Molecular mechanism for the operation of nitrogen control in cyanobacteria.

Luque, Ignacio; Flores, Enrique; Herrero, Antonia

doi:10.1002/j.1460-2075.1994.tb06580.x

Cited by 225 publications

(333 citation statements)

References 24 publications

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“…1). The consensus DNA sequences recognized by NtcA [2][3][4] and cAMP receptor protein (CRP) [5,6] (called NtcA and CRP boxes, respectively) are quite similar (Fig. 1, bottom table), raising the question of whether there is cross-talk between CRP and NtcA so that one transcription factor can interact with promoters having boxes for the other transcription factor (Fig.…”

Section: Introductionmentioning

confidence: 99%

SPR analysis of promoter binding of Synechocystis PCC6803 transcription factors NtcA and CRP suggests cross‐talk and sheds light on regulation by effector molecules

2014

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Edited by Miguel De la RosaKeywords: Protein-protein interaction PipX protein 2-Oxoglutarate Cyanobacteria Catabolite gene activator protein Nitrogen metabolism a b s t r a c t Surface plasmon resonance monitoring of the binding of transcription factors cAMP receptor protein (CRP) and nitrogen control factor of cyanobacteria (NtcA) from Synechocystis sp. PCC6803 to promoter fragments of glnA, glnN (NtcA regulon) and cccS (CRP regulon), revealed exclusive CRP binding to cccS, whereas NtcA was bound to all three promoters with different affinities, which were strongly increased by the NtcA activator 2-oxoglutarate. Effective NtcA affinity for 2-oxoglutarate varied with the promoter. High-affinity promoters and the NtcA-coactivating protein PII-interacting protein X (PipX) increased NtcA affinity towards 2-oxoglutarate, suggesting PipX-stabilization of the 2-oxoglutarate-bound NtcA conformation. PipX binding to NtcA required 2-oxoglutarate and was much tighter (K d % 85 nM) than to the PipX-sequestering PII protein. NtcA appears to require more strongly PipX and 2-oxoglutarate (2OG) for estimulating gene expression at promoters having ''imperfect'' NtcA binding sites.

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Section: Introductionmentioning

confidence: 99%

SPR analysis of promoter binding of Synechocystis PCC6803 transcription factors NtcA and CRP suggests cross‐talk and sheds light on regulation by effector molecules

2014

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“…Two putative binding sites were identified upstream of ntcA in Anabaena PCC 7120 (Muro-Pastor et al, 2002), but they were not positioned at 40.5 nt as in most NtcA-activated promoters (Luque et al, 1994;Herrero et al, 2001). NtcA is required for heterocyst formation but its requirement for expression of the nif genes is not well established (Frias et al, 1994;Ramasubramanian et al, 1994;Muro-Pastor et al, 1999).…”

Section: Introductionmentioning

confidence: 99%

Decoupling of ammonium regulation and ntcA transcription in the diazotrophic marine cyanobacterium Trichodesmium sp. IMS101

2011

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Nitrogen (N) physiology in the marine cyanobacterium Trichodesmium IMS101 was studied along with transcript accumulation of the N-regulatory gene ntcA and of two of its target genes: napA (nitrate assimilation) and nifH (N 2 fixation). N 2 fixation was impaired in the presence of nitrite, nitrate and urea. Strain IMS101 was capable of growth on these combined N sources at o2 lM but growth rates declined at elevated concentrations. Assimilation of nitrate and urea was impaired in the presence of ammonium. Whereas ecologically relevant N concentrations (2-20 lM) suppressed growth and assimilation, much higher concentrations were required to affect transcript levels. Transcripts of nifH accumulated under nitrogen-fixing conditions; these transcript levels were maintained in the presence of nitrate (100 lM) and ammonium (20 lM). However, nifH transcript levels were below detection at ammonium concentrations 420 lM. napA mRNA was found at low levels in both N 2 -fixing and ammonium-utilizing filaments, and it accumulated in filaments grown with nitrate. The positive effect of nitrate on napA transcription was abolished by ammonium additions of 4200 lM. This effect was restored upon addition of the glutamine synthetase inhibitor L-methionin-DL-sulfoximine. Surprisingly, ntcA transcript levels remained high in the presence of ammonium, even at elevated concentrations. These findings indicate that ammonium repression is decoupled from transcriptional activation of ntcA in Trichodesmium IMS101.

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“…It has been shown in Synechococcus sp. strain PCC 7942 that mRNA levels of genes encoding proteins for nitrate and ammonium assimilation are negatively regulated by ammonium (9). Furthermore, the presence of ammonium results in inhibition of nitrogen fixation and heterocyst development in Anabaena sp.…”

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confidence: 99%

“…1). It has been demonstrated in PCC 7942 and PCC 7120 that NtcA binds to the promoter region of and activates genes involved in nitrogen control such as glnA, nir, and ntcA itself (3,9,12,13). Given its similarity to the NtcA proteins from PCC 7942 and PCC 7120, it is possible that the Cyanothece NtcA protein may bind similar target sequences.…”

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confidence: 99%

Cloning, sequencing, and regulation of the global nitrogen regulator gene ntcA in the unicellular diazotrophic cyanobacterium Cyanothece sp. strain BH68K

Bradley

Reddy

1997

J Bacteriol

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In cyanobacteria, ammonium represses expression of proteins involved in nitrogen fixation and assimilation. The global nitrogen regulator gene ntcA encodes a DNA-binding protein, NtcA, that is a transcriptional activator of genes subject to nitrogen control. We report the cloning and sequencing of the ntcA gene from a nitrogen-fixing unicellular cyanobacterium, Cyanothece sp. strain BH68K. The gene comprises 678 nucleotides, and the deduced NtcA protein contains 226 amino acids with a predicted molecular weight of 25,026. In addition, ntcA mRNA levels were measured in cells grown under different nitrogen regimes. Under nitrogenfixing conditions, ntcA transcripts were weakly expressed. Furthermore, ntcA expression was diminished or inversely proportional to nifHDK expression. Conversely, ntcA expression increased in nitrate-grown cells, and a concentration-dependent increase was seen in ammonium-grown cells up to 1 mM NH 4 Cl. These results indicate that ntcA is involved more in nitrogen assimilation than in nitrogen fixation and also imply that the rhythmic expression of ntcA and nifHDK transcription may be under the control of a circadian clock.

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Molecular mechanism for the operation of nitrogen control in cyanobacteria.

Cited by 225 publications

References 24 publications

SPR analysis of promoter binding of Synechocystis PCC6803 transcription factors NtcA and CRP suggests cross‐talk and sheds light on regulation by effector molecules

SPR analysis of promoter binding of Synechocystis PCC6803 transcription factors NtcA and CRP suggests cross‐talk and sheds light on regulation by effector molecules

Decoupling of ammonium regulation and ntcA transcription in the diazotrophic marine cyanobacterium Trichodesmium sp. IMS101

Cloning, sequencing, and regulation of the global nitrogen regulator gene ntcA in the unicellular diazotrophic cyanobacterium Cyanothece sp. strain BH68K

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