LOW-ANGLE X-RAY DIAGRAM OF VERTEBRATE STRIATED MUSCLE AND ITS BEHAVIOUR DURING CONTRACTION AND RIGOR
LOW-ANGLE X-RAY DIAGRAM OF VERTEBRATE STRIATED MUSCLE AND ITS BEHAVIOUR DURING CONTRACTION AND RIGOR
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DOI：
10.1016/s0022-2836(67)80046-9
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发表时间：
1967-01-01
影响因子：
5.6
通讯作者：
BROWN, W
中科院分区：
文献类型：
--
作者：
HUXLEY, HE;BROWN, W
以前的低角X射线研究由于难以以足够的速度和分辨率记录模式而受到阻碍。新型的低角度相机被开发出来，它在这两个因素上都有相当大的收益，并被用来研究肌肉模式，包括一些细节上的肌肉收缩。X射线图的一部分来自肌动蛋白单体在肌肉细丝中的螺旋排列；该螺旋的节距约为2 x 360 A至2 x 370 A。其他反射来自粗丝上肌球蛋白交叉桥的螺旋排列，该粗丝大约位于节距429 A的6/2螺旋上。进一步的低角度反射来自粗丝和细丝的附加成分，这些重复周期与相关螺旋结构不同。其他的反射也是从固定长度的细丝上产生的。僵直的肌肉(当横桥永久地附着在细丝上时)给出的X光图与静息肌肉的X光图有很大的不同。这些变化主要发生在肌球蛋白成分中，结果表明，当肌球蛋白交叉桥与肌动蛋白细丝上的位置结合时，可能会发生肌球蛋白交叉桥螺旋排列的协同重组，从而最大化接近配准的点数。肌动蛋白细丝似乎表现为相对不变的结构，尽管节距的微小变化不能被排除在外。在活跃收缩的肌肉中，肌球蛋白和肌动蛋白细丝的整体重复周期几乎保持不变(除了肌球蛋白亚单位间距增加了约1%)。然而，在某些低角度反射中，强度发生了较大的变化，表明跨桥在收缩过程中发生了运动。这种模式的行为表明，跨桥的倾斜和/或纵向位置的有限变化伴随着它们的方位和可能的径向位置的更实质性的变化。各交叉桥的位置变化不同步。在收缩过程中，肌动蛋白模式没有发现变化。
Previous low-angle X-ray studies were hampered by the difficulty of recording the pattern with sufficient speed and resolution. New types of low-angle camera were developed which gave rather large gains in both these factors and were used to study muscle patterns including those given by contracting muscles in some detail. Part of the X-ray diagram arose from the helical arrangement of actin monomers in the thin filaments of muscle; the pitch of this helix was approximately 2 x 360 A to 2 x 370 A. Other reflections came from the helical arrangement of myosin cross-bridges on the thick filaments which lie approximately on a 6/2 helix of pitch 429 A. Further low-angle reflections arose from additional components of the thick and thin filaments and these had repeated periodicities different from those of the associated helical structures. Other reflections still arose from the fixed lengths of the filaments. Muscles in rigor (when the cross-bridges were permanently attached to the thin filaments) gave X-ray diagram which differ very considerably from those of resting muscle. The changes took place largely in the myosin component and the results indicated that a co-operative re-organization of the helical arrangement of myosin cross-bridges may occur when they bind to the sites on the actin filaments in such a way as to maximize the number of points of near-registration. The actin filaments appeared to behave as relatively invariant structures though small changes in pitch could not be excluded. In an actively contracting muscle, the over-all repeating periodicities along both the myosin and the actin filaments remained virtually constant (apart from an approximately 1% increase in the myosin subunit spacing). However, large changes in intensity took place in certain of the low-angle reflections, and showed that movement of cross-bridges takes place during contraction. The behavior of the pattern indicated that a limited change in tilt and/or longitudinal position of the cross-bridges was accompanied by more substantial changes in their azimuthal and possibly radial positions. The changes in position of individual cross-bridges were not synchronized with each other. No changes were detected in the actin pattern during contraction.