SHAPE OF T-EVEN BACTERIOPHAGE HEAD
SHAPE OF T-EVEN BACTERIOPHAGE HEAD
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DOI：
10.1016/0042-6822(65)90319-3
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发表时间：
1965-01-01
期刊：
影响因子：
3.7
通讯作者：
MOODY, MF
中科院分区：
文献类型：
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作者：
MOODY, MF
t型平头的电子显微照片没有提供有效的理由来相信头部形状一定是双棱锥六边形棱镜，因为其他多面体也给出了与t型平头相似的六边形轮廓。正常头部与各种缺陷头部的结构比较表明：(1)分子在头部膜内可能呈六边形排列；(2)头部蛋白质分子在末端和非末端顶点的局部排列是相同的。在描述的四个假设中，只有两个与这一证据一致；两者都要求正常头部具有等距衣壳结构，具有二十面体对称，其中中间部分已经延伸。在这两种假设中，头的形状最令人满意的是一个假设，根据这个假设，正常的头有52个对称，其形状是由一个正二十面体的中部延伸而来的（“长二十面体”）。这表明，它是有可能容纳这个头部的5倍轴与6倍对称的底板。
Electron micrographs of T-even heads have provided no valid reason for believing that the head shape must be a bipyramidal hexagonal prism, as other polyhedra also give hexagonal profiles similar to those shown by T-even heads. Comparison of the structure of the normal head with various defective head forms shows that (1) the molecules are probably hexagonally packed in the head membrane and (2) the local packing of head protein molecules is the same round a terminal and a nonterminal vertex. Of four hypotheses which are described, only two are consistent with this evidence; both require the normal head to have the structure of an isometric capsid with icosa-hedral symmetry, in which the middle portion has been extended. Of these two hypotheses, the head shape is most satisfactorily accounted for by a hypothesis according to which the normal head has 52 symmetry and has a shape derived from a regular icosahedron by the extension of its middle section (''prolate icosahedron''). It is shown that it is possible to accommodate the 5-fold axis of this head with the 6-fold symmetry of the base plate.