Brewer G J
J Supramol Struct. 1976;5(1):73-9. doi: 10.1002/jss.400050108.
The regulation of membrane formation in bacteriophage PM2 serves as a simple model for changes in membrane structure in eukaryotic cells. Prior to Pseudomonas host lysis, wild-type virions mature to an icosahedral morphology at the inner face of the cytoplasmic membrane. The preliminary characterization of two temperature-sensitive mutants of PM2 is described. In cells infected at the restrictive temperature with ts 1, an abundance of "empty" virus-size membrane vesicles are seen. Synthesis of DNA is also reduced in ts 1 infected cells. The preponderance of vesicles is not seen in cells infected with wild-type virus or with ts 1 at the permissive temperature. The "empty" appearance of the viral membranes suggests that viral DNA is not encapsulated. The major viral capsid protein (MW 26,000) is located just outside the viral membrane and normally sidiments with host and virus membranes. This protein made by mutant ts 5 does not pellet with these membranes; instead, large amounts of capsid protein can be precipitated from the supernatant with TCA. Compared to cells infected with wild type virus, cells infected with ts 5 at the restrictive temperature produced inside the cell an abundance of virus-size membrane vesicles. Taken together, these results with viral mutants suggest that formation of a viral membrane of the proper size does not require a DNA core around which to form, or an outer scaffolding of coat protein against which to form a spherical bilayer.
噬菌体PM2中膜形成的调控可作为真核细胞膜结构变化的一个简单模型。在假单胞菌宿主裂解之前，野生型病毒粒子在细胞质膜的内表面成熟为二十面体形态。本文描述了PM2的两个温度敏感突变体的初步特征。在用ts 1在限制温度下感染的细胞中，可以看到大量“空的”病毒大小的膜囊泡。在ts 1感染的细胞中DNA合成也减少。在用野生型病毒或在允许温度下用ts 1感染的细胞中看不到大量的囊泡。病毒膜的“空”外观表明病毒DNA没有被包裹。主要的病毒衣壳蛋白（分子量26,000）位于病毒膜的外侧，通常与宿主膜和病毒膜一起沉降。由突变体ts 5产生的这种蛋白不会与这些膜一起沉淀；相反，大量的衣壳蛋白可以用三氯乙酸从上清液中沉淀出来。与用野生型病毒感染的细胞相比，在用ts 5在限制温度下感染的细胞中，在细胞内产生了大量病毒大小的膜囊泡。综合起来，这些关于病毒突变体的结果表明，形成合适大小的病毒膜不需要围绕其形成的DNA核心，也不需要衣壳蛋白的外部支架来形成球形双层膜。
