Poulsen F R, Lowy J, Cooke P H, Bartels E M, Elliott G F, Hughes R A
Biophys J. 1987 Jun;51(6):959-67. doi: 10.1016/S0006-3495(87)83423-9.
X-ray results are presented concerning the structural state of myosin heads of synthetic filaments in threads. These were made from purified rabbit skeletal muscle myosin and studied by x-ray diffraction and electron microscopy by Cooke et al. (Cooke, P. H., E. M. Bartels, G. F. Elliott, and R. A. Hughes, 1987, Biophys. J., 51:947-957). X-ray patterns show a meridional peak at a spacing of 14.4 nm. We concentrate here on the only other feature of the axial pattern: this is a central region of diffuse scatter, which we find to be similar to that obtained from myosin heads in solution (Mendelson, R. A., K. M. Kretzschmar, 1980, Biochemistry, 19:4103-4108). This means that the myosin heads have very large random displacements in all directions from their average positions, and that they are practically randomly oriented. The myosin heads do not contribute to the 14.4-nm peak, which must come entirely from the backbone. Comparison with x-ray data from the unstriated Taenia coli muscle of the guinea pig indicates that in this muscle at least 75% of the diffuse scatter comes from disordered myosin heads. The results confirm that the diffuse scatter in x-ray patterns from specimens that contain myosin filaments can yield information about the structural behavior of the myosin heads.
本文给出了有关细丝中合成丝肌球蛋白头部结构状态的X射线结果。这些细丝由纯化的兔骨骼肌肌球蛋白制成，并由库克等人通过X射线衍射和电子显微镜进行研究（库克，P.H.，E.M.巴特尔，G.F.埃利奥特，和R.A.休斯，1987，《生物物理学杂志》，51:947 - 957）。X射线图谱显示在14.4纳米间距处有一个子午线峰。我们在此集中关注轴向图谱的另一个特征：这是一个漫散射的中心区域，我们发现它与溶液中肌球蛋白头部得到的漫散射区域相似（门德尔松，R.A.，K.M.克雷茨施马尔，1980，《生物化学》，19:4103 - 4108）。这意味着肌球蛋白头部从其平均位置向各个方向有非常大的随机位移，并且它们实际上是随机取向的。肌球蛋白头部对14.4纳米的峰没有贡献，该峰必定完全来自主干。与豚鼠无横纹结肠肌的X射线数据比较表明，在这种肌肉中至少75%的漫散射来自无序的肌球蛋白头部。结果证实，含有肌球蛋白丝的标本的X射线图谱中的漫散射能够产生有关肌球蛋白头部结构行为的信息。
