MACROMOLECULAR STRUCTURE

病毒结构已被分析的情况下（i）单纯疱疹病毒 我们通过电子显微照片的计算机图像处理 二十面体衣壳的主要衣壳是一个155 kDa的六聚体， 蛋白质，呈长14 nm的圆柱体形式，具有中央通道 其在外表面上约为4 nm，但在内表面上窄得多 面 (ii)噬菌体T7的尾纤维已在 通过关联60 kDa的二级结构预测实现高分辨率 gp 17多肽与个体的计算机处理电子图像 纤维 每根纤维都是平行链的低聚物（可能是二聚物） 由三个领域组成。 氨基末端结构域连接 纤维的尾巴;中央域形成一个卷曲螺旋α-螺旋 近端半纤维由绳状结构组成，长度为19 nm; 羧基末端结构域形成链间交叉的β-片层， 在远端半纤维中的四个结节的线性序列，也是19 nm长。 此外，我们还确定了细菌的螺旋结构， 百日咳博德特氏菌血清型#2和#6菌毛，使用 纯化菌毛的类晶体。 在这两种情况下，菌毛都是 一种含有五个拷贝的菌毛蛋白的单起始螺旋 （22 kDa）的两个螺旋圈，对应于13 nm的轴向位移。 的 菌毛外径约6 nm。 径向密度映射 波形蛋白和表皮角蛋白的中间丝显示了它们两者 具有平均直径均匀的主链，直径为9- 10 nm 被相对分散的外围密度的壳包围， 外径约为15 nm。 脊椎骨似乎是由 的保守的α螺旋棒域的螺旋包装的 IF亚基（311个氨基酸），而外周密度是由 通过高度可变的非α-螺旋末端结构域， 总质量的三分之一。 该模型认为，末端结构域赋予 不同类型中间体的个别功能特异性 细丝。

Virus Structures have been analyzed in the caes of (i) Herpes Simplex Virus where we have shown by computer image processing of electron micrographs that the major capsomer of the icosahedral capsid is a hexamer of a 155kDa protein, in the form of a cylinder 14nm in length, with a central channel that is about 4nm at the outer surface but much narrower on the inner surface. (ii) The tail fibers of bacteriophage T7 have been analyzed at high resolution by correlating secondary structure predictions of the 60kDa gp17 polypeptide with computer-processed electron images of individual fibers. Each fiber is an oligomer (probably a dimer) of parallel chains that are composed of three domains. The amino-terminal domains link the fibers to the tail; the central domains form a coiled-coil Alpha-helical rope to make up the proximal half-fiber, 19nm in length; the carboxy-terminal domains form inter-chain crossed Beta-sheets which form a linear sequence of four nodules in the distal half-fiber, also 19nm long. In addition we have determined the helical structures of the bacterial fimbriae of sertotypes #2 and #6 from, Bordetella pertussis, using paracrystals of purified fimbriae. In both cases, the fimbria is a single-start helix which contains five copies of the fimbrial portein (22kDa) in two helical turns, corresponding to an axial shift of 13nm. The outer diameter of the fimbria is about 6nm. Radial density mapping of intermediate filaments of vimentin and of epidermal keratin shows them both to have backbones of uniform average desneity with a diameter of 9-10nm surrounded by a shell of relatively diffuse perpheral density extending to an outer diameter of approximately 15nm. The backbone appears to be made up of a helical packing of the conservative Alph-helical rod-domains of the IF subunits (311 amino acids) whereas the peripheral density is contributed by the highly variable non-Alpha-helical end-domains which contain one third of the total mass. This model holds that the end-domain confer the individual functional specificities of different types of intermediate filaments.