Kato H, Fujisawa H, Minagawa T
Virology. 1985 Oct 15;146(1):12-21. doi: 10.1016/0042-6822(85)90048-0.
Bacteriophage T3 virions have six tail fibers composed of the product of gene 17 (gp17). Each tail fiber is a trimer of gp17 polypeptide. To characterize the assembly process of the tail fiber, temperature-sensitive (ts) mutants of gene 17 (ts17) were analyzed by SDS-polyacrylamide gel electrophoresis and by extract complementation. Newly synthesized gp17 polypeptide chains matured to SDS-resistant native trimers with a half time of about 7.5 min at 30 degrees. Although all ts17 mutants had similar plating efficiencies at restrictive temperature (41.5 degrees or 42 degrees), they showed different phenotypes. tsNG75, whose mutation was located in the carboxyl-terminal region of gene 17, was defective in trimer assembly at 41.5 degrees. The ts tail fibers formed at 30 degrees lost the ability to attach to the tail upon treatment at 41.5 degrees. There was a change in temperature sensitivity of tsNG75 tail fibers upon attachment to the tail, suggesting that the tail fiber may change conformation after attachment to the tail. tsNG215 and tsNG169, whose mutation sites were located in the amino-terminal region of gene 17, were not defective in the trimer assembly and attachment to the tail at the restrictive temperature. tsNG215 tail fibers formed at 41.5 degrees appear to be aberrant because they were not active in extract complementation and their attachment to fiberless particles resulted in production of noninfectious phage. Tail fibers produced by cells infected with tsNG169 at the restrictive temperature were active in extract complementation. Phage particles were formed in tsNG169-infected cells at the restrictive temperature. These particles were infectious at the permissive temperature and the mutant was non-infectious only if infection was continued at the restrictive temperature. These phenotypic differences exhibited by different gene 17 mutants may indicate the regions within the gene 17 polypeptide that play a role(s) in the folding and assembly of gp17 and in the biological activity of the mature tail fiber.
噬菌体T3病毒粒子有6根由基因17产物（gp17）组成的尾丝。每根尾丝是gp17多肽的三聚体。为了表征尾丝的组装过程，通过SDS-聚丙烯酰胺凝胶电泳和提取物互补分析了基因17的温度敏感（ts）突变体（ts17）。新合成的gp17多肽链在30℃下约7.5分钟的半衰期成熟为抗SDS的天然三聚体。尽管所有ts17突变体在限制温度（41.5℃或42℃）下具有相似的平板效率，但它们表现出不同的表型。tsNG75的突变位于基因17的羧基末端区域，在41.5℃下三聚体组装有缺陷。在30℃形成的ts尾丝在41.5℃处理后失去了附着在尾部的能力。tsNG75尾丝附着在尾部后温度敏感性发生了变化，这表明尾丝在附着到尾部后可能会改变构象。tsNG215和tsNG169的突变位点位于基因17的氨基末端区域，在限制温度下三聚体组装和附着到尾部没有缺陷。在41.5℃形成的tsNG215尾丝似乎异常，因为它们在提取物互补中无活性，并且它们附着到无纤维颗粒上导致产生无感染性的噬菌体。在限制温度下感染tsNG169的细胞产生的尾丝在提取物互补中具有活性。在限制温度下tsNG169感染的细胞中形成了噬菌体颗粒。这些颗粒在允许温度下具有感染性，并且只有在限制温度下继续感染时该突变体才无感染性。不同的基因17突变体表现出的这些表型差异可能表明基因17多肽中在gp17的折叠和组装以及成熟尾丝的生物学活性中起作用的区域。
