Three-dimensional reconstruction of thin filaments decorated with a Ca2+-regulated myosin.
Three-dimensional reconstruction of thin filaments decorated with a Ca2+-regulated myosin.
复制标题
用 Ca2 调节肌球蛋白装饰的细丝的三维重建。
DOI：
10.1016/0022-2836(82)90236-4
复制
发表时间：
1982
影响因子：
5.6
通讯作者：
Craig,R
中科院分区：
文献类型：
--
作者：
Vibert,P;Craig,R
对“带刺的”和“钝化的”箭头的三维重建(Craiget al.，1980)表明，这两种形式源于扇贝肌球蛋白亚片段(S1)的排列，在存在调控轻链的情况下，这两种亚片段的出现时间比没有调控轻链时长约40？部分修饰的细丝中单个肌球蛋白亚片段的图像也表明了表观长度上的类似差异。额外的质量位于离肌动蛋白最远的亚片段末端，可能包括调控轻链的一部分以及肌球蛋白重链的一段。事实上，带刺的箭头也是由脊椎动物条纹和光滑肌肉的肌球蛋白亚片段组成的，这意味着这些肌球蛋白中的同源轻链具有与扇贝轻链相似的位置。扇贝轻链可能不会延伸到肌球蛋白头部的肌动蛋白结合部位，因此不太可能在物理上干扰结合。相反，轻链对肌动蛋白-肌球蛋白相互作用的调节可能涉及肌球蛋白头部-尾部连接附近区域结构的钙依赖变化。重建建议的肌动蛋白和原肌球蛋白相对于肌球蛋白的位置类似于Taylor&Amos(1981)提出的位置，并与原肌球蛋白调节的空间位阻模型相一致。从这些重建的肌动蛋白中鉴定肌动蛋白得到了部分修饰细丝图像的支持，这些图像显示了肌动蛋白螺旋相对于结合的肌球蛋白亚片段的极性。
Three-dimensional reconstructions of “barbed” and “blunted” arrowheads (Craiget al., 1980) show that these two forms arise from arrangement of scallop myosin subfragments (S1) that appear about 40 Å longer in the presence of the regulatory light chain than in its absence. A similar difference in apparent length is indicated by images of single myosin subfragments in partially decorated filaments. The extra mass is located at the end of the subfragment furthest from actin, and probably comprises part of the regulatory light chain as well as a segment of the myosin heavy chain. The fact that barbed arrowheads are also formed by myosin subfragments from vertebrate striated and smooth muscles implies that the homologous light chains in these myosins have locations similar to that of the scallop light chain.The scallop light chain probably does not extend into the actin-binding site on the myosin head, and is therefore unlikely to interfere physically with binding. Rather, regulation of actin-myosin interaction by light chains may involve Ca2+-dependent changes in the structure of a region near the head-tail junction of myosin.The reconstructions suggest locations for actin and tropomyosin relative to myosin that are similar to those proposed by Taylor & Amos (1981) and are consistent with a revised steric blocking model for regulation by tropomyosin. The identification of actin from these reconstructions is supported by images of partially decorated filaments that display the polarity of the actin helix relative to that of bound myosin subfragments.