The extracytoplasmic linker peptide of the sensor protein SaeS tunes the kinase activity required for staphylococcal virulence in response to host signals.
The extracytoplasmic linker peptide of the sensor protein SaeS tunes the kinase activity required for staphylococcal virulence in response to host signals.
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DOI：
10.1371/journal.ppat.1004799
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发表时间：
2015-04
期刊：
影响因子：
6.7
通讯作者：
Bae T
中科院分区：
文献类型：
--
作者：
Liu Q;Cho H;Yeo WS;Bae T
细菌病原体通常采用双组分系统（TCS），通常由传感器激酶和反应调节剂组成，以控制一组毒力基因的表达，以响应不断变化的宿主环境。在金黄色葡萄球菌中，SaeRS TCS对于细菌的体内存活至关重要。膜内感测组氨酸激酶SaeS含有沿着C-末端激酶结构域、由两个跨膜螺旋和9个氨基酸长的胞质外接头肽组成的简单N-末端结构域。作为一种分子开关，SaeS维持低但显著的基础激酶活性，并响应于诱导信号如人中性粒细胞肽1（HNP 1）而增加其激酶活性。在这里，我们表明，连接肽的SaeS控制SaeS的基础激酶活性和连接肽的氨基酸序列高度优化其功能。没有接头肽，SaeS显示异常升高的激酶活性，即使在没有诱导信号的情况下，并且不响应HNP 1。此外，接头肽氨基酸被丙氨酸取代的SaeS变体表现出改变的基础激酶活性和/或对HNP 1的无反应性。生化分析表明，这些SaeS变体具有改变的自激酶和磷酸转移酶活性。最后，动物实验表明，接头肽介导的SaeS激酶活性的微调对于病原体的存活至关重要。我们的研究结果表明，在SaeS中的接头肽的功能是一个高度进化的功能，具有非常优化的氨基酸序列，我们建议，在其他SaeS样膜内感应组氨酸激酶，胞外连接肽积极精细控制他们的激酶。细菌病原体金黄色葡萄球菌利用SaeRS双组分系统控制多种毒素的产生，导致人类多种疾病。传感器激酶SaeS是膜内感应组氨酸激酶（IM-HKs）的成员，其缺乏感觉结构域并且具有简单的N-末端结构域，其具有两个跨膜螺旋和短的接头肽。目前认为IM-HK的连接肽将外界信号传递到胞质催化结构域以控制HK的激酶活性。然而，目前尚不清楚外部信号输入如何通过接头传播以调节HK的激酶活性。在这里，我们表明，连接肽的SaeS是至关重要的，在保持基础激酶活性和功能的一部分，“绊网”，以启动激活的SaeRS系统暴露于特定的主机信号。我们建立了一个单一的氨基酸取代的接头肽改变SaeS的激酶活性，导致不同的表达水平的SaeR激活的基因和改变小鼠的细菌毒力。我们的研究为致病细菌如何利用简单的蛋白质结构域来控制其致病潜力以响应宿主免疫信号提供了新的分子见解。
Bacterial pathogens often employ two-component systems (TCSs), typically consisting of a sensor kinase and a response regulator, to control expression of a set of virulence genes in response to changing host environments. In Staphylococcus aureus, the SaeRS TCS is essential for in vivo survival of the bacterium. The intramembrane-sensing histidine kinase SaeS contains, along with a C-terminal kinase domain, a simple N-terminal domain composed of two transmembrane helices and a nine amino acid-long extracytoplasmic linker peptide. As a molecular switch, SaeS maintains low but significant basal kinase activity and increases its kinase activity in response to inducing signals such as human neutrophil peptide 1 (HNP1). Here we show that the linker peptide of SaeS controls SaeS’s basal kinase activity and that the amino acid sequence of the linker peptide is highly optimized for its function. Without the linker peptide, SaeS displays aberrantly elevated kinase activity even in the absence of the inducing signal, and does not respond to HNP1. Moreover, SaeS variants with alanine substitution of the linker peptide amino acids exhibit altered basal kinase activity and/or irresponsiveness to HNP1. Biochemical assays reveal that those SaeS variants have altered autokinase and phosphotransferase activities. Finally, animal experiments demonstrate that the linker peptide-mediated fine tuning of SaeS kinase activity is critical for survival of the pathogen. Our results indicate that the function of the linker peptide in SaeS is a highly evolved feature with very optimized amino acid sequences, and we propose that, in other SaeS-like intramembrane sensing histidine kinases, the extracytoplasmic linker peptides actively fine-control their kinases. A bacterial pathogen Staphylococcus aureus uses the SaeRS two-component system to control the production of multiple toxins, resulting in a wide range of diseases in human. The sensor kinase SaeS is a member of the intramembrane-sensing histidine kinases (IM-HKs) that lacks a sensory domain and harbors a simple N-terminal domain with two transmembrane helices and a short linker peptide. It’s been considered that the linker peptide of IM-HKs transmits the external signals into the cytoplasmic catalytic domain to control the HK’s kinase activity. However, it is unclear how the external signal input propagates through the linker to modulate the kinase activity of HKs. Here we show that the linker peptide of SaeS is critical in maintaining the basal kinase activity and functions as a part of a “tripwire” to jumpstart the activation of the SaeRS system upon exposure to the specific host signals. We establish that a single amino acid substitution of the linker peptide alters SaeS’s kinase activity, resulting in different expression levels of the SaeR-activated genes and alteration of the bacterial virulence in mice. Our study provides new molecular insights into how the pathogenic bacterium utilizes the simple protein domain to control its disease-causing potentials in response to host immune signals.
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