Conformational shifts in a chemoreceptor helical hairpin control kinase signaling in Escherichia coli
Conformational shifts in a chemoreceptor helical hairpin control kinase signaling in Escherichia coli
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DOI：
10.1073/pnas.1902521116
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发表时间：
2019-07-30
影响因子：
11.1
通讯作者：
Parkinson, John S.
中科院分区：
文献类型：
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作者：
Gao, Qun;Cheng, Anchun;Parkinson, John S.
运动的大肠杆菌细胞使用化学感受器信号阵列以极其精确的方式跟踪化学梯度。化学感受器分子的细胞质发夹尖端中的高度保守残基促进基于三聚体的信号传导复合物的组装并调节其CheA激酶伴侣的活性。为了探索丝氨酸受体Tsr的发夹尖端输出状态，我们表征了盐桥残基对E385-R388处氨基酸替换的信号传导后果。所有突变受体组装三聚体和信号复合物，但大多数未能支持丝氨酸趋化性在软琼脂测定。在任一残基处的小侧链替换产生响应于野生型丝氨酸刺激的OFF-或ON-移位输出，这表明这些受体与野生型一样，作为双态信号传导装置操作。较大的脂肪族或芳香族侧链引起缓慢或部分激酶控制反应，证明依赖于促进阵列协同性的核心信号单元之间的连接。在缺少两个关键接头-激酶接触点之一的突变体中（界面2），这些突变体受体表现出更多的野生型行为。最后，具有带电氨基酸置换的突变体受体组装信号传导复合物，其锁定在激酶开启（E385 K竖线R）或激酶关闭（R388 D竖线E）输出中。突变受体的发夹尖端具有这些更异常的信号传导特性，可能具有非天然的结构或动力学行为。我们的研究结果表明，化学效应刺激和适应性修饰影响核心信号单元之间的合作连接。该阵列重塑过程可能涉及受体核心信号传导复合物的CheW和CheA.P5组分之间的界面1和2相互作用的相对强度的活性依赖性变化。
Motile Escherichia coli cells use chemoreceptor signaling arrays to track chemical gradients with exquisite precision. Highly conserved residues in the cytoplasmic hairpin tip of chemoreceptor molecules promote assembly of trimer-based signaling complexes and modulate the activity of their CheA kinase partners. To explore hairpin tip output states in the serine receptor Tsr, we characterized the signaling consequences of amino acid replacements at the salt-bridge residue pair E385-R388. All mutant receptors assembled trimers and signaling complexes, but most failed to support serine chemotaxis in soft agar assays. Small side-chain replacements at either residue produced OFF-or ON-shifted outputs that responded to serine stimuli in wild-type fashion, suggesting that these receptors, like the wild-type, operate as two-state signaling devices. Larger aliphatic or aromatic side chains caused slow or partial kinase control responses that proved dependent on the connections between core signaling units that promote array cooperativity. In a mutant lacking one of two key adapter-kinase contacts (interface 2), those mutant receptors exhibited more wild-type behaviors. Lastly, mutant receptors with charged amino acid replacements assembled signaling complexes that were locked in kinase-ON (E385K vertical bar R) or kinase-OFF (R388D vertical bar E) output. The hairpin tips of mutant receptors with these more aberrant signaling properties probably have nonnative structures or dynamic behaviors. Our results suggest that chemoeffector stimuli and adaptational modifications influence the cooperative connections between core signaling units. This array remodeling process may involve activity-dependent changes in the relative strengths of interface 1 and 2 interactions between the CheW and CheA.P5 components of receptor core signaling complexes.