A lipid-mediated conformational switch modulates the thermosensing activity of DesK
A lipid-mediated conformational switch modulates the thermosensing activity of DesK
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DOI：
10.1073/pnas.1317147111
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发表时间：
2014-03-04
影响因子：
11.1
通讯作者：
Estefania Cybulski, Larisa
中科院分区：
文献类型：
--
作者：
Eugenia Inda, Maria;Vandenbranden, Michel;Estefania Cybulski, Larisa
温度传感器DesK是一种多通道跨膜组氨酸激酶，允许细菌枯草芽孢杆菌调节优化膜脂质流动性所需的不饱和脂肪酸水平。DesK的胞质催化结构域在低温下表现为激酶，在高温下表现为磷酸酶。温度传感涉及由位于第一跨膜（TM）区段的N末端附近的一组亲水残基引起的内在不稳定性。这些残基在低温下被埋在脂质相中，在较高温度下随着膜的变薄而部分“浮”到水相，促进所需的构象变化。然而，核心问题仍然知之甚少：跨膜区感知的信息如何转化为胞质催化结构域的重排以控制DesK活性？在这里，我们确定了一个“接头区”（KSRKEERLEEK），连接TM传感器结构域与参与信号传递的细胞质催化结构域。接头响应于温度依赖性膜厚度变化而采用两种构象状态：（i）随机卷曲并结合到水-膜界面处的磷脂头部基团，促进磷酸酶状态或（ii）未结合并形成跨越从膜到细胞质的区域的连续螺旋，促进激酶状态。我们的研究结果支持这样的观点，即接头被赋予螺旋/无规卷曲构象的二元性，使其能够表现得像一个传输开关，与螺旋中断降低激酶/磷酸酶活性比，如所需的调节DesK输出响应。
The thermosensor DesK is a multipass transmembrane histidine-kinase that allows the bacterium Bacillus subtilis to adjust the levels of unsaturated fatty acids required to optimize membrane lipid fluidity. The cytoplasmic catalytic domain of DesK behaves like a kinase at low temperature and like a phosphatase at high temperature. Temperature sensing involves a built-in instability caused by a group of hydrophilic residues located near the N terminus of the first transmembrane (TM) segment. These residues are buried in the lipid phase at low temperature and partially "buoy" to the aqueous phase at higher temperature with the thinning of the membrane, promoting the required conformational change. Nevertheless, the core question remains poorly understood: How is the information sensed by the transmembrane region converted into a rearrangement in the cytoplasmic catalytic domain to control DesK activity? Here, we identify a "linker region" (KSRKERERLEEK) that connects the TM sensor domain with the cytoplasmic catalytic domain involved in signal transmission. The linker adopts two conformational states in response to temperature-dependent membrane thickness changes: (i) random coiled and bound to the phospholipid head groups at the water-membrane interface, promoting the phosphatase state or (ii) unbound and forming a continuous helix spanning a region from the membrane to the cytoplasm, promoting the kinase state. Our results uphold the view that the linker is endowed with a helix/random coil conformational duality that enables it to behave like a transmission switch, with helix disruption decreasing the kinase/phosphatase activity ratio, as required to modulate the DesK output response.