Serwer P, Watson R H, Hayes S J
J Virol. 1982 May;42(2):583-94. doi: 10.1128/JVI.42.2.583-594.1982.
It has previously been shown that: (i) during infection of its host, the DNA bacteriophage T7 assembles a DNA-free procapsid (capsid I), a capsid with an envelope differing physically and chemically from the capsid of the mature bacteriophage, and (ii) capsid I converts to a capsid (capsid II) with a bacteriophage-like envelope as it packages DNA. Lysates of phage T7-infected Escherichia coli contained a particle (AG particle) which copurified with capsid II during buoyant density sedimentation, velocity sedimentation, and solid support-free electrophoresis, but was distinguished from capsid II by its apparent diversity during electrophoresis in agarose gels. Treatment of AG particles with trypsin converted most of them to particles that comigrated with trypsin-treated capsid II during electrophoresis in agarose gels. Irreversible binding of AG particles to agarose gels was shown to contribute to the apparent diversity of AG particles during agarose gel electrophoresis. The results of quantitation of AG particles and of capsid I and capsid II in lysates of a nonpermissive host infected with T7 amber mutants suggested that, in site of their capsid II-like properties, most AG particles were produced during assembly of capsid I and not during DNA packaging. The presence of AG particles in T7 lysates explains contradictions in previous data concerning the pathway of T7 assembly.
（i）在感染宿主期间，DNA噬菌体T7组装无DNA的原衣壳（衣壳I），一种具有在物理和化学性质上与成熟噬菌体衣壳不同的包膜的衣壳，并且（ii）衣壳I在包装DNA时转变为具有类似噬菌体包膜的衣壳（衣壳II）。噬菌体T7感染的大肠杆菌裂解物含有一种颗粒（AG颗粒），在浮力密度沉降、速度沉降和无固相支持物电泳过程中，它与衣壳II共同纯化，但在琼脂糖凝胶电泳过程中，其明显的多样性使其与衣壳II区分开来。用胰蛋白酶处理AG颗粒，在琼脂糖凝胶电泳过程中，大多数AG颗粒转变为与经胰蛋白酶处理的衣壳II迁移一致的颗粒。已表明AG颗粒与琼脂糖凝胶的不可逆结合导致了琼脂糖凝胶电泳过程中AG颗粒明显的多样性。对感染T7琥珀突变体的非允许宿主裂解物中AG颗粒、衣壳I和衣壳II的定量结果表明，尽管AG颗粒具有类似衣壳II的性质，但大多数AG颗粒是在衣壳I组装过程中产生的，而不是在DNA包装过程中产生的。T7裂解物中AG颗粒的存在解释了先前关于T7组装途径的数据中的矛盾之处。
