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Reversible membrane association of dinitrogenase reductase activating glycohydrolase in the regulation of nitrogenase activity in Rhodospirillum rubrum; dependence on GlnJ and AmtB1
Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.
Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.
Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.
2005 (English)In: FEMS Microbiology Letters, ISSN 0378-1097, Vol. 253, no 2, 273-279 p.Article in journal (Refereed) Published
Abstract [en]

In the photosynthetic bacterium Rhodospirillum rubrum nitrogenase activity is regulated by reversible ADP-ribosylation of dinitrogenase reductase in response to external so called “switch-off” effectors. Activation of the modified, inactive form is catalyzed by dinitrogenase reductase activating glycohydrolase (DRAG) which removes the ADP-ribose moiety. This study addresses the signal transduction between external effectors and DRAG. R. rubrum, wild-type and PII mutant strains, were studied with respect to DRAG localization. We conclude that GlnJ clearly has an effect on the association of DRAG to the membrane in agreement with the effect on regulation of nitrogenase activity. Furthermore, we have generated a R. rubrum mutant lacking the putative ammonium transporter AmtB1 which was shown not to respond to “switch-off” effectors; no loss of nitrogenase activity and no ADP-ribosylation. Interestingly, DRAG was mainly localized to the cytosol in this mutant. Overall the results support our model in which association to the membrane is part of the mechanism regulating DRAG activity.

Place, publisher, year, edition, pages
2005. Vol. 253, no 2, 273-279 p.
Keyword [en]
Nitrogenase regulation; Rhodospirillum rubrum; AmtB
URN: urn:nbn:se:su:diva-14862DOI: 10.1016/j.femsle.2005.09.049PubMedID: 16243452OAI: diva2:181382
Available from: 2008-11-06 Created: 2008-11-06 Last updated: 2009-09-08Bibliographically approved
In thesis
1. Metabolic regulation of nitrogen fixation in Rhodospirillum rubrum
Open this publication in new window or tab >>Metabolic regulation of nitrogen fixation in Rhodospirillum rubrum
2009 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Nitrogen, along with carbon, hydrogen and oxygen, is amongst the most abundant elements in all living cells. The capability to convert atmospheric dinitrogen to biologically usable nitrogen compounds is only found in some prokaryotes. Biological nitrogen fixation, the reduction of dinitrogen to ammonia, is the entry step into the global nitrogen cycle. Nitrogenase, the enzyme responsible for dinitrogen reduction, requires large amounts of ATP and reducing equivalents. Consequently, the nitrogen fixation process is subjected to sophisticated regulatory networks that respond to multiple environmental stimuli. In the free-living photosynthetic nitrogen-fixing bacterium Rhodospirillum rubrum, the activity of nitrogenase is tightly regulated at the post-translational level by reversible ADP-ribosylation in response to cellular changes in nitrogen and energy status, the so-called “switch-off” effect. Our studies have been focused on identifying the intracellular signal(s) and protein components acting during “switch-off”, and elucidating the mechanism underlying this regulation. We have shown that PII signal transduction proteins and the ammonium transporter AmtB1 play central roles in the signal transduction pathway leading to the post-translational regulation of nitrogenase, in particular, the involvement of AmtB1-PII complex formation during ammonium “switch-off”. In contrast, a different signaling pathway is operating during the energy “switch-off”, and several interesting differences are highlighted here. In addition, we have solved a high-resolution structure of Dinitrogenase Reductase Activating Glycohydrolase (DRAG) using X-ray crystallography. A detailed mechanism of ADP-ribose removal by DRAG is proposed, with our structural and functional studies on DRAG supporting a reversible membrane association mechanism of regulating its activity, further controlling the activity of nitrogenase.

Place, publisher, year, edition, pages
Stockholm: Department of Biochemistry and Biophysics, Stockholm University, 2009. 64 p.
Rhodospirillum rubrum, nitrogen fixation, switch-off, PII, AmtB1, DRAG
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Research subject
urn:nbn:se:su:diva-29404 (URN)978-91-7155-920-3 (ISBN)
Public defence
2009-10-02, Magnélisalen, Kemiska övningslaboratoriet, Svante Arrhenius väg 16 B, Stockholm, 10:00 (English)
At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 2: Submitted. Paper 4: Submitted.Available from: 2009-09-10 Created: 2009-08-26 Last updated: 2009-09-08Bibliographically approved

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Wang, HeNordlund, StefanNorén, Agneta
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