Gedeon Patrick C, Thomas James R, Madura Jeffry D
Department of Biomedical Engineering, Duke University, Durham, NC, 27708, USA.
Methods Mol Biol. 2015;1215:253-87. doi: 10.1007/978-1-4939-1465-4_12.
Molecular dynamics simulation provides a powerful and accurate method to model protein conformational change, yet timescale limitations often prevent direct assessment of the kinetic properties of interest. A large number of molecular dynamic steps are necessary for rare events to occur, which allow a system to overcome energy barriers and conformationally transition from one potential energy minimum to another. For many proteins, the energy landscape is further complicated by a multitude of potential energy wells, each separated by high free-energy barriers and each potentially representative of a functionally important protein conformation. To overcome these obstacles, accelerated molecular dynamics utilizes a robust bias potential function to simulate the transition between different potential energy minima. This straightforward approach more efficiently samples conformational space in comparison to classical molecular dynamics simulation, does not require advanced knowledge of the potential energy landscape and converges to the proper canonical distribution. Here, we review the theory behind accelerated molecular dynamics and discuss the approach in the context of modeling protein conformational change. As a practical example, we provide a detailed, step-by-step explanation of how to perform an accelerated molecular dynamics simulation using a model neurotransmitter transporter embedded in a lipid cell membrane. Changes in protein conformation of relevance to the substrate transport cycle are then examined using principle component analysis.
分子动力学模拟为蛋白质构象变化建模提供了一种强大且准确的方法,然而时间尺度限制常常阻碍对感兴趣的动力学性质进行直接评估。对于罕见事件的发生,需要大量的分子动力学步骤,这使得系统能够克服能量障碍并从一个势能最小值构象转变为另一个。对于许多蛋白质而言,能量图景因众多势能阱而进一步复杂化,每个势能阱由高自由能障碍分隔开,并且每个势能阱都可能代表一种功能上重要的蛋白质构象。为了克服这些障碍,加速分子动力学利用一种强大的偏置势能函数来模拟不同势能最小值之间的转变。与经典分子动力学模拟相比,这种直接的方法能更有效地对构象空间进行采样,不需要对势能图景有先验知识,并且能收敛到正确的正则分布。在此,我们回顾加速分子动力学背后的理论,并在蛋白质构象变化建模的背景下讨论该方法。作为一个实际例子,我们详细逐步解释了如何使用嵌入脂质细胞膜中的模型神经递质转运体进行加速分子动力学模拟。然后使用主成分分析来研究与底物转运循环相关的蛋白质构象变化。