Chew M W, Squire J M
Biophysics Section, Blackett Laboratory, Imperial College of Science, Technology and Medicine, London, United Kingdom.
J Struct Biol. 1995 Nov-Dec;115(3):233-49. doi: 10.1006/jsbi.1995.1048.
Muscle myosin filament backbones are aggregates of long coiled-coil alpha-helical myosin rods, with the myosin heads arranged approximately helically on the filament surface, but the details of the rod packing are not known. Computed Fourier transforms of plausible molecular packing models for the vertebrate striated muscle myosin filament have been compared with observed high-angle X-ray diffraction patterns from plaice fin muscle. Models considered include those in which the coiled-coil rod parts of myosin are packed into various kinds of subfilaments or into a curved molecular crystalline layer. A general conclusion is that if the myosin rods are tilted by less than about 1 degree or more than about 3 degrees from the filament long axis, very poor agreement is obtained between the computed and observed high-angle diffraction patterns. Qualitative comparison of calculated Fourier transforms, taken together with electron micrograph information, shows that the curved molecular crystal model and a model with hexagonally close-packed 4-nm subfilaments appear to explain the whole set of observations more satisfactorily than the alternatives. It is argued on other grounds that of these two possibilities the curved molecular crystal model is the more plausible.
肌肉肌球蛋白丝主干是由长的卷曲螺旋α-螺旋肌球蛋白杆聚集而成，肌球蛋白头部大致呈螺旋状排列在丝表面，但杆的堆积细节尚不清楚。已将脊椎动物横纹肌肌球蛋白丝的合理分子堆积模型的计算傅里叶变换与从鲽鱼鳍肌肉观察到的高角度X射线衍射图谱进行了比较。所考虑的模型包括那些肌球蛋白的卷曲螺旋杆部分被包装成各种亚丝或弯曲分子晶体层的模型。一个普遍的结论是，如果肌球蛋白杆与丝长轴的倾斜度小于约1度或大于约3度，则计算出的和观察到的高角度衍射图谱之间的一致性很差。计算出的傅里叶变换的定性比较，结合电子显微镜信息表明，弯曲分子晶体模型和具有六方密堆积4纳米亚丝的模型似乎比其他模型更能令人满意地解释整个观察结果。基于其他理由认为，在这两种可能性中，弯曲分子晶体模型更合理。
