We have investigated the pressure- and temperature-induced conformational changes associated with the low complexity domain of hnRNP A1, an RNA-binding protein able to phase separate in response to cellular stress. Solution NMR spectra of the hnRNP A1 low-complexity domain fused with protein-G B1 domain were collected from 1 to 2500 bar and from 268 to 290 K. While the GB1 domain shows the typical pressure-induced and cold temperature-induced unfolding expected for small globular domains, the low-complexity domain of hnRNP A1 exhibits unusual pressure and temperature dependences. We observed that the low-complexity domain is pressure sensitive, undergoing a major conformational transition within the prescribed pressure range. Remarkably, this transition has the inverse temperature dependence of a typical folding-unfolding transition. Our results suggest the presence of a low-lying extended and fully solvated state(s) of the low-complexity domain that may play a role in phase separation. This study highlights the exquisite sensitivity of solution NMR spectroscopy to observe subtle conformational changes and illustrates how pressure perturbation can be used to determine the properties of metastable conformational ensembles.

中文翻译：

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高压核磁共振揭示hnRNP A1低复杂域的热力学稳定性

我们研究了与 hnRNP A1 的低复杂性结构域相关的压力和温度诱导的构象变化，hnRNP A1 是一种能够响应细胞压力而相分离的 RNA 结合蛋白。在 1 至 2500 bar 和 268 至 290 K 范围内收集与蛋白质-G B1 结构域融合的 hnRNP A1 低复杂度结构域的溶液 NMR 光谱。而 GB1 结构域显示出预期的典型压力诱导和低温诱导展开小球状域，hnRNP A1 的低复杂度域表现出不寻常的压力和温度依赖性。我们观察到低复杂度域是压力敏感的，在规定的压力范围内经历主要的构象转变。值得注意的是，这种转变具有典型的折叠-展开转变的逆温度依赖性。我们的结果表明存在可能在相分离中起作用的低复杂度域的低位扩展和完全溶剂化状态。这项研究强调了溶液 NMR 光谱在观察细微构象变化方面的出色灵敏度，并说明了如何使用压力扰动来确定亚稳态构象集合的性质。