Milam L, Erickson H P
J Cell Biol. 1982 Sep;94(3):592-6. doi: 10.1083/jcb.94.3.592.
Unidirectional and rotary shadowing techniques have been applied in studying the surface structure of two types of intermediate filaments. Keratin filaments and neurofilaments demonstrate a approximately 21-nm axial periodicity which probably indicates the helical pitch of the outer shell of the filament. Analysis of unidirectionally shadowed keratin showed that the helix is left-handed. The observation of a left-handed helix of 21-nm pitch supports the three-stranded protofilament model of Fraser, Macrae, and Suzuki (1976, J. Mol. Biol. 108:435-452), and indicates that keratin filaments probably consist of 10 three-stranded protofilaments surrounding a core of three such protofilaments, as predicted by models based on x-ray diffraction of hard keratin filaments. Neurofilaments do not demonstrate an easily identifiable hand, so their consistency with the model is, as yet, uncertain.
单向和旋转阴影技术已被应用于研究两种中间丝的表面结构。角蛋白丝和神经丝显示出大约21纳米的轴向周期性,这可能表明了丝外壳的螺旋间距。对单向阴影角蛋白的分析表明,螺旋是左手螺旋。观察到21纳米间距的左手螺旋支持了弗雷泽、麦克雷和铃木(1976年,《分子生物学杂志》108:435 - 452)的三链原纤维模型,并表明角蛋白丝可能由围绕三条这样的原纤维核心的10条三链原纤维组成,正如基于硬角蛋白丝X射线衍射的模型所预测的那样。神经丝没有显示出易于识别的旋向,因此它们与该模型的一致性目前尚不确定。