Department of Inorganic and Analytical Chemistry, University of Szeged, Dóm tér 7, Szeged, 6720, Hungary.
Institute of Enzymology, Genome Stability Research Group, Research Centre for Natural Sciences, Magyar tudósok körútja 2, Budapest, 1117, Hungary.
Eur Biophys J. 2021 May;50(3-4):491-500. doi: 10.1007/s00249-021-01539-z. Epub 2021 Apr 28.
The response of CueR towards environmental changes in solution was investigated. CueR is a bacterial metal ion selective transcriptional metalloregulator protein, which controls the concentration of copper ions in the cell. Although several articles have been devoted to the discussion of the structural and functional features of this protein, CueR has not previously been extensively characterized in solution. Here, we studied the effect of change in pH, temperature, and the presence of specific or non-specific binding partners on the secondary structure of CueR with circular dichroism (CD) spectroscopy. A rather peculiar reversible pH-dependent secondary structure transformation was observed, elucidated and supplemented with pK estimation by PROPKA and CpHMD simulations suggesting an important role of His(76) and His(94) in this process. CD experiments revealed that the presence of DNA prevents this structural switch, suggesting that DNA locks CueR in the α-helical-rich form. In contrast to the non-cognate metal ions Hg, Cd and Zn, the presence of the cognate Ag ion affects the secondary structure of CueR, most probably by stabilizing the metal ion and DNA-binding domains of the protein.
我们研究了环境变化对溶液中 CueR 的响应。CueR 是一种细菌金属离子选择转录金属调控蛋白，它控制细胞内铜离子的浓度。尽管已经有几篇文章致力于讨论这种蛋白质的结构和功能特征，但 CueR 以前并没有在溶液中得到广泛的研究。在这里，我们使用圆二色性（CD）光谱法研究了 pH 值、温度变化以及特定或非特定结合伴侣的存在对 CueR 二级结构的影响。我们观察到了一种相当特殊的可逆 pH 依赖性二级结构转变，并通过 PROPKA 和 CpHMD 模拟阐明了这一转变，并对 pK 值进行了估计，结果表明 His(76)和 His(94)在这一过程中起着重要作用。CD 实验表明，DNA 的存在阻止了这种结构转变，这表明 DNA 将 CueR 锁定在富含α-螺旋的形式中。与非配位金属离子 Hg、Cd 和 Zn 不同，配位的 Ag 离子会影响 CueR 的二级结构，这很可能是通过稳定金属离子和蛋白质的 DNA 结合结构域来实现的。
