/jb.185.7.2104-2111.2003] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The NarX and NarQ sensor-histidine kinases control phosphorylation of the NarL and NarP response regulators in response to the respiratory oxidants nitrate and nitrite. Target operon transcription is activated by the Fnr protein in response to anaerobiosis, and it is further activated and/or repressed by the phospho-NarL and phospho-NarP proteins, which bind to heptamer DNA sequences. The location and arrangement of heptamers vary widely among different target operon control regions. We have constructed a series of monocopy lac operon control region constructs in which the primary operator O1-lac has been replaced by 7-2-7 heptamer pairs from the nrfA, nirB, napF, and fdnG operon control regions. These constructs provide tools for dissecting various aspects of ligand interactions with sensor-kinases, sensor interactions with response regulators, and phospho-response regulator interactions with DNA targets. Expression of the lacZ gene from these constructs was repressed to various degrees by nitrate and nitrite. In response to nitrate, the nrfA and nirB operon 7-2-7 heptamer pairs at operator O1 each mediated greater than 100-fold repression of lacZ gene expression, whereas the napF operon 7-2-7 heptamer pair mediated approximately tenfold repression. Introduction of narL, narP, narX, and narQ null alleles in various combinations allowed the in vivo interactions between different sensor-regulator pairs to be evaluated and compared.
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Affiliation(s)
- Valley Stewart
- Section of Microbiology, University of California, Davis, California 95616-8665, USA.
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