Activation of the bacterial thermosensor DesK involves a serine zipper dimerization motif that is modulated by bilayer thickness
Activation of the bacterial thermosensor DesK involves a serine zipper dimerization motif that is modulated by bilayer thickness
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DOI：
10.1073/pnas.1422446112
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发表时间：
2015-05-19
影响因子：
11.1
通讯作者：
Killian, J. Antoinette
中科院分区：
文献类型：
--
作者：
Cybulski, Larisa Estefania;Ballering, Joost;Killian, J. Antoinette
Desk是一种细菌温度传感器蛋白，参与维持细胞膜的流动性以响应环境温度的变化。最有可能的是，蛋白质被膜厚度的变化激活，但感知和信号传递的分子机制仍然知之甚少。在这里，我们旨在通过研究所谓的最小感应台(MS-Desk)来阐明Desk的作用模式。在MS-Desk中，感知和信号被捕获在单个跨膜片段中。这种简化版本的传感器可以简单地使用合成肽来研究膜厚度依赖的蛋白质-脂相互作用，这些合成肽对应于MS-Desk的功能和非功能突变体的跨膜部分，这些突变体被结合在不同厚度的脂质双层中。通过圆二色谱、色氨酸荧光和分子模拟研究了这些多肽的脂依赖行为。这些实验与MS-Desk突变体的体内功能研究相辅相成。基于这些结果，我们构建了一个模型，该模型提出了一种新的传感机制，即蛋白质以二聚体的形式存在，并通过C末端亲水基序的膜掺入来响应双层厚度的增加。这导致三个丝氨酸暴露在MS-Desk的跨膜螺旋的同一侧，触发二聚界面的切换，以允许形成丝氨酸拉链。最终结果是MS-Desk的激酶状态被激活。
DesK is a bacterial thermosensor protein involved in maintaining membrane fluidity in response to changes in environmental temperature. Most likely, the protein is activated by changes in membrane thickness, but the molecular mechanism of sensing and signaling is still poorly understood. Here we aimed to elucidate the mode of action of DesK by studying the so-called "minimal sensor DesK" (MS-DesK), in which sensing and signaling are captured in a single transmembrane segment. This simplified version of the sensor allows investigation of membrane thickness-dependent protein-lipid interactions simply by using synthetic peptides, corresponding to the membrane-spanning parts of functional and nonfunctional mutants of MS-DesK incorporated in lipid bilayers with varying thicknesses. The lipid-dependent behavior of the peptides was investigated by circular dichroism, tryptophan fluorescence, and molecular modeling. These experiments were complemented with in vivo functional studies on MS-DesK mutants. Based on the results, we constructed a model that suggests a new mechanism for sensing in which the protein is present as a dimer and responds to an increase in bilayer thickness by membrane incorporation of a C-terminal hydrophilic motif. This results in exposure of three serines on the same side of the transmembrane helices of MS-DesK, triggering a switching of the dimerization interface to allow the formation of a serine zipper. The final result is activation of the kinase state of MS-DesK.