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首页> 外文期刊>Nature >Muscle force is generated by myosin heads stereospecifically attached to actin
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Muscle force is generated by myosin heads stereospecifically attached to actin

机译：肌力由肌动蛋白头部立体定向地附着于肌动蛋白产生

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摘要

Muscle force is generated by myosin crossbridges interacting with actin. As estimated from stiffness and equatorial X-ray diffraction of muscle and muscle fibres, most myosin crossbridges are attached to actin during isometric contraction, but a much smaller fraction is bound stereospecifically. To determine the fraction of crossbridges contributing to tension and the structural changes that attached crossbridges undergo when generating force, we monitored the X-ray diffraction pattern during temperature-induced tension rise in fully activated permeabilized frog muscle fibres. Temperature jumps from 5-6 degrees C to 16-19 degrees C initiated a 1.7-fold increase in tension without significantly changing fibre stiffness or the intensities of the (1,1) equatorial and (14.5 nm)(-1) meridional X-ray reflections. However, tension rise was accompanied by a 20% decrease in the intensity of the (1,0) equatorial reflection and an increase in the intensity of the first actin layer line by approximately 13% of that in rigor. Our results show that muscle force is associated with a transition of the crossbridges from a state in which they are nonspecifically attached to actin to one in which stereospecifically bound myosin crossbridges label the actin helix.
机译：肌球蛋白跨桥与肌动蛋白相互作用产生肌肉力。从肌肉和肌肉纤维的刚度和赤道X射线衍射估计，大多数肌球蛋白横桥在等轴测收缩过程中会附着在肌动蛋白上，但立体定向结合的比例要小得多。为了确定产生张力的横桥部分以及产生力时连接的横桥所经历的结构变化，我们在完全激活的透化青蛙肌肉纤维中，在温度引起的张力上升过程中，监测了X射线衍射图。温度从5-6摄氏度跃升至16-19摄氏度，使张力增加了1.7倍，而没有显着改变纤维刚度或（1,1）赤道和（14.5 nm）（-1）子午线X-射线反射。但是，张力上升伴随着（1,0）赤道反射强度的降低20％，第一肌动蛋白层线的强度提高了约13％。我们的结果表明，肌肉力与跨桥从非特异性连接肌动蛋白的状态过渡到立体定向结合的肌球蛋白跨桥标记肌动蛋白螺旋的状态有关。

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