Post-Translational Regulation of Nitrogenase in Photosynthetic Bacteria

Abstract

The photosynthetic bacteria are remarkable for their range of metabolic capabilities and, as a result, the ability to survive under a wide range of environmental conditions, including nitrogen limitation. The photosynthetic bacteria are members of the alpha subdivision of the proteobacteria (Imhoff et al., 1984;Woese et al., 1984) and, with a single known exception, the wild-type strains of all purple sulfur bacteria and all purple non-sulfur bacteria are capable of N 2 fixation (Madigan et al., 1984). Most of the work that will be described in this chapter has been performed on a few species of purple, non-sulfur bacteria, including Rhodospirillum rubrum and Rhodobacter capsulatus. This chapter will focus on the biochemistry and physiology of N 2 fixation by photosynthetic bacteria and the regulation of nitrogenase activity by reversible ADP-ribosylation of the dinitrogenase reductase (Fe protein). ADP-ribosylation has also been found in Azospirillum and other genera and, where relevant, that work will be included. Other chapters in this series will cover the genes of the nif, anf and rnf regulons of the photosynthetic bacteria and the regulation of the expression of those genes. Although this chapter will discuss aspects of the nitrogenase enzyme, the mechanistic and structural details of nitrogenase will be covered in more detail in Volume 1 of this series.

Interaction of the signal transduction protein GlnJ with the cellular targets AmtB1, GlnE and GlnD in Rhodospirillum rubrum: dependence on manganese, 2-oxoglutarate and the ADP/ATP ratio

“…The activity of nitrogenase is strictly controlled by reversible post-translational ADP ribosylation in response to socalled 'switch-off' effectors, e.g. addition of ammonium or exposure of the cells to darkness (Nordlund & Ludden, 2004).…”

Mechanism of ADP-ribosylation removal revealed by the structure and ligand complexes of the dimanganese mono-ADP-ribosylhydrolase DraG

“…In the phototrophic bacterium Rhodospirillum rubrum, ADPribosylation plays a key role in nitrogen fixation as it controls the activity of dinitrogenase reductase (14). Dinitrogenase reductase ADP-ribosyltransferase (DraT) catalyses the inactivation of dinitrogenase reductase by attachment of a single ADP-ribose molecule to an arginine residue (Arg-101) in one of the subunits of the homodimeric protein.…”

“…Dinitrogenase reductase ADP-ribosyltransferase (DraT) catalyses the inactivation of dinitrogenase reductase by attachment of a single ADP-ribose molecule to an arginine residue (Arg-101) in one of the subunits of the homodimeric protein. DraT activity increases in response to environmental stimuli such as darkness and excess of a fixed nitrogen source (14). The reverse reaction is catalyzed by the monomeric 32 kDa dinitrogenase reductase-activating glycohydrolase (DraG), which removes ADP-ribose upon exposure of the bacteria to light or depletion of the nitrogen source added, regenerating the arginine guanidino group and activating the dinitrogenase reductase dimer (14).…”

“…DraT activity increases in response to environmental stimuli such as darkness and excess of a fixed nitrogen source (14). The reverse reaction is catalyzed by the monomeric 32 kDa dinitrogenase reductase-activating glycohydrolase (DraG), which removes ADP-ribose upon exposure of the bacteria to light or depletion of the nitrogen source added, regenerating the arginine guanidino group and activating the dinitrogenase reductase dimer (14). In R. rubrum DraG has been shown to reversibly associate to the membrane as part of a regulatory mechanism (15)(16)(17).…”

“…In R. rubrum DraG has been shown to reversibly associate to the membrane as part of a regulatory mechanism (15)(16)(17). DraG has long served as the model enzyme for the de-ADP-ribosylation process in numerous biochemical and functional studies (14,(18)(19)(20)(21), but structural and mechanistic data have been lacking.…”