Regulation of Ammonium Assimilation in Cyanobacteria

Florencio, Francisco J.; Reyes, José Carlos Castañeda

doi:10.1007/0-306-48138-3_7

Cited by 4 publications

(3 citation statements)

References 132 publications

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“…Albeit featuring a similar structure, subunit composition, physicochemical properties, and enzymatic performance compared to the GS of other cyanobacteria, early studies in Prochlorococcus illustrated that N shortage causes a different response compared to other cyanobacteria [139,140]. For instance, GS activity in Prochlorococcus MED4 was shown to be substantially enhanced during long-term N starvation, while GS protein levels remained relatively constant under these conditions [140] thus contrasting common regulatory traits of other cyanobacterial GSs in which N deprivation causes a significant increase in GS protein abundance and activity [141].…”

Section: Cyanobacteria Evolved Exceptional Gs Regulatory Mechanismsmentioning

confidence: 99%

The Distinctive Regulation of Cyanobacterial Glutamine Synthetase

Bolay

Muro‐Pastor

Florencio

et al. 2018

Life

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Glutamine synthetase (GS) features prominently in bacterial nitrogen assimilation as it catalyzes the entry of bioavailable nitrogen in form of ammonium into cellular metabolism. The classic example, the comprehensively characterized GS of enterobacteria, is subject to exquisite regulation at multiple levels, among them gene expression regulation to control GS abundance, as well as feedback inhibition and covalent modifications to control enzyme activity. Intriguingly, the GS of the ecologically important clade of cyanobacteria features fundamentally different regulatory systems to those of most prokaryotes. These include the interaction with small proteins, the so-called inactivating factors (IFs) that inhibit GS linearly with their abundance. In addition to this protein interaction-based regulation of GS activity, cyanobacteria use alternative elements to control the synthesis of GS and IFs at the transcriptional level. Moreover, cyanobacteria evolved unique RNA-based regulatory mechanisms such as glutamine riboswitches to tightly tune IF abundance. In this review, we aim to outline the current knowledge on the distinctive features of the cyanobacterial GS encompassing the overall control of its activity, sensing the nitrogen status, transcriptional and post-transcriptional regulation, as well as strain-specific differences.

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Section: Cyanobacteria Evolved Exceptional Gs Regulatory Mechanismsmentioning

confidence: 99%

The Distinctive Regulation of Cyanobacterial Glutamine Synthetase

Bolay

Muro‐Pastor

Florencio

et al. 2018

Life

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“…It is a key enzyme of nitrogen assimilation, integrating the nitrogen and carbon metabolisms; therefore it is finely regulated through mechanisms that have been particularly well studied in E. coli , involving complex cascades of adenylylation (Stadtman, 1990). Because of its status as a model enzyme, glutamine synthetase from cyanobacteria has also been the subject of a number of studies (for review, see Flores and Herrero, 1994; Florencio and Reyes, 2002); cyanobacterial glutamine synthetase activity is apparently not regulated by covalent modification; furthermore, a novel regulatory process by protein–protein interaction has been recently described in Synechocystis PCC 6803 (García‐Domínguez et al ., 1999; 2000; Florencio and Reyes, 2002). On the other hand, transcriptional control of glnA expression is exerted through the global regulator of nitrogen assimilation in cyanobacteria, NtcA (Herrero et al ., 2001).…”

Section: Introductionmentioning

confidence: 99%

Glutamine synthetase from the marine cyanobacteria Prochlorococcus spp.: characterization, phylogeny and response to nutrient limitation

Alaoui

Dı́ez

Toribio

et al. 2003

Environmental Microbiology

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The regulation of glutamine synthetase (EC 6.3.1.2) from Prochlorococcus was previously shown to exhibit unusual features: it is not upregulated by nitrogen starvation and it is not inactivated by darkness (El Alaoui et al. (2001) Appl Environ Microbiol 67: 2202-2207). These are probably caused by adaptations to oligotrophic environments, as confirmed in this work by the marked decrease in the enzymatic activity when cultures were subjected to iron or phosphorus starvation. In order to further understand the adaptive features of ammonium assimilation in this cyanobacterium, glutamine synthetase was purified from two Prochlorococcus strains: PCC 9511 (high-light adapted) and SS120 (low-light adapted). We obtained approximately 100-fold purified samples of glutamine synthetase electrophoretically homogeneous, with a yield of approximately 30%. The estimated molecular mass of the subunits was roughly the same for both strains: 48.3 kDa. The apparent Km constants for the biosynthetic activity were 0.30 mM for ammonium, 1.29 mM for glutamate and 1.35 mM for ATP; the optimum pH was 8.0. Optimal temperature was surprisingly high (55 degrees C). Phylogenetic analysis of glnA from three Prochlorococcus strains (MED4, MIT9313 and SS120) showed they group closely with marine Synechococcus isolates, in good agreement with other studies based on 16 S RNA sequences. All of our results suggest that the structure and kinetics of glutamine synthetase in Prochlorococcus have not been significantly modified during the evolution within the cyanobacterial radiation, in sharp contrast with its regulatory properties.

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“…Prokaryotic GSI is composed of 12 identical subunits of about 50 kDa each ( Valentine et al, 1968 ; Yamashita et al, 1989 ). Some cyanobacterial strains have, in addition to GSI, an hexameric GS (known as GS type III, GSIII), encoded by glnN ( Reyes and Florencio, 1994 ; García-Domínguez et al, 1997 ; Reyes et al, 1997 ; Crespo et al, 1998 ; Sauer et al, 2000 ; Florencio and Reyes, 2002 ). Although these two types of GS are quite different in amino acid sequence, they share five domains that can be found in all known GSs ( Reyes and Florencio, 1994 ; Crespo et al, 1998 ).…”

Section: Introductionmentioning

confidence: 99%

Physiological Studies of Glutamine Synthetases I and III from Synechococcus sp. WH7803 Reveal Differential Regulation

2016

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The marine picocyanobacterium Synechococcus sp. WH7803 possesses two glutamine synthetases (GSs; EC 6.3.1.2), GSI encoded by glnA and GSIII encoded by glnN. This is the first work addressing the physiological regulation of both enzymes in a marine cyanobacterial strain. The increase of GS activity upon nitrogen starvation was similar to that found in other model cyanobacteria. However, an unusual response was found when cells were grown under darkness: the GS activity was unaffected, reflecting adaptation to the environment where they thrive. On the other hand, we found that GSIII did not respond to nitrogen availability, in sharp contrast with the results observed for this enzyme in other cyanobacteria thus far studied. These features suggest that GS activities in Synechococcus sp. WH7803 represent an intermediate step in the evolution of cyanobacteria, in a process of regulatory streamlining where GSI lost the regulation by light, while GSIII lost its responsiveness to nitrogen. This is in good agreement with the phylogeny of Synechococcus sp. WH7803 in the context of the marine cyanobacterial radiation.

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Regulation of Ammonium Assimilation in Cyanobacteria

Cited by 4 publications

References 132 publications

The Distinctive Regulation of Cyanobacterial Glutamine Synthetase

The Distinctive Regulation of Cyanobacterial Glutamine Synthetase

Glutamine synthetase from the marine cyanobacteria Prochlorococcus spp.: characterization, phylogeny and response to nutrient limitation

Physiological Studies of Glutamine Synthetases I and III from Synechococcus sp. WH7803 Reveal Differential Regulation

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