scholarly journals Regulation of nitrogenase A and R concentrations in Rhodopseudomonas capsulata by glutamine synthetase

1980 ◽  
Vol 187 (1) ◽  
pp. 273-276 ◽  
Author(s):  
D C Yoch
Keyword(s):  
Glutamine Synthetase ◽  
Nitrogenase Activity ◽  
Photosynthetic Bacterium ◽  
Rhodopseudomonas Capsulata ◽  
Wild Type ◽  
Sulphur Bacteria ◽  
Intracellular Concentrations ◽  
Methionine Sulphoximine ◽  
Negative Mutant

Nitrogen-starved purple non-sulphur bacteria have an active unregulated form of nitrogenase (nitrogenase A); however, the nitrogenase of a glutamine synthetase-negative mutant of Rhodopseudomonas capsulata, when nitrogen-starved, was predominantly inactive and required activation by Mn2+ and activating-factor protein. This regulatory form of nitrogenase has been called nitrogenase R. Treatment of wild-type cells (containing nitrogenase A) with methionine sulphoximine, an inhibitor of glutamine synthetase, converted the enzyme into nitrogenase R. Glutamine synthetase thus appears to control the intracellular concentrations of nitrogenase A and R and in this way regulates nitrogenase activity in the photosynthetic bacterium.

scholarly journals Membrane Sequestration of PII Proteins and Nitrogenase Regulation in the Photosynthetic Bacterium Rhodobacter capsulatus

2007 ◽  
Vol 189 (16) ◽  
pp. 5850-5859 ◽  
Author(s):  
Pier-Luc Tremblay ◽  
Thomas Drepper ◽  
Bernd Masepohl ◽  
Patrick C. Hallenbeck
Keyword(s):  
Gel Electrophoresis ◽  
Membrane Fraction ◽  
Rhodobacter Capsulatus ◽  
Nitrogenase Activity ◽  
Polyacrylamide Gel Electrophoresis ◽  
Photosynthetic Bacterium ◽  
Wild Type ◽  
Native Polyacrylamide Gel Electrophoresis ◽  
Pii Proteins ◽  
High Level

ABSTRACT Both Rhodobacter capsulatus PII homologs GlnB and GlnK were found to be necessary for the proper regulation of nitrogenase activity and modification in response to an ammonium shock. As previously reported for several other bacteria, ammonium addition triggered the AmtB-dependent association of GlnK with the R. capsulatus membrane. Native polyacrylamide gel electrophoresis analysis indicates that the modification/demodification of one PII homolog is aberrant in the absence of the other. In a glnK mutant, more GlnB was found to be membrane associated under these conditions. In a glnB mutant, GlnK fails to be significantly sequestered by AmtB, even though it appears to be fully deuridylylated. Additionally, the ammonium-induced enhanced sequestration by AmtB of the unmodifiable GlnK variant GlnK-Y51F follows the wild-type GlnK pattern with a high level in the cytoplasm without the addition of ammonium and an increased level in the membrane fraction after ammonium treatment. These results suggest that factors other than PII modification are driving its association with AmtB in the membrane in R. capsulatus.

Short-Term Regulation of Nitrogenase Activity by NH4+ in Rhodobacter capsulatus: Multiple In Vivo Nitrogenase Responses to NH4+ Addition

1998 ◽  
Vol 180 (23) ◽  
pp. 6392-6395 ◽  
Author(s):  
Alexander F. Yakunin ◽  
Patrick C. Hallenbeck
Keyword(s):  
Type Strain ◽  
Wild Type Strain ◽  
Rhodobacter Capsulatus ◽  
Nitrogenase Activity ◽  
Photosynthetic Bacterium ◽  
Wild Type ◽  
Magnitude Response ◽  
Short Term ◽  
Reversible Inhibition

ABSTRACT The photosynthetic bacterium Rhodobacter capsulatus has been shown to carry out nitrogenase “switch-off,” a rapid, reversible inhibition of in vivo activity. Here, we demonstrate that highly nitrogen-limited cultures of both the wild-type strain and adraT draG mutant are capable of nitrogenase switch-off while moderately nitrogen-limited cultures show instead a “magnitude” response, with a decrease in in vivo nitrogenase activity that is proportional to the amount of added NH4 +.

scholarly journals Mutagenesis and Functional Characterization of theglnB, glnA, and nifA Genes from the Photosynthetic Bacterium Rhodospirillum rubrum

2000 ◽  
Vol 182 (4) ◽  
pp. 983-992 ◽  
Author(s):  
Yaoping Zhang ◽  
Edward L. Pohlmann ◽  
Paul W. Ludden ◽  
Gary P. Roberts
Keyword(s):  
Nitrogen Fixation ◽  
Rhodospirillum Rubrum ◽  
Nitrogenase Activity ◽  
Functional Characterization ◽  
Photosynthetic Bacterium ◽  
Wild Type ◽  
Adp Ribosylation ◽  
Dinitrogenase Reductase ◽  
Adp Ribosyltransferase

ABSTRACT Nitrogen fixation is tightly regulated in Rhodospirillum rubrum at two different levels: transcriptional regulation ofnif expression and posttranslational regulation of dinitrogenase reductase by reversible ADP-ribosylation catalyzed by the DRAT-DRAG (dinitrogenase reductase ADP-ribosyltransferase–dinitrogenase reductase-activating glycohydrolase) system. We report here the characterization ofglnB, glnA, and nifA mutants and studies of their relationship to the regulation of nitrogen fixation. Two mutants which affect glnB (structural gene for PII) were constructed. While PII-Y51F showed a lower nitrogenase activity than that of wild type, a PIIdeletion mutant showed very little nif expression. This effect of PII on nif expression is apparently the result of a requirement of PII for NifA activation, whose activity is regulated by NH4 + in R. rubrum. The modification of glutamine synthetase (GS) in theseglnB mutants appears to be similar to that seen in wild type, suggesting that a paralog of PII might exist inR. rubrum and regulate the modification of GS. PII also appears to be involved in the regulation of DRAT activity, since an altered response to NH4 + was found in a mutant expressing PII-Y51F. The adenylylation of GS plays no significant role in nif expression or the ADP-ribosylation of dinitrogenase reductase, since a mutant expressing GS-Y398F showed normal nitrogenase activity and normal modification of dinitrogenase reductase in response to NH4 + and darkness treatments.

scholarly journals Enhanced Nitrogenase Activity in Strains of Rhodobacter capsulatus That Overexpress the rnf Genes

2000 ◽  
Vol 182 (5) ◽  
pp. 1208-1214 ◽  
Author(s):  
Ho-Sang Jeong ◽  
Yves Jouanneau
Keyword(s):  
Rhodobacter Capsulatus ◽  
Nitrogenase Activity ◽  
Photosynthetic Bacterium ◽  
Wild Type ◽  
Wild Type Level ◽  
Intracellular Content ◽  
Nitrogenase Activities ◽  
Membrane Bound

ABSTRACT In the photosynthetic bacterium Rhodobacter capsulatus, a putative membrane-bound complex encoded by the rnfABCDGEHoperon is thought to be dedicated to electron transport to nitrogenase. In this study, the whole rnf operon was cloned under the control of the nifH promoter in plasmid pNR117 and expressed in several rnf mutants. Complementation analysis demonstrated that transconjugants which integrated plasmid pNR117 directed effective biosynthesis of a functionally competent complex inR. capsulatus. Moreover, it was found that strains carrying pNR117 displayed nitrogenase activities 50 to 100% higher than the wild-type level. The results of radioactive labeling experiments indicated that the intracellular content of nitrogenase polypeptides was marginally altered in strains containing pNR117, whereas the levels of the RnfB and RnfC proteins present in the membrane were four- and twofold, respectively, higher than the wild-type level. Hence, the enhancement of in vivo nitrogenase activity was correlated with a commensurate overproduction of the Rnf polypeptides. In vitro nitrogenase assays performed in the presence of an artificial electron donor indicated that the catalytic activity of the enzyme was not increased in strains overproducing the Rnf polypeptides. It is proposed that the supply of reductants through the Rnf complex might be rate limiting for nitrogenase activity in vivo. Immunoprecipitation experiments performed on solubilized membrane proteins revealed that RnfB and RnfC are associated with each other and with additional polypeptides which may be components of the membrane-bound complex.

scholarly journals The Synechococcus Strain PCC 7942glnN Product (Glutamine Synthetase III) Helps Recovery from Prolonged Nitrogen Chlorosis

2000 ◽  
Vol 182 (19) ◽  
pp. 5615-5619 ◽  
Author(s):  
Jörg Sauer ◽  
Ulrike Dirmeier ◽  
Karl Forchhammer
Keyword(s):  
Glutamine Synthetase ◽  
Transcriptional Start Site ◽  
Binding Motif ◽  
Class Iii ◽  
Wild Type ◽  
Cloning And Sequencing ◽  
Gene Encoding ◽  
Low Concentrations ◽  
Synechococcus Strain ◽  
Pcc 7942

ABSTRACT We report the cloning and sequencing of the glnN gene encoding a class III glutamine synthetase from the cyanobacteriumSynechococcus strain PCC 7942. Mapping of the transcriptional start site revealed a DNA sequence in the promoter region that resembles an imperfect NtcA binding motif. Expression ofglnN is impaired in NtcA- and PII-deficient mutants. The only parameter which was negatively affected in theglnN mutant compared to the wild type was the recovery rate of prolonged nitrogen-starved cells with low concentrations of combined nitrogen.

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