X-ray diffraction studies of the contractile mechanism in single muscle fibres
X-ray diffraction studies of the contractile mechanism in single muscle fibres
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DOI：
10.1098/rstb.2004.1557
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发表时间：
2004-12-29
影响因子：
6.3
通讯作者：
Irving, M
中科院分区：
文献类型：
--
作者：
Lombardi, V;Piazzesi, G;Irving, M
用X射线衍射法研究了完整肌纤维中肌肉收缩的分子机制。通过施加纤维长度的快速变化产生的轴向X射线反射强度的变化建立了主动等长收缩期间肌球蛋白头的平均构象。并且示出了在对纤维长度变化的弹性响应期间以及在基本力产生过程（工作冲程）期间，头部倾斜。每根肌丝中肌球蛋白头部的两个阵列之间的X射线干涉允许头部的轴向运动在力从等距水平突然下降后以前所未有的精度原位测量。在低负载下，平均工作行程为12 nm。这与晶体学研究一致。在较高的负载下，工作冲程较小且较慢。肌动蛋白和肌球蛋白丝的顺应性也从力阶跃后X射线反射的轴向间距的变化中确定，并被证明是负责大部分肌节顺应性的。肌节的力学性质取决于肌球蛋白头的运动以及肌球蛋白和肌动蛋白丝的顺应性。
The molecular mechanism of muscle contraction was investigated in intact muscle fibres by X-ray diffraction. Changes in the intensities of the axial X-ray reflections produced by imposing rapid changes in fibre length establish the average conformation of the myosin heads during active isometric contraction. and show that the heads tilt during the elastic response to a change in fibre length and during the elementary force generating process: the working stroke. X-ray interference between the two arrays of myosin heads in each filament allows the axial motions of the heads following a sudden drop in force from the isometric level to be measured in situ with unprecedented precision. At low load, the average working stroke is 12 nm. which is consistent with crystallographic studies. The working stroke is smaller and slower at a higher load. The compliance of the actin and myosin filaments was also determined from the change in the axial spacings of the Xray reflections following a force step, and shown to be responsible for most of the sarcomere compliance. The mechanical properties of the sarcomere depend on both the motor actions of the myosin heads and the compliance of the myosin and actin filaments.