Skubiszak Ludmila, Kowalczyk Leszek
Laboratory of Computer Simulation of Muscle Contraction, Institute of Biocybernetics and Biomedical Engineering of the Polish Academy of Sciences, Ks Trojdena 4, 02-109 Warszawa, Poland.
Acta Biochim Pol. 2002;49(4):841-53.
Computer simulation of mass distribution within the model and Fourier transforms of images depicting mass distribution are explored for verification of two alternative modes of the myosin molecule arrangement within the vertebrate skeletal muscle thick filaments. The model well depicting the complete bipolar structure of the thick filament and revealing a true threefold-rotational symmetry is a tube covered by two helices with a pitch of 2 x 43 nm due to arrangement of the myosin tails along a helical path and grouping of all myosin heads in the crowns rotated by 240 degrees and each containing three cross-bridges separated by 0 degrees, 120 degrees, and 180 degrees. The cross-bridge crown parameters are verified by EM images as well as by optical and low-angle X-ray diffraction patterns found in the literature. The myosin tail arrangement, at which the C-terminus of about 43-nm length is near-parallel to the filament axis and the rest of the tail is quite strongly twisted around, is verified by the high-angle X-ray diffraction patterns. A consequence of the new packing is a new way of movement of the myosin cross-bridges, namely, not by bending in the hinge domains, but by unwrapping from the thick filament surface towards the thin filaments along a helical path.
通过探索模型内质量分布的计算机模拟以及描绘质量分布的图像的傅里叶变换，来验证脊椎动物骨骼肌粗肌丝中肌球蛋白分子排列的两种替代模式。该模型很好地描绘了粗肌丝的完整双极结构，并揭示了真正的三重旋转对称性，它是一个由两个螺旋覆盖的管，螺距为2×43nm，这是由于肌球蛋白尾部沿螺旋路径排列，且所有肌球蛋白头部在冠部成组，冠部旋转240度，每组包含三个相隔0度、120度和180度的横桥。横桥冠部参数通过电子显微镜图像以及文献中发现的光学和低角度X射线衍射图谱进行验证。肌球蛋白尾部的排列方式，即约43nm长的C末端几乎与肌丝轴平行，而尾部其余部分则强烈扭曲，通过高角度X射线衍射图谱得到验证。新堆积方式的一个结果是肌球蛋白横桥的一种新的运动方式，即不是通过在铰链结构域弯曲，而是沿着螺旋路径从粗肌丝表面向细肌丝展开。
