K+ Supply, Osmotic Stress, and the KdpD/KdpE Two-component System
Ralf Heermann and Kirsten Jung
from: Two-Component Systems in Bacteria (Edited by: Roy Gross and Dagmar Beier). Caister Academic Press, U.K. (2012)
The KdpD/KdpE system is one of the most distributed histidine kinase/response regulator systems in bacteria. This two-component system controls expression of the kdpFABC operon encoding the high affinity K+ uptake system KdpFABC. KdpD/KdpE is activated whenever the constitutively expressed K+ uptake systems are unable to keep up with the cellular need for K+. Typical KdpD/KdpE activating conditions comprise K+ limitation or osmotic stress. The histidine kinase KdpD is composed of several 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 KdpE receiver domain gives insights into the activation mechanism of this transcriptional regulator. Two accessory proteins, the universal stress protein UspC and the phosphotransferase system component IIANtr, interact with KdpD, whereby kdpFABC expression is modulated under certain physiological conditions. Here we will review the nature of the stimulus of KdpD/KdpE in correlation with structural features as well as the interconnectivity of KdpD/KdpE with K+ supply, osmotic stress response and virulence read more ...