The relationship between curvature, flexibility and persistence length in the tropomyosin coiled-coil
The relationship between curvature, flexibility and persistence length in the tropomyosin coiled-coil
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DOI：
10.1016/j.jsb.2010.01.016
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发表时间：
2010-05-01
影响因子：
3
通讯作者：
Fischer, Stefan
中科院分区：
文献类型：
--
作者：
Li, Xiaochuan (Edward);Lehman, William;Fischer, Stefan
棒状原肌球蛋白卷曲螺旋固有的灵活性是限制原肌球蛋白在肌动蛋白丝上复杂位置动力学的重要因素。伸长的直分子的柔性通常通过持久长度（persistence length）来评估，持久长度是纵向热弯曲波动的量度。然而，如果一个分子的平衡构象是弯曲的，这个公式会产生一个“表观”的持久性长度（类似于100 nm的原肌球蛋白），测量偏离理想化的直线构象，然后高估实际的动态灵活性。为了获得“动态”持久长度，一个真正的测量弯曲刚度，分子的平均曲率必须考虑在内。在我们的研究中使用的不同方法直接从分子动力学（MD）模拟的原肌球蛋白的动态持续长度测量在这里详细描述。发现的动态持续长度为460 +/- 40 nm，类似于原肌球蛋白的12倍长和表观持续长度的5倍，表明原肌球蛋白比以前认为的要硬得多。MD过程中原肌球蛋白的纵向扭转行为表明，当原肌球蛋白采用其近平均构象时，端-端扭转波动幅度接近30度。所测得的弯曲和扭曲的灵活性被用来评估不同的模型的原肌球蛋白运动F-肌动蛋白。(C)2010年爱思唯尔公司All rights reserved.
The inherent flexibility of rod-like tropomyosin coiled-coils is a significant factor that constrains tropomyosin's complex positional dynamics on actin filaments. Flexibility of elongated straight molecules typically is assessed by persistence length, a measure of lengthwise thermal bending fluctuations. However, if a molecule's equilibrium conformation is curved, this formulation yields an "apparent" persistence length (similar to 100 nm for tropomyosin), measuring deviations from idealized straight conformations which then overestimate actual dynamic flexibility. To obtain the "dynamic" persistence length, a true measurement of flexural stiffness, the average curvature of the molecule must be taken into account. Different methods used in our studies for measuring the dynamic persistence length directly from Molecular Dynamics (MD) simulations of tropomyosin are described here in detail. The dynamic persistence length found, 460 +/- 40 nm, is similar to 12-times longer than tropomyosin and 5-times the apparent persistence length, showing that tropomyosin is considerably stiffer than previously thought. The longitudinal twisting behavior of tropomyosin during MD shows that the amplitude of end-to-end twisting fluctuation is similar to 30 degrees when tropomyosin adopts its near-average conformation. The measured bending and twisting flexibilities are used to evaluate different models of tropomyosin motion on F-actin. (C) 2010 Elsevier Inc. All rights reserved.