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首页> 外文期刊>Journal of Molecular Biology >Evidence against the 'Y-T coupling' mechanism of activation in the response regulator NtrC.
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Evidence against the 'Y-T coupling' mechanism of activation in the response regulator NtrC.

机译：响应调节器NtrC中激活“ Y-T耦合”机制的证据。

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摘要

The dominant theory on the mechanism of response regulators activation in two-component bacterial signaling systems is the "Y-T coupling" mechanism, wherein the χ1 rotameric state of a highly conserved aromatic residue correlates with the activation of the protein via structural rearrangements coupled to a conserved tyrosine. In this paper, we present evidence that, in the receiver domain of the response regulator nitrogen regulatory protein C (NtrC(R)), the interconversion of this tyrosine (Y101) between its rotameric states is actually faster than the rate of inactive/active conversion and is not correlated to the activation process. Data gathered from NMR relaxation dispersion experiments show that a subset of residues surrounding the conserved tyrosine sense a process that is occurring at a faster rate than the inactive/active conformational transition. We show that this process is related to χ1 rotamer exchange of Y101 and that mutation of this aromatic residue to a leucine eliminated this second faster process without affecting activation. Computational simulations of NtrC(R) in its active conformation further demonstrate that the rotameric state of Y101 is uncorrelated with the global conformational transition during activation. Moreover, the tyrosine does not appear to be involved in the stabilization of the active form upon phosphorylation and is not essential in propagating the signal downstream for ATPase activity of the central domain. Our data provide experimental evidence against the generally accepted "Y-T coupling" mechanism of activation in NtrC(R).
机译：关于两组分细菌信号系统中反应调节因子激活机制的主要理论是“ YT偶联”机制，其中高度保守的芳香族残基的χ1旋转异构体状态通过与保守分子偶联的结构重排与蛋白质的激活相关酪氨酸。在本文中，我们提供的证据表明，在响应调节剂氮调节蛋白C（NtrC（R））的受体域中，该酪氨酸（Y101）在其互变异构状态之间的相互转化实际上快于无活性/有活性的速率转换，并且与激活过程无关。从NMR弛豫分散实验中收集的数据表明，保守酪氨酸周围的残基子集感觉到该过程的发生速率比无活性/活性构象转变快。我们表明，该过程与Y101的χ1旋转异构体交换有关，并且该芳香族残基向亮氨酸的突变消除了该第二个较快的过程，而不影响激活。 NtrC（R）处于主动构象的计算模拟进一步表明，Y101的旋转异构体状态与激活过程中的整体构象转变无关。此外，酪氨酸似乎不参与磷酸化后活性形式的稳定化，并且在向下游传播中央结构域的ATP酶活性的信号中不是必需的。我们的数据提供了针对NtrC（R）中激活的普遍接受的“ Y-T偶联”机制的实验证据。

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