X-ray fiber diffraction modeling of structural changes of the thin filament upon activation of live vertebrate skeletal muscles.
X-ray fiber diffraction modeling of structural changes of the thin filament upon activation of live vertebrate skeletal muscles.
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DOI：
10.2142/biophysics.6.13
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发表时间：
2010
期刊：
影响因子：
--
通讯作者：
Wakabayashi K
中科院分区：
文献类型：
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作者：
Matsuo T;Ueno Y;Takezawa Y;Sugimoto Y;Oda T;Wakabayashi K
为了阐明骨骼肌收缩过程中细肌丝结构的变化及其调控机制，研究了在松弛状态和激活状态下，青蛙骨骼肌非肌丝重叠长度处X射线纤维衍射图谱中基于细肌丝的反射强度。建模的结构变化的整个细丝由于Ca 2+激活系统地进行使用的晶体学数据的组成分子（肌动蛋白，原肌球蛋白和肌钙蛋白核心结构域）作为出发点，以确定调节蛋白和肌动蛋白的结构变化。结果表明，肌钙蛋白球状核心区向肌丝轴方向移动了1.66 °，并反方向旋转了1.16 °（从尖端观察）通过Ca 2+结合肌钙蛋白C围绕肌丝轴，原肌球蛋白与肌钙蛋白T的尾部一起从松弛位置向肌动蛋白内部区域方位角移动了12°，径向移动了17 °，可能部分打开了肌动蛋白内部区域。肌动蛋白的肌球蛋白结合区。我们获得的青蛙肌肉细丝的F-actin中的肌动蛋白分子的结构域结构与Holmes F-actin模型在松弛状态下的结构域结构略有不同，并且在激活时，肌动蛋白的所有亚结构域都向关闭核苷酸结合口袋的方向移动，使肌动蛋白分子更加紧凑。我们认为，肌钙蛋白的运动和肌动蛋白分子内的结构变化激活后的调节机制，除了空间阻断运动的原肌球蛋白也是至关重要的组成部分。
In order to clarify the structural changes of the thin filaments related to the regulation mechanism in skeletal muscle contraction, the intensities of thin filament-based reflections in the X-ray fiber diffraction patterns from live frog skeletal muscles at non-filament overlap length were investigated in the relaxed state and upon activation. Modeling the structural changes of the whole thin filament due to Ca2+-activation was systematically performed using the crystallographic data of constituent molecules (actin, tropomyosin and troponin core domain) as starting points in order to determine the structural changes of the regulatory proteins and actin. The results showed that the globular core domain of troponin moved toward the filament axis by ∼6 Å and rotated by ∼16° anticlockwise (viewed from the pointed end) around the filament axis by Ca2+-binding to troponin C, and that tropomyosin together with the tail of troponin T moved azimuthally toward the inner domains of actin by ∼12° and radially by ∼7 Å from the relaxed position possibly to partially open the myosin binding region of actin. The domain structure of the actin molecule in F-actin we obtained for frog muscle thin filament was slightly different from that of the Holmes F-actin model in the relaxed state, and upon activation, all subdomains of actin moved in the direction to closing the nucleotide-binding pocket, making the actin molecule more compact. We suggest that the troponin movements and the structural changes within actin molecule upon activation are also crucial components of the regulation mechanism in addition to the steric blocking movement of tropomyosin.