FORM-DETERMINING FUNCTION OF GENES REQUIRED FOR ASSEMBLY OF HEAD OF BACTERIOPHAGE-T4
FORM-DETERMINING FUNCTION OF GENES REQUIRED FOR ASSEMBLY OF HEAD OF BACTERIOPHAGE-T4
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DOI：
10.1016/0022-2836(70)90379-7
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发表时间：
1970-01-01
影响因子：
5.6
通讯作者：
KELLENBERGER, E
中科院分区：
文献类型：
--
作者：
LAEMMLI, UK;MOLBERT, E;KELLENBERGER, E
涉及 T4 头形成的基因的条件致死突变的生理表现已被重新检查。如果基因 20 或 40 的产物有缺陷，则会合成开放式管状结构（多头）。基因 22 突变体的感染导致多头的形成，其中约 70% 由两个或多个同心层（多层多头）组成。感染基因 21 和 24 突变体的细胞产生衣壳样颗粒（τ 颗粒）和多头的混合爆发，其中许多具有半球形帽。τ 颗粒的高分辨率显微照片揭示了与多头显微照片上相似的子结构，与表面上看不到任何细节的正常衣壳相反。对头相关结构形成动力学的研究表明，特定的基因产物导致有效利用晚期噬菌体蛋白来形成多头或τ-颗粒。此外，多层多头形成的动力学研究表明，单层多头可以作为“核心”，在其上添加后续层。通过检查一系列双突变体的感染，确定了形成各种头相关结构所需的活性产物的头基因的最小数量。当基因 22 的产物有缺陷时产生的多层多头需要仅研究的七个头基因中的两个的活性产物，即基因 23 和 31。然而，在被基因 20 或 40 的突变体感染的细胞中产生的单层多头，除了基因 23 和 31 之外，还需要基因 22 的产物。如果基因 21 和 24 存在缺陷，则出现所谓的 τ 粒子。单独或一起突变，并且需要所有其他头部基因的功能产物来形成它们。这些结果表明一些基因产物具有形状指定作用。基因 22 与衣壳形成的起始过程相关，基因 20 和 40 与半球形帽的形成相关。基因 21 和 24 似乎决定衣壳的大小和表面结构，从而使它们易于 DNA 整合。它们的主要功能也可能是充当噬菌体 DNA 的浓缩因子。
The physiological manifestation of conditional lethal mutations in the genes involved in the formation of the T4 head have been re-examined. If the product of genes 20 or 40 is defective, open-ended tubular structures (polyheads) are synthesized. Infection with mutants in gene 22 leads to the formation of polyheads, about 70% of which consist of two or more concentric layers (multilayered polyheads). Cells infected with mutants in gene 21 and 24 yield a mixed burst of capsid-like particles (τ-particles) and polyheads, many of which have hemispherical caps.High resolution micrographs of τ-particles reveal a substructure similar to that seen on micrographs of polyheads, in contrast to normal capsids on whose surface no detail can be visualized.Studies of the kinetics of formation of the head-related structures show that the absence or malfunctioning of a particular gene product results in an efficient use of the late phage proteins for the formation of either polyheads or τ-partieles. Furthermore, kinetic studies of multilayered polyhead formation suggest that single-layered polyheads can serve as a “core” onto which subsequent layers are added.The minimum number of head genes whose active product is needed to form the various head-related structures has been determined by examining infection by a series of double mutants. Multilayered polyheads produced when the product of gene 22 is defective need for their assembly the active product of only two of the seven head genes studied, namely, genes 23 and 31. Single-layered polyheads, however, which are produced in cells infected either with mutants in gene 20 or 40 need, in addition to genes 23 and 31, the product of gene 22. The so-called τ-particles appear if the genes 21 and 24 are mutated either singly or together and require for their formation the functional product of all the other head genes.These results suggest that some of the gene products have a shape-specifying role. Gene 22 is associated with the initiation process in capsid formation and genes 20 and 40 with the formation of the hemispherical cap. Genes 21 and 24 appear to determine the size and surface structure of the capsids thus rendering them susceptible to DNA integration. It is also possible that their primary function is to act as a condensing factor for phage DNA.