Structure of the tubular variants of the head of bacteriophage T4 (polyheads). I. Arrangement of subunits in some classes of polyheads.
Structure of the tubular variants of the head of bacteriophage T4 (polyheads). I. Arrangement of subunits in some classes of polyheads.
复制标题
噬菌体 T4 头部管状变体的结构（多头）。
DOI：
10.1016/0022-2836(72)90202-1
复制
发表时间：
1972
影响因子：
5.6
通讯作者：
A. Klug
中科院分区：
文献类型：
--
作者：
D. J. DeRosier;A. Klug
通过光学衍射和过滤分析了由基因20突变引起的T4噬菌体头部管状变体的电子显微照片。已经观察到四种主要类型的管。最常见的管的宽度约为800微米，具有由简单的近六边形排列的壳粒组成的“粗糙”结构，壳粒被分解成六个规则排列的结构单元，间隔约33微米。这些单位可以用头部的主要蛋白质成分来识别。六聚体的边缘相对于晶格方向形成斜角。宽度大于1000 μ m的聚合物头，其来自原始多层管的外层，构成第二类。基本结构与第一类相似，为“粗六边形”，但壳粒扭曲，排列方向不同，第三类的管光滑，类似于空壳粒。这一类的亚结构与第一类的亚结构密切相关，并且可能是从第一类亚结构衍生而来的。亚单元再次被组织成六聚体，但后者的间距增加了10%，并且相对于晶格方向旋转，以便它们紧密地结合在一起。六聚体的中心区域也经常包含一个额外的单元，因此我们有一种新型的壳粒或形态单元，即“6 + 1”单元。六聚体的密集堆积以及中心单元的存在导致了管的光滑外观。第四类管的管壁具有更细的颗粒外观，并且通常填充有一些内部物质，使得它们染色非常严重。它们的结构在随附的论文中描述。描述了一种特殊的仪器，它允许通过光学衍射快速测量电子显微镜板。还给出了光学滤波程序的细节。
Electron micrographs of tubular variants of the head of bacteriophage T4 arising from a mutation in gene 20 have been analysed by means of optical diffraction and filtering. Four main classes of tube have been observed. The most commonly occurring tube is of width about 800 Å and has a “coarse” structure consisting of a simple near-hexagonal arrangement of capsomeres, which are resolved into six regularly disposed structural units spaced about 33 Å apart. These units can be identified with the major protein component of the head. The edges of the hexamers make a skew angle with respect to the lattice directions. Polyheads of widths greater than 1000 Å which derive from outer layers of originally multi-layered tubes constitute a second class. The basic structure is “coarse-hexagonal” like that of the first class, but the capsomeres are distorted and those in alternate rows have different orientations.The tubes of the third class have a smooth appearance similar to that of empty capsids. The substructure in this class is closely related to that in the first class and may be derived from it. Subunits are again organised into hexamers but the latter are now spaced 10% further apart and are rotated with respect to the lattice directions so that they fit snugly together. The central region of the hexamer also often appears to contain an additional unit, so that we have a new type of capsomere or morphological unit, the “6 + 1” unit. The denser packing of hexamers, together with the presence of the central units, leads to the smooth appearance of the tubes.The tubes of the fourth class have walls of an even more finely grained appearance and are generally filled with some internal substance so that they stain very heavily. Their structure is described in the accompanying paper.A special instrument is described which allows the rapid survey of electron micrograph plates by optical diffraction. Details are also given of optical filtering procedures.