Effect of pyruvate on the metabolic regulation of nitrogenase activity in Rhodospirillum rubrum in darkness

Microbiology ◽  
2011 ◽  
Vol 157 (6) ◽  
pp. 1834-1840 ◽  
Author(s):  
Tiago Toscano Selao ◽  
Tomas Edgren ◽  
He Wang ◽  
Agneta Norén ◽  
Stefan Nordlund
Keyword(s):  
Nitrogen Source ◽  
Metabolic Regulation ◽  
Rhodospirillum Rubrum ◽  
De Novo ◽  
Nitrogenase Activity ◽  
Signal Transduction Pathway ◽  
Nitrogen Sources ◽  
Synthetase Activity ◽  
Glutamine Synthetase Activity ◽  
Fe Protein

Rhodospirillum rubrum, a photosynthetic diazotroph, is able to regulate nitrogenase activity in response to environmental factors such as ammonium ions or darkness, the so-called switch-off effect. This is due to reversible modification of the Fe-protein, one of the two components of nitrogenase. The signal transduction pathway(s) in this regulatory mechanism is not fully understood, especially not in response to darkness. We have previously shown that the switch-off response and metabolic state differ between cells grown with dinitrogen or glutamate as the nitrogen source, although both represent poor nitrogen sources. In this study we show that pyruvate affects the response to darkness in cultures grown with glutamate as nitrogen source, leading to a response similar to that in cultures grown with dinitrogen. The effects are related to PII protein uridylylation and glutamine synthetase activity. We also show that pyruvate induces de novo protein synthesis and that inhibition of pyruvate formate-lyase leads to loss of nitrogenase activity in the dark.

scholarly journals Nitrogenase Switch-Off and Regulation of Ammonium Assimilation in Response to Light Deprivation in Rhodospirillum rubrum Are Influenced by the Nitrogen Source Used during Growth

2009 ◽  
Vol 192 (5) ◽  
pp. 1463-1466 ◽  
Author(s):  
Pedro Filipe Teixeira ◽  
He Wang ◽  
Stefan Nordlund
Keyword(s):  
Nitrogen Fixation ◽  
Glutamine Synthetase ◽  
Nitrogen Source ◽  
Rhodospirillum Rubrum ◽  
Light Availability ◽  
Ammonium Assimilation ◽  
Synthetase Activity ◽  
Glutamine Synthetase Activity ◽  
Light Deprivation

ABSTRACT Nitrogen fixation and ammonium assimilation in Rhodospirillum rubrum are regulated in response to changes in light availability, and we show that the response in terms of glutamine synthetase activity and PII modification is dependent on the nitrogen source used for growth, N2 or glutamate, although both lead to nitrogenase derepression.

scholarly journals AmtB Is Necessary for NH4+-Induced Nitrogenase Switch-Off and ADP-Ribosylation in Rhodobacter capsulatus

2002 ◽  
Vol 184 (15) ◽  
pp. 4081-4088 ◽  
Author(s):  
Alexander F. Yakunin ◽  
Patrick C. Hallenbeck
Keyword(s):  
Rhodobacter Capsulatus ◽  
Nitrogenase Activity ◽  
Growth Defect ◽  
Synthetase Activity ◽  
Glutamine Synthetase Activity ◽  
Adp Ribosylation ◽  
Fe Protein ◽  
Knockout Mutants

ABSTRACT Rhodobacter capsulatus possesses two genes potentially coding for ammonia transporters, amtB and amtY. In order to better understand their role in the physiology of this bacterium and their possible significance in nitrogen fixation, we created single-knockout mutants. Strains mutated in either amtB or amtY did not show a growth defect under any condition tested and were still capable of taking up ammonia at nearly wild-type rates, but an amtB mutant was no longer capable of transporting methylamine. The amtB strain but not the amtY strain was also totally defective in carrying out ADP-ribosylation of Fe-protein or the switch-off of in vivo nitrogenase activity in response to NH4 + addition. ADP-ribosylation in response to darkness was unaffected in amtB and amtBY strains, and glutamine synthetase activity was normally regulated in these strains in response to ammonium addition, suggesting that one role of AmtB is to function as an ammonia sensor for the processes that regulate nitrogenase activity.

scholarly journals GlnD Is Essential for NifA Activation, NtrB/NtrC-Regulated Gene Expression, and Posttranslational Regulation of Nitrogenase Activity in the Photosynthetic, Nitrogen-Fixing Bacterium Rhodospirillum rubrum

2005 ◽  
Vol 187 (4) ◽  
pp. 1254-1265 ◽  
Author(s):  
Yaoping Zhang ◽  
Edward L. Pohlmann ◽  
Gary P. Roberts
Keyword(s):  
Gene Expression ◽  
Glutamine Synthetase ◽  
Nitrogen Source ◽  
Rhodospirillum Rubrum ◽  
Synthetase Activity ◽  
Posttranslational Regulation ◽  
Glutamine Synthetase Activity ◽  
Sole Nitrogen Source ◽  
Nitrogen Fixing ◽  
Regulated Gene Expression

ABSTRACT GlnD is a bifunctional uridylyltransferase/uridylyl-removing enzyme and is thought to be the primary sensor of nitrogen status in the cell. It plays an important role in nitrogen assimilation and metabolism by reversibly regulating the modification of PII proteins, which in turn regulate a variety of other proteins. We report here the characterization of glnD mutants from the photosynthetic, nitrogen-fixing bacterium Rhodospirillum rubrum and the analysis of the roles of GlnD in the regulation of nitrogen fixation. Unlike glnD mutations in Azotobacter vinelandii and some other bacteria, glnD deletion mutations are not lethal in R. rubrum. Such mutants grew well in minimal medium with glutamate as the sole nitrogen source, although they grew slowly with ammonium as the sole nitrogen source (MN medium) and were unable to fix N2. The slow growth in MN medium is apparently due to low glutamine synthetase activity, because a ΔglnD strain with an altered glutamine synthetase that cannot be adenylylated can grow well in MN medium. Various mutation and complementation studies were used to show that the critical uridylyltransferase activity of GlnD is localized to the N-terminal region. Mutants with intermediate levels of uridylyltransferase activity are differentially defective in nif gene expression, the posttranslational regulation of nitrogenase, and NtrB/NtrC function, indicating the complexity of the physiological role of GlnD. These results have implications for the interpretation of results obtained with GlnD in many other organisms.

Metabolic pathways implicated in the kinetic impairment of muscle glutamine homeostasis in adult and old glucocorticoid-treated rats

2004 ◽  
Vol 287 (4) ◽  
pp. E671-E676 ◽  
Author(s):  
R. Minet-Quinard ◽  
C. Moinard ◽  
F. Villie ◽  
M. P. Vasson ◽  
L. Cynober
Keyword(s):  
De Novo ◽  
Muscle Protein ◽  
Glutamine Metabolism ◽  
Control Group ◽  
Synthetase Activity ◽  
Glutamine Synthetase Activity ◽  
Protein Breakdown ◽  
Adult Rats ◽  
Old Rats ◽  
Glutamine Production

An impairment of muscle glutamine metabolism in response to dexamethasone (DEX) occurs with aging. To better characterize this alteration, we have investigated muscle glutamine release with regard to muscle glutamine production (net protein breakdown, de novo glutamine synthesis) in adult and old glucocorticoid-treated rats. Male Sprague-Dawley rats (3 or 24 mo old) were divided into seven groups: three groups received 1.5 mg/kg of DEX once a day by intraperitoneal injection for 3, 5, or 7 days; three groups were pair fed to the three treated groups, respectively; and one control group of healthy rats was fed ad libitum. Muscle glutamine synthetase activity increased earlier in old rats ( day 3) than in adult rats ( day 7), whereas an increase in muscle glutamine release occurred later in old rats ( day 5) than in adult DEX-treated rats ( day 3). Consequently, muscle glutamine concentration decreased later in old rats ( day 5) than in adults ( day 3). Finally, net muscle protein breakdown increased only in old DEX-treated rats ( day 7). In conclusion, the impairment of muscle glutamine metabolism is due to a combination of an increase in glutamine production and a delayed increase in glutamine release.

scholarly journals In Vivo Regulation of Glutamine Synthetase Activity in the Marine Chlorophyll b-Containing CyanobacteriumProchlorococcus sp. Strain PCC 9511 (Oxyphotobacteria)

2001 ◽  
Vol 67 (5) ◽  
pp. 2202-2207 ◽  
Author(s):  
Sabah El Alaoui ◽  
Jesús Diez ◽  
Lourdes Humanes ◽  
Fermı́n Toribio ◽  
Frédéric Partensky ◽  
...  
Keyword(s):  
Glutamine Synthetase ◽  
Nitrogen Starvation ◽  
Glutamate Synthase ◽  
Nitrogen Sources ◽  
Synthetase Activity ◽  
Glutamine Synthetase Activity ◽  
Protein Determination ◽  
Physiological Regulation ◽  
Gs Protein

ABSTRACT The physiological regulation of glutamine synthetase (GS; EC6.3.1.2 ) in the axenic Prochlorococcus sp. strain PCC 9511 was studied. GS activity and antigen concentration were measured using the transferase and biosynthetic assays and the electroimmunoassay, respectively. GS activity decreased when cells were subjected to nitrogen starvation or cultured with oxidized nitrogen sources, which proved to be nonusable forProchlorococcus growth. The GS activity in cultures subjected to long-term phosphorus starvation was lower than that in equivalent nitrogen-starved cultures. Azaserine, an inhibitor of glutamate synthase, provoked an increase in enzymatic activity, suggesting that glutamine is not involved in GS regulation. Darkness did not affect GS activity significantly, while the addition of diuron provoked GS inactivation. GS protein determination showed that azaserine induces an increase in the concentration of the enzyme. The unusual responses to darkness and nitrogen starvation could reflect adaptation mechanisms of Prochlorococcus for coping with a light- and nutrient-limited environment.

scholarly journals Adenine nucleotide levels in Rhodospirillum rubrum during switch-off of whole-cell nitrogenase activity

1984 ◽  
Vol 224 (3) ◽  
pp. 961-969 ◽  
Author(s):  
T D Paul ◽  
P W Ludden
Keyword(s):  
Protein Modification ◽  
Rhodospirillum Rubrum ◽  
Adenine Nucleotide ◽  
Nitrogenase Activity ◽  
Energy Charge ◽  
Whole Cell ◽  
Fe Protein ◽  
Nucleotide Pools ◽  
Phenazine Methosulphate

Adenine nucleotide pools were measured in Rhodospirillum rubrum cultures that contained nitrogenase. The average energy charge [([ATP] + 1/2[ADP])/([ATP] + [ADP] + [AMP])] was found to be 0.66 and 0.62 in glutamate-grown and N-limited cultures respectively. Treatment of glutamate-grown cells with darkness, ammonia, glutamine, carbonyl cyanide m-chlorophenylhydrazone, or phenazine methosulphate resulted in perturbations in the adenine nucleotide pools, and led to loss of whole-cell nitrogenase activity and modification in vivo of the Fe protein. Treatment of N-limited cells resulted in similar changes in adenine nucleotide pools but not enzyme modification. No correlations were found between changes in adenine nucleotide pools or ratios of these pools and switch-off of nitrogenase activity by Fe protein modification in vivo. Phenazine methosulphate inhibited whole-cell activity at low concentrations. The effect on nitrogenase activity was apparently independent of Fe protein modification.

Glutamine synthetase from Mycobacterium avium

1984 ◽  
Vol 30 (3) ◽  
pp. 353-359 ◽  
Author(s):  
Maria E. Alvarez ◽  
C. M. McCarthy
Keyword(s):  
Enzyme Activity ◽  
Glutamine Synthetase ◽  
Nitrogen Source ◽  
Mycobacterium Avium ◽  
Specific Activity ◽  
Sedimentation Coefficient ◽  
Ammonia Assimilation ◽  
Methionine Sulfoximine ◽  
Synthetase Activity ◽  
Glutamine Synthetase Activity

Mycobacterium avium was previously shown to be dependent upon ammonia or glutamine as a nitrogen source. In an effort to assess the physiology of ammonia assimilation by M. avium, a characterization of its glutamine synthetase was performed. The enzyme from M. avium was purified by streptomycin sulfate treatment, ammonium sulfate precipitation, and affinity chromatography. The enzyme was unusual in that it had a pH optimum of 6.4 and maximum enzyme activity was obtained between 50 and 60 °C as shown by the transferase assay. The glutamine synthetase activity from batch-cultured cells decreased with increasing concentration of ammonium chloride in the range of 0.25–5 μ mol/mL of medium, which demonstrated a response to environmental supply of a nitrogen source. The mycobacterial enzyme was similar to the other bacterial glutamine synthetases in terms of molecular weight and sedimentation coefficient which were 600 000 and 19.5 S, respectively, and enzyme activity was lost by treatment with a glutamate analog, methionine sulfoximine. The isoelectric point was, however, pH 4.5. Treatment of the enzyme with snake venom phosphodiesterase resulted in an increase in specific activity. AMP was released by the phosphodiesterase treatment, thus demonstrating that M. avium glutamine synthetase was regulated by adenylylation modification.

scholarly journals The role of NAD+ as a signal during nitrogenase switch-off in Rhodospirillum rubrum

1997 ◽  
Vol 322 (3) ◽  
pp. 829-832 ◽  
Author(s):  
Agneta NORÉN ◽  
Abdelhamid SOLIMAN ◽  
Stefan NORDLUND
Keyword(s):  
Metabolic Regulation ◽  
Opposite Effect ◽  
Rhodospirillum Rubrum ◽  
Nitrogenase Activity ◽  
Regulatory System ◽  
Glutamate Synthase ◽  
The Other ◽  
Dinitrogenase Reductase ◽  
Adp Ribosyltransferase

The role of NAD+ in the metabolic regulation of nitrogenase, the ‘switch-off’ effect, in Rhodospirillum rubrum has been studied. We now show that the decrease in nitrogenase activity upon addition of NAD+ to R. rubrum is due to modification of dinitrogenase reductase. There was no effect when NAD+ was added to a mutant of R. rubrumdevoid of dinitrogenase reductase ADP-ribosyltransferase, indicating that NAD+ ‘switch-off’ is an effect of the same regulatory system as ammonium ‘switch-off’. We also show that oxaloacetate and α-ketoglutarate function as ‘switch-off’ effectors. On the other hand β-hydroxybutyrate has the opposite effect by shortening the ‘switch-off’ period. Furthermore, by using an inhibitor of glutamate synthase the role of this enzyme in ‘switch-off’ was investigated. The results are discussed in relation to our proposal that changes in the concentration of NAD+ are involved in initiating ‘switch-off’.

Studies on nitrogen fixation by antibiotic-resistant mutants ofAzospirillum brasilenseand their interaction with cheena (Panicum miliaceumL.) genotypes in calcareous soil

1985 ◽  
Vol 105 (2) ◽  
pp. 261-270 ◽  
Author(s):  
R. Rai
Keyword(s):  
Nitrogen Fixation ◽  
Calcareous Soil ◽  
Nitrogenase Activity ◽  
Dry Weight ◽  
Resistant Mutant ◽  
Hydrogenase Activity ◽  
Synthetase Activity ◽  
Glutamine Synthetase Activity ◽  
Antibiotic Resistant ◽  
Mutant Strains

SUMMARYAzospirillum brasilense was treated with nitrosoguanidine and five antibiotic-resistant mutant strains isolated. Variations in growth, N2-fixation, ultraviolet-dark survival and level of antibiotic resistance were found between the mutant strains. Mutant strains STR 112 and KR 2051 showed maximum nitrogenase activity, glutamine synthetase activity and hydrogenase activity (H2uptake) at 32 °C and 40 °C respectively. Inoculation of cheena genotypes withA. brasilenseand its mutants led to significant increase in associative nitrogen fixation, dry weight of roots and grain yield compared with the uninoculated control, with significant strains × genotypes interactions in calcareous soil. It was also noted that under laboratory conditionsAzospirilluminoculation may have produced its response by hormonal means and/or associative N2-fixation.

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