1
|
Magnani GS, Cruz LM, Weber H, Bespalhok JC, Daros E, Baura V, Yates MG, Monteiro RA, Faoro H, Pedrosa FO, Souza EM. Culture-independent analysis of endophytic bacterial communities associated with Brazilian sugarcane. Genet Mol Res 2013; 12:4549-58. [PMID: 24222230 DOI: 10.4238/2013.october.15.3] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Abstract
Sugarcane is an economically important culture in Brazil. Endophytic bacteria live inside plants, and can provide many benefits to the plant host. We analyzed the bacterial diversity of sugarcane cultivar RB-72454 by cultivation-independent techniques. Total DNA from sugarcane stems from a commercial plantation located in Paraná State was extracted. Partial 16S rRNA genes were amplified and sequenced for library construction. Of 152 sequences obtained, 52% were similar to 16S rRNA from Pseudomonas sp, and 35.5% to Enterobacter sp. The genera Pantoea, Serratia, Citrobacter, and Klebsiella were also represented. The endophytic communities in these sugarcane samples were dominated by the families Enterobacteriaceae and Pseudomonadaceae (class Gammaproteobacteria).
Collapse
Affiliation(s)
- G S Magnani
- Departamento de Bioquímica e Biologia Molecular, Universidade Federal do Paraná, Curitiba, PR, Brasil
| | | | | | | | | | | | | | | | | | | | | |
Collapse
|
2
|
Marin AM, Souza EM, Pedrosa FO, Souza LM, Sassaki GL, Baura VA, Yates MG, Wassem R, Monteiro RA. Naringenin degradation by the endophytic diazotroph Herbaspirillum seropedicae SmR1. Microbiology (Reading) 2012; 159:167-175. [PMID: 23125118 DOI: 10.1099/mic.0.061135-0] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Several bacteria are able to degrade flavonoids either to use them as carbon sources or as a detoxification mechanism. Degradation pathways have been proposed for several bacteria, but the genes responsible are not known. We identified in the genome of the endophyte Herbaspirillum seropedicae SmR1 an operon potentially associated with the degradation of aromatic compounds. We show that this operon is involved in naringenin degradation and that its expression is induced by naringenin and chrysin, two closely related flavonoids. Mutation of fdeA, the first gene of the operon, and fdeR, its transcriptional activator, abolished the ability of H. seropedicae to degrade naringenin.
Collapse
Affiliation(s)
- A M Marin
- Department of Biochemistry and Molecular Biology, Universidade Federal do Paraná, CP 19046, 81531-980, Curitiba, PR, Brazil
| | - E M Souza
- Department of Biochemistry and Molecular Biology, Universidade Federal do Paraná, CP 19046, 81531-980, Curitiba, PR, Brazil
| | - F O Pedrosa
- Department of Biochemistry and Molecular Biology, Universidade Federal do Paraná, CP 19046, 81531-980, Curitiba, PR, Brazil
| | - L M Souza
- Department of Biochemistry and Molecular Biology, Universidade Federal do Paraná, CP 19046, 81531-980, Curitiba, PR, Brazil
| | - G L Sassaki
- Department of Biochemistry and Molecular Biology, Universidade Federal do Paraná, CP 19046, 81531-980, Curitiba, PR, Brazil
| | - V A Baura
- Department of Biochemistry and Molecular Biology, Universidade Federal do Paraná, CP 19046, 81531-980, Curitiba, PR, Brazil
| | - M G Yates
- Department of Biochemistry and Molecular Biology, Universidade Federal do Paraná, CP 19046, 81531-980, Curitiba, PR, Brazil
| | - R Wassem
- Department of Genetics, Universidade Federal do Paraná, CP 19071, 81531-980, Curitiba, PR, Brazil
| | - R A Monteiro
- Department of Biochemistry and Molecular Biology, Universidade Federal do Paraná, CP 19046, 81531-980, Curitiba, PR, Brazil
| |
Collapse
|
3
|
Galvão CW, Souza EM, Etto RM, Pedrosa FO, Chubatsu LS, Yates MG, Schumacher J, Buck M, Steffens MBR. The RecX protein interacts with the RecA protein and modulates its activity in Herbaspirillum seropedicae. Braz J Med Biol Res 2012; 45:1127-34. [PMID: 23044625 PMCID: PMC3854219 DOI: 10.1590/s0100-879x2012007500160] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2012] [Accepted: 08/14/2012] [Indexed: 11/22/2022] Open
Abstract
DNA repair is crucial to the survival of all organisms. The bacterial RecA protein is a central component in the SOS response and in recombinational and SOS DNA repairs. The RecX protein has been characterized as a negative modulator of RecA activity in many bacteria. The recA and recX genes of Herbaspirillum seropedicae constitute a single operon, and evidence suggests that RecX participates in SOS repair. In the present study, we show that the H. seropedicae RecX protein (RecX Hs) can interact with the H. seropedicaeRecA protein (RecA Hs) and that RecA Hs possesses ATP binding, ATP hydrolyzing and DNA strand exchange activities. RecX Hs inhibited 90% of the RecA Hs DNA strand exchange activity even when present in a 50-fold lower molar concentration than RecA Hs. RecA Hs ATP binding was not affected by the addition of RecX, but the ATPase activity was reduced. When RecX Hs was present before the formation of RecA filaments (RecA-ssDNA), inhibition of ATPase activity was substantially reduced and excess ssDNA also partially suppressed this inhibition. The results suggest that the RecX Hs protein negatively modulates the RecA Hs activities by protein-protein interactions and also by DNA-protein interactions.
Collapse
Affiliation(s)
- C W Galvão
- Departamento de Biologia Estrutural, Molecular e Genética, Universidade Estadual de Ponta Grossa, Ponta Grossa, PR, Brasil.
| | | | | | | | | | | | | | | | | |
Collapse
|
4
|
Abstract
This review summarizes recent aspects of (di)nitrogen fixation and (di)hydrogen metabolism, with emphasis on cyanobacteria. These organisms possess several types of the enzyme complexes catalyzing N(2) fixation and/or H(2) formation or oxidation, namely, two Mo nitrogenases, a V nitrogenase, and two hydrogenases. The two cyanobacterial Ni hydrogenases are differentiated as either uptake or bidirectional hydrogenases. The different forms of both the nitrogenases and hydrogenases are encoded by different sets of genes, and their organization on the chromosome can vary from one cyanobacterium to another. Factors regulating the expression of these genes are emerging from recent studies. New ideas on the potential physiological and ecological roles of nitrogenases and hydrogenases are presented. There is a renewed interest in exploiting cyanobacteria in solar energy conversion programs to generate H(2) as a source of combustible energy. To enhance the rates of H(2) production, the emphasis perhaps needs not to be on more efficient hydrogenases and nitrogenases or on the transfer of foreign enzymes into cyanobacteria. A likely better strategy is to exploit the use of radiant solar energy by the photosynthetic electron transport system to enhance the rates of H(2) formation and so improve the chances of utilizing cyanobacteria as a source for the generation of clean energy.
Collapse
Affiliation(s)
- Hermann Bothe
- Botanical Institute, The University of Cologne, Zülpicher Str. 47b, D-50923 Cologne, Germany.
| | | | | | | |
Collapse
|
5
|
Assumpção MC, de Souza EM, Yates MG, de Oliveira Pedrosa F, Benelli EM. Purification and characterisation of Azospirillum brasilense N-truncated NtrX protein. Protein Expr Purif 2007; 53:302-8. [PMID: 17306559 DOI: 10.1016/j.pep.2007.01.003] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2006] [Revised: 01/03/2007] [Accepted: 01/05/2007] [Indexed: 11/21/2022]
Abstract
The NtrX protein has been identified as a transcriptional activator of genes involved in the metabolic control of alternative nitrogen sources, acting as a member of a two-component regulatory system. The in silico analysis of the NtrX amino acid sequence shows that this protein contains an N-terminal receiver domain, a central AAA+ superfamily domain and a C-terminal DNA binding domain. To over-express and purify this protein, the ntrX gene of Azospirillum brasilense lacking the first eight codons was cloned into the vector pET29a+. The NtrX protein was over-expressed as an S.Tag fusion protein induced by l-arabinose in the Escherichia coli strain BL21AI and purified by ion exchange and affinity chromatography. The ATPase activity of NtrX was measured by coupling the ATP conversion to ADP with NADH oxidation. The ATPase activity of NtrX was stimulated in the presence of A. brasilense sigma(54)/NtrC-dependent promoter of the glnBA gene. Phosphorylation by carbamyl-phosphate also stimulated ATPase, in a manner similar to the NtrC protein. Together our results suggest that NtrX is active in the phosphorylated form and that there may be a cross-talk between the NtrYX and NtrBC regulatory systems in A. brasilense.
Collapse
|
6
|
Maltempi de Souza E, de Oliveira Pedrosa F, Wassem R, Ford CM, Yates MG. Genes involved in Sec-independent membrane targeting of hydrogenase in Azotobacter chroococcum. Res Microbiol 2007; 158:272-8. [PMID: 17368855 DOI: 10.1016/j.resmic.2007.01.001] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2006] [Revised: 12/09/2006] [Accepted: 01/04/2007] [Indexed: 11/30/2022]
Abstract
Sec-independent translocation systems have been characterised in Escherichia coli and other bacteria and differ from the Sec-dependent system by transporting fully folded proteins using the transmembrane proton electrochemical gradient. Proteins transported by this system bear a twin-arginine motif (tat) in the N-terminal signal peptide and include several cofactor-containing proteins. Azotobacter chroococcum strain (MCD124) has a soluble hydrogenase, which exhibited low O(2)-dependent H(2) uptake, and a shift in the pH of the culture to a more alkaline range during growth. We show that the DNA region capable of complementing this strain contains the tatABC genes and that mutations in the tatA gene reproduced the soluble hydrogenase and the culture pH shift phenotypes. We also show that insertional mutation in the tatC gene at a position corresponding to its C-terminal region had no effect on hydrogenase activity, but induced the pH shift of the culture. Sequence and mutagenesis analyses of this genomic region suggest that these genes form an operon that does not contain a tatD-like gene. A mutation in hupZ of the main hup gene region, coding for a possible b-type cytochrome also yielded a soluble hydrogenase, but not the pH-shift phenotype.
Collapse
Affiliation(s)
- Emanuel Maltempi de Souza
- Department of Biochemistry and Molecular Biology, Universidade Federal do Paraná, Caixa Postal 19046, CEP 81531-990, Curitiba, Paraná, Brazil.
| | | | | | | | | |
Collapse
|
7
|
Rego FGM, Pedrosa FO, Chubatsu LS, Yates MG, Wassem R, Steffens MBR, Rigo LU, Souza EM. The expression ofnifBgene fromHerbaspirillum seropedicaeis dependent upon the NifA and RpoN proteins. Can J Microbiol 2006; 52:1199-207. [PMID: 17473889 DOI: 10.1139/w06-085] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The putative nifB promoter region of Herbaspirillum seropedicae contained two sequences homologous to NifA-binding site and a –24/–12 type promoter. A nifB::lacZ fusion was assayed in the backgrounds of both Escherichia coli and H. seropedicae. In E. coli, the expression of nifB::lacZ occurred only in the presence of functional rpoN and Klebsiella pneumoniae nifA genes. In addition, the integration host factor (IHF) stimulated the expression of the nifB::lacZ fusion in this background. In H. seropedicae, nifB expression occurred only in the absence of ammonium and under low levels of oxygen, and it was shown to be strictly dependent on NifA. DNA band shift experiments showed that purified K. pneumoniae RpoN and E. coli IHF proteins were capable of binding to the nifB promoter region, and in vivo dimethylsulfate footprinting showed that NifA binds to both NifA-binding sites. These results strongly suggest that the expression of the nifB promoter of H. seropedicae is dependent on the NifA and RpoN proteins and that the IHF protein stimulates NifA activation of nifB promoter.Key words: Herbaspirillum seropedicae, nif, nitrogen fixation, NifA, RpoN.
Collapse
Affiliation(s)
- Fabiane G M Rego
- Departamento de Bioquímica e Biologia Molecular, Universidade Federal do Paraná, Curitiba, PR, Brazil
| | | | | | | | | | | | | | | |
Collapse
|
8
|
Klassen G, Souza EM, Yates MG, Rigo LU, Costa RM, Inaba J, Pedrosa FO. Nitrogenase switch-off by ammonium ions in Azospirillum brasilense requires the GlnB nitrogen signal-transducing protein. Appl Environ Microbiol 2005; 71:5637-41. [PMID: 16151168 PMCID: PMC1214662 DOI: 10.1128/aem.71.9.5637-5641.2005] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Nitrogenase activity in several diazotrophs is switched off by ammonium and reactivated after consumption. The signaling pathway to this system in Azospirillum brasilense is not understood. We show that ammonium-dependent switch-off through ADP-ribosylation of Fe protein was partial in a glnB mutant of A. brasilense but absent in a glnB glnZ double mutant. Triggering of inactivation by anaerobic conditions was not affected in either mutant. The results suggest that glnB is necessary for full ammonium-dependent nitrogenase switch-off in A. brasilense.
Collapse
Affiliation(s)
- Giseli Klassen
- Universidade Federal do Paraná, Departamento de Bioquímica e Biologia Molecular, Caixa Postal 19046 CEP-81531-990, Curitiba, Paraná, Brazil
| | | | | | | | | | | | | |
Collapse
|
9
|
Huergo LF, Filipaki A, Chubatsu LS, Yates MG, Steffens MB, Pedrosa FO, Souza EM. Effect of the over-expression of PII and PZ proteins on the nitrogenase activity of Azospirillum brasilense. FEMS Microbiol Lett 2005; 253:47-54. [PMID: 16239079 DOI: 10.1016/j.femsle.2005.09.026] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2005] [Accepted: 09/12/2005] [Indexed: 11/30/2022] Open
Abstract
The Azospirillum brasilense PII and PZ proteins, encoded by the glnB and glnZ genes respectively, are intracellular transducers of nitrogen levels with distinct functions. The PII protein participates in nif regulation by controlling the activity of the transcriptional regulator NifA. PII is also involved in transducing the prevailing nitrogen levels to the Fe-protein ADP-ribosylation system. PZ regulates negatively ammonium transport and is involved in nitrogenase reactivation. To further investigate the role of PII and PZ in the regulation of nitrogen fixation, broad-host-range plasmids capable of over-expressing the glnB and glnZ genes under control of the ptac promoter were constructed and introduced into A. brasilense. The nitrogenase activity and nitrate-dependent growth was impaired in A. brasilense cells over-expressing the PII protein. Using immunoblot analysis we observed that the reduction of nitrogenase activity in cells over-expressing PII was due to partial ADP-ribosylation of the Fe-protein under derepressing conditions and a reduction in the amount of Fe-protein. These results support the hypothesis that the unmodified PII protein act as a signal to the DraT enzyme to ADP-ribosylate the Fe-protein in response to ammonium shock, and that it also inhibits nif gene expression. In cells over-expressing the PZ protein the nitrogenase reactivation after an ammonium shock was delayed indicating that the PZ protein is involved in regulation of DraG activity.
Collapse
Affiliation(s)
- Luciano F Huergo
- Department of Biochemistry and Molecular Biology, Universidade Federal do Paraná, CP 19046, 81531-990, Curitiba, PR, Brazil
| | | | | | | | | | | | | |
Collapse
|
10
|
Galvão CW, Pedrosa FO, Souza EM, Yates MG, Chubatsu LS, Steffens MBR. Expression, purification, and DNA-binding activity of the Herbaspirillum seropedicae RecX protein. Protein Expr Purif 2005; 35:298-303. [PMID: 15135406 DOI: 10.1016/j.pep.2004.01.014] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2003] [Revised: 01/27/2004] [Indexed: 11/18/2022]
Abstract
The Herbaspirillum seropedicae RecX protein participates in the SOS response: a process in which the RecA protein plays a central role. The RecX protein of the H. seropedicae, fused to a His-tag sequence (RecX His-tagged), was over-expressed in Escherichia coli and purified by metal-affinity chromatography to yield a highly purified and active protein. DNA band-shift assays showed that the RecX His-tagged protein bound to both circular and linear double-stranded DNA and also to circular single-stranded DNA. The apparent affinity of RecX for DNA decreased in the presence of Mg(2+) ions. The ability of RecX to bind DNA may be relevant to its function in the SOS response.
Collapse
Affiliation(s)
- Carolina W Galvão
- Department of Biochemistry and Molecular Biology, Universidade Federal do Paraná, C.P. 19046, Curitiba, PR 81531-990, Brazil
| | | | | | | | | | | |
Collapse
|
11
|
Bonatto AC, Souza EM, Pedrosa FO, Yates MG, Benelli EM. Effect of T- and C-loop mutations on the Herbaspirillum seropedicae GlnB protein in nitrogen signalling. Res Microbiol 2005; 156:634-40. [PMID: 15950123 DOI: 10.1016/j.resmic.2005.01.015] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2004] [Revised: 01/19/2005] [Accepted: 01/24/2005] [Indexed: 11/28/2022]
Abstract
Proteins of the PII family are found in species of all kingdoms. Although these proteins usually share high identity, their functions are specific to the different organisms. Comparison of structural data from Escherichia coli GlnB and GlnK and Herbaspirillum seropedicae GlnB showed that the T-loop and C-terminus were variable regions. To evaluate the role of these regions in signal transduction by the H. seropedicae GlnB protein, four mutants were constructed: Y51F, G108A/P109a, G108W and Q3R/T5A. The activities of the native and mutated proteins were assayed in an E. coli background constitutively expressing the Klebsiella pneumoniae nifLA operon. The results suggested that the T-loop and C-terminus regions of H. seropedicae GlnB are involved in nitrogen signal transduction.
Collapse
Affiliation(s)
- Ana C Bonatto
- Departamento de Bioquímica e Biologia Molecular, Universidade Federal do Paraná, C. Postal 19046, CEP 81531-990, Curitiba, PR, Brazil
| | | | | | | | | |
Collapse
|
12
|
Huergo LF, Souza EM, Steffens MBR, Yates MG, Pedrosa FO, Chubatsu LS. Effects of over-expression of the regulatory enzymes DraT and DraG on the ammonium-dependent post-translational regulation of nitrogenase reductase in Azospirillum brasilense. Arch Microbiol 2005; 183:209-17. [PMID: 15723223 DOI: 10.1007/s00203-005-0763-z] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2004] [Revised: 01/20/2005] [Accepted: 01/28/2005] [Indexed: 10/25/2022]
Abstract
Nitrogen fixation in Azospirillum brasilense is regulated at transcriptional and post-translational levels. Post-translational control occurs through the reversible ADP-ribosylation of dinitrogenase reductase (Fe Protein), mediated by the dinitrogenase reductase ADP-ribosyltransferase (DraT) and dinitrogenase reductase glycohydrolase (DraG). Although the DraT and DraG activities are regulated in vivo, the molecules responsible for such regulation remain unknown. We have constructed broad-host-range plasmids capable of over-expressing, upon IPTG induction, the regulatory enzymes DraT and DraG as six-histidine-N-terminal fused proteins (His). Both DraT-His and DraG-His are functional in vivo. We have analyzed the effects of DraT-His and DraG-His over-expression on the post-translational modification of Fe Protein. The DraT-His over-expression led to Fe Protein modification in the absence of ammonium addition, while cells over-expressing DraG-His showed only partial ADP-ribosylation of Fe Protein by adding ammonium. These results suggest that both DraT-His and DraG-His lose their regulation upon over-expression, possible by titrating out negative regulators.
Collapse
Affiliation(s)
- Luciano F Huergo
- Department of Biochemistry and Molecular Biology, Universidade Federal do Paraná, CP 19046, 81531-990 Curitiba, PR, Brazil
| | | | | | | | | | | |
Collapse
|
13
|
Huergo LF, Assumpção MC, Souza EM, Steffens MBR, Yates MG, Chubatsu LS, Pedrosa FO. Repressor mutant forms of the Azospirillum brasilense NtrC protein. Appl Environ Microbiol 2004; 70:6320-3. [PMID: 15466584 PMCID: PMC522079 DOI: 10.1128/aem.70.10.6320-6323.2004] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The Azospirillum brasilense mutant strains FP8 and FP9, after treatment with nitrosoguanidine, showed a null Nif phenotype and were unable to use nitrate as their sole nitrogen source. Sequencing of the ntrC genes revealed single nucleotide mutations in the NtrC nucleotide-binding site. The phenotypes of these strains are discussed in relation to their genotypes.
Collapse
Affiliation(s)
- Luciano F Huergo
- Department of Biochemistry and Molecular Biology, Universidade Federal do Paraná, CP 19046, 81531-990 Curitiba, Paraná, Brazil
| | | | | | | | | | | | | |
Collapse
|
14
|
Klassen G, de Oliveira Pedrosa F, de Souza EM, Yates MG, Rigo LU. Nitrogenase activity of Herbaspirillum seropedicae grown under low iron levels requires the products of nifXorf1 genes. FEMS Microbiol Lett 2003; 224:255-9. [PMID: 12892890 DOI: 10.1016/s0378-1097(03)00453-1] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Herbaspirillum seropedicae strains mutated in the nifX or orf1 genes showed 90% or 50% reduction in nitrogenase activity under low levels of iron or molybdenum respectively. Mutations in nifX or orf1 genes did not affect nif gene expression since a nifH::lacZ fusion was fully active in both mutants. nifX and the contiguous gene orf1 are essential for maximum nitrogen fixation under iron limitation and are probably involved in synthesis of nitrogenase iron or iron-molybdenum clusters.
Collapse
Affiliation(s)
- Giseli Klassen
- Departamento de Patologia Básica, Universidade Federal do Paraná, CP 19046, 81531-990 Curitiba PR, Brazil.
| | | | | | | | | |
Collapse
|
15
|
Twerdochlib AL, Chubatsu LS, Souza EM, Pedrosa FO, Steffens MBR, Yates MG, Rigo LU. Expression, purification, and DNA-binding activity of the solubilized NtrC protein of Herbaspirillum seropedicae. Protein Expr Purif 2003; 30:117-23. [PMID: 12821329 DOI: 10.1016/s1046-5928(03)00074-3] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
NtrC is a bacterial enhancer-binding protein (EBP) that activates transcription by the sigma54 RNA polymerase holoenzyme. NtrC has a three domain structure typical of EBP family. In Herbaspirillum seropedicae, an endophytic diazotroph, NtrC regulates several operons involved in nitrogen assimilation, including glnAntrBC. In order to over-express and purify the NtrC protein, DNA fragments containing the complete structural gene for the whole protein, and for the N-terminal+Central and Central+C-terminal domains were cloned into expression vectors. The NtrC and NtrC(N-terminal+Central) proteins were over-expressed as His-tag fusion proteins upon IPTG addition, solubilized using N-lauryl-sarcosyl and purified by metal affinity chromatography. The over-expressed His-tag-NtrC(Central+C-terminal) fusion protein was partially soluble and was also purified by affinity chromatography. DNA band-shift assays showed that the NtrC protein and the Central+C-terminal domains bound specifically to the H. seropedicae glnA promoter region. The C-terminal domain is presumably necessary for DNA-protein interaction and DNA-binding does not require a phosphorylated protein.
Collapse
Affiliation(s)
- Adriana L Twerdochlib
- Department of Biochemistry and Molecular Biology, Universidade Federal do Paraná, Caixa Postal 19046, Curitiba, PR 81531-990, Brazil
| | | | | | | | | | | | | |
Collapse
|
16
|
Huergo LF, Souza EM, Steffens MBR, Yates MG, Pedrosa FO, Chubatsu LS. Regulation of glnB gene promoter expression in Azospirillum brasilense by the NtrC protein. FEMS Microbiol Lett 2003; 223:33-40. [PMID: 12798997 DOI: 10.1016/s0378-1097(03)00346-x] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022] Open
Abstract
In Azospirillum brasilense the glnB and glnA genes are clustered in an operon regulated by three different promoters: two located upstream of glnB (glnBp1-sigma(70), and glnBp2-sigma(N)) and one as yet unidentified promoter, in the glnBA intergenic region. We have investigated the expression of the glnB gene promoter using glnB-lacZ gene fusions, mutation analysis, heterologous expression and DNA band-shift assays. Deletion of the glnB promoter region showed that NtrC-binding sequences were essential for glnB expression under nitrogen limitation. The A. brasilense NtrC protein activated transcription of glnB-lacZ fusions in the heterologous genetic background of Escherichia coli. Expression of glnB-lacZ fusions in two A. brasilense ntrC mutants differed from that in the wild-type strain. In vitro studies also indicated that the purified NtrC protein from E. coli was able to bind to the glnB promoter region of A. brasilense. Our results show that the NtrC protein activates glnBglnA expression under nitrogen limitation in A. brasilense.
Collapse
Affiliation(s)
- Luciano F Huergo
- Department of Biochemistry and Molecular Biology, Universidade Federal do Paraná, CP 19046, 81531-990, PR, Curitiba, Brazil
| | | | | | | | | | | |
Collapse
|
17
|
Monteiro RA, de Souza EM, Yates MG, Pedrosa FO, Chubatsu LS. Fnr is involved in oxygen control of Herbaspirillum seropedicae N-truncated NifA protein activity in Escherichia coli. Appl Environ Microbiol 2003; 69:1527-31. [PMID: 12620839 PMCID: PMC150060 DOI: 10.1128/aem.69.3.1527-1531.2003] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Herbaspirillum seropedicae is an endophytic diazotroph belonging to the beta-subclass of the class Proteobacteria, which colonizes many members of the Gramineae. The activity of the NifA protein, a transcriptional activator of nif genes in H. seropedicae, is controlled by ammonium ions through its N-terminal domain and by oxygen through mechanisms that are not well understood. Here we report that the NifA protein of H. seropedicae is inactive and more susceptible to degradation in an fnr Escherichia coli background. Both effects correlate with oxygen exposure and iron deprivation. Our results suggest that the oxygen sensitivity and iron requirement for H. seropedicae NifA activity involve the Fnr protein.
Collapse
Affiliation(s)
- Rose A Monteiro
- Department of Biochemistry and Molecular Biology, Universidade Federal do Paraná, CP 19046, Curitiba, PR 81531-990, Brazil
| | | | | | | | | |
Collapse
|
18
|
Monteiro RA, Souza EM, Geoffrey Yates M, Steffens MBR, Pedrosa FO, Chubatsu LS. Expression, purification, and functional analysis of the C-terminal domain of Herbaspirillum seropedicae NifA protein. Protein Expr Purif 2003; 27:313-8. [PMID: 12597891 DOI: 10.1016/s1046-5928(02)00635-6] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
The Herbaspirillum seropedicae NifA protein is responsible for nif gene expression. The C-terminal domain of the H. seropedicae NifA protein, fused to a His-Tag sequence (His-Tag-C-terminal), was over-expressed and purified by metal-affinity chromatography to yield a highly purified and active protein. Band-shift assays showed that the NifA His-Tag-C-terminal bound specifically to the H. seropedicae nifB promoter region in vitro. In vivo analysis showed that this protein inhibited the Central + C-terminal domains of NifA protein from activating the nifH promoter of K. pneumoniae in Escherichia coli, indicating that the protein must be bound to the NifA-binding site (UAS site) at the nifH promoter region to activate transcription.
Collapse
Affiliation(s)
- Rose A Monteiro
- Department of Biochemistry and Molecular Biology, Universidade Federal do Paraná CP 19046, Curitiba, PR 81531-990, Brazil
| | | | | | | | | | | |
Collapse
|
19
|
Galvão CW, Pedrosa FO, Souza EM, Yates MG, Chubatsu LS, Steffens MBR. The recX gene product is involved in the SOS response in Herbaspirillum seropedicae. Can J Microbiol 2003; 49:145-50. [PMID: 12718403 DOI: 10.1139/w03-010] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The recA and the recX genes of Herbaspirillum seropedicae were sequenced. The recX is located 359 bp downstream from recA. Sequence analysis indicated the presence of a putative operator site overlapping a probable sigma70-dependent promoter upstream of recA and a transcription terminator downstream from recX, with no apparent promoter sequence in the intergenic region. Transcriptional analysis using lacZ promoter fusions indicated that recA expression increased three- to fourfold in the presence of methyl methanesulfonate (MMS). The roles of recA and recX genes in the SOS response were determined from studies of chromosomal mutants. The recA mutant showed the highest sensitivity to MMS and UV, and the recX mutant had an intermediate sensitivity, compared with the wild type (SMR1), confirming the essential role of the RecA protein in cell viability in the presence of mutagenic agents and also indicating a role for RecX in the SOS response.
Collapse
Affiliation(s)
- Carolina W Galvão
- Department of Biochemistry and Molecular Biology, Universidade Federal do Parana, C.P. 19046, 81531-990, Curitiba, PR, Brazil
| | | | | | | | | | | |
Collapse
|
20
|
Monteiro RA, de Souza EM, Wassem R, Yates MG, Pedrosa FO, Chubatsu LS. Inter-domain cross-talk controls the NifA protein activity of Herbaspirillum seropedicae. FEBS Lett 2001; 508:1-4. [PMID: 11707257 DOI: 10.1016/s0014-5793(01)03017-4] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Herbaspirillum seropedicae is an endophytic diazotroph, which colonizes sugar cane, wheat, rice and maize. The activity of NifA, a transcriptional activator of nif genes in H. seropedicae, is controlled by ammonium ions through a mechanism involving its N-terminal domain. Here we show that this domain interacts specifically in vitro with the N-truncated NifA protein, as revealed by protection against proteolysis, and this interaction caused an inhibitory effect on both the ATPase and DNA-binding activities of the N-truncated NifA protein. We suggest that the N-terminal domain inhibits NifA-dependent transcriptional activation by an inter-domain cross-talk between the catalytic domain of the NifA protein and its regulatory N-terminal domain in response to fixed nitrogen.
Collapse
Affiliation(s)
- R A Monteiro
- Department of Biochemistry and Molecular Biology, Universidade Federal do Paraná, P.O. Box 19046, Curitiba, PR 81531-990, Brazil
| | | | | | | | | | | |
Collapse
|
21
|
Abstract
The glnZ mutant of Azospirillum brasilense (strain 7611) showed only partial recovery (20 to 40%) after 80 min of ammonia-induced nitrogenase switch-off, whereas the wild type recovered totally within 10 min. In contrast, the two strains showed identical anoxic-induced switch-on/switch-off, indicating no cross talk between the two reactivation mechanisms.
Collapse
Affiliation(s)
- G Klassen
- Departamento de Bioquímica e Biologia Molecular, Universidade Federal do Paraná, 81531-970, Curitiba, Paraná, Brazil
| | | | | | | | | | | |
Collapse
|
22
|
Abstract
The PII protein is apparently involved in the control of NifA activity in Herbaspirillum seropedicae. To evaluate the probable role of PII in signal transduction, uridylylation assays were conducted with purified H. seropedicae PII and Escherichia coli GlnD, or a cell-free extract of H. seropedicae as sources of uridylylating activity. The results showed that alpha-ketoglutarate and ATP stimulate uridylylation whereas glutamine inhibits uridylylation. Deuridylylation of PII-UMP was dependent on glutamine and inhibited by ATP and alpha-ketoglutarate. PII uridylylation and (or) deuridylylation in response to these effectors suggests that PII is a nitrogen level signal transducer in H. seropedicae.
Collapse
Affiliation(s)
- E M Benelli
- Department of Biochemistry, Federal University of Parana, Curitiba, Brazil
| | | | | | | | | |
Collapse
|
23
|
Pedrosa FO, Benelli EM, Yates MG, Wassem R, Monteiro RA, Klassen G, Steffens MB, Souza EM, Chubatsu LS, Rigo LU. Recent developments in the structural organization and regulation of nitrogen fixation genes in Herbaspirillum seropedicae. J Biotechnol 2001; 91:189-95. [PMID: 11566390 DOI: 10.1016/s0168-1656(01)00343-1] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Herbaspirillum seropedicae is a nitrogen-fixing bacterium found in association with economically important gramineae. Regulation of nitrogen fixation involves the transcriptional activator NifA protein. The regulation of NifA protein and its truncated mutant proteins is described and compared with that of other nitrogen fixation bacteria. Nitrogen fixation control in H. seropedicae, of the beta-subgroup of Proteobacteria, has regulatory features in common with Klebsiella pneumoniae, of the gamma-subgroup, at the level of nifA expression and with rhizobia and Azospirillum brasilense, of the alpha-subgroup, at the level of control of NifA by oxygen.
Collapse
Affiliation(s)
- F O Pedrosa
- Department of Biochemistry, Universidade Federal do Paraná, C. Postal 19046, CEP 81531-990 PR, Curitiba, Brazil.
| | | | | | | | | | | | | | | | | | | |
Collapse
|
24
|
Abstract
Three Azospirillum brasilense mutants constitutive for nitrogen fixation (Nif(C)) in the presence of NH4(+) and deficient in nitrate-dependent growth were used as tools to define the roles of the glnB and ntrYX genes in this organism. Mutant HM14 was complemented for nitrate-dependent growth and NH4(+) regulation of nitrogenase by plasmid pL46 which contains the ntrYX genes of A. brasilense. Mutant HM26 was restored for NH4(+) regulation and nitrate-dependent growth by plasmid pJC1, carrying the A. brasilense glnB gene expressed from a constitutive promoter. Mutant HM053, on the other hand, was not complemented for NH4(+) regulation of nitrogenase and nitrate-dependent growth by both plasmids pJCI and pL46. The levels and control of glutamine synthetase activity of all mutants were not affected by both plasmids pL46 (ntrYX) and pJC1 (glnB). These results support the characterization of strains HM14 as an ntrYX mutant and strain HM26 as a glnB mutant and the involvement of ntrYX and glnB in the regulation of the general nitrogen metabolism in A. brasilense.
Collapse
Affiliation(s)
- J C Vitorino
- Department of Biochemistry, UFPR, Curitiba, Brazil
| | | | | | | | | | | |
Collapse
|
25
|
Persuhn DC, Souza EM, Steffens MB, Pedrosa FO, Yates MG, Rigo LU. The transcriptional activator NtrC controls the expression and activity of glutamine synthetase in Herbaspirillum seropedicae. FEMS Microbiol Lett 2000; 192:217-21. [PMID: 11064198 DOI: 10.1111/j.1574-6968.2000.tb09385.x] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022] Open
Abstract
The role of the Ntr system in Herbaspirillum seropedicae was determined via ntrB and ntrC mutants. Three phenotypes were identified in these mutants: Nif(-), deficiency in growth using nitrate, and low glutamine synthetase (GS) activity. All phenotypes were restored by the plasmid pKRT1 containing the intact glnA, ntrB and ntrC genes of H. seropedicae. The promoter region of glnA was subcloned into a beta-galactosidase fusion vector and the results suggested that NtrC positively regulates the glnA promoter in response to low nitrogen. The H. seropedicae ntrC and ntrB mutant strains showed a deficiency of adenylylation/deadenylylation of GS, indicating that NtrC and NtrB are involved in both transcription and activity control of GS in this organism.
Collapse
Affiliation(s)
- D C Persuhn
- Departamento de Bioquímica, Universidade Federal do Paraná, C. Postal 19046, 81531-990, PR, Curitiba, Brazil
| | | | | | | | | | | |
Collapse
|
26
|
Monteiro RA, Souza EM, Yates MG, Pedrosa FO, Chubatsu LS. Use of lactose to induce expression of soluble NifA protein domains of Herbaspirillum seropedicae in Escherichia coli. Can J Microbiol 2000; 46:1087-90. [PMID: 11109500 DOI: 10.1139/w00-094] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Overexpression and purification are procedures used to allow functional and structural characterization of proteins. Many overexpressed proteins are partially or completely insoluble, and can not be easily purified. The NifA protein is an enhancer-binding protein involved in activating the expression of nif and some fix genes. The NifA protein from many organisms is usually insoluble when over-expressed, and therefore difficult to work with in vitro. In this work we have overexpressed the central + C-terminal and the central domains of the Herbaspirrilum seropedicae NifA protein in an Escherichia coli background. Expression was induced with either IPTG or lactose. The data showed that induction with lactose promoted a significantly higher percentage of these proteins in the soluble fraction than with IPTG. This probably reflects a slower kinetics of induction by lactose.
Collapse
Affiliation(s)
- R A Monteiro
- Department of Biochemistry, Universidade Federal do Paraná, Curitiba, Brazil
| | | | | | | | | |
Collapse
|
27
|
Abstract
Azospirillum species are plant-associated diazotrophs of the alpha subclass of Proteobacteria. The genomes of five of the six Azospirillum species were analyzed by pulsed-field gel electrophoresis. All strains possessed several megareplicons, some probably linear, and 16S ribosomal DNA hybridization indicated multiple chromosomes in genomes ranging in size from 4.8 to 9.7 Mbp. The nifHDK operon was identified in the largest replicon.
Collapse
Affiliation(s)
- C C Martin-Didonet
- Departamento de Bioquímica, Universidade Federal do Paraná, CEP-81531-990, Curitiba-PR, Brazil
| | | | | | | | | | | | | | | |
Collapse
|
28
|
Souza EM, Pedrosa FO, Rigo LU, Machado HB, Yates MG. Expression of the nifA gene of Herbaspirillum seropedicae: role of the NtrC and NifA binding sites and of the -24/-12 promoter element. Microbiology (Reading) 2000; 146 ( Pt 6):1407-1418. [PMID: 10846219 DOI: 10.1099/00221287-146-6-1407] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
The nifA promoter of Herbaspirillum seropedicae contains potential NtrC, NifA and IHF binding sites together with a -12/-24 sigma(N)-dependent promoter. This region has now been investigated by deletion mutagenesis for the effect of NtrC and NifA on the expression of a nifA::lacZ fusion. A 5' end to the RNA was identified at position 641, 12 bp downstream from the -12/-24 promoter. Footprinting experiments showed that the G residues at positions -26 and -9 are hypermethylated, and that the region from -10 to +10 is partially melted under nitrogen-fixing conditions, confirming that this is the active nifA promoter. In H. seropedicae nifA expression from the sigma(N)-dependent promoter is repressed by fixed nitrogen but not by oxygen and is probably activated by the NtrC protein. NifA protein is apparently not essential for nifA expression but it can still bind the NifA upstream activating sequence.
Collapse
Affiliation(s)
- E M Souza
- BBSRC, IPSR - Nitrogen Fixation Laboratory, University of Norwich, Norwich, UK1
| | - F O Pedrosa
- Departamento de Bioquı́mica - UFPR, C. Postal 19046, 81531-970, Curitiba, PR, Brazil2
| | - L U Rigo
- Departamento de Bioquı́mica - UFPR, C. Postal 19046, 81531-970, Curitiba, PR, Brazil2
| | - H B Machado
- Departamento de Farmacologia, UFPR, 81531-990, Curitiba, PR, Brazil3
| | - M G Yates
- BBSRC, IPSR - Nitrogen Fixation Laboratory, University of Norwich, Norwich, UK1
| |
Collapse
|
29
|
Abstract
Control of transcription in prokaryotes often involves direct contact of regulatory proteins with RNA polymerase. For the sigma54 RNA polymerase, regulatory proteins bound to distally located enhancers engage the polymerase via DNA looping. The sigma54-dependent nifA promoter of Herbaspirillum seropedicae (Hs) is activated under nitrogen-limiting growth conditions. Potential enhancers for the nitrogen control activators NTRC and NIFA and binding sites for integration host factor (IHF) and sigma54-holoenzyme were identified. DNA footprinting experiments showed that these sites functioned for protein binding. Their involvement in the promoter regulation was explored. In vitro, activation of the Hs nifA promoter by NTRC is stimulated by the DNA bending protein IHF. In marked contrast, activation by NIFA is greatly reduced by IHF, thus diminishing potentially destabilizing autoactivation of the nifA promoter by NIFA. Additionally, high levels of NIFA appear to limit NTRC-dependent activation. This inhibition is IHF dependent. Therefore, IHF acts positively and negatively at the nifA promoter to restrict transcription activation to NTRC and one signal transduction pathway.
Collapse
Affiliation(s)
- R Wassem
- Departamento de Bioquímica, Universidade Federal do Paraná, Caixa Postal 19046, Curitiba - PR, CEP 81531-990, Brazil
| | | | | | | | | |
Collapse
|
30
|
Monteiro RA, Souza EM, Yates MG, Pedrosa FO, Chubatsu LS. Use of lactose to induce expression of soluble NifA protein domains of <i>Herbaspirillum seropedicae </i>in <i>Escherichia coli</i>. Can J Microbiol 2000. [DOI: 10.1139/cjm-46-11-1087] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
|
31
|
Klassen G, Pedrosa FO, Souza EM, Yates MG, Rigo LU. Sequencing and functional analysis of the nifENXorf1orf2 gene cluster of Herbaspirillum seropedicae. FEMS Microbiol Lett 1999; 181:165-70. [PMID: 10564803 DOI: 10.1111/j.1574-6968.1999.tb08840.x] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
Abstract
A 5.1-kb DNA fragment from the nifHDK region of H. seropedicae was isolated and sequenced. Sequence analysis showed the presence of nifENXorf1orf2 but nifTY were not present. No nif or consensus promoter was identified. Furthermore, orf1 expression occurred only under nitrogen-fixing conditions and no promoter activity was detected between nifK and nifE, suggesting that these genes are expressed from the upstream nifH promoter and are parts of a unique nif operon. Mutagenesis studies indicate that nifN was essential for nitrogenase activity whereas nifXorf1orf2 were not. High homology between the C-terminal region of the NifX and NifB proteins from H. seropedicae was observed. Since the NifX and NifY proteins are important for FeMo cofactor (FeMoco) synthesis, we propose that alternative proteins with similar activities exist in H. seropedicae.
Collapse
Affiliation(s)
- G Klassen
- Departamento de Bioquímica, Universidade Federal do Paraná, C.P. 19046, 81531-990, Curitiba-PR, Brazil
| | | | | | | | | |
Collapse
|
32
|
Monteiro RA, Souza EM, Yates MG, Pedrosa FO, Chubatsu LS. In-trans regulation of the N-truncated-NIFA protein of Herbaspirillum seropedicae by the N-terminal domain. FEMS Microbiol Lett 1999; 180:157-61. [PMID: 10556706 DOI: 10.1111/j.1574-6968.1999.tb08790.x] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022] Open
Abstract
The NifA protein is responsible for transcription activation of nif genes in the endophytic diazotroph Herbaspirillum seropedicae. When expressed in Escherichia coli this NifA protein is unable to activate the transcription of a Klebsiella pneumoniae nifH::lacZ fusion. However, a form of NifA lacking the N-terminal domain did activate transcription and its activity was not inhibited by ammonium. In this work we show that when expressed separately, the N-terminal domain of H. seropedicae NifA protein can restore ammonium control of the N-truncated NifA activity in E. coli. This effect is dependent on the relative concentrations of the N-terminal domain and the N-truncated protein and suggests that the N-terminal domain behaves in this respect in a manner similar to that of NifL of the gamma proteobacteria.
Collapse
Affiliation(s)
- R A Monteiro
- Department of Biochemistry, Universidade Federal do Paraná, CP 19046, Curitiba, Brazil
| | | | | | | | | |
Collapse
|
33
|
Fadel-Picheth CM, Souza EM, Rigo LU, Funayama S, Yates MG, Pedrosa FO. Regulation of Azospirillum brasilense nifA gene expression by ammonium and oxygen. FEMS Microbiol Lett 1999; 179:281-8. [PMID: 10518727 DOI: 10.1111/j.1574-6968.1999.tb08739.x] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
Abstract
The structure and activity of the nifA promoter of Azospirillum brasilense was studied using deletion analysis. An essential region for nifA promoter activity was identified between nucleotides -67 and -47 from the identified transcription start site. A sequence resembling a sigma(70) recognition site occurs in this region and may constitute the nifA gene promoter. The regulation of the nifA gene was studied in plasmid and chromosomal nifA::lacZ fusions. Full expression was obtained under low oxygen levels and in the absence of ammonium ions. Repression of nifA expression involves a synergistic effect between oxygen and ammonium.
Collapse
Affiliation(s)
- C M Fadel-Picheth
- Department of Medical Pathology, UFPR, C. Postal 19046, CEP 81531-990, Curitiba, Brazil
| | | | | | | | | | | |
Collapse
|
34
|
Monteiro RA, Souza EM, Funayama S, Yates MG, Pedrosa FO, Chubatsu LS. Expression and functional analysis of an N-truncated NifA protein of Herbaspirillum seropedicae. FEBS Lett 1999; 447:283-6. [PMID: 10214962 DOI: 10.1016/s0014-5793(99)00314-2] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
In Herbaspirillum seropedicae, an endophytic diazotroph, nif gene expression is under the control of the transcriptional activator NifA. We have over-expressed and purified a protein containing the central and C-terminal domains of the H. seropedicae NifA protein, N-truncated NifA, fused to a His-Tag sequence. This fusion protein was found to be partially soluble and was purified by affinity chromatography. Band shift and footprinting assays showed that the N-truncated NifA protein was able to bind specifically to the H. seropedicae nifB promoter region. In vivo analysis showed that this protein activated the nifH promoter of Klebsiella pneumoniae in Escherichia coli only in the absence of oxygen and this activation was not negatively controlled by ammonium ions.
Collapse
Affiliation(s)
- R A Monteiro
- Department of Biochemistry, Universidade Federal do Paraná, Curitiba PR, Brazil
| | | | | | | | | | | |
Collapse
|
35
|
Abstract
The activity of a truncated form of Herbaspirillum seropedicae NifA in different genetic backgrounds showed that its regulatory domain is involved in nitrogen control but not in O2 sensitivity or Fe dependence. The model for nitrogen control involving PII could thus apply to the proteobacteria at large. NifA may have a role in controlling ADP-ribosylation of nitrogenase in Azospirillum brasilense.
Collapse
Affiliation(s)
- E M Souza
- Department of Biochemistry and Department of Pharmacology, Universidade Federal do Paranà, Curitiba, PR, Brazil.
| | | | | | | | | |
Collapse
|
36
|
Machado IM, Yates MG, Machado HB, Souza EM, Pedrosa FO. Cloning and sequencing of the nitrogenase structural genes nifHDK of Herbaspirillum seropedicae. Braz J Med Biol Res 1996; 29:1599-602. [PMID: 9222418] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
The nitrogenase structural genes (nifHDK) of the endophytic diazotroph Herbaspirillum seropedicae were isolated from a genomic bank by plate hybridization. Sequence analysis of the DNA showed a consensus promoter region upstream for the nifH gene containing a -24/-12 type promoter together with NifA- and integration host factor (IHF)- binding sites. The derived protein sequences of NifH, NifD and NifK contained conserved cysteine residues for binding iron-sulfur clusters and the iron-molybdenum cofactor. These protein sequences showed the strongest similarities to the nifHDK gene products of the symbiotic diazotroph Bradyrhizobium japonicum (93.5%, 91.3% and 83.3%, respectively), the plant-associated diazotroph Azospirillum brasilense (90.0%, 83.7% and 75.1%, respectively) and to Thiobacillus ferrooxidans (91.0%, 83.4% and 81.1%, respectively) of the same phylogenetic group of the protobacteria.
Collapse
Affiliation(s)
- I M Machado
- Departamento de Bioquímica, Universidade Federal do Paraná, Curitiba, PR, Brasil
| | | | | | | | | |
Collapse
|
37
|
Machado HB, Yates MG, Funayama S, Rigo LU, Steffens MB, Souza EM, Pedrosa FO. The ntrBC genes of Azospirillum brasilense are part of a nifR3-like-ntrB-ntrC operon and are negatively regulated. Can J Microbiol 1995; 41:674-84. [PMID: 7553451 DOI: 10.1139/m95-093] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
A cosmid able to complement the Nif- and nitrate-dependent growth phenotypes of the Azospirillum brasilense mutant FP9 was isolated from a genomic library of the wild-type strain FP2. A 6-kb DNA region was sequenced and showed two open reading frames (ORFs) identified as the ntrB and ntrC genes. An ORF1 located upstream from the ntrB gene and coding for a 36-kDa polypeptide showed similarity to the nifR3 gene of Rhodobacter capsulatus and the ORF1 of Rhizobium leguminosarum, both located upstream from the ntrB gene in a complex operon. Two other unidentified ORFs (ORF5 and partial ORF4) coding for hydrophobic polypeptides were also observed. delta ORF1-ntrBC, ORF1, ntrB, and ntrC mutants obtained by recombination of suicide plasmids containing an insertion of a promoterless lacZ kanamycin cassette showed decreased nitrogenase activities and were unable to grow on nitrate as the sole N source. These phenotypes were restored by complementation with plasmids containing the ntrC gene. Analysis of lacZ transcriptional fusions suggested that the ORF1-ntrBC operon in Azospirillum brasilense is expressed from a promoter located upstream from the ORF1 and that it is negatively regulated by the ntrC gene product.
Collapse
Affiliation(s)
- H B Machado
- Department of Pharmacology, Universidade Federal do Paraná, Curitiba, PR, Brazil
| | | | | | | | | | | | | |
Collapse
|
38
|
Du L, Tibelius KH, Souza EM, Garg RP, Yates MG. Sequences, organization and analysis of the hupZMNOQRTV genes from the Azotobacter chroococcum hydrogenase gene cluster. J Mol Biol 1994; 243:549-57. [PMID: 7966281 DOI: 10.1016/0022-2836(94)90029-9] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
Hydrogen-uptake (Hup) activity in Azotobacter chroococcum depends upon a cluster of genes spread over 13,687 bp of the chromosome. Six accessory genes of the cluster, hupABYCDE, begin 4.8 kb downstream of the structural genes, hupSL, and are required for the formation of a functional [NiFe] hydrogenase. The sequencing of the intervening 4.8 kb of hup-specific DNA has now been completed. This revealed eight additional closely linked ORFs, which we designated hupZ, hupM, hupN, hupO, hupQ, hupR, hupT and hupV. These genes potentially encode polypeptides with predicted masses of 27.7, 22.3, 11.4, 16.2, 31.3, 8.1, 16.2 and 36.7 kDa, respectively. All eight genes are transcribed from the same strand as hupSL and hupABYCDE. A chroococcum, therefore, has a total of 16 contiguous genes affecting hydrogenase activity beginning with hupS and ending with hupE. The amino acid sequence deduced from hupZ has the characteristics of a b-type cytochrome. Insertion mutagenesis of hupZ resulted in a mutant incapable of supporting O2-dependent H2 oxidation. The deduced amino acid sequence of hupR shares high homology with bacterial rubredoxins. HupZ and HupR may both be involved in transferring electrons from hydrogenase to the electron transport chain. A mutation in hupV knocked out hydrogenase activity entirely; this gene may be involved in processing the large subunit of hydrogenase. It is now clear that the genes controlling [NiFe] hydrogenase activity in many bacteria including Azotobacter chroococcum, Alcaligenes eutrophus, Rhizobium leguminosarum, Rhodobacter capsulatus and Escherichia coli are highly conserved, organized in much the same manner, and likely derived from a common ancestor.
Collapse
Affiliation(s)
- L Du
- Department of Microbiology, McGill University, Quebec, Canada
| | | | | | | | | |
Collapse
|
39
|
Souza EM, Funayama S, Rigo LU, Yates MG, Pedrosa FO. Sequence and structural organization of a nif A-like gene and part of a nifB-like gene of Herbaspirillum seropedicae strain Z78. J Gen Microbiol 1991; 137:1511-22. [PMID: 1840608 DOI: 10.1099/00221287-137-7-1511] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
The deduced amino acid sequence derived from the sequence of a fragment of DNA from the free-living diazotroph Herbaspirillum seropedicae was aligned to the homologous protein sequences encoded by the nifA genes from Azorhizobium caulinodans, Rhizobium leguminosarum, Rhizobium meliloti and Klebsiella pneumoniae. High similarity was found in the central domain and in the C-terminal region. The H. seropedicae putative NifA sequence was also found to contain an interdomain linker similar to that conserved among rhizobial NifA proteins, but not K. pneumoniae or Azotobacter vinelandii. Analysis of the regulatory sequences found 5' from nifA indicated that the expression of this gene in H. seropedicae is likely to be controlled by NifA, NtrC and RpoN, as judged by the presence of specific NifA- and NtrC-binding sites and characteristic -24/-12 promoters. Possible additional regulatory features included an 'anaerobox' and a site for integration host factor. The N-terminus of another open reading frame was found 3' from nifA and tentatively identified as nifB by amino acid sequence comparison. The putative nifB promoter sequence suggests that expression of H. seropedicae nifB may be activated by NifA and dependent on RpoN.
Collapse
Affiliation(s)
- E M Souza
- Universidade Federal do Paraná, Department of Biochemistry, Curitiba, PR, Brazil
| | | | | | | | | |
Collapse
|
40
|
Kelly MJ, Poole RK, Yates MG, Kennedy C. Cloning and mutagenesis of genes encoding the cytochrome bd terminal oxidase complex in Azotobacter vinelandii: mutants deficient in the cytochrome d complex are unable to fix nitrogen in air. J Bacteriol 1990; 172:6010-9. [PMID: 2170336 PMCID: PMC526923 DOI: 10.1128/jb.172.10.6010-6019.1990] [Citation(s) in RCA: 127] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
The genome of Azotobacter vinelandii contains DNA sequences homologous to the structural genes for the Escherichia coli cytochrome bd terminal oxidase complex. Two recombinant clones bearing cydA- and cydB-like sequence were isolated from an A. vinelandii gene library and subcloned into the plasmid vector pACYC184. Physical mapping demonstrated that the cydA- and cydB-like regions in A. vinelandii are contiguous. The cydAB and flanking DNA was mutagenized by the insertion of Tn5-B20. Mutations in the cydB-hybridizing region resulted in the loss of spectral features associated with cytochromes b595 and d. A new locus, cydB, encoding cytochromes b595 and d in A. vinelandii is proposed. A second region adjacent to cydB was also involved in expression of the cytochrome bd complex in A. vinelandii, since mutations in this region resulted in an increase in the levels of both cytochrome b595 and cytochrome d. The regions involved in expression of the cytochrome bd complex and cydB are transcribed in the same direction. Mutants deficient in cytochromes b595 and d were unable to grow on N-deficient medium when incubated in air but could fix nitrogen when the environmental O2 concentration was reduced to 1.5% (vol/vol). It is proposed that the branch of the respiratory chain terminated by the cytochrome bd complex supports the high respiration rates required for the respiratory protection of nitrogenase.
Collapse
Affiliation(s)
- M J Kelly
- Division of Biosphere Sciences, Kings College London, United Kingdom
| | | | | | | |
Collapse
|
41
|
Ford CM, Garg N, Garg RP, Tibelius KH, Yates MG, Arp DJ, Seefeldt LC. The identification, characterization, sequencing and mutagenesis of the genes (hupSL) encoding the small and large subunits of the H2-uptake hydrogenase of Azotobacter chroococcum. Mol Microbiol 1990; 4:999-1008. [PMID: 2215219 DOI: 10.1111/j.1365-2958.1990.tb00672.x] [Citation(s) in RCA: 48] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
The structural genes (hupSL) of the membrane-bound NiFe-containing H2-uptake hydrogenase (Hup) of Azotobacter chroococcum were identified by oligonucleotide screening and sequenced. The small subunit gene (hupS) encodes a signal sequence of 34 amino acids followed by a 310-amino-acid, 34156D protein containing 12 cysteine residues. The large subunit gene (hupL) overlaps hupS by one base and codes for a predicted 601-amino-acid, 66433D protein. There are two regions of strong homology with other Ni hydrogenases: a Cys-Thr-Cys-Cys-Ser motif near the N-terminus of HupS and an Asp-Pro-Cys-Leu-Ala-Cys motif near the carboxy-terminus of HupL. Strong overall homology exists between Azotobacter, Bradyrhizobium japonicum and Rhodobacter capsulatus Hup proteins but less exists between the Azotobacter proteins and hydrogenases from Desulfovibrio strains. Mutagenesis of either hupS or hupL genes of A. chroococcum yielded Hup- phenotypes but some of these mutants retained a partial H2-evolving activity. Hybridization experiments at different stages of gene segregation confirmed the multicopy nature of the Azotobacter genome.
Collapse
Affiliation(s)
- C M Ford
- AFRC Institute of Plant Science Research, Nitrogen Fixation Laboratory, University of Sussex, Brighton, UK
| | | | | | | | | | | | | |
Collapse
|
42
|
George SJ, Richards AJ, Thomson AJ, Yates MG. Azotobacter chroococcum 7Fe ferredoxin. Two pH-dependent forms of the reduced 3Fe clusters and its conversion to a 4Fe cluster. Biochem J 1984; 224:247-51. [PMID: 6095817 PMCID: PMC1144420 DOI: 10.1042/bj2240247] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
Abstract
Ferredoxin from Azotobacter chroococcum has been studied by low-temperature magnetic-circular-dichroism and electron-paramagnetic-resonance spectroscopy. When aerobically isolated ferredoxin contains a [3Fe-4S] and [4Fe-4S] cluster. Anaerobic treatment with dithionite in the presence of ethanediol reduces the [3Fe-4S] cluster to give two spectroscopically distinct forms RI and RII which are reversibly interconvertible with a pKa approximately 7.5. The higher-pH form, RII, has a high affinity for ferrous ion and converts readily to a [4Fe-4S]1+ cluster, scavenging iron from the medium. The presence of the iron chelator EDTA inhibits this conversion.
Collapse
|
43
|
Partridge CD, Yates MG. Effect of chelating agents on hydrogenase in Azotobacter chroococcum. Evidence that nickel is required for hydrogenase synthesis. Biochem J 1982; 204:339-44. [PMID: 7052066 PMCID: PMC1158350 DOI: 10.1042/bj2040339] [Citation(s) in RCA: 57] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
Abstract
The chelating agents EDTA, o-phenanthroline, nitrilotriacetic acid (NTA), ethylenediamine-bis(o-hydroxyphenylacetic acid) (EDDA) or dimethylglyoxime prevented the expression of hydrogenase activity in batch cultures of nitrogen-fixing Azotobacter chroococcum, but did not inhibit preformed enzyme. The inhibition was reversed either by adding a mixture of trace elements (Cu2+, Mn2+, Zn2+, Co2+) or Ni2+ or, to a lesser degree, Co2+ alone. Ni2+ or Ni2+ + Fe2+ also enhanced the rate of hydrogenase derepression in A. chroococcum in the absence of any added chelator, if the medium was first extracted with 8-hydroxyquinoline. A. chroococcum accumulated 63Ni2+ by an energy-independent mechanism. Both, Ni2+ uptake and hydrogenase synthesis were equally inhibited by either NTA, EDTA, EDDA or dimethylglyoxime. The evidence suggests a role for Ni2+ in hydrogenase synthesis.
Collapse
|
44
|
Miller RW, Robson RL, Yates MG, Eady RR. Catalysis of exchange of terminal phosphate groups of ATP and ADP by purified nitrogenase proteins. Can J Biochem 1980; 58:542-8. [PMID: 7004607 DOI: 10.1139/o80-074] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Abstract
A crude Azotobacter nitrogenase complex contained a highly active adenylate kinase which caused rapid equilibration of AMP, ADP, and ATP. Purified molybdenum-iron protein preparations also contained measurable adenylate kinase activity which could be removed by adsorption and elution from hydroxylapatite. Independent of adenylate kinase, the highly purified molybdenum-iron protein from both Klebsiella pneumoniae and Azotobacter chroococcum catalyzed the exchange of [32P]orthophosphate with the terminal phosphate of ATP or ADP. The exchange labeling of ATP was stimulated by ferricyanide ion due to the inhibition of ATP hydrolysis linked to substrate reductions which cannot occur in the absence of reductant. This exchange reaction is responsible for reported ATP synthesis by crude nitrogenase preparations. Binding of ATP labeled with 32P in the terminal phosphate group was measured directly with concentrated solutions of the molybdenum-iron nitrogenase protein from K. pneumoniae by the column gel filtration method. The protein was saturated with ATP at a calculated ratio of 4.0 +/- 0.3 mol ATP/mol protein; half-saturation of 220 microM protein occurred at 600 +/- 100 microM. The interactions between adenine nucleotides and the molybdenum-iron protein suggest the involvement of the nucleotides in a role distinct from the established reactions with the iron protein of the nitrogenase complex. A dual role for ATP in the reduction of dinitrogen by isolated nitrogenase proteins would be consistent with the existence of binding sites for ATP on both the iron and molybdenum-iron proteins.
Collapse
|
45
|
Abstract
H2 will support nitrogenase activity (C2H2 reduction) in Azotobacter chroococcum with or without added carbon substrate. Results show that H2 is metabolised to transfer electrons to nitrogenase and to the respiratory chain to produce ATP. H2-supported nitrogenase activity is most significant at low carbon substrate concentrations, but also occurs at saturating concentration. Continuous cultures of N2-fixing A. chroococcum evolved H2 from nitrogenase under O2-N2- and C-limited conditions. This H2 represented a significant proportion of nitrogenase activity. Hydrogenase activity was consistently high under C-limited conditions, but low or undetectable under O2- and N2-limitations. Pre-treatment with 40 per cent C2H2 inhibited hydrogenase activity in C-limited cultures, and H2 evolution increased under air and under Ar:O2 (4:1) mixtures. We deduce that hydrogenase : I, recycles H2 produced by nitrogenase to provide electrons and energy for N2 reduction: II, supports respiratory protection for nitrogenase under C-limited conditions, and III, does not act to prevent any inhibition of N2 reduction by H2 produced by nitrogenase. A scheme for the H2 cycle in N2-fixing A. chroococcum is proposed.
Collapse
|
46
|
Berndt H, Lowe DJ, Yates MG. The nitrogen-fixing system of Corynebacterium autotrophicum. Purification and properties of the nitrogenase components and two ferredoxins. Eur J Biochem 1978; 86:133-42. [PMID: 207515 DOI: 10.1111/j.1432-1033.1978.tb12292.x] [Citation(s) in RCA: 37] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
|
47
|
Yates MG, O'Donnell MJ, Lowe DJ, Bothe H. Ferredoxins from nitrogen-fixing bacteria. Physical and chemical characterisation of two ferredoxins from Mycobacterium flavum 301. Eur J Biochem 1978; 85:291-9. [PMID: 205419 DOI: 10.1111/j.1432-1033.1978.tb12238.x] [Citation(s) in RCA: 22] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
|
48
|
Bothe H, Tennigkeit J, Eisbrenner G, Yates MG. The hydrogenase-nitrogenase relationship in the blue-green algaAnabaena cylindrica. Planta 1977; 133:237-242. [PMID: 24425256 DOI: 10.1007/bf00380683] [Citation(s) in RCA: 57] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/24/1976] [Accepted: 09/23/1976] [Indexed: 06/03/2023]
Abstract
Nitrogen-fixingAnabaena cylindrica cells are found to evolve hydrogen in high quantities in the presence of CO plus C2H2. Studies with the inhibitors dichlorophenyldimethylurea (DCMU), disalicylidenepropanediamine (DSPD), dibromothymoquinone (DBMIB), undecylbenzimidazole (UDB) and chloro-carbonyl-cyanide-phenylhydrazone (CCCP) and also withAnabaena grown on nitrate- and ammonia-nitrogen show that the H2-formation is due to the ATP-dependent H3O(+)-reduction catalysed by nitrogenase. In control experiments CO plus C2H2 inhibited the activities of a cell-free hydrogenase fromClostridium pasteurianum. It is concluded that Anabaena has a hydrogenase whose natural function is to recycle the H2 lost by the action of nitrogenase.
Collapse
Affiliation(s)
- H Bothe
- Botanisches Institut der Universität Heidelberg, Hofmeisterweg 4, D-6900, Heidelberg, Germany
| | | | | | | |
Collapse
|
49
|
Yates MG, Lowe DJ. Nitrogenase of Azotobacter chroococcum: a new electron-paramagnetic-resonance signal associated with a transient species of the Mo-Fe protein during catalysis. FEBS Lett 1976; 72:121-6. [PMID: 187450 DOI: 10.1016/0014-5793(76)80826-5] [Citation(s) in RCA: 23] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
|
50
|
|