Protein thermostability is important to evolution, diseases, and industrial applications. Proteins use diverse molecular strategies to achieve stability at high temperature, yet reducing the entropy of unfolding seems required. We investigated five small α‐proteins and five β‐proteins with known, distinct structures and thermostability (T _m) using multi‐seed molecular dynamics simulations at 300, 350, and 400 K. The proteins displayed diverse changes in hydrogen bonding, solvent exposure, and secondary structure with no simple relationship to T _m. Our dynamics were in good agreement with experimental B‐factors at 300 K and insensitive to force‐field choice. Despite the very distinct structures, the native‐state (300 + 350 K) free‐energy landscapes (FELs) were significantly broader for the two most thermostable proteins and smallest for the three least stable proteins in both the α‐ and β‐group and with both force fields studied independently (tailed t ‐test, 95% confidence level). Our results suggest that entropic ensembles stabilize proteins at high temperature due to reduced entropy of unfolding, viz., ΔG = ΔH − T ΔS . Supporting this mechanism, the most thermostable proteins were also the least kinetically stable, consistent with broader FELs, typified by villin headpiece and confirmed by specific comparison to a mesophilic ortholog of Thermus thermophilus apo‐pyrophosphate phosphohydrolase. We propose that molecular strategies of protein thermostabilization, although diverse, tend to converge toward highest possible entropy in the native state consistent with the functional requirements. We speculate that this tendency may explain why many proteins are not optimally structured and why molten‐globule states resemble native proteins so much.

中文翻译：

---

通过分子动力学研究了小的α-蛋白和β-蛋白的热稳定性的常见机理。

蛋白质的热稳定性对于进化，疾病和工业应用很重要。蛋白质使用多种分子策略来实现高温下的稳定性，但似乎需要降低展开的熵。我们使用300、350和400 K的多种子分子动力学模拟研究了五个具有已知的不同结构和热稳定性（T _m）的小α蛋白和五个β蛋白。这些蛋白在氢键，溶剂暴露方面表现出多种变化和与T _m没有简单关系的二级结构。我们的动力学与300 K时的实验B因子非常吻合，并且对力场选择不敏感。尽管结构非常不同，但在α-和β-基团中，两种最热稳定的蛋白的原始状态（300 + 350 K）的自由能态（FEL）明显更宽，而对于三种最不稳定的蛋白，其自由能态（FEL）则最小。对两个力场进行了独立研究（尾部t检验，置信度为95％）。我们的研究结果表明，熵合奏稳定在高温下的蛋白质，由于减少了展开，即的熵，Δ。ģ =Δ ħ - Ť Δ小号。支持这种机制的是，最热稳定的蛋白质在动力学上也最不稳定，与较宽的FEL一致，以villin头型为代表，并通过与嗜热栖热菌嗜磷酸焦磷酸磷酸水解酶的嗜温直系同源物进行特异性比较得到证实。我们建议蛋白质热稳定的分子策略，尽管多样，但趋向于收敛到与功能需求一致的天然状态下的最高熵。我们推测这种趋势可以解释为什么许多蛋白质的结构都不理想，以及熔融球状状态为何如此类似于天然蛋白质。