Dharan Nadiv, Farago Oded
Department of Biomedical Engineering, Ben Gurion University of the Negev, Be'er Sheva 84105, Israel.
Phys Rev E Stat Nonlin Soft Matter Phys. 2013 May;87(5):052714. doi: 10.1103/PhysRevE.87.052714. Epub 2013 May 23.
Cooperative action of molecular motors is essential for many cellular processes. One possible regulator of motor coordination is the elasticity-mediated crosstalk (EMC) coupling between myosin II motors whose origin is the tensile stress that they collectively generate in actin filaments. Here, we use a statistical mechanical analysis to investigate the influence of the EMC effect on the sarcomere -- the basic contractile unit of skeletal muscles. We demonstrate that the EMC effect leads to an increase in the attachment probability of motors located near the end of the sarcomere while simultaneously decreasing the attachment probability of the motors in the central part. Such a polarized attachment probability would impair the motors' ability to cooperate efficiently. Interestingly, this undesired phenomenon becomes significant only when the system size exceeds that of the sarcomere in skeletal muscles, which provides an explanation for the remarkable lack of sarcomere variability in vertebrates. Another phenomenon that we investigate is the recently observed increase in the duty ratio of the motors with the tension in muscle. We reveal that the celebrated Hill's equation for muscle contraction is very closely related to this observation.
分子马达的协同作用对许多细胞过程至关重要。马达协调的一种可能调节因子是肌球蛋白II马达之间的弹性介导串扰（EMC）耦合，其起源是它们在肌动蛋白丝中共同产生的拉伸应力。在这里，我们使用统计力学分析来研究EMC效应对肌节（骨骼肌的基本收缩单位）的影响。我们证明，EMC效应导致位于肌节末端附近的马达的附着概率增加，同时降低中部马达的附着概率。这种极化的附着概率会损害马达有效协作的能力。有趣的是，这种不良现象仅在系统尺寸超过骨骼肌中肌节的尺寸时才变得显著，这为脊椎动物中肌节显著缺乏变异性提供了解释。我们研究的另一个现象是最近观察到的马达占空比随肌肉张力增加的情况。我们揭示，著名的肌肉收缩希尔方程与这一观察结果密切相关。
