Transcription factor TnrA inhibits the biosynthetic activity of glutamine synthetase in Bacillus subtilis

• The transcription factor TnrA inhibits the GS activity in vivo and in vitro.
• TnrA enhances the effect of feedback inhibitors, in particular, of glutamine.
• GlnK counteracts the binding of GS to TnrA by competitive association with TnrA.
• The benefit of binding of TnrA to GlnK could be prevention of TnrA–GS interactions.

The Bacillus subtilis glutamine synthetase (GS) plays a dual role in cell metabolism by functioning as catalyst and regulator. GS catalyses the ATP-dependent synthesis of glutamine from glutamate and ammonium. Under nitrogen-rich conditions, GS becomes feedback-inhibited by high intracellular glutamine levels and then binds transcription factors GlnR and TnrA, which control the genes of nitrogen assimilation. While GS-bound TnrA is no longer able to interact with DNA, GlnR–DNA binding is shown to be stimulated by GS complex formation. In this paper we show a new physiological feature of the interaction between glutamine synthetase and TnrA. The transcription factor TnrA inhibits the biosynthetic activity of glutamine synthetase in vivo and in vitro, while the GlnR protein does not affect the activity of the enzyme.

Structured summary of protein interactionsGS physically interacts with TnrA by anti bait coimmunoprecipitation (View interaction)TnrA binds to GS by pull down (View interaction)TnrA binds to GS by surface plasmon resonance (View interaction)GlnK physically interacts with TnrA by anti bait coimmunoprecipitation (View interaction)GlnK binds to GS by pull down (View interaction)