Hydrogen exchange of chemoreceptors in functional complexes suggests protein stabilization mediates long-range allosteric coupling
Hydrogen exchange of chemoreceptors in functional complexes suggests protein stabilization mediates long-range allosteric coupling
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DOI：
10.1074/jbc.ra119.009865
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发表时间：
2019-11-01
影响因子：
4.8
通讯作者：
Thompson, Lynmarie K.
中科院分区：
文献类型：
--
作者：
Li, Xuni;Eyles, Stephen J.;Thompson, Lynmarie K.
细菌趋化性受体形成扩展的六边形阵列，整合和放大信号以控制游泳行为。跨膜信号开始于一个2-？配体诱导的位移？螺旋在周质和跨膜结构域，但它是未知的细胞质结构域如何传播信号的额外200？以控制激酶CheA结合到受体的膜远端尖端。受体胞质结构域先前已被证明是高度动态的细胞质片段（CF）和完整的化学感受器内;其动态的调制被认为在信号传播中发挥关键作用。这种氢氘交换-MS（HDX-MS）的功能复合物的CF，CheA，和CheW结合到囊泡在天然样阵列的研究表明，CF是有序的，只有在其蛋白质相互作用区域，它结合CheA和CheW。我们观察到快速交换整个CF的其余部分，与不相关（EX 2）和相关（EX 1）交换模式，表明受体胞质结构域保留的障碍，即使在功能复合物。HDX率增加的输入，有利于激酶关闭状态。我们建议，化学感受器实现远程变构控制的激酶通过耦合平衡：CheA结合在一个激酶上的构象稳定的胞质结构域，和信号输入，使这个结构域（配体结合和去甲基化）不稳定不利于CheA结合，使其失去关键的接触，并恢复到一个激酶关闭状态。这项研究揭示了一个跨膜受体的内在无序区域在长程变构中的机制作用。
Bacterial chemotaxis receptors form extended hexagonal arrays that integrate and amplify signals to control swimming behavior. Transmembrane signaling begins with a 2-? ligand-induced displacement of an ? helix in the periplasmic and transmembrane domains, but it is unknown how the cytoplasmic domain propagates the signal an additional 200 ? to control the kinase CheA bound to the membrane-distal tip of the receptor. The receptor cytoplasmic domain has previously been shown to be highly dynamic as both a cytoplasmic fragment (CF) and within the intact chemoreceptor; modulation of its dynamics is thought to play a key role in signal propagation. This hydrogen deuterium exchange-MS (HDX-MS) study of functional complexes of CF, CheA, and CheW bound to vesicles in native-like arrays reveals that the CF is well-ordered only in its protein interaction region where it binds CheA and CheW. We observe rapid exchange throughout the rest of the CF, with both uncorrelated (EX2) and correlated (EX1) exchange patterns, suggesting the receptor cytoplasmic domain retains disorder even within functional complexes. HDX rates are increased by inputs that favor the kinase-off state. We propose that chemoreceptors achieve long-range allosteric control of the kinase through a coupled equilibrium: CheA binding in a kinase-on conformation stabilizes the cytoplasmic domain, and signaling inputs that destabilize this domain (ligand binding and demethylation) disfavor CheA binding such that it loses key contacts and reverts to a kinase-off state. This study reveals the mechanistic role of an intrinsically disordered region of a transmembrane receptor in long-range allostery.