Nitrogenase Synthesis in Klebsiella pneumoniae: Enhanced nif Expression without Accumulation of Guanosine 5'-Diphosphate 3'-Diphosphate

Nair, Mrinalini; Eady, Robert R.

doi:10.1099/00221287-130-12-3063

Cited by 4 publications

(5 citation statements)

References 36 publications

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“…The addition of glutamine (0.69 mM), which stimulates the derepression of C2H 2reducing activity in K. pneumoniae [22], markedly enhanced derepression in RK5279 (pRD1) and RK4353 (pRD1); by 5 h the specific activity ranged from 8 to 14 and 11 to 25 respectively. Differences in N source did not markedly affect activity although when inocula were grown in LB in place of NB the specific activities in mutant and wild-type strains were lower.…”

Section: C2h 2 Reduction By Fnr-e Coli (Prdi) Transconjugantsmentioning

confidence: 99%

Redox regulation of enteric nif expression is independent of the fnr gene product

Hill

1985

FEMS Microbiology Letters

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Section: C2h 2 Reduction By Fnr-e Coli (Prdi) Transconjugantsmentioning

confidence: 99%

Redox regulation of enteric nif expression is independent of the fnr gene product

Hill

1985

FEMS Microbiology Letters

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“…Among the latter is ppGpp, which is known to increase in amino acid-or N-starved bacteria, including K. pneumoniae (13,19). However, ppGpp is apparently not necessary for nif gene expression, since N-starved K. pneumoniae cultures supplemented with glutamine had nitrogenase activity but failed to accumulate significant ppGpp (18).…”

Section: Resultsmentioning

confidence: 99%

Regulation of nitrogenase synthesis in histidine auxotrophs of Klebsiella pneumoniae with altered levels of adenylate nucleotides

Stougaard

Kennedy

1988

J Bacteriol

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A histidine auxotrophic (hisA) mutant of Kiebsiella pneumoniae is phenotypically Nif-when grown with 20,ug of histidine ml-' but Nif+ when supplied with histidine at 100 Fg ml-'. Reversion to Nif' at 20 ,ug of histidine ml' occurs phenotypically by the addition Qf 2-thiazolyl-DL-alanine or genetically by mutation in hisG; 2-thiazolyl-DL-alanine inhibits and hisG encodes phosphoribosyl phosphotransferase, the first enzyme of the histidine biosynthetic pathway which consumes ATP. Physiological studies of the hisA mutant JS85 showed that after removal of NH4+ from a culture of the mutant grown with 20 ,g of histidine ml-, synthesis of nitrogenase polypeptides occurred at a rate similar to that in the wild type for about 3 h and acetylene reduction activity reached about 10% of the fully derepressed wild-type level. Shortly thereafter the concentration of intracellular adenylates decreased; in particular, ATP fell to about 10% of normal levels. Also, nitrogenase proteins (nifHDK products) and the nifJ gene product stopped being synthesized. These effects were not due to impairment of growth or protein synthesis by histidine starvation. Inhibition of phosphoribosyl phosphotransferase with 2-thiazolyl-DL-alanine restored nitrogenase activity and synthesis, indicating that the effect of the hisA mutation on nif expression was probably a consequence of lowered energy resources that occurred during anaerobic N starvation. Nif+ when supplied with 100 ,ug of histidine ml-' (7). Other histidine auxotrophs with mutations in hisC, hisB, hisD, hisF, or hisG were Nif+ even in low-histidine medium, although nitrogenase activity was slightly reduced in some of them. These results indicated that histidine starvation per se did not cause the Nif-phenotype in the hisA mutants. In liquid cultures of one hisA mutant, JS85, nitrogenase activity was never more than 10% of wild-type levels when histidine was supplied at 20 jxg ml-l but was 100% when histidine was at 100 pLg ml-. ATP levels in JS85 decreased to 10% of that of His' strains during derepression and appeared to correlate with a cessation of nitrogenase synthesis.The reversal of JS85 to Nif+ by the addition of adenine or 2-thiazolyl-DL-alanine (2TA) to low-histidine, N-free agar medium also indicated that histidine starvation was not the cause of the Nif phenotype (7). 2TA is an analog of histidine that is not incorporated into proteins and has no effect on protein synthesis but inhibits the activity of the first enzyme of the histidine biosynthetic pathway. This is phosphoribosyl phosphotransferase, an ATP-consuming enzyme (Fig. 1). The hisA mutation prevents formation of the biosynthetic intermediate 5-'aminoimidazole-4-carboxamide-1-ribonucleotide, which normally restores the purine precursor pool. Thus, physiological evidence indicated that a loss of ATP or a consequent energy imbalance correlated with the Nif-phenotype of JS85.This hisA mutant, JS85, has now been further characterized by examining Nif* revertants, by measuring adenylate levels and rates of nitrogenase syn...

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“…The effect of the nzjH product on nzp-lac expression was tested by introducing a derivative of the low-copy plasrriid pHSG415, either pWPH6B or pWPH7B (Paul & Merrick, 1989), into UNF686(pMF183). UNF686 carries a his-nif deletion which is complemented by pMF183, except that the latter is NifH-, D-and K-as it bears the nzJTI-lac fusion.…”

Section: Autoregulation and The Nifh Productmentioning

confidence: 99%

“…UNF686 carries a his-nif deletion which is complemented by pMF183, except that the latter is NifH-, D-and K-as it bears the nzJTI-lac fusion. The recombinant plasmids carry n z f l and M (pWPH7B) or nzJH, M and 2 (pWPH6B), and both encode an active Fe protein of nitrogenase (Paul & Merrick, 1989). The expression of nzfTrl-lac in these strains was compared with that in the strain carrying the veccor pHSG415 after 18 h of N-limited growth on 100 pg serine ml-' under either Ar or the assay conditions (microaerobic) of Dixon etal.…”

Section: Autoregulation and The Nifh Productmentioning

confidence: 99%

“…Transcription from all other nzf operons is activated by the n i f A product (Merrick, 1992; Buck, 1990). The activity of the n i f A product is inhibited by the nzfL product in response to repressive levels of environmental fixed N or 0, (Merrick e t al., 1982;Merrick, 1992 ; (1980) Paul & Merrick (1989) scription of the n z f z A operon precedes that of nzflDKY and other nifoperons tested (Cannon e t al., 1985), but at least an hour elapses after nzjHDKY transcription and translation are detected and before nitrogenase activity can be measured. This lag probably reflects the complexity of the processing of the polypeptides (Govezensky et d., 1991).…”

Section: Introductionmentioning

confidence: 99%

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Autoregulation of nitrogenase expression in Klebsiella pneumoniae

Hill

Kavanagh

1994

Microbiology

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An investigation into the influence of N, on the expression of Klebsiella pneumoniae nitrogenase has led to a reassessment of the role of the nitrogenase MoFe protein in autoregulation. Anaerobic derepression of nitrogenase (C,H,-reducing) activity, of Nif D and K polypeptides, and of nifH-/ac expression, following the removal of excess NH; , were greater under N, than Ar. This enhancement occurred in Nif+ but not in Nif-strains, and in Nif+ strains was prevented by CZH, , an inhibitor of N, fixation. Thus N, fixation is important for maintaining derepression. Derepression of nifH-lac under Ar in various Nif' and Nif-strains (including NifH-, NifD-, NifB-and NifL-mutants) and of wild-type lac under N, or Ar in a Nif' strain were measured to investigate the regulation. The mechanism regulating the enhancement under N, neither involved the MoFe protein of nitrogenase, as proposed by Dixon et a/. (1980, Nature 286, 12&132)# nor the nifL product, but was probably due to a general upgrading of the N status. Moreover, during batch growth limited by a non-repressing fixed N source, the levels of nifH-lac expression in the Nif+ and Nif-strains suggested that the nifH gene product (or Fe protein) may have a positive autoregulatory function.

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Nitrogenase Synthesis in Klebsiella pneumoniae: Enhanced nif Expression without Accumulation of Guanosine 5'-Diphosphate 3'-Diphosphate

Cited by 4 publications

References 36 publications

Redox regulation of enteric nif expression is independent of the fnr gene product

Redox regulation of enteric nif expression is independent of the fnr gene product

Regulation of nitrogenase synthesis in histidine auxotrophs of Klebsiella pneumoniae with altered levels of adenylate nucleotides

Autoregulation of nitrogenase expression in Klebsiella pneumoniae

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