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Nitrogenase switch-off and regulation of ammonium assimilation in response to light deprivation in Rhodospirillum rubrum are influnced by the nitrogen source used during growth
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.
2010 (English)In: Journal of Bacteriology, ISSN 0021-9193, E-ISSN 1098-5530, Vol. 192, no 5, 1463-1466 p.Article in journal (Refereed) Published
Abstract [en]

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.

Place, publisher, year, edition, pages
2010. Vol. 192, no 5, 1463-1466 p.
National Category
Biochemistry and Molecular Biology
Identifiers
URN: urn:nbn:se:su:diva-29611DOI: 10.1128/JB.01456-09OAI: oai:DiVA.org:su-29611DiVA: diva2:234454
Available from: 2009-09-08 Created: 2009-09-08 Last updated: 2017-12-13Bibliographically 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.
Keyword
Rhodospirillum rubrum, nitrogen fixation, switch-off, PII, AmtB1, DRAG
National Category
Dentistry
Research subject
Biochemistry
Identifiers
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)
Opponent
Supervisors
Note
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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