ARRANGEMENT OF THE HEADS OF MYOSIN IN RELAXED THICK FILAMENTS FROM TARANTULA MUSCLE
ARRANGEMENT OF THE HEADS OF MYOSIN IN RELAXED THICK FILAMENTS FROM TARANTULA MUSCLE
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DOI：
10.1016/0022-2836(85)90292-x
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发表时间：
1985-01-01
影响因子：
5.6
通讯作者：
CRAIG, R
中科院分区：
文献类型：
--
作者：
CROWTHER, RA;PADRON, R;CRAIG, R
在松弛条件下（Mg-ATP和EGTA）保持狼蛛腿部肌肉的粗纤维，用最小电子剂量进行负染色和拍照。根据颗粒的一般视觉外观和其光学衍射图案的强度和对称性，选择颗粒进行三维图像重建，其中最好的扩展到1/5 nm-1的间距。螺旋对称是这样的，在给定的层线上，不同阶的贝塞尔函数的贡献开始以相当低的分辨率重叠，因此必须通过组合来自不同视图的数据来计算分离。独立重建的结果吻合良好，比先前重建的鲎和扇贝的粗丝显示了更多的细节。最强的特点是一组4长节距右旋螺旋脊（节距4倍）。43.5 nm)，由细长的肌凝蛋白头形成。长螺距螺旋被调制成轴向间距为14.5 nm的脊线，脊线位于与灯丝轴大致垂直的平面上，并沿周向运行。这表明后者可能是由来自1个肌球蛋白分子的亚片段1 （S1）头部堆叠在来自轴向邻近分子的S1上形成的。图中的内部特征表明一个近似的局部2重轴与分子内假定的头部有关。头看起来沿着丝轴指向相反的方向，并且位于非常靠近丝主干的位置。因此，在松弛条件下，肌凝蛋白分子的2个头似乎在天然粗丝中被可视化。
Thick filaments from leg muscle of tarantula, maintained under relaxing conditions (Mg-ATP and EGTA), were negatively stained and photographed with minimal electron dose. Particles were selected for 3-dimensional image reconstruction by general visual appearance and by the strength and symmetry of their optical diffraction patterns, the best of which extend to spacings of 1/5 nm-1. The helical symmetry is such that, on a given layer-line, Bessel function contributions of different orders start to overlap at fairly low resolution and must therefore be separated computationally by combining data from different views. Independent reconstructions agree well and show more detail than previous reconstructions of thick filaments from Limulus and scallop. The strongest feature is a set of 4 long-pitch right-handed helical ridges (pitch 4 .times. 43.5 nm) formed by the elongated myosin heads. The long-pitch helices are modulated to give ridges with an axial spacing of 14.5 nm, lying in planes roughly normal to the filament axis and running circumferentially. It is suggested that the latter may be formed by the stacking of a subfragment 1 (S1) head from 1 myosin molecule on an S1 from an axially neighboring molecule. Internal features in the map indicate an approximate local 2-fold axis relating the putative heads within a molecule. The heads appear to point in opposite directions along the filament axis and are located very close to the filament backbone. Thus, for the first time, the 2 heads of the myosin molecule appear to have been visualized in a native thick filament under relaxing conditions.