Sumathy S, Satyanarayana S V M
Department of Physics, Pondicherry University, R.Venkataraman Nagar, Kalapet, Puducherry 605 014, India.
Department of Physics, Pondicherry University, R.Venkataraman Nagar, Kalapet, Puducherry 605 014, India.
J Theor Biol. 2015 Sep 7;380:48-52. doi: 10.1016/j.jtbi.2015.04.029. Epub 2015 May 2.
Cytoplasmic dynein exhibits a directional processive movement on microtubule filaments and is known to move in steps of varying length based on the number of ATP molecules bound to it and the load that it carries. It is experimentally observed that dynein takes occasional backward steps and the frequency of such backward steps increases as the load approaches the stall force. Using a stochastic process model, we investigate the bidirectional movement of single head of a dynein motor. The probability for backward step is implemented based on fluctuation theorem of non-equilibrium statistical mechanics. We find that the movement of dynein motor is characterized with negative velocity implying backward motion beyond stall force. We observe that the motor moves backward for super stall forces by hydrolyzing the ATP exactly the same way as it does while moving forward for sub-stall forces. Movement of dynein is also simulated using a kinetic Monte Carlo method and the simulated velocities are in good agreement with velocities obtained using a stochastic rate equation model.
细胞质动力蛋白在微管丝上呈现定向的持续性运动，并且已知其会根据结合的ATP分子数量及其所承载的负载以不同长度的步长移动。实验观察到动力蛋白偶尔会向后退，并且随着负载接近失速力，这种向后退的频率会增加。使用随机过程模型，我们研究了动力蛋白马达单头的双向运动。基于非平衡统计力学的涨落定理实现了向后退的概率。我们发现动力蛋白马达的运动具有负速度，这意味着在超过失速力时会向后运动。我们观察到，对于超失速力，马达通过水解ATP向后移动，其方式与在亚失速力下向前移动时完全相同。还使用动力学蒙特卡罗方法模拟了动力蛋白的运动，模拟速度与使用随机速率方程模型获得的速度高度吻合。
