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.
KeywordsBiological Nitrogen Fixation Azospirillum Brasilense Rhodospirillum Rubrum DraG Activity DraG Localization
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