Journal
SCIENCE
Volume 329, Issue 5992, Pages 686-689Publisher
AMER ASSOC ADVANCEMENT SCIENCE
DOI: 10.1126/science.1191484
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Funding
- Japan Ministry of Education, Culture, Sports, Science, and Technology
- Japan Science and Technology Agency
- Japan Society for the Promotion of Science
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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.
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