Adenine nucleotide levels in <i>Rhodospirillum rubrum</i> during switch-off of whole-cell nitrogenase activity

Paul, Tanmay; Ludden, Paul W.

doi:10.1042/bj2240961

Cited by 37 publications

(28 citation statements)

References 46 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…There have been differences of opinion as to whether phototrophs grown on NH4+-limited medium are capable of NH4+ switch-off. Switch-off was reported under these conditions in R. rubrum (4,6,17,29,30), but others have not been able to reproduce this effect in either this organism or other phototrophs (1,2,5,10,21,23,24,25), with the exception of Rhodopseudomonas capsulata (2).…”

Section: Resultsmentioning

confidence: 99%

Changes in amino acid and nucleotide pools of Rhodospirillum rubrum during switch-off of nitrogenase activity initiated by NH4+ or darkness

Li¹,

Hu²,

Yoch³

1987

J Bacteriol

View full text Add to dashboard Cite

Amino acid and nucleotide pools were measured in nitrogenase-containing Rhodospirillum rubrum cultures during NH4+-or dark-induced inactivation (switch-off) of the Fe protein. A big increase in the glutamine pool size preceded NH4+ switch-off of nitrogenase activity, but the glutamine pool rqmained unchanged during dark switch-off. Furthermore, methionine sulfoximine had no effect on the rate of dark switch-off, suggesting that glutamine plays no role in this process. In the absence of NH4' azaserine, an inhibitor of glutamate synthate, raised glutamine pool levels sufficiently to initiate switch-off in vivo. While added NH4L substantially increased the size of the nucleotide pools in N-limited cells, the kinetics of nucleotide synthesis were all similar and followed (rather than preceded) Fe protein inactivatioi. Darkness had little effect on nucleotide pool sizes. Glutamate pool sizes were also found to be important in NH4' switch-off because of the role of this molecule as a glutamine precursor. Much of the diversity reported in the observations on NH4' switch-off appears to be due to variations in glutamate pool sizes prior to the NH4+ shock. The nitrogen nutritional background is an important factor in determnining whether darkness initiates nitrogenase switch-off; however, no link has yet been established between this and NH4' (glutamine) switch-off.The nonsulfur photosynthetic bacteria are among a group of N2-fixing bacteria with nitrogenase activity that is subject to regulation by NH4'. Carithers et al. (4) and Nordlund and Eriksspn (17) showed that the inhibitory effect of NH4' on nitrogenase activity (switch-off) is related to the covalent modification and concurrent inactivation of the nitrogenase Fe protein extracted from glutamate-and N2-grown cells (13,14,18). Similar to the inactive Fe protein isolated from glutamate-grown cells, Fe protein extracted from NH4+-inhibited cells (4, 17) was inactive and could be reactivated by a membrane-bound activating enzyme (13, 18). Switch-off of nitrogenase activity by NH4' catalyzes the covalent modification of one of the two Fe protein subunits (6, 23) with one molecule of ADP-ribose (22).The role of NH4' as an in vivo signal to activate an Fe protein-inactivating enzyme has been the subject of numerous investigations. Glutamine mimics NH4' (16) and methionine sulfoximine (MSX), an inhibitor of glutamine synthetase (GS), prevents NH4' switch-off in Rhodospirillum rubrum (5,25,30) and all other N2 fixers that are capable of switch-off regulation (3, 9). 6-Diazo-5-oxo-L-norleucine (30) and azaserine (7) are inhibitors of glutamate synthase (GOGAT), and both initiate switch-off in the absence of NH4', presumably by blocking the normal flux of nitrogen through the GS-GOGAT pathway. This results in a glutamine buildup sufficient to initiate switch-off.The confirmed and extended to show that R. rubrum could rapidly reverse this process in the light (10). It is not readily apparent what glutamine and darkness have in common that leads to the activation of the Fe...

show abstract

Section: Resultsmentioning

confidence: 99%

Changes in amino acid and nucleotide pools of Rhodospirillum rubrum during switch-off of nitrogenase activity initiated by NH4+ or darkness

Li¹,

Hu²,

Yoch³

1987

J Bacteriol

View full text Add to dashboard Cite

show abstract

“…The notion that ATP levels can fluctuate and have important biological effects has been clearly demonstrated in the regulation of rRNA expression in E. coli (Paul et al, 2004;Schneider et al, 2002). However, the adenylate and pyridine nucleotide pools have been analysed in R. rubrum in response to darkness and NH z 4 treatments (Nordlund & Höglund, 1986;Paul & Ludden, 1984) and only a slight transient decrease of the ATP pool was found after a shift to darkness (Paul & Ludden, 1984). Because of the obvious role of ATP in modulating P II function in vitro, we favour the general model that energy deprivation (darkness in our system) creates an ATP-deficient form of P II that behaves sufficiently like unmodified P II , irrespective of the actual presence of UMP, at least in terms of regulation of nitrogenase activity.…”

Section: Discussionmentioning

confidence: 99%

Effect of AmtB homologues on the post-translational regulation of nitrogenase activity in response to ammonium and energy signals in Rhodospirillum rubrum

et al. 2006

View full text Add to dashboard Cite

The AmtB protein transports uncharged NH 3 into the cell, but it also interacts with the nitrogen regulatory protein P II , which in turn regulates a variety of proteins involved in nitrogen fixation and utilization. Three P II homologues, GlnB, GlnK and GlnJ, have been identified in the photosynthetic bacterium Rhodospirillum rubrum, and they have roles in at least four overlapping and distinct functions, one of which is the post-translational regulation of nitrogenase activity. In R. rubrum, nitrogenase activity is tightly regulated in response to NH + 4 addition or energy depletion (shift to darkness), and this regulation is catalysed by the post-translational regulatory system encoded by draTG. Two amtB homologues, amtB 1 and amtB 2 , have been identified in R. rubrum, and they are linked with glnJ and glnK, respectively. Mutants lacking AmtB 1 are defective in their response to both NH + 4 addition and darkness, while mutants lacking AmtB 2 show little effect on the regulation of nitrogenase activity. These responses to darkness and NH + 4 appear to involve different signal transduction pathways, and the poor response to darkness does not seem to be an indirect result of perturbation of internal pools of nitrogen. It is also shown that AmtB 1 is necessary to sequester detectable amounts GlnJ to the cell membrane. These results suggest that some element of the AmtB 1 -P II regulatory system senses energy deprivation and a consistent model for the integration of nitrogen, carbon and energy signals by P II is proposed. Other results demonstrate a degree of specificity in interaction of AmtB 1 with the different P II homologues in R. rubrum. Such interaction specificity might be important in explaining the way in which P II proteins regulate processes involved in nitrogen acquisition and utilization.

show abstract

“…Although there have been several studies of possible metabolic signals for these stimuli, including the effect of energy (11,20), pools of amino acids and pyridine nucleotides (11,14,18,24), and metal ions (19,27), the nature of the signals for the DRAT/DRAG system is still unknown. In A. brasilense, NH 4 ϩ and anaerobic stimuli may have at least partially divergent signal transduction pathways, as the mutational loss of ntrBC causes a dramatically altered NH 4 ϩ switch-off but has little effect on anaerobic switch-off (29).…”

Section: Discussionmentioning

confidence: 99%

Comparison studies of dinitrogenase reductase ADP-ribosyl transferase/dinitrogenase reductase activating glycohydrolase regulatory systems in Rhodospirillum rubrum and Azospirillum brasilense

et al. 1995

Self Cite

View full text Add to dashboard Cite

Reversible ADP ribosylation of dinitrogenase reductase, catalyzed by the dinitrogenase reductase ADPribosyl transferase (DRAT)/dinitrogenase reductase activating glycohydrolase (DRAG) regulatory system, has been characterized in both Rhodospirillum rubrum and Azospirillum brasilense. Although the general functions of DRAT and DRAG are very similar in these two organisms, there are a number of interesting differences, e.g., in the timing and extent of the regulatory response to different stimuli. In this work, the basis of these differences has been studied by the heterologous expression of either draTG or nifH from A. brasilense in R. rubrum mutants that lack these genes, as well as the expression of draTG from R. rubrum in an A. brasilense draTG mutant. In general, these hybrid strains respond to stimuli in a manner similar to that of the wild-type parent of the recipient strain rather than the wild-type source of the introduced genes. These results suggest that the differences seen in the regulatory response in these organisms are not primarily a result of different properties of DRAT, DRAG, or dinitrogenase reductase. Instead, the differences are likely the result of different signal pathways that regulate DRAG and DRAT activities in these two organisms. Our results also suggest that draT and draG are cotranscribed in A. brasilense.The posttranslational regulation of nitrogenase activity, which is also termed switch-off (31), has been found in many diverse nitrogen-fixing bacteria. However, this regulation has been well characterized only in Rhodospirillum rubrum, Azospirillum brasilense, Azospirillum lipoferum, and Rhodobacter capsulatus, in which it involves reversible mono-ADP ribosylation of dinitrogenase reductase, catalyzed by the dinitrogenase reductase ADP-ribosyl transferase (DRAT)/dinitrogenase reductase activating glycohydrolase (DRAG) regulatory system (5,6,17,30). DRAT (the gene product of draT) catalyzes the transfer of the ADP-ribose from NAD to the Arg-101 residue of one subunit of the dinitrogenase reductase dimer and thereby inactivates the enzyme. The ADP-ribose group attached to dinitrogenase reductase can be removed by another enzyme, DRAG (the gene product of draG), thus restoring nitrogenase activity (16).draT and draG have been cloned and sequenced from R. rubrum, R. capsulatus, and A. brasilense (5, 17, 30). The sequence comparison of draTG from these strains showed an extensive similarity, with some conserved regions (17). draTG mutants also were constructed and physiologically characterized in these organisms (15,17,30).In the cases of A. brasilense and R. rubrum, the activities of DRAG and DRAT themselves are subject to some form of posttranslational regulation by an unknown mechanism. Under derepressing (nitrogen-fixing) conditions, DRAG is active and DRAT is inactive (7,15,28,30). In A. brasilense, for example, shifting a culture from microaerobic to anaerobic conditions eliminates the preferred energy source. In response to this shift, DRAG activity ceases rapidly and DRAT activ...

show abstract

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

Cited by 37 publications

References 46 publications

Changes in amino acid and nucleotide pools of Rhodospirillum rubrum during switch-off of nitrogenase activity initiated by NH4+ or darkness

Changes in amino acid and nucleotide pools of Rhodospirillum rubrum during switch-off of nitrogenase activity initiated by NH4+ or darkness

Effect of AmtB homologues on the post-translational regulation of nitrogenase activity in response to ammonium and energy signals in Rhodospirillum rubrum

Comparison studies of dinitrogenase reductase ADP-ribosyl transferase/dinitrogenase reductase activating glycohydrolase regulatory systems in Rhodospirillum rubrum and Azospirillum brasilense

Contact Info

Product

Resources

About