The Universal Stress Protein UspC Scaffolds the KdpD/KdpE Signaling Cascade of Escherichia coli under Salt Stress
The Universal Stress Protein UspC Scaffolds the KdpD/KdpE Signaling Cascade of Escherichia coli under Salt Stress
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DOI：
10.1016/j.jmb.2008.12.007
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发表时间：
2009-02-13
影响因子：
5.6
通讯作者：
Jung, Kirsten
中科院分区：
文献类型：
--
作者：
Heermann, Ralf;Weber, Arnim;Jung, Kirsten
传感器激酶KdpD和响应调节因子KdpE控制kdpFABC操纵子的诱导，该操纵子编码响应于K+限制或盐胁迫的高亲和力K+转运系统KdpFABC。在K+限制条件下，Kdp系统恢复细胞内K+浓度，而在盐胁迫下，K+积累远高于正常含量。KdpD的激酶活性在高浓度的K+下受到抑制，因此如何激活该传感器来响应盐胁迫一直是个难题。在这里，我们表明，通用应力蛋白UspC作为一个支架蛋白的KdpD/KdpE信号级联反应的Usp结构域在盐胁迫下的UspA亚家族的KdpD相互作用。大肠杆菌编码该亚家族的三个单结构域蛋白，UspA、UspC和UspD，其表达在各种胁迫条件下上调。在这些蛋白质中，只有UspC刺激体外重建的信号级联（KdpD -> KdpE -> DNA），导致KdpE在K+浓度下磷酸化，否则几乎阻止磷酸化。在协议中，在三角洲uspC突变体KdpFABC生产下调显着时，细胞暴露于盐胁迫，但在K+限制不变。生化研究表明，UspC与KdpD的刺激感知N端结构域中的Usp结构域特异性相互作用。此外，UspC类似于P/DNA复合物稳定KdpD/KdpE，因此被认为充当支架蛋白。本研究描述了由支架蛋白在不同的应激条件下刺激细菌双组分系统，并突出了通用应激蛋白的新作用。(C)2008爱思唯尔有限公司保留所有权利。
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 Delta uspC 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 similar to 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. (C) 2008 Elsevier Ltd. All rights reserved.