Low-barrier hydrogen bonds in enzyme cooperativity
Low-barrier hydrogen bonds in enzyme cooperativity
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DOI：
10.1038/s41586-019-1581-9
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发表时间：
2019-09-26
期刊：
影响因子：
64.8
通讯作者：
Tittmann, Kai
中科院分区：
文献类型：
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作者：
Dai, Shaobo;Funk, Lisa-Marie;Tittmann, Kai
对于许多蛋白质，协同性和变构调节的潜在分子机制是很好理解的，血红蛋白和天冬氨酸转氨甲酰酶是典型的例子（1，2）。效应物的结合通常导致蛋白质的结构转变，该结构转变通过信号传导途径传播到远程位点，并且涉及三级水平上的显著变化，有时甚至四级水平上的显著变化（1-5）。然而，这些信号的起源和原子水平上的远程信号传导的分子机制仍不清楚（5-8）。信号通路中不同的空间尺度和时间尺度使得实验观察具有挑战性;特别是，移动的质子的位置和运动不能通过当前的结构分析方法可视化。在这里，我们报告的实验观察波动的低垒氢键作为开关元件的多聚体酶的协同性途径。我们已经观察到这些低势垒氢键在超高分辨率的X-射线晶体结构的两个多聚体酶，并验证了它们的分配使用计算计算。活性位点的催化事件在由酸性侧链和水分子组成的电路中的低势垒氢键和普通氢键之间切换，通过质子的集体重新定位传递信号，表现为原子牛顿摇篮。由此产生的通信在低聚物中催化。我们的研究不仅为蛋白质中低势垒氢键的存在提供了几条证据和一个工作模型，而且还与酶的协同性有关。这一发现提出了药物和酶设计的新原则，其中可以有目的地包括残基序列，以实现远程通信，从而调节工程生物分子。
The underlying molecular mechanisms of cooperativity and allosteric regulation are well understood for many proteins, with haemoglobin and aspartate transcarbamoylase serving as prototypical examples(1,2). The binding of effectors typically causes a structural transition of the protein that is propagated through signalling pathways to remote sites and involves marked changes on the tertiary and sometimes even the quaternary level(1-5). However, the origin of these signals and the molecular mechanism of long-range signalling at an atomic level remain unclear(5-8). The different spatial scales and timescales in signalling pathways render experimental observation challenging; in particular, the positions and movement of mobile protons cannot be visualized by current methods of structural analysis. Here we report the experimental observation of fluctuating low-barrier hydrogen bonds as switching elements in cooperativity pathways of multimeric enzymes. We have observed these low-barrier hydrogen bonds in ultra-high-resolution X-ray crystallographic structures of two multimeric enzymes, and have validated their assignment using computational calculations. Catalytic events at the active sites switch between low-barrier hydrogen bonds and ordinary hydrogen bonds in a circuit that consists of acidic side chains and water molecules, transmitting a signal through the collective repositioning of protons by behaving as an atomistic Newton's cradle. The resulting communication synchronizes catalysis in the oligomer. Our studies provide several lines of evidence and a working model for not only the existence of low-barrier hydrogen bonds in proteins, but also a connection to enzyme cooperativity. This finding suggests new principles of drug and enzyme design, in which sequences of residues can be purposefully included to enable long-range communication and thus the regulation of engineered biomolecules.