Muscle force is generated by myosin heads stereospecifically attached to actin

Article

关键词: X-RAY-DIFFRACTION;    SKELETAL-MUSCLE;    CROSS-BRIDGES;    CONTRACTING MUSCLE;    STRUCTURAL-CHANGES;    STRIATED-MUSCLE;    FIBERS;    REFLECTIONS;    MOVEMENTS;    STATES;   

DOI  :  10.1038/40651

来源: SCIE

【 摘 要 】

Muscle force is generated by myosin crossbridges interacting with actin. As estimated from stiffness(1,2) and equatorial X-ray diffraction(3) of muscle and muscle fibres, most myosin cross-bridges are attached to actin during isometric contraction, but a much smaller fraction is bound stereospecifically(4-7). 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(8) 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 similar to 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.

【 授权许可】

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