Control of AmtB-GlnK Complex Formation by Intracellular Levels of ATP, ADP, and 2-Oxoglutarate

P-II proteins are one of the most widespread families of signal transduction proteins in nature, being ubiquitous throughout bacteria, archaea, and plants. They play a major role in coordinating nitrogen metabolism by interacting with, and regulating the activities of, a variety of enzymes, transcription factors, and membrane transport proteins. The regulatory properties of P-II proteins derive from their ability to bind three effectors: ATP, ADP, and 2-oxoglutarate. However, a clear model to integrate physiological changes with the consequential structural changes that mediate P-II interaction with a target protein has so far not been developed. In this study, we analyzed the fluctuations in intracellular effector pools in Escherichia coli during association and dissociation of the P-II protein GlnK with the ammonia channel AmtB. We determined that key features promoting AmtB-GlnK complex formation are the rapid drop in the 2-oxoglutarate pool upon ammonium influx and a simultaneous, but transient, change in the ATP/ADP ratio. We were also able to replicate AmtB-GlnK interactions in vitro using the same effector combinations that we observed in vivo. This comprehensive data set allows us to propose a model that explains the way in which interactions between GlnK and its effectors influence the conformation of GlnK and thereby regulate its interaction with AmtB.