The role of glutamine synthetase in the regulation of nitrogenase activity (?switch off? effect) in Rhodospirillum rubrum

1982 ◽  
Vol 132 (3) ◽  
pp. 251-253 ◽  
Author(s):  
Gunnar Falk ◽  
Bo C. Johansson ◽  
Stefan Nordlund
Keyword(s):  
Glutamine Synthetase ◽  
Rhodospirillum Rubrum ◽  
Nitrogenase Activity

scholarly journals Role of the Dinitrogenase Reductase Arginine 101 Residue in Dinitrogenase Reductase ADP-Ribosyltransferase Binding, NAD Binding, and Cleavage

2001 ◽  
Vol 183 (1) ◽  
pp. 250-256 ◽  
Author(s):  
Yan Ma ◽  
Paul W. Ludden
Keyword(s):  
Rhodospirillum Rubrum ◽  
Nitrogenase Activity ◽  
Site Directed Mutagenesis ◽  
Directed Mutagenesis ◽  
Adp Ribosylation ◽  
Dinitrogenase Reductase ◽  
Adp Ribosyltransferase

ABSTRACT Dinitrogenase reductase is posttranslationally regulated by dinitrogenase reductase ADP-ribosyltransferase (DRAT) via ADP-ribosylation of the arginine 101 residue in some bacteria.Rhodospirillum rubrum strains in which the arginine 101 of dinitrogenase reductase was replaced by tyrosine, phenylalanine, or leucine were constructed by site-directed mutagenesis of thenifH gene. The strain containing the R101F form of dinitrogenase reductase retains 91%, the strain containing the R101Y form retains 72%, and the strain containing the R101L form retains only 28% of in vivo nitrogenase activity of the strain containing the dinitrogenase reductase with arginine at position 101. In vivo acetylene reduction assays, immunoblotting with anti-dinitrogenase reductase antibody, and [adenylate-32P]NAD labeling experiments showed that no switch-off of nitrogenase activity occurred in any of the three mutants and no ADP-ribosylation of altered dinitrogenase reductases occurred either in vivo or in vitro. Altered dinitrogenase reductases from strains UR629 (R101Y) and UR630 (R101F) were purified to homogeneity. The R101F and R101Y forms of dinitrogenase reductase were able to form a complex with DRAT that could be chemically cross-linked by 1-ethyl-3-(3-dimethylaminopropyl)-carbodiimide. The R101F form of dinitrogenase reductase and DRAT together were not able to cleave NAD. This suggests that arginine 101 is not critical for the binding of DRAT to dinitrogenase reductase but that the availability of arginine 101 is important for NAD cleavage. Both DRAT and dinitrogenase reductase can be labeled by [carbonyl-14C]NAD individually upon UV irradiation, but most 14C label is incorporated into DRAT when both proteins are present. The ability of R101F dinitrogenase reductase to be labeled by [carbonyl-14C]NAD suggested that Arg 101 is not absolutely required for NAD binding.

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’.

scholarly journals The role of Mg2+ and Mn2+ in the enzyme-catalysed activation of nitrogenase Fe protein from Rhodospirillum rubrum

1983 ◽  
Vol 213 (3) ◽  
pp. 741-749 ◽  
Author(s):  
J H Guth ◽  
R H Burris
Keyword(s):  
Metal Ion ◽  
Rhodospirillum Rubrum ◽  
Nitrogenase Activity ◽  
Optimal Conditions ◽  
Fe Protein ◽  
C2h2 Reduction ◽  
Site Of Action ◽  
A Site ◽  
Free Metal

The activation of the Fe protein of nitrogenase (Rr2) from glutamate-grown Rhodospirillum rubrum by activating enzyme (AE) was investigated. AE is confirmed to have Mr about 20 000 and is shown to operate catalytically. There is a role in activation for metal-ion-ATP, which can be met by either MnATP or MgATP. There is also a site of action for free metal ions. This site prefers Mn2+ (apparent Kd approx. 20 microM) over Mg2+ (apparent Kd approx. 20 mM) by a factor of 1000-fold. Non-activated Rr2 does not contain this binding site. MnATP is an inhibitor of C2H2 reduction, and excess Mg2+ inhibits both AE activity and C2H2 reduction, when each is studied independently under otherwise optimal conditions. The activity of AE is increased in normal reaction mixtures (in which AE activity and nitrogenase activity occur simultaneously) by Mg2+ concentrations in excess of ATP concentrations; this occurs because the excess Mg2+ prevents ATP from chelating the free Mn2+ necessary for optimal AE activity.

scholarly journals The Overexpression of Glutamine Synthetase in Transgenic Poplar: A Review

2006 ◽  
Vol 55 (1-6) ◽  
pp. 278-284 ◽  
Author(s):  
E. G. Kirby ◽  
F. Gallardo ◽  
H. Man ◽  
R. El-Khatib
Keyword(s):  
Glutamine Synthetase ◽  
Woody Plant ◽  
Forest Tree ◽  
Considerable Effort ◽  
Physiological Mechanisms ◽  
Enhanced Resistance ◽  
Enhanced Expression ◽  
Use Efficiency

Abstract In investigating the pivotal role of glutamine synthetase in woody plant development, we have strived to develop an understanding of the biochemical and physiological mechanisms whereby enhanced expression of glutamine synthetase (GS) in poplar contributes to vegetative growth through enhanced nitrogen use efficiency. Considerable effort has also centered on characterization of enhanced resistance of transgenic GS overexpressor lines to abiotic stresses and proposed mechanisms. This summary of our work also focuses on future applications in forest tree improvement.

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