Astrid Agneta NorénResearcher

Regulation of nitrogen fixation in photosynthetic bacteria

This project is a collaboration with Stefan Nordlund
Nitrogen metabolism plays a central role in any organism and our studies concern the process leading to conversion of atmospheric nitrogen, N2, to forms that can be used in the cell through ammonia assimilation. We have in particular focussed on the regulation of these processes in the beautiful photosynthetic bacterium Rhodospirillum rubrum. Over the years we have narrowed down our efforts to understanding of the metabolic regulation of nitrogenase, the enzyme catalyzing nitrogen fixation.

This fascinating control system involves reversible covalent modification of one of the two components of nitrogenase, the Fe-protein. The modified protein is inactive. We are aiming at identifying the signal(s) to the two enzymes DRAT, which catalyzes the modification, and DRAG catalysing the removal of the modifying group, an ADP-ribose.

We are in addition interested in more specifically identify the difference in the pattern of proteins expressed when the bacterium fixes nitrogen compared with conditions when nitrogenase is not synthesized, i.e. when there is sufficient usabele nitrogen compounds available.

The methods we employ span from basic biochemistry and molecular biology to proteomics.

 

 

Selected Publications

• Selao, T.S., Branca, R., Chae, P.S., Lehtiö, J., Gellman, S.H., Rasmussen, S.G.F., Nordlund, S. and Norén, A. (2011) Identification of chromatophore membrane protein complexes formed under different nitrogen availability conditions in Rhodospirillum rubrum. J. Proteome. 10:2703-2714.

• Berthold, C., Wang, H., Nordlund, S., and Högbom, H. (2009) Mechanism of ADP-ribosylation removal revealed by the structure and ligand complexes of thedimanganese mono-ADP-ribosylhydrolase DraG. Proc. Natl. Acad. Sci. USA 106:14247-14252.

• Wang, H., Franke, C.C., Nordlund, S. and Norén, A. (2005). Reversible membrane association of dinitrogenase reductase activating glycohydrolase in the regulation of nitrogenase activity in Rhodospirillum rubrum; dependence on GlnJ and AmtB1. FEMS Microbiol. Lett. 253:273-279.

• Nordlund, S. and Ludden, P.W. (2004) “Post-translational regulation of nitrogenase in photsynthetic bacteria”, in “Genetics and regulation of nitrogen fixing bacteria”, (Klipp, W., Masephol, B., Gallon, J.R. and Newton, W.E. eds.) Kluwer Academic Press, the Netherlands. 175-196.