Protein thermal stability is an important field since thermally stable proteins are desirable in many academic and industrial settings. Information on protein thermal stabilization can be obtained by comparing homologous proteins from organisms living at distinct temperatures. Here, we report structural and mutational analyses of adenylate kinases (AKs) from psychrophilic Bacillus globisporus (AKp) and mesophilic Bacillus subtilis (AKm). Sequence and structural comparison showed suboptimal hydrophobic packing around Thr26 in the CORE domain of AKp, which was replaced with an Ile residue in AKm. Mutations that improved hydrophobicity of the Thr residue increased the thermal stability of the psychrophilic AKp, and the largest stabilization was observed for a Thr-to-Ile substitution. Furthermore, a reverse Ile-to-Thr mutation in the mesophilic AKm significantly decreased thermal stability. We determined the crystal structures of mutant AKs to confirm the impact of the residue substitutions on the overall stability. Taken together, our results provide a structural basis for the stability difference between psychrophilic and mesophilic AK homologues and highlight the role of hydrophobic interactions in protein thermal stability.

中文翻译：

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嗜冷和嗜温腺苷酸激酶的结构和突变分析强调了疏水相互作用在蛋白质热稳定性中的作用。

蛋白质热稳定性是一个重要领域，因为热稳定蛋白质在许多学术和工业环境中都是理想的。关于蛋白质热稳定性的信息可以通过比较生活在不同温度下的生物体的同源蛋白质来获得。在这里，我们报告了嗜冷球孢芽孢杆菌 (AKp) 和嗜温枯草芽孢杆菌 (AKm) 腺苷酸激酶 (AK) 的结构和突变分析。序列和结构比较显示 AKp CORE 结构域中 Thr26 周围的疏水性包装不理想，该结构域被 AKm 中的 Ile 残基取代。改善 Thr 残基疏水性的突变增加了嗜冷 AKp 的热稳定性，并且在 Thr-to-Ile 取代中观察到最大的稳定性。此外，嗜温 AKm 中的反向 Ile-to-Thr 突变显着降低了热稳定性。我们确定了突变 AK 的晶体结构，以确认残基取代对整体稳定性的影响。总而言之，我们的结果为嗜冷和嗜温 AK 同系物之间的稳定性差异提供了结构基础，并强调了疏水相互作用在蛋白质热稳定性中的作用。