Nitrogen and Carbon Status Are Integrated at the Transcriptional Level by the Nitrogen Regulator NtrC
 In Vivo

Schumacher, Joerg; Behrends, Volker; Pan, Zhensheng; Brown, D.; Heydenreich, Franziska M.; Lewis, Matthew R.; Bennett, Mark H.; Razzaghi, Banafsheh; Komorowski, Michał; Barahona, Mauricio; Stumpf, Michael; Wigneshweraraj, Sivaramesh; Bundy, Jacob G.; Buck, Martin

doi:10.1128/mbio.00881-13

Cited by 67 publications

(82 citation statements)

References 58 publications

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“…This ratio is known to control the activity of the NtrB/C system through the uridylyl transferase PII (Schumacher et al, 2013). Similar general indicators, such as the 2-OG/ glutamine ratio, could also be used by the CbrA/B to respond to carbon availability.…”

Section: Discussionmentioning

confidence: 99%

Hierarchical management of carbon sources is regulated similarly by the CbrA/B systems in Pseudomonas aeruginosa and Pseudomonas putida

et al. 2014

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The CbrA/B system in pseudomonads is involved in the utilization of carbon sources and carbon catabolite repression (CCR) through the activation of the small RNAs crcZ in Pseudomonas aeruginosa, and crcZ and crcY in Pseudomonas putida. Interestingly, previous works reported that the CbrA/B system activity in P. aeruginosa PAO1 and P. putida KT2442 responded differently to the presence of different carbon sources, thus raising the question of the exact nature of the signal(s) detected by CbrA. Here, we demonstrated that the CbrA/B/CrcZ(Y) signal transduction pathway is similarly activated in the two Pseudomonas species. We show that the CbrA sensor kinase is fully interchangeable between the two species and, moreover, responds similarly to the presence of different carbon sources. In addition, a metabolomics analysis supported the hypothesis that CCR responds to the internal energy status of the cell, as the internal carbon/nitrogen ratio seems to determine CCR and non-CCR conditions. The strong difference found in the 2-oxoglutarate/glutamine ratio between CCR and non-CCR conditions points to the close relationship between carbon and nitrogen availability, or the relationship between the CbrA/B and NtrB/C systems, suggesting that both regulatory systems sense the same sort or interrelated signal.

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Section: Discussionmentioning

confidence: 99%

Hierarchical management of carbon sources is regulated similarly by the CbrA/B systems in Pseudomonas aeruginosa and Pseudomonas putida

et al. 2014

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“…Furthermore, conversion of measured metabolite levels to molar concentrations within the cell is complicated by a number of factors, e.g., the internal cell volume may fluctuate (15), and it is hard to predict how the measured values correlate to free metabolites, as a fraction of metabolites are likely to be bound to proteins. Despite these challenges, many studies have determined the levels of 2-OG in E. coli cell extracts by applying either coupled enzymatic assays (16)(17)(18), mass spectrometry (9,(19)(20)(21), or high-pressure liquid chromatography (HPLC) methods (13). More recently, engineered fluorescent protein probes, or biosensors, have been developed to allow monitoring of 2-OG levels in cell extracts or directly inside living cells (22)(23)(24).…”

Section: Fluctuations In the 2-og Pool In Response To Nitrogen Availamentioning

confidence: 99%

The Emergence of 2-Oxoglutarate as a Master Regulator Metabolite

Huergo

Dixon

2015

Microbiol Mol Biol Rev

247

221

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SUMMARYThe metabolite 2-oxoglutarate (also known as α-ketoglutarate, 2-ketoglutaric acid, or oxoglutaric acid) lies at the intersection between the carbon and nitrogen metabolic pathways. This compound is a key intermediate of one of the most fundamental biochemical pathways in carbon metabolism, the tricarboxylic acid (TCA) cycle. In addition, 2-oxoglutarate also acts as the major carbon skeleton for nitrogen-assimilatory reactions. Experimental data support the conclusion that intracellular levels of 2-oxoglutarate fluctuate according to nitrogen and carbon availability. This review summarizes how nature has capitalized on the ability of 2-oxoglutarate to reflect cellular nutritional status through evolution of a variety of 2-oxoglutarate-sensing regulatory proteins. The number of metabolic pathways known to be regulated by 2-oxoglutarate levels has increased significantly in recent years. The signaling properties of 2-oxoglutarate are highlighted by the fact that this metabolite regulates the synthesis of the well-established master signaling molecule, cyclic AMP (cAMP), inEscherichia coli.

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“…Congruent results were reported by Jahn et al [2013], who also observed almost complete phosphorylation of EIIA Ntr in wild-type cells when grown on 20 m M of ammonia. These deviating observations are surprising since ammonia concentrations exceeding 10 m M are considered nitrogen replete conditions for E. coli [Schumacher et al, 2013]. It remains to be determined whether extraordinarily high ammonia concentrations are required to allow for accumulation of nonphosphorylated EIIA Ntr or whether differences in the experimental setup accounted for the observed discrepancies.…”

Section: Discussionmentioning

confidence: 70%

Cross-Talk between the Canonical and the Nitrogen-Related Phosphotransferase Systems Modulates Synthesis of the KdpFABC Potassium Transporter in Escherichia coli

2015

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Many Proteobacteria possess the regulatory nitrogen-related phosphotransferase system (PTS^Ntr), which operates in parallel to the transport PTS. PTS^Ntr is composed of the proteins EI^Ntr and NPr and the final phosphate acceptor EIIA^Ntr. Both PTSs can exchange phosphoryl groups among each other. Proteins governing K⁺ uptake represent a major target of PTS^Ntr in Escherichia coli. Nonphosphorylated EIIA^Ntr binds and stimulates the K⁺ sensor KdpD, which activates expression of the kdpFABC operon encoding a K⁺ transporter. Here we show that this regulation also operates in an ilvG⁺ strain ruling out previous concern about interference with a nonfunctional ilvG allele present in many strains. Furthermore, we analyzed phosphorylation of EIIA^Ntr. In wild-type cells EIIA^Ntr is predominantly phosphorylated, regardless of the growth stage and the utilized carbon source. However, cross-phosphorylation of EIIA^Ntr by the transport PTS becomes apparent in the absence of EI^Ntr: EIIA^Ntr is predominantly nonphosphorylated when cells grow on a PTS sugar and phosphorylated when a non-PTS carbohydrate is utilized. These differences in phosphorylation are transduced into corresponding kdpFABC transcription levels. Thus, the transport PTS may affect phosphorylation of EIIA^Ntr and accordingly modulate processes controlled by EIIA^Ntr. Our data suggest that this cross-talk becomes most relevant under conditions that would inhibit activity of EI^Ntr.

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Nitrogen and Carbon Status Are Integrated at the Transcriptional Level by the Nitrogen Regulator NtrC In Vivo

Cited by 67 publications

References 58 publications

Hierarchical management of carbon sources is regulated similarly by the CbrA/B systems in Pseudomonas aeruginosa and Pseudomonas putida

Hierarchical management of carbon sources is regulated similarly by the CbrA/B systems in Pseudomonas aeruginosa and Pseudomonas putida

The Emergence of 2-Oxoglutarate as a Master Regulator Metabolite

Cross-Talk between the Canonical and the Nitrogen-Related Phosphotransferase Systems Modulates Synthesis of the KdpFABC Potassium Transporter in <b><i>Escherichia coli</i></b>

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