Department of Physics, Graduate School of Science, University of Tokyo, 7-3-1 Hongo, Bunkyou-ku, Tokyo, 113-0033 Japan.
Science. 2010 Aug 6;329(5992):686-9. doi: 10.1126/science.1191484.
Using optical trapping and fluorescence imaging techniques, we measured the step size and stiffness of single skeletal myosins interacting with actin filaments and arranged on myosin-rod cofilaments that approximate myosin mechanics during muscle contraction. Stiffness is dramatically lower for negatively compared to positively strained myosins, consistent with buckling of myosin's subfragment 2 rod domain. Low stiffness minimizes drag of negatively strained myosins during contraction at loaded conditions. Myosin's elastic portion is stretched during active force generation, reducing apparent step size with increasing load, even though the working stroke is approximately constant at about 8 nanometers. Taking account of the nonlinear nature of myosin elasticity is essential to relate myosin's internal structural changes to physiological force generation and filament sliding.
我们使用光阱和荧光成像技术，测量了与肌动蛋白丝相互作用并排列在肌球蛋白原丝上的单个骨骼肌肌球蛋白的步长和刚性，这些肌球蛋白原丝近似于肌肉收缩期间的肌球蛋白力学。与正应变肌球蛋白相比，负应变肌球蛋白的刚性显著降低，这与肌球蛋白亚基 2 杆域的屈曲一致。低刚性最小化了在加载条件下收缩时负应变肌球蛋白的阻力。在主动力产生过程中，肌球蛋白的弹性部分被拉伸，随着负载的增加，表观步长减小，尽管工作行程约为 8 纳米，保持不变。考虑肌球蛋白弹性的非线性性质对于将肌球蛋白的内部结构变化与生理力产生和细丝滑动相关联至关重要。
