Defining the Roles PII and AmtB Proteins in the NH4+-Induced Post-Translational Control of Nitrogenase Activity
In some diazothophs, such as Azospirillum brasilense and Rhodospirillum rubrum, nitrogenase is post-translationally controlled by ADP-ribosylation of nitrogenase reductase (NifH). In response to addition of NH4+ to the medium, an ADP-ribose is linked to NifH resulting in nitrogenase inactivation (switch-off). This process is catalyzed by the DraT enzyme. When the added NH4+ is exhausted by cellular metabolism, the ADPribose group is removed by the DraG enzyme leading to nitrogenase activation (switch-on). The activities of both DraT and DraG are regulated by the cellular nitrogen status, although the signaling pathway is not fully understood.
KeywordsRibose Azospirillum Azoarcus
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