Duda R L, Eiserling F A
J Virol. 1982 Aug;43(2):714-20. doi: 10.1128/JVI.43.2.714-720.1982.
The length of the T4 tail is precisely regulated in vivo at the time of polymerization of the tail core protein onto the baseplate. Since no mutations which alter tail length have been identified, a study of in vivo-assembled tail cores was begun to determine whether the structural properties of assembled cores would reveal the mechanism of length regulation. An assembly intermediate consisting of a core attached to a baseplate (core-baseplate) was purified from cells infected with a T4 mutant in gene 15. When core-base plates were treated with guanidine hydrochloride, cores were released from baseplates. The released cores had the same mean length as cores attached to baseplates. Electron micrographs of these cores showed partial penetration of negative stain into one end, and, at the opposite end, a modified tip which often appeared as a short fiber projecting from the core. When cores were purified and analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, two minor proteins and the major core protein were detected. One minor protein, the product of gene 48 (gp48), was present in at least 72% of the amount found in core-baseplates, relative to the amount of the major core protein. These findings suggest that cores contain a fibrous structure, possibly composed of gp48, which may form a "ruler" that specifies the length of the T4 tail.
在尾核心蛋白聚合到底板上的过程中，T4噬菌体尾部的长度在体内受到精确调控。由于尚未发现改变尾部长度的突变，因此开始对体内组装的尾核心进行研究，以确定组装核心的结构特性是否能揭示长度调控机制。从感染了基因15的T4突变体的细胞中纯化出一种由附着到底板上的核心组成的组装中间体（核心-底板）。当核心-底板用盐酸胍处理时，核心从底板上释放出来。释放出的核心与附着在底板上的核心具有相同的平均长度。这些核心的电子显微镜照片显示，负染剂部分渗透到一端，而在另一端，有一个经过修饰的尖端，通常看起来像是从核心伸出的短纤维。当核心被纯化并通过十二烷基硫酸钠-聚丙烯酰胺凝胶电泳进行分析时，检测到两种次要蛋白质和主要的核心蛋白。其中一种次要蛋白质是基因48的产物（gp48），相对于主要核心蛋白的量，其在核心-底板中发现的量至少占72%。这些发现表明，核心含有一种纤维状结构，可能由gp48组成，它可能形成一个“尺子”来确定T4噬菌体尾部的长度。
