Sensation of α-ketoglutarate, adenylate energy charge, and glutamine, and signal integration by the nitrogen assimilation control system of Escherichia coli
Alexander J. Ninfa and Peng Jiang
from: Sensory Mechanisms in Bacteria: Molecular Aspects of Signal Recognition (Edited by: Stephen Spiro and Ray Dixon). Caister Academic Press, U.K. (2010)
In Escherichia coli and related bacteria, nitrogen assimilation is coordinated with carbon assimilation and cellular energy status to provide for balanced metabolism and optimal growth under a variety of conditions. Part of this regulation is accomplished by a signal transduction system that includes two bicyclic cascades of covalent modification, controlling the activity of glutamine synthetase and the transcription of nitrogen-regulated genes, respectively. Here, we review our current state of understanding of these bicyclic cascade systems, with an emphasis on the mechanisms of sensation and signal integration. We also address systems level questions relevant to sensation, focusing on how the relative levels of the proteins constituting the signal transduction system affects the sensitivity to signals, how zero-order and multi-step ultrasensitivity affect the sensitivity to signals, and how downstream targets of the signaling systems may influence sensation of stimuli and signal transduction read more ...