Quantum and Molecular Engineering Laboratory, Department of Chemical Engineering, Indian Institute of Technology Kharagpur, Kharagpur, India.
PLoS One. 2021 Apr 15;16(4):e0249866. doi: 10.1371/journal.pone.0249866. eCollection 2021.
Molecular basis of protein stability at different temperatures is a fundamental problem in protein science that is substantially far from being accurately and quantitatively solved as it requires an explicit knowledge of the temperature dependence of folding free energy of amino acid residues. In the present study, we attempted to gain insights into the thermodynamic stability of SazCA and its implications on protein folding/unfolding. We report molecular dynamics simulations of water solvated SazCA in a temperature range of 293-393 K to study the relationship between the thermostability and flexibility. Our structural analysis shows that the protein maintains the highest structural stability at 353 K and the protein conformations are highly flexible at temperatures above 353 K. Larger exposure of hydrophobic surface residues to the solvent medium for conformations beyond 353 K were identified from H-bond analysis. Higher number of secondary structure contents exhibited by SazCA at 353 K corroborated the conformations at 353 K to exhibit the highest thermal stability. The analysis of thermodynamics of protein stability revealed that the conformations that denature at higher melting temperatures tend to have greater maximum thermal stability. Our analysis shows that 353 K conformations have the highest melting temperature, which was found to be close to the experimental optimum temperature. The enhanced protein stability at 353 K due the least value of heat capacity at unfolding suggested an increase in folding. Comparative Gibbs free energy analysis and funnel shaped energy landscape confirmed a transition in folding/unfolding pathway of SazCA at 353 K.
蛋白质在不同温度下稳定性的分子基础是蛋白质科学中的一个基本问题，远未得到准确和定量的解决，因为它需要明确了解氨基酸残基折叠自由能随温度的变化。在本研究中，我们试图深入了解 SazCA 的热力学稳定性及其对蛋白质折叠/展开的影响。我们报告了在 293-393 K 的温度范围内对水溶剂化 SazCA 的分子动力学模拟，以研究热稳定性和柔韧性之间的关系。我们的结构分析表明，蛋白质在 353 K 时保持最高的结构稳定性，并且蛋白质构象在 353 K 以上的温度下具有很高的灵活性。从氢键分析中发现，超过 353 K 的构象中疏水性表面残基更大程度地暴露于溶剂介质中。在 353 K 时 SazCA 表现出更高数量的二级结构含量，这证实了在 353 K 时表现出最高热稳定性的构象。蛋白质稳定性的热力学分析表明，在较高熔点下变性的构象往往具有更大的最大热稳定性。我们的分析表明，353 K 的构象具有最高的熔点，这与实验最佳温度接近。由于展开时热容最小，蛋白质在 353 K 时的稳定性增强，这表明折叠增加。比较吉布斯自由能分析和漏斗形能量景观证实了 SazCA 在 353 K 时折叠/展开途径的转变。
