PMID:19101563
| Citation |
Heermann, R, Weber, A, Mayer, B, Ott, M, Hauser, E, Gabriel, G, Pirch, T and Jung, K (2009) The universal stress protein UspC scaffolds the KdpD/KdpE signaling cascade of Escherichia coli under salt stress. J. Mol. Biol. 386:134-48 |
|---|---|
| Abstract |
The sensor kinase KdpD and the response regulator KdpE control induction of the kdpFABC operon encoding the high-affinity K(+)-transport system KdpFABC in response to K(+) limitation or salt stress. Under K(+) limiting conditions the Kdp system restores the intracellular K(+) concentration, while in response to salt stress K(+) is accumulated far above the normal content. The kinase activity of KdpD is inhibited at high concentrations of K(+), so it has been puzzling how the sensor can be activated in response to salt stress. Here, we demonstrate that the universal stress protein UspC acts as a scaffolding protein of the KdpD/KdpE signaling cascade by interacting with a Usp domain in KdpD of the UspA subfamily under salt stress. Escherichia coli encodes three single domain proteins of this subfamily, UspA, UspC, and UspD, whose expression is up-regulated under various stress conditions. Among these proteins only UspC stimulated the in vitro reconstructed signaling cascade (KdpD-->KdpE-->DNA) resulting in phosphorylation of KdpE at a K(+) concentration that would otherwise almost prevent phosphorylation. In agreement, in a DeltauspC mutant KdpFABC production was down-regulated significantly when cells were exposed to salt stress, but unchanged under K(+) limitation. Biochemical studies revealed that UspC interacts specifically with the Usp domain in the stimulus perceiving N-terminal domain of KdpD. Furthermore, UspC stabilized the KdpD/KdpE~P/DNA complex and is therefore believed to act as a scaffolding protein. This study describes the stimulation of a bacterial two-component system under distinct stress conditions by a scaffolding protein, and highlights a new role of the universal stress proteins. |
| Links |
PubMed Online version:10.1016/j.jmb.2008.12.007 |
| Keywords |
Binding Sites; Escherichia coli/genetics; Escherichia coli/metabolism; Escherichia coli Proteins/genetics; Escherichia coli Proteins/metabolism; Heat-Shock Proteins/genetics; Heat-Shock Proteins/metabolism; Models, Biological; Models, Molecular; Potassium/metabolism; Protein Conformation; Protein Kinases/metabolism; Protein Structure, Tertiary; Signal Transduction; Sodium Chloride/metabolism; Surface Plasmon Resonance; Trans-Activators/metabolism |
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