Microscopic stability of cold shock protein a examined by NMR native state hydrogen exchange as a function of urea and trimethylamine N‐oxide
Microscopic stability of cold shock protein a examined by NMR native state hydrogen exchange as a function of urea and trimethylamine N‐oxide
复制标题
通过 NMR 天然态氢交换检查冷休克蛋白 a 的微观稳定性作为尿素和三甲胺 N-氧化物的函数
作者：
V. Jaravine;K. Rathgeb‐Szabo;A. Alexandrescu
冷休克蛋白A （CspA）的天然态氢交换被表征为变性剂尿素和稳定剂三甲胺氧化氮（TMAO）的功能。CspA具有5股β -薄片结构。链β1 - β4具有强保护的酰胺质子，基于实验作为尿素的功能，通过简单的全或全无全局展开机制进行交换。相比之下，酰胺质子对链β5的保护太弱，无法在水中测量。链β5与链β3和链β4形成氢键，两者都对溶剂交换有很强的保护作用。高斯网络模型（GNM）模拟，假设保护程度取决于天然结构中的三级接触密度，准确预测了在链β1 - β4中观察到的强保护，但未能解释链β5中的弱保护。链β5最显著的特征是低序列疏水性。在氧化三甲胺的存在下，链β 1‐β4的保护作用增强，并且保护作用扩展到蛋白质更亲水部分的酰胺质子，包括链β5和连接β‐链的环。由于TMAO与暴露的肽主链之间高度不利的相互作用，TMAO通过提高变性态的自由能来稳定蛋白质。因此，预计氧化三甲胺的稳定作用相对独立于序列疏水性。目前的结果表明，溶剂交换保护的大小更多地取决于易交换构象集合中的溶剂可及性，而不是天然结构中氢键相互作用的强度。
Native state hydrogen exchange of cold shock protein A (CspA) has been characterized as a function of the denaturant urea and of the stabilizing agent trimethylamine N‐oxide (TMAO). The structure of CspA has five strands of β‐sheet. Strands β1‐β4 have strongly protected amide protons that, based on experiments as a function of urea, exchange through a simple all‐or‐none global unfolding mechanism. By contrast, the protection of amide protons from strand β5 is too weak to measure in water. Strand β5 is hydrogen bonded to strands β3 and β4, both of which afford strong protection from solvent exchange. Gaussian network model (GNM) simulations, which assume that the degree of protection depends on tertiary contact density in the native structure, accurately predict the strong protection observed in strands β1‐β4 but fail to account for the weak protection in strand β5. The most conspicuous feature of strand β5 is its low sequence hydrophobicity. In the presence of TMAO, there is an increase in the protection of strands b̊1‐β4, and protection extends to amide protons in more hydrophilic segments of the protein, including strand β5 and the loops connecting the β‐strands. TMAO stabilizes proteins by raising the free energy of the denatured state, due to highly unfavorable interactions between TMAO and the exposed peptide backbone. As such, the stabilizing effects of TMAO are expected to be relatively independent of sequence hydrophobicity. The present results suggest that the magnitude of solvent exchange protection depends more on solvent accessibility in the ensemble of exchange susceptible conformations than on the strength of hydrogen‐bonding interactions in the native structure.
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影响因子：
2.9
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