JB
Home Help [Feedback] [For Subscribers] [Archive] [Search] [Contents]
This Article
Right arrow Full Text
Right arrow Full Text (PDF)
Right arrow Alert me when this article is cited
Right arrow Alert me if a correction is posted
Services
Right arrow Similar articles in this journal
Right arrow Similar articles in PubMed
Right arrow Alert me to new issues of the journal
Right arrow Download to citation manager
Right arrow Copyright Information
Right arrow Books from ASM Press
Right arrow MicrobeWorld
Citing Articles
Right arrow Citing Articles via HighWire
Right arrow Citing Articles via Google Scholar
Google Scholar
Right arrow Articles by Elsen, S.
Right arrow Articles by Bauer, C. E.
Right arrow Search for Related Content
PubMed
Right arrow PubMed Citation
Right arrow Articles by Elsen, S.
Right arrow Articles by Bauer, C. E.

Journal of Bacteriology, May 2000, p. 2831-2837, Vol. 182, No. 10
0021-9193/00/$04.00+0
Copyright © 2000, American Society for Microbiology. All rights reserved.

Expression of Uptake Hydrogenase and Molybdenum Nitrogenase in Rhodobacter capsulatus Is Coregulated by the RegB-RegA Two-Component Regulatory System

Sylvie Elsen,1,dagger Wanda Dischert,2 Annette Colbeau,2 and Carl E. Bauer1,*

Department of Biology, Indiana University, Bloomington, Indiana 47405,1 and UMR 5092 CEA-CNRS-UJF, Laboratoire de Biochimie et Biophysique des Systèmes Intégrés, Département de Biologie Moléculaire et Structurale, CEA/Grenoble, 38054 Grenoble cedex 9, France2

Received 2 December 1999/Accepted 16 February 2000

Purple photosynthetic bacteria are capable of generating cellular energy from several sources, including photosynthesis, respiration, and H2 oxidation. Under nutrient-limiting conditions, cellular energy can be used to assimilate carbon and nitrogen. This study provides the first evidence of a molecular link for the coregulation of nitrogenase and hydrogenase biosynthesis in an anoxygenic photosynthetic bacterium. We demonstrated that molybdenum nitrogenase biosynthesis is under the control of the RegB-RegA two-component regulatory system in Rhodobacter capsulatus. Footprint analyses and in vivo transcription studies showed that RegA indirectly activates nitrogenase synthesis by binding to and activating the expression of nifA2, which encodes one of the two functional copies of the nif-specific transcriptional activator, NifA. Expression of nifA2 but not nifA1 is reduced in the reg mutants up to eightfold under derepressing conditions and is also reduced under repressing conditions. Thus, although NtrC is absolutely required for nifA2 expression, RegA acts as a coactivator of nifA2. We also demonstrated that in reg mutants, [NiFe]hydrogenase synthesis and activity are increased up to sixfold. RegA binds to the promoter of the hydrogenase gene operon and therefore directly represses its expression. Thus, the RegB-RegA system controls such diverse processes as energy-generating photosynthesis and H2 oxidation, as well as the energy-demanding processes of N2 fixation and CO2 assimilation.

* Corresponding author. Mailing address: Department of Biology, Indiana University, Jordan Hall, Bloomington, IN 47405. Phone: (812) 855-6595. Fax: (812) 855-6705. E-mail: cbauer{at}bio.indiana.edu.

dagger Present address: UMR 5092 CEA-CNRS-UJF, Laboratoire de Biochimie et Biophysique des Systèmes Intégrés, Département de Biologie Moléculaire et Structurale, CEA/Grenoble, 38054 Grenoble cedex 9, France.

Journal of Bacteriology, May 2000, p. 2831-2837, Vol. 182, No. 10
0021-9193/00/$04.00+0
Copyright © 2000, American Society for Microbiology. All rights reserved.


This article has been cited by other articles:



Home Help [Feedback] [For Subscribers] [Archive] [Search] [Contents]
Appl. Environ. Microbiol. Infect. Immun. Eukaryot. Cell
Mol. Cell. Biol. J. Virol. Microbiol. Mol. Biol. Rev.
ALL ASM JOURNALS

Copyright © 2000 by the American Society for Microbiology. All rights reserved.