The complexity of the 'simple' two-component system KdpD/KdpE in Escherichia coli.
The KdpD/KdpE two-component system of Escherichia coli activates the expression of the kdpFABC operon encoding the high-affinity K(+) uptake system KdpFABC in response to K(+) limitation or salt stress. Earlier, it was proposed that the histidine kinase KdpD is a turgor sensor; recent studies suggest that KdpD integrates three chemical stimuli from the cytoplasm. The histidine kinase KdpD contains several structural features and subdomains that are important for stimulus perception, modulation of the kinase to phosphatase ratio, and signaling. The response regulator KdpE receives the phosphoryl group from KdpD and induces kdpFABC transcription. The three-dimensional structure of the receiver domain was resolved, providing insights into the activation mechanism of this transcriptional regulator. Two accessory components, the universal stress protein UspC and the phosphotransferase system component IIA(Ntr), are known to interact with KdpD, allowing the modulation of kdpFABC expression under certain physiological conditions. Here, we will discuss the complexity of a 'simple' two-component system and its interconnectivity with metabolism and the general stress response.
Heermann
Ralf
R
Munich Center for integrated Protein Science (CiPSM) at Ludwig-Maximilians-Universität München, Biozentrum, Bereich Mikrobiologie, Martinsried, Germany. heermann@lmu.de
Jung
Kirsten
K
D004926:Escherichia coli / Q000502:physiology*; D029968:Escherichia coli Proteins / Q000737:chemistry / Q000378:metabolism*; D015964:Gene Expression Regulation, Bacterial; D026901:Membrane Transport Proteins / Q000096:biosynthesis; D011188:Potassium / Q000378:metabolism; D011485:Protein Binding; D011494:Protein Kinases / Q000737:chemistry / Q000378:metabolism*; D017434:Protein Structure, Tertiary; D015398:Signal Transduction; D015534:Trans-Activators / Q000737:chemistry / Q000378:metabolism*
D029968:Escherichia coli Proteins; D026901:Membrane Transport Proteins; D015534:Trans-Activators; C075615:kdpE protein, E coli; C489580:KdpD protein, E coli; D011494:Protein Kinases; D011188:Potassium