The universal stress protein UspC scaffolds the KdpD/KdpE signaling cascade of Escherichia coli under salt stress.
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.
Heermann
Ralf
R
Ludwig-Maximilians-Universität München, Bereich Mikrobiologie, Grosshaderner Str. 2-4, D-82152 Planegg-Martinsried, Germany.
Weber
Arnim
A
Mayer
Bettina
B
Ott
Melanie
M
Hauser
Elisabeth
E
Gabriel
Günther
G
Pirch
Torsten
T
Jung
Kirsten
K
D001665:Binding Sites; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism*; D029968:Escherichia coli Proteins / Q000235:genetics / Q000378:metabolism*; D006360:Heat-Shock Proteins / Q000235:genetics / Q000378:metabolism*; D008954:Models, Biological; D008958:Models, Molecular; D011188:Potassium / Q000378:metabolism*; D011487:Protein Conformation; D011494:Protein Kinases / Q000378:metabolism*; D017434:Protein Structure, Tertiary; D015398:Signal Transduction; D012965:Sodium Chloride / Q000378:metabolism*; D020349:Surface Plasmon Resonance; D015534:Trans-Activators / Q000378:metabolism*
D029968:Escherichia coli Proteins; D006360:Heat-Shock Proteins; D015534:Trans-Activators; C075615:kdpE protein, E coli; C538839:universal stress protein A, E coli; D012965:Sodium Chloride; C489580:KdpD protein, E coli; D011494:Protein Kinases; D011188:Potassium