Regulation of glutamine synthetase by metal-catalyzed oxidative modification in the marine oxyphotobacterium Prochlorococcus

Gómez‐Baena, Guadalupe; Dı́ez, Jesús; Garcı́a-Fernández, José Manuel; Alaoui, Sabah El; Humanes, Lourdes

doi:10.1016/s0304-4165(01)00226-4

Cited by 23 publications

(22 citation statements)

References 46 publications

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“…4A), but not the degradation of the enzyme (Fig. 4B); this effect was enhanced by the addition of ascorbate, which in combination with Fe 3+ forms a MCO system capable of inactivating GS in enterobacteria [72], cyanobacteria [21], [25] and green algae [73]. Furthermore, this MCO system induced as well the degradation of ICDH after 60 min (Fig.…”

Section: Resultsmentioning

confidence: 86%

“…To this goal, cell extracts of Prochlorococcus sp. PCC 9511 were subjected to the effect of a metal-catalyzed oxidative (MCO) system composed by Fe 3+ and ascorbate (described in detail previously [21], [25]) for 60 min. The results are shown in Fig.…”

Section: Resultsmentioning

confidence: 99%

“…For the inactivation of ICDH by the Fe 3+ /ascorbate system [21], [25], incubations were carried out at 4°C in a solution containing 50 mM Tris-HCl buffer pH 7.6, 0.2 mM FeCl 3 and variable concentrations of ascorbate (1, 5 or 10 mM). The ascorbate solution was prepared as follows: 100 µL of 20 mM dithiothreitol were added to 9 mL of 100 mM ascorbate, in order to keep ascorbate under reduced conditions; after carefully neutralizing this solution with 1 mM NaOH, the volume was adjusted to 10 mL.…”

Section: Methodsmentioning

confidence: 99%

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Physiological Regulation of Isocitrate Dehydrogenase and the Role of 2-Oxoglutarate in Prochlorococcus sp. Strain PCC 9511

et al. 2014

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The enzyme isocitrate dehydrogenase (ICDH; EC 1.1.1.42) catalyzes the oxidative decarboxylation of isocitrate, to produce 2-oxoglutarate. The incompleteness of the tricarboxylic acids cycle in marine cyanobacteria confers a special importance to isocitrate dehydrogenase in the C/N balance, since 2-oxoglutarate can only be metabolized through the glutamine synthetase/glutamate synthase pathway. The physiological regulation of isocitrate dehydrogenase was studied in cultures of Prochlorococcus sp. strain PCC 9511, by measuring enzyme activity and concentration using the NADPH production assay and Western blotting, respectively. The enzyme activity showed little changes under nitrogen or phosphorus starvation, or upon addition of the inhibitors DCMU, DBMIB and MSX. Azaserine, an inhibitor of glutamate synthase, induced clear increases in the isocitrate dehydrogenase activity and icd gene expression after 24 h, and also in the 2-oxoglutarate concentration. Iron starvation had the most significant effect, inducing a complete loss of isocitrate dehydrogenase activity, possibly mediated by a process of oxidative inactivation, while its concentration was unaffected. Our results suggest that isocitrate dehydrogenase responds to changes in the intracellular concentration of 2-oxoglutarate and to the redox status of the cells in Prochlorococcus.

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Section: Resultsmentioning

confidence: 86%

Section: Resultsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

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Physiological Regulation of Isocitrate Dehydrogenase and the Role of 2-Oxoglutarate in Prochlorococcus sp. Strain PCC 9511

et al. 2014

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“…Glutamine synthetase transferase activity was determined as previously described (88), during 30 min at 37°C. The reaction mixture contained 100 mM glutamine, 10 mM sodium hydroxylamine, 50 µM manganese chloride, 10 µM ADP, and 50 mM sodium arsenate in 0.2 M morpholinepropanesulfonic acid (MOPS) (pH 7.0) for 30 min at 37°C.…”

Section: Methodsmentioning

confidence: 99%

Quantitative Proteomics Shows Extensive Remodeling Induced by Nitrogen Limitation in Prochlorococcus marinus SS120

et al. 2017

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Prochlorococcus is the most abundant photosynthetic organism on Earth, contributing significantly to global primary production and playing a prominent role in biogeochemical cycles. Here we study the effects of extreme nitrogen limitation, a feature of the oligotrophic oceans inhabited by this organism. Quantitative proteomics allowed an accurate quantification of the Prochlorococcus proteome, finding three main responses to nitrogen limitation: upregulation of nitrogen assimilation-related proteins, including transporters; downregulation of ribosome proteins; and induction of the photosystem II cyclic electron flow. This suggests that nitrogen limitation affects a range of metabolic processes far wider than initially believed, with the ultimate goal of saving nitrogen and maximizing the nitrogen uptake and assimilation capabilities of the cell.

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“…Interestingly, the amino acid sequence, isoelectric point, molecular size, and kinetic parameters of GS from Prochlorococcus have been shown to be very similar to those of the enzymes from other cyanobacteria, either freshwater or marine strains (10), indicating very slight modifications of the properties of this enzyme during evolution. Regulation of GS by oxidative modification in Prochlorococcus has also been shown to occur (17), in a process that induces the inactivation and subsequent degradation of the enzyme. Catalase and peroxidase, but not superoxide dismutase, effectively protected GS against inactivation, suggesting the mediation of hydrogen peroxide.…”

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confidence: 99%

Streamlined Regulation and Gene Loss as Adaptive Mechanisms in Prochlorococcus for Optimized Nitrogen Utilization in Oligotrophic Environments

García-Fernández

Marsac

Dı́ez

2004

Microbiol Mol Biol Rev

110

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Prochlorococcus is one of the dominant cyanobacteria and a key primary producer in oligotrophic intertropical oceans. Here we present an overview of the pathways of nitrogen assimilation in Prochlorococcus, which have been significantly modified in these microorganisms for adaptation to the natural limitations of their habitats, leading to the appearance of different ecotypes lacking key enzymes, such as nitrate reductase, nitrite reductase, or urease, and to the simplification of the metabolic regulation systems. The only nitrogen source utilizable by all studied isolates is ammonia, which is incorporated into glutamate by glutamine synthetase. However, this enzyme shows unusual regulatory features, although its structural and kinetic features are unchanged. Similarly, urease activities remain fairly constant under different conditions. The signal transduction protein PII is apparently not phosphorylated in Prochlorococcus, despite its conserved amino acid sequence. The genes amt1 and ntcA (coding for an ammonium transporter and a global nitrogen regulator, respectively) show noncorrelated expression in Prochlorococcus under nitrogen stress; furthermore, high rates of organic nitrogen uptake have been observed. All of these unusual features could provide a physiological basis for the predominance of Prochlorococcus over Synechococcus in oligotrophic oceans

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Regulation of glutamine synthetase by metal-catalyzed oxidative modification in the marine oxyphotobacterium Prochlorococcus

Cited by 23 publications

References 46 publications

Physiological Regulation of Isocitrate Dehydrogenase and the Role of 2-Oxoglutarate in Prochlorococcus sp. Strain PCC 9511

Physiological Regulation of Isocitrate Dehydrogenase and the Role of 2-Oxoglutarate in Prochlorococcus sp. Strain PCC 9511

Quantitative Proteomics Shows Extensive Remodeling Induced by Nitrogen Limitation in Prochlorococcus marinus SS120

Streamlined Regulation and Gene Loss as Adaptive Mechanisms in Prochlorococcus for Optimized Nitrogen Utilization in Oligotrophic Environments

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