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Zumft WG. The molecular basis of biological dinitrogen fixation. STRUCTURE AND BONDING 2007. [DOI: 10.1007/bfb0116518] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/11/2023]
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Siemann S, Schneider K, Oley M, Müller A. Characterization of a tungsten-substituted nitrogenase isolated from Rhodobacter capsulatus. Biochemistry 2003; 42:3846-57. [PMID: 12667075 DOI: 10.1021/bi0270790] [Citation(s) in RCA: 39] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
In the phototrophic non-sulfur bacterium Rhodobacter capsulatus, the biosynthesis of the conventional Mo-nitrogenase is strictly Mo-regulated. Significant amounts of both dinitrogenase and dinitrogenase reductase were only formed when the growth medium was supplemented with molybdate (1 microM). During cell growth under Mo-deficient conditions, tungstate, at high concentrations (1 mM), was capable of partially (approximately 25%) substituting for molybdate in the induction of nitrogenase synthesis. On the basis of such conditions, a tungsten-substituted nitrogenase was isolated from R. capsulatus with the aid of anfA (Fe-only nitrogenase defective) mutant cells and partially purified by Q-sepharose chromatography. Metal analyses revealed the protein to contain an average of 1 W-, 16 Fe-, and less than 0.01 Mo atoms per alpha(2)beta(2)-tetramer. The tungsten-substituted (WFe) protein was inactive in reducing N(2) and marginally active in acetylene reduction, but it was found to show considerable activity with respect to the generation of H(2) from protons. The EPR spectrum of the WFe protein, recorded at 4 K, exhibited three distinct signals: (i) an S = 3/2 signal, which dominates the low-field region of the spectrum (g = 4.19, 3.93) and is indicative of a tungsten-substituted cofactor (termed FeWco), (ii) a marginal S = 3/2 signal (g = 4.29, 3.67) that can be attributed to residual amounts of FeMoco present in the protein, and (iii) a broad S = 1/2 signal (g = 2.09, 1.95, 1.86) arising from at least two paramagnetic species. Redox titrational analysis of the WFe protein revealed the midpoint potential of the FeWco (E(m) < -200 mV) to be shifted to distinctly lower potentials as compared to that of the FeMoco (E(m) approximately -50 mV) present in the native enzyme. The P clusters of both the WFe and the MoFe protein appear indistinguishable with respect to their midpoint potentials. EPR spectra recorded with the WFe protein under turnover conditions exhibited a 20% decrease in the intensity of the FeWco signal, indicating that the cofactor can be enzymatically reduced only to a small extent. The data presented in the current study demonstrate the pivotal role of molybdenum in optimal N(2) fixation and provides direct evidence that the inability of a tungsten-substituted nitrogenase to reduce N(2) is due to the difficulty to effectively reduce the FeW cofactor beyond its semi-reduced state.
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Affiliation(s)
- Stefan Siemann
- Department of Chemistry, University of Waterloo, Waterloo, Ontario, N2L 3G1, Canada
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McDowell L, Cohen E, Schaefer J. Two-dimensional, rotational-echo double-resonance NMR of cell culture metabolism. J Biol Chem 1993. [DOI: 10.1016/s0021-9258(19)36849-8] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
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Rodríguez-Quiñones F, Bosch R, Imperial J. Expression of the nifBfdxNnifOQ region of Azotobacter vinelandii and its role in nitrogenase activity. J Bacteriol 1993; 175:2926-35. [PMID: 8491713 PMCID: PMC204610 DOI: 10.1128/jb.175.10.2926-2935.1993] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023] Open
Abstract
The nifBQ transcriptional unit of Azotobacter vinelandii has been previously shown to be required for activity of the three nitrogenase systems, Mo nitrogenase, V nitrogenase, and Fe nitrogenase, present in this organism. We studied regulation of expression and the role of the nifBQ region by means of translational beta-galactosidase fusions to each of the five open reading frames: nifB, orf2 (fdxN), orf3 (nifO), nifQ, and orf5. Expression of the first three open reading frames was observed under all three diazotrophic conditions; expression of orf5 was never observed. Genes nifB and fdxN were expressed at similar levels. With Mo, expression of nifO and nifQ was approximately 20- and approximately 400-fold lower than that of fdxN, respectively. Without Mo, expression of nifB dropped three- to fourfold and that of nifQ dropped to the detection limit. However, expression of nifO increased threefold. The products of nifB, fdxN, nifO, and nifQ have been visualized in A. vinelandii as beta-galactosidase fusion proteins with the expected molecular masses. The NifB- fusion lacked activity for any of the three nitrogenase systems and showed an iron-molybdenum cofactor-deficient phenotype in the presence of Mo. The FdxN- mutation resulted in reduced nitrogenase activities, especially when V was present. Dinitrogenase activity in extracts was similarly affected, suggesting a role of FdxN in iron-molybdenum cofactor synthesis. The NifO(-)-producing mutation did not affect any of the nitrogenases under standard diazotrophic conditions. The NifQ(-)-producing mutation resulted in an increased (approximately 1,000-fold) Mo requirement for Mo nitrogenase activity, a phenotype already observed with Klebsiella pneumoniae. No effect of the NifQ(-)-producing mutation on V or Fe nitrogenase was found; this is consistent with its very low expression under those conditions. Mutations in orf5 had no effect on nitrogenase activity.
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Affiliation(s)
- F Rodríguez-Quiñones
- Institut d'Estudis Avançats, Consejo Superior de Investigaciones Cientificas, Universitat de les Illes Balears, Ctra. de Valldemossa, Palma de Mallorca, Spain
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Karzanov VV, Correa CM, Bogatsky YG, Netrusov AI. Alternative NAD+-dependent formate dehydrogenases in the facultative methylotrophMycobacterium vaccae10. FEMS Microbiol Lett 1991. [DOI: 10.1111/j.1574-6968.1991.tb04719.x] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
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Jacob GS, Schaefer J, Garbow JR, Stejskal EO. Solid-state NMR studies of Klebsiella pneumoniae grown under nitrogen-fixing conditions. J Biol Chem 1987. [DOI: 10.1016/s0021-9258(19)75919-5] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022] Open
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The nifH, nifM and nifN genes of Azotobacter vinelandii: Characterisation by Tn5 mutagenesis and isolation from pLAFR1 gene banks. ACTA ACUST UNITED AC 1986. [DOI: 10.1007/bf00430445] [Citation(s) in RCA: 95] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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Collins JJ, Roberts GP, Brill WJ. Posttranscriptional control of Klebsiella pneumoniae nif mRNA stability by the nifL product. J Bacteriol 1986; 168:173-8. [PMID: 2428807 PMCID: PMC213434 DOI: 10.1128/jb.168.1.173-178.1986] [Citation(s) in RCA: 53] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
Posttranscriptional control of nif mRNA stability was demonstrated by functional and chemical analyses, using specific probes for four nif transcripts. In the wild type, nif transcripts (except nifLA) were stable during derepression, with half-lives of approximately 30 min. They were dramatically destabilized by O2 or elevated temperature (41 degrees C) and to a lesser extent by NH4+. In contrast, the nifLA message was not particularly stable, and posttranscriptional control was not evident. In NifL- strains, both forms of analysis indicated that the nifL product was involved in nif mRNA destabilization in the presence of O2 and NH4+.
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Ugalde RA, Imperial J, Shah VK, Brill WJ. Biosynthesis of the iron-molybdenum cofactor and the molybdenum cofactor in Klebsiella pneumoniae: effect of sulfur source. J Bacteriol 1985; 164:1081-7. [PMID: 3905765 PMCID: PMC219300 DOI: 10.1128/jb.164.3.1081-1087.1985] [Citation(s) in RCA: 37] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023] Open
Abstract
NifQ- and Mol- mutants of Klebsiella pneumoniae show an elevated molybdenum requirement for nitrogen fixation. Substitution of cystine for sulfate as the sulfur source in the medium reduced the molybdenum requirement of these mutants to levels required by the wild type. Cystine also increased the intracellular molybdenum accumulation of NifQ- and Mol- mutants. Cystine did not affect the molybdenum requirement or accumulation in wild-type K. pneumoniae. Sulfate transport and metabolism in K. pneumoniae were repressed by cystine. However, the effect of cystine on the molybdenum requirement could not be explained by an interaction between sulfate and molybdate at the transport level. Cystine increased the molybdenum requirement of Mol- mutants for nitrate reductase activity by at least 100-fold. Cystine had the same effect on the molybdenum requirement for nitrate reductase activity in Escherichia coli ChlD- mutants. This shows that cystine does not have a generalized effect on molybdenum metabolism. Millimolar concentrations of molybdate inhibited nitrogenase and nitrate reductase derepression with sulfate as the sulfur source, but not with cystine. The inhibition was the result of a specific antagonism of sulfate metabolism by molybdate. The effects of nifQ and mol mutations on nitrogenase could be suppressed either by the addition of cystine or by high concentrations of molybdate. This suggests that a sulfur donor and molybdenum interact at an early step in the biosynthesis of the iron-molybdenum cofactor. This interaction might occur nonenzymatically when the levels of the reactants are high.
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Imperial J, Ugalde RA, Shah VK, Brill WJ. Mol- mutants of Klebsiella pneumoniae requiring high levels of molybdate for nitrogenase activity. J Bacteriol 1985; 163:1285-7. [PMID: 3897191 PMCID: PMC219276 DOI: 10.1128/jb.163.3.1285-1287.1985] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023] Open
Abstract
Mol- mutants of Klebsiella pneumoniae requiring high levels of molybdate for nitrogenase and nitrate reductase activity were characterized. The effects of mol mutations on nitrogenase activity were very similar to those caused by nifQ mutations. Mol- mutants of K. pneumoniae appear to be equivalent to ChlD- mutants of Escherichia coli.
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Abstract
Four probes, each specific for a single nif transcript, were used for an analysis of the regulation of nif mRNA synthesis. Transcription of the nifLA operon was repressed by NH4+ but not by amino acids, O2, or temperatures above 37 degrees C. The nifA gene product was required for the activation of transcription of the other nif operons but not nifLA. Synthesis of the other nif transcripts was rapidly turned off by the addition of O2, NH4+, serine, or glutamine. These regulatory effects required the nifL product. However, the nifL product was not required for the cessation of synthesis of these transcripts at elevated temperatures.
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Ugalde RA, Imperial J, Shah VK, Brill WJ. Biosynthesis of iron-molybdenum cofactor in the absence of nitrogenase. J Bacteriol 1984; 159:888-93. [PMID: 6384184 PMCID: PMC215742 DOI: 10.1128/jb.159.3.888-893.1984] [Citation(s) in RCA: 71] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023] Open
Abstract
Klebsiella pneumoniae accumulates molybdenum during nitrogenase derepression. The molybdenum is primarily in nitrogenase component I in the form of iron-molybdenum cofactor (FeMo-co). Mutations in any of three genes (nifB, nifN, and nifE) involved in the biosynthesis of FeMo-co resulted in very low molybdenum accumulation and in a molybdenum-free nitrogenase component I. A mutant lacking both subunits of nitrogenase component I accumulated 60% of the amount of molybdenum present in the wild type. The molybdenum was in protein-bound form and behaved differently than that in the wild type with respect to electrophoretic mobility, size, and extractability by organic solvents. Two forms of molybdenum could be extracted from the protein fraction of the mutant; one of them was not detected in the wild type, and the other behaved like FeMo-co in nonaqueous gel filtration chromatography. Crude extracts of this mutant were able to complement in vitro K. pneumoniae or Azotobacter vinelandii mutants unable to produce FeMo-co. These data show that biosynthesis of FeMo-co does not require the presence of nitrogenase component I. In its absence, FeMo-co is accumulated on a different protein, presumably an intermediate in the normal FeMo-co biosynthetic pathway.
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Imperial J, Ugalde RA, Shah VK, Brill WJ. Role of the nifQ gene product in the incorporation of molybdenum into nitrogenase in Klebsiella pneumoniae. J Bacteriol 1984; 158:187-94. [PMID: 6370956 PMCID: PMC215397 DOI: 10.1128/jb.158.1.187-194.1984] [Citation(s) in RCA: 119] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023] Open
Abstract
NifQ- mutants of Klebsiella pneumoniae are defective in nitrogen fixation due to an elevated requirement for molybdenum. When millimolar concentrations of molybdate were added to the medium, the effects of the nifQ mutations were suppressed. NifQ- mutants were not impaired in the uptake of molybdate, but molybdate accumulation was defective in these mutants. All of the nif-coded proteins were present in NifQ- cells derepressed in the absence of molybdenum. Molybdenum-activatable nitrogenase component I was found at the same level observed in the wild type. Molybdenum, thus, does not play a role in nif expression or in the short-term stability of nif-coded proteins. The defect in NifQ- mutants was in the incorporation of molybdenum into nitrogenase component I. The nifQ gene product acts together with the products of nifB, nifN, and nifE in the biosynthesis of the iron-molybdenum cofactor of nitrogenase.
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Merrick M, Hill S, Hennecke H, Hahn M, Dixon R, Kennedy C. Repressor properties of the nifL gene product in Klebsiella pneumoniae. ACTA ACUST UNITED AC 1982. [DOI: 10.1007/bf00333793] [Citation(s) in RCA: 118] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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Houmard J, Bogusz D. Kinetic study of the expression of Klebsiella pneumoniae nitrogen fixation (nif) genes under conditions of inhibited transcription. Biochem Biophys Res Commun 1981; 100:1237-44. [PMID: 7023480 DOI: 10.1016/0006-291x(81)91956-2] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
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Pienkos PT, Brill WJ. Molybdenum accumulation and storage in Klebsiella pneumoniae and Azotobacter vinelandii. J Bacteriol 1981; 145:743-51. [PMID: 7007348 PMCID: PMC217174 DOI: 10.1128/jb.145.2.743-751.1981] [Citation(s) in RCA: 91] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023] Open
Abstract
In Klebsiella pneumoniae, Mo accumulation appeared to be coregulated with nitrogenase synthesis. O2 and NH+4, which repressed nitrogenase synthesis, also prevented Mo accumulation. In Azotobacter vinelandii, Mo accumulation did not appear to be regulated Mo was accumulated to levels much higher than those seen in K. pneumoniae even when nitrogenase synthesis was repressed. Accumulated Mo was bound mainly to a Mo storage protein, and it could act as a supply for the Mo needed in component I synthesis when extracellular Mo had been exhausted. When A. vinelandii was grown in the presence of WO2-(4) rather than MoO2-(4), it synthesized a W-containing analog of the Mo storage protein. The Mo storage protein was purified from both NH+4 and N2-grown cells of A. vinelandii and found to be a tetramer of two pairs of different subunits binding a minimum of 15 atoms of Mo per tetramer.
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MacNeil D, Zhu J, Brill WJ. Regulation of nitrogen fixation in Klebsiella pneumoniae: isolation and characterization of strains with nif-lac fusions. J Bacteriol 1981; 145:348-57. [PMID: 7007318 PMCID: PMC217279 DOI: 10.1128/jb.145.1.348-357.1981] [Citation(s) in RCA: 60] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023] Open
Abstract
Strains with lac fused to each of the seven nif operons were isolated by two different methods. Repressing conditions prevented expression of all nif operons, whereas derepressing conditions led to the expression of all nif operons. No differences in Nif regulation were observed between Escherichia coli and Klebsiella pneumoniae with the same nif-lac fusions. Most derivatives of nif-lac fusion strains selected on lactose and NH4+ contained nif operator mutations. Some derivative contained deletions, which establishes that the direction of transcription of all seven nif operons is toward his
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MacNeil D, Brill WJ. Mutations in nif genes that cause Klebsiella pneumoniae to be derepressed for nitrogenase synthesis in the presence of ammonium. J Bacteriol 1980; 144:744-51. [PMID: 7000753 PMCID: PMC294724 DOI: 10.1128/jb.144.2.744-751.1980] [Citation(s) in RCA: 33] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023] Open
Abstract
Four Nif+ revertants from strains with polar insertions in nifL, were insensitive to ammonium and amino acid repression of nitrogenase synthesis. These strains have mutations located in or near the nifL region. The derepressed phenotype was dominant in a merodiploid containing a nif+ plasmid. These nif regulatory mutations also suppressed the Nif- phenotype of Gln- strains. Thus, regulation by fixed nitrogen (possible via glutamine synthetase) occurs on the nifLA operon but not on the other six nif operons.
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Abstract
Products of nifV, M, A, and F of Klebsiella pneumoniae have been identified, and suggestive evidence exists for the assignment of products for nifS, U, and L. These assignments confirm previous descriptions of transcriptional polarity and suggest that existence of several more nif genes whose products are apparently not essential for nitrogen fixation under standard laboratory conditions of growth. Although the nifA product is essential for expression of other nif transcripts, it is not involved in the regulation of its own transcript, nifRLA. The stability of nif-encoded proteins under anaerobic conditions was examined in a variety of mutants, confirming previously reported protein-protein interactions and suggesting several new ones. The stability of nif-encoded proteins in ammonia was found to be comparable to that in ammonia-free conditions, whereas all nif-gene products appeared to be labile in the presence of oxygen.
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Hallenbeck PC, Benemann JR. Effect of molybdenum starvation and tungsten on the synthesis and activity of nitrogenase inAnabaena cylindrica. FEMS Microbiol Lett 1980. [DOI: 10.1111/j.1574-6968.1980.tb05620.x] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
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Dixon R, Eady RR, Espin G, Hill S, Iaccarino M, Kahn D, Merrick M. Analysis of regulation of Klebsiella pneumoniae nitrogen fixation (nif) gene cluster with gene fusions. Nature 1980; 286:128-32. [PMID: 6995849 DOI: 10.1038/286128a0] [Citation(s) in RCA: 149] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Abstract
Gene fusions in which the lac genes are under the control of each promoter in the Klebsiella pneumoniae, nitrogen fixation (nif) gene cluster have been constructed. These fusions have been used to examine positive control of the cluster and the response of individual genes to repression by ammonia and oxygen. De-repression of nif transcriptional units is coordinate and molybdate is required for maximal expression of the structural gene operon, which is autogenously regulated.
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MacNeil D, Howe MM, Brill WJ. Isolation and characterization of lambda specialized transducing bacteriophages carrying Klebsiella pneumoniae nif genes. J Bacteriol 1980; 141:1264-71. [PMID: 6245064 PMCID: PMC293822 DOI: 10.1128/jb.141.3.1264-1271.1980] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023] Open
Abstract
Seve lambda dnif specialized transducing bacteriophages were isolated from Escherichia coli strains containing plasmids carrying the his-nif region of Klebsiella pneumoniae. These phages collectively carry deoxyribonucleic acid for all of the genes in the nif regulon and adjacent deoxyribonucleic acid of K. pneumoniae. The phages were isolated by using Mu insertions in the nif region to direct the integration of lambda pMu phages in nif via formation of lambda pMu-Mu dilysogens which, upon induction, yielded lambda dnif phages. This procedure should be generally applicable for isolating lambda specialized transducing phages carrying genes from E. coli or other bacteria.
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Abstract
We measured some of the kinetic parameters of nitrogenase to intact systems of Clostridium pasteurianum and Klebsiella pneumoniae to compare them with the kinetics of the enzyme in vitro. We found that the enzyme showed multiple apparent Km values for acetylene reduction in vivo, as it does in vitro. Carbon monoxide was a noncompetitive inhibitor of acetylene reduction; azide was a noncompetitive inhibitor of acetylene reduction, and nitrogen was a partial inhibitor of acetylene reduction. Cyanide was a noncompetitive inhibitor of acetylene reduction in C. pasteurianum but it was a metabolic poison in K. pneumoniae, in addition to being an inhibitor of nitrogenase. The partial nature of nitrogen inhibition was apparent in assays where both nitrogen and CO were present. Nitrogen did not alter the apparent Ki for CO, nor did the presence of CO enhance the competitive effectiveness of nitrogen. By using recombined nitrogenase fractions, we found that the ability of nitrogen to inhibit hydrogen evolution or acetylene reduction varied with the ratio of protein components. The in vivo inhibition of acetylene reduction by dinitrogen was comparable to that obtained with an excess of the Fe protein in vitro. We conclude that there is an effective excess of the Fe protein available under active growth conditions in vivo.
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MacNeil T, MacNeil D, Roberts GP, Supiano MA, Brill WJ. Fine-structure mapping and complementation analysis of nif (nitrogen fixation) genes in Klebsiella pneumoniae. J Bacteriol 1978; 136:253-66. [PMID: 361693 PMCID: PMC218656 DOI: 10.1128/jb.136.1.253-266.1978] [Citation(s) in RCA: 142] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
Four hundred and eighty-nine independent Nif- strains containing 260 point, 130 millimicron-induced, and 99 deletion mutations in nif in the Klebsiella pneumoniae chromosome were isolated. Three hundred and ninety insertion and point mutations were mapped with millimicron-induced deletions carried on 44 plasmids derived from pTM4010, a recombinant R factor containing the his-nif region of K. pneumoniae. The 99 chromosomal deletions in the nif region were mapped with 69 derivatives of pTM4010 carrying insertion and point mutations in nif. Complementation analysis between 84 derivatives of pTM4010 carrying nif mutations and Rec- derivatives of the 390 Nif- mutants identified 14 genes. The nif mutations were ordered into 49 deletion groups with a gene order of his...nifQBALFMVSNEKDHJ. Complementation analysis of millimicron-induced, amber, frameshift, and deletion mutations indicates there are five polycistronic and two monocistronic operons: nifQ nifB, nifA nifL, nifF, nifM nifV nifS, nifN nifE, nifK nifD nifH, and nifJ. Transcription is from right to left in all polycistronic operons.
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MacNeil D, Brill WJ. 6-cyanopurine, a color indicator useful for isolating mutations in the nif (nitrogen fixation) genes of Klebsiella pneumoniae. J Bacteriol 1978; 136:247-52. [PMID: 361692 PMCID: PMC218655 DOI: 10.1128/jb.136.1.247-252.1978] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
6-Cyanopurine (6-CP) can be used as a color indicator for certain classes of nif (N2 fixation) mutations in Klebsiella pneumoniae. Under N2-fixing conditions, Nif+ colonies and most Nif- colonies are purple on media containing 6-CP. Twenty-two Nif- mutants with altered color on medium containing 6-CP were isolated. All white mutants contained mutations in the regulatory genes, nifAA-nifL. Mutants which were more darkly colored than the wild type had mutations distributed among six nif genes. Medium with 6-CP was used to isolate Nif- mutants with deletions internal to the nif genes, and 6-CP was used to identify strains depressed for nitrogenase synthesis in the presence of NH4+.
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Roberts GP, MacNeil T, MacNeil D, Brill WJ. Regulation and characterization of protein products coded by the nif (nitrogen fixation) genes of Klebsiella pneumoniae. J Bacteriol 1978; 136:267-79. [PMID: 361694 PMCID: PMC218657 DOI: 10.1128/jb.136.1.267-279.1978] [Citation(s) in RCA: 230] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
Two hundred and thirty-five Nif- strains of Klebsiella pneumoniae were characterized by two-dimensional polyacrylamide gel electrophoresis. Forty-two of these strains were tested further by in vitro acetylene reduction assays. By these techniques, nine nif-coded polypeptides were identified, and eight of these were assigned to specific nif genes. Nitrogenase component I required nifK and nifD, which coded for the beta and alpha subunits, and nifB, -E, and -N were required for the iron-molybdenum cofactor, which is a part of the active site of nitrogenase. nifH coded for the structural protein of component II, and nifM and nifS products seemed to be necessary for the synthesis of an active component II. There were two genes, nifF and nifJ, that were required for N2 fixation in vivo but not for N2 fixation in vitro. There were at least two cases (nifE and nifN, nifK and nifD) of two proteins that seemed to require each other for stability in vivo. Regulation of N2 fixation is apparently complex, and this is reflected by the assignment of regulatory functions to the gene products of nifA, nifL, nifK, nifD, nifH, and NIFJ.
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MacNeil T, Brill WJ, Howe MM. Bacteriophage mu-induced deletions in a plasmid containing the nif (N2 fixation) genes of Klebsiella pneumoniae. J Bacteriol 1978; 134:821-9. [PMID: 350851 PMCID: PMC222328 DOI: 10.1128/jb.134.3.821-829.1978] [Citation(s) in RCA: 31] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
Five plasmids with insertions of a heat-inducible Mu prophage in a Mu-sensitive and P1-sensitive derivative of plasmid pRD1, a recombinant R factor containing the his-nif region of Klebsiella pneumoniae, were isolated and characterized. In one plasmid containing the Mu prophage integrated at the his-distal end of nif, selection for heat resistance resulted in the generation of deletions extending from the Mu prophage into the nif region. Thirty of these deltions were used to map 26 point mutations in nif.
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Nagatani HH, Haselkorn R. Molybdenum independence of nitrogenase component synthesis in the non-heterocystous cyanobacterium Plectonema. J Bacteriol 1978; 134:597-605. [PMID: 96092 PMCID: PMC222292 DOI: 10.1128/jb.134.2.597-605.1978] [Citation(s) in RCA: 27] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
The cyanobacterium Plectonema boryanum (IU 594-UTEX 594) fixes N2 only in the absence of combined N and of O2. We induced nitrogenase by transfer to anaerobic N-free medium and studied the effect of Mo starvation on nitrogenase activity and synthesis. Activity was first detected within 3 h after transfer by the acetylene reduction assay in controls, increasing for at least 25 h. Cells grown on nitrate and Mo and then transferred to N-free, Mo-free medium produced 8% of the control nitrogenase activity. Addition of W to the Mo-free medium reduced the activity to 0.5%. Under both Mo starvation conditions, nitrogenase protein components were synthesized. Component II of the cyanobacterial enzyme was detected by in vitro complementation with Mo-containing component I from Klebsiella pneumoniae or Azotobacter vinelandii but not Clostridium pasteurianum. Component I activity was restored by addition of Mo to cultures in which new enzyme synthesis was blocked by chloramphenicol. Acidified extracts of Plectonema induced in Mo-containing medium contained the Fe-Mo cofactor required to activate extracts of the Azotobacter mutant UW45 in vitro, but they did not activate extracts of Mo-starved Plectonema. Analysis of 35SO4(2-)-labeled proteins by polyacrylamide gel electrophoresis suggested that Mo is required for the conversion of a high-molecular-weight precursor to component I in Plectonema.
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Singh HN, Vaishampayan A, Singh RK. Evidence for the involvement of a genetic determinant controlling functional specificity of group VI B elements in the metabolism of N2 and NO-3 in the blue-green alga Nostoc muscorum. Biochem Biophys Res Commun 1978; 81:67-74. [PMID: 418780 DOI: 10.1016/0006-291x(78)91631-5] [Citation(s) in RCA: 30] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
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Bahadur K, Jyotishmati U. Microbial fixation of nitrogen in presence of sodium tungstate. ZENTRALBLATT FUR BAKTERIOLOGIE, PARASITENKUNDE, INFEKTIONSKRANKHEITEN UND HYGIENE. ZWEITE NATURWISSENSCHAFTLICHE ABTEILUNG: MIKROBIOLOGIE DER LANDWIRTSCHAFT DER TECHNOLOGIE UND DES UMWELTSCHUTZES 1978; 133:623-7. [PMID: 749407 DOI: 10.1016/s0323-6056(78)80064-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
The effect of sodium tungstate in the culture media of three different species of Azotobacter, isolated from Allahabad soil, was studied. It was observed that the presence of tungstate in the culture media of bacterial sample A2 and A3 decreased the fixation of nitrogen, except in the bacterial sample A1.
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Abstract
A method for the isolation of an iron-molybdenum cofactor (FeMoCo) from component I of nitrogenase is described. This method is used to isolate FeMoCo from aerobic, anaerobic, facultative, and photosynthetic nitrogen-fixing organisms. The Fe/Mo ratio in the FeMoCo from Azotobacter vinelandii and Clostridium pasteurianum is 8:1. The FeMoCo contains six atoms of acid-labile sulfide per eight Fe atoms. Crystalline component I from A. vinelandii contains 2 Mo, 33 Fe, and 27 acid-labile sulfide atoms per molecular weight of 250,000. The specific activity of FeMoCo is 425 nmol of C(2)H(4) formed/min per nmol of Mo. There is better than 98% reconstitution between FeMoCo and inactive component I in A. vinelandii mutant strain UW45. The FeMoCo yield from component I is about 90%. FeMoCo from nitrogenase component I of C. pasteurianum, Klebsiella pneumoniae, Bacillus polymyxa, and Rhodospirillum rubrum activates inactive component I in an extract from mutant strain UW45 and follows saturation kinetics. The FeMoCo in various nitrogen-fixing organisms seems to be very similar. Wild-type A. vinelandii derepressed for nitrogenase synthesis in tungsten-containing medium and K. pneumoniae mutant strain UN109 are also activated in vitro by FeMoCo. The FeMoCo is very sensitive to oxygen, but is stable even at room temperature as long as it is kept anaerobic and in N-methylformamide, the solvent used for its isolation. FeMoCo is unstable in an aqueous environment, even though it is kept strictly anaerobic. Knowledge of the structure of this cofactor should be useful for understanding the role of molybdenum at the active site of nitrogenase, role of ligands close to molybdenum in electron and proton transfer, and the catalytic mechanism of nitrogen fixation. The FeMoCo might be used as a model for synthesizing catalysts for chemical nitrogen fixation.
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The structure and function of nitrogenase: A review of the evidence for the role of molybdenum. ACTA ACUST UNITED AC 1977. [DOI: 10.1016/0022-5088(77)90069-8] [Citation(s) in RCA: 22] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
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Abstract
The regulation of the molybdate (MoO42-) transport activity of Clostridium pasteurianum has been studied by observing the effects of NH3, carbamyl phosphate, MoO42-, and chloramphenicol on the ability of cells to take up MoO42-. Compared with cells fixing N2, cells grown in the presence of 1 mM NH3 are greater than 95% repressed for MoO42- transport. Uptake activity begins to increase just before NH exhaustion (under Ar or N2) and continues to increase throughout the lag period as cells shift from NH3-growing to N2-fixing conditions. When cells are shifted from N2-fixing to NH3-growing conditions the transport activity per fixed number of cells decreases by increase of bells in absence of transport synthesis. Carbamyl phosphate (greater than or equal to 15 mM) but not NH3 inhibits 58% of the in vitro uptake activity. When 1 mM carbamyl phosphate is added just before the exhaustion of NH3, the transport activity, measured 2 h later, is 100% repressed. Cells grown in the presence of high MoO42- (1mM) are 80% repressed for MoO42- transport. Synthesis of the MoO42- transport system is also completely stopped when chloramphenicol (300 mug/ml) is added just before the exhaustion oNH 3 from the medium. These findings demonstrate that the ability of cells to transport MoO42- is dependent upon new protein synthesis and can be repressed by high levels of substrate. The regulation of MoO42- uptake by NH3 or carbamyl phosphate closely parallels the regulation of nitrogenase activity. Activity of neither nitrogenase component (Fe protein or MoFe protein) was detected even 3 h after the exhaustion of the NH3 if either MoO42- was absent or if WO42- was present in place of MoO42-. The duration of the diauxic lag increases with decreasing concentration of MoO42- in the medium. If no MoO42- is present the lag continues indefinitely. If MoO42- is added late in the lag period, growth under N2-fixing conditions resumes but only after a normal induction period.
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Collmer A, Lamborg M. Arrangement and regulation of the nitrogen fixation genes in Klebsiella pneumoniae studied by depression kinetics. J Bacteriol 1976; 126:806-13. [PMID: 816785 PMCID: PMC233217 DOI: 10.1128/jb.126.2.806-813.1976] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
Abstract
Events underlying depression of the nitrogen fixation (nif) genes in Klebsiella pneumoniae M5A1 were analyzed in vivo by comparing the effects of selective inhibitors of transcription and translation on subsequent nitrogenase activity (rate of acetylene reduction). When batch cultures were induced for depression, an 87-min lag separated ammonium ion/oxygen removal and the appearance of activity.
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Abstract
The transport of 99MoO42- into dinitrogen-fixing cells of Clostridium pasteurianum was investigated. Transport of molybdate in this organism is energy dependent; sucrose is required in the minimal media, and the system is inhibited by the glycolysis inhibitors, NaF, iodoacetic acid, and arsenate. The cells accumulate molybdate against a concentration gradient, and the uptake shows a marked dependence on temperature (optimum 37 C) and pH (optimum 6.0). The rate of molybdate uptake with increasing molybdate concentrations shows saturation kinetics with an apparent Km and Vmax of 4.8 X 10(-5) M and 55 nmol/g of dry cells per min, respectively. Inhibition studies with the anions SO42-, S2O32-, WO42-, and VO32- show that SO42- and WO42- competitively inhibit MoO42- uptake (apparent Ki [SO42-] is 3.0 X 10(-5) M; apparent Ki [WO42-] is 2.4 X 10(-5), whereas S2O32- and VO32- have no inhibitory effect. Exchange experiments with MoO42- show that only a small percentage of the 99MoO42- taken up by the cells is exchangeable. Exchange experiments with WO42- and SO42- indicate that once inside the cells WO42- and SO42- cannot substitute for MoO42-.
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Abstract
The role of Mo in the activity and synthesis of the nitrogenase components of Clostridium pasteurianum has been studied by observing the competition of Mo with its structural analogue W. Clostridial cells when fixing N2 appeared strictly dependent upon the available Mo, showing maximal N2-fixing activity at molybdate concentrations in the media of 10 muM. Cells grown in media with 3 times 10(-6) muM Mo, although showing good growth, had only 15% as much N2-fixing activity. In the presence of W the synthesis of both nitrogenase components, molybdoferredoxin and azoferredoxin, was affected. Attempts to produce nitrogenase in W-grown cells by addition of high molybdenum to the media in the presence of inhibitors of protein synthesis showed that Mo incorporation into a possible inactive preformed apoenzyme did not occur. Unlike other molybdoenzyme-containing cells, in which W either is incorporated in place of Mo to yield inactive protein or initiates the production of apoprotein, C. pasteurianum forms neither a tungsten substituted molybdoferredoxin nor an apoprotein. It is concluded that in C. pasteurianum molybdenum is an essential requirement for both the biosynthesis and activity of its nitrogenase.
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Ljungdahl LG, Andreesen JR. Tungsten, a component of active formate dehydrogenase from Clostridium thermoacetium. FEBS Lett 1975; 54:279-82. [PMID: 1132514 DOI: 10.1016/0014-5793(75)80092-5] [Citation(s) in RCA: 45] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
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St John RT, Johnston HM, Seidman C, Garfinkel D, Gordon JK, Shah VK, Brill WJ. Biochemistry and genetics of Klebsiella pneumoniae mutant strains unable to fix N2. J Bacteriol 1975; 121:759-65. [PMID: 1090602 PMCID: PMC246000 DOI: 10.1128/jb.121.3.759-765.1975] [Citation(s) in RCA: 73] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Abstract
Selected mutant strains of Klebsiella pneumoniae that are unable to fix nitrogen have been characterized according to nitrogenase component activity as well as antigenic cross-reacting material. The lesions in these strains have been mapped by transduction, and the results indicate that there are at least five genes specifically responsible for nitrogen fixation in vivo. Besides genes that specify the structure of the two nitrogenase components, there is a gene for a factor that is required for component I activity and a gene that codes for a factor possibly involved in electron transport to component II. A mutation in another site does not allow the organism to produce either of the nitrogenase components. All of these genes are co-transducible with the gene that specifics the structure of histidinol dehydrogenase.
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Nagatani HH, Brill WJ. Nitrogenase V. The effect of Mo, W and V on the synthesis of nitrogenase components in Azotobacter vinelandii. BIOCHIMICA ET BIOPHYSICA ACTA 1974; 362:160-6. [PMID: 4422774 DOI: 10.1016/0304-4165(74)90037-3] [Citation(s) in RCA: 53] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
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St John RT, Shah VK, Brill WJ. Regulation of nitrogenase synthesis by oxygen in Klebsiella pneumoniae. J Bacteriol 1974; 119:266-9. [PMID: 4600701 PMCID: PMC245598 DOI: 10.1128/jb.119.1.266-269.1974] [Citation(s) in RCA: 58] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023] Open
Abstract
Klebsiella pneumoniae does not fix N(2) under aerobic conditions. The two protein components required for nitrogenase activity were studied during aeration of cells in nitrogen-free media. Component II of nitrogenase was inactivated more slowly in vivo than component I during aeration. The rate of loss of component II was less than the rate of component II synthesis during derepression. No inactive components were detected in cells that had been growing on NH(4) (+) and then aerated in nitrogen-free medium. This supports the hypothesis that O(2) somehow represses the formation of nitrogenase.
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