A large and distinct rotation of the myosin light chain domain occurs upon muscle contraction
A large and distinct rotation of the myosin light chain domain occurs upon muscle contraction
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DOI：
10.1073/pnas.95.6.2944
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发表时间：
1998-03-17
影响因子：
11.1
通讯作者：
Thomas, DD
中科院分区：
文献类型：
--
作者：
Baker, JE;Brust-Mascher, I;Thomas, DD
30多年来，分子运动学的基本目标一直是解决产生力的马达蛋白质的结构变化。虽然低分辨率的结构研究已经提供了肌肉激活时产生肌球蛋白旋转的力量的证据，但这些研究并没有解决收缩肌肉中肌球蛋白的结构状态。利用电子顺磁共振，我们观察到在松弛的扇贝肌肉纤维中，肌球蛋白轻链结构域上的一个位置上的自旋标记有两种不同的取向。两个探针的方向被36度+5度的轴向旋转隔开，在肌肉激活时没有改变，但它们之间的分布发生了实质性的变化，表明部分(17%+/-2%)的肌球蛋白头部在力产生和肌肉收缩时经历了肌球蛋白轻链结构域的大(至少300)轴向旋转。由此产生的模型有助于解释为什么这一观察仍然如此难以捉摸，并提供了对发动机蛋白质结构转变驱动分子运动性的机制的洞察。
For more than 30 years, the fundamental goal in molecular motility has been to resolve force-generating motor protein structural changes. Although low-resolution structural studies have provided evidence for force generating myosin rotations upon muscle activation, these studies did not resolve structural states of myosin in contracting muscle. Using electron paramagnetic resonance, we observed two distinct orientations of a spin label attached specifically to a single site on the light chain domain of myosin in relaxed scallop muscle fibers. The two probe orientations, separated by a 36 degrees + 5 degrees axial rotation, did not change upon muscle activation, but the distribution between them changed substantially, indicating that a fraction (17% +/- 2%) of myosin heads undergoes a large (at least 300) axial rotation of the myosin light chain domain upon force generation and muscle contraction. The resulting model helps explain why this observation has remained so elusive and provides insight into the mechanisms by which motor protein structural transitions drive molecular motility.