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Structural changes of skeletal muscle upon shortening

缩短时骨骼肌的结构变化

基本信息

批准号：
04680252
负责人：
YAGI Naoto
金额：
$ 1.28万
依托单位：
Tohoku University
依托单位国家：
日本
项目类别：
Grant-in-Aid for General Scientific Research (C)
财政年份：
1992
资助国家：
日本
起止时间：
1992 至 1993
项目状态：
已结题

项目摘要

Using an imaging plate exchanger and a synchrotron X-ray source, X-ray diffraction patterns were recorded from frog skeletal muscles shortening near the maximum velocity from a sarcomere length of 2.6 to 2.1 mum. The major findings were as follows : (1) The intensity of the second-order myosin meridional reflection, which decreased to 18 % of the resting value during isometric contraction, increased to 34 % during shortening, showing that the perturbation in the axial arrangement of myosin heads recovered. (2) The intensity of the third-order myosin meridional reflection increased by 32 % on isometric contraction and decreased to 51 % of the resting intensity during rapid shortening, showing disorder in the axial arrangement of the myosin heads. (3) The axial Bragg spacing of the third-order meridional reflectioon, which increased by 1.22 % during isometric contraction, was still 0.47 % larger than the resting value during shortening, indicating that the increase is not entirely due to extension of the filament by tension. (4) The intensity ratio of the (1,0) and (1,1) equatorial reflections increased a small extent (from 0.57 to 0.62) during shortening, while the 5.9- and 5.1-nm actin layr-lines showed large intensity decreases (126 to 101 % and 190 to 124 % of the resting intensity, respectively), suggesting that a considerable number of myosin heads are in the vicinity of the thin filament but not tightly bound to actin molecules during rapid shortening. These results are consistent with a model of muscle contraction in which myosin heads attach to actin in two different manners with weak and strong affinities and shows that, during shortening, the number of tightly attached heads decreases by half while the total number of attached heads decreases only slightly.

使用成像板交换器和同步辐射X射线源，X射线衍射图案记录从青蛙骨骼肌缩短附近的最大速度从肌节长度为2.6至2.1微米。主要结果如下：（1）肌球蛋白的二级反射强度在等长收缩期下降到静息值的18%，在缩短期上升到34%，表明肌球蛋白头部轴向排列的紊乱得到恢复。(2)三级肌球蛋白经向反射强度在等长收缩时增加32%，在快速缩短期间下降至静息强度的51%，显示肌球蛋白头轴向排列紊乱。(3)在等长收缩过程中，三阶反射的轴向布拉格间距增加了1.22%，但在缩短过程中仍比静止值大0.47%，这表明这种增加并不完全是由于张力引起的细丝伸长。(4)（1，0）和（1，1）赤道反射的强度比略有增加（从0.57到0.62），而5.9和5.1纳米的肌动蛋白层线显示出大的强度下降（分别为静息强度的126 - 101%和190 - 124%），这表明在快速缩短过程中，相当数量的肌球蛋白头位于细丝附近，但并不与肌动蛋白分子紧密结合。这些结果是一致的肌肉收缩模型，其中肌球蛋白头连接到肌动蛋白以两种不同的方式与弱和强的亲和力，并表明，在缩短过程中，紧密连接的头的数量减少了一半，而连接的头的总数只略有减少。