Hohn T
Philos Trans R Soc Lond B Biol Sci. 1976 Nov 30;276(943):143-50. doi: 10.1098/rstb.1976.0105.
In complex DNA bacteriophages like lambda, T4, T7, P22, P2, the DNA is packaged into a preformed precursor particle which sometimes has a smaller size and often a shape different from that of the phage head. This packaging mechanism is different from the one suggested for the RNA phages, according to which RNA nucleates the shell formation. The different mechanisms could be understood by comparing the genomes to be packaged: single stranded fII RNA has a very compact structure with high helix content. It might easily form quasispherical structures in solution (as seen in the electron microscope by Thach & Thach (1973)) around which the capsid could assemble. Double stranded phage DNA, on the other hand, is a rigid molecule which occupies a large volume in solution and has to be concentrated 15-fold during packaging into the preformed capsid, and the change in the capsid structure observed hereby might provide the necessary DNA condensation energy.
在诸如λ噬菌体、T4噬菌体、T7噬菌体、P22噬菌体、P2噬菌体等复杂的DNA噬菌体中，DNA被包装到一个预先形成的前体颗粒中，该颗粒有时尺寸较小，且形状通常与噬菌体头部不同。这种包装机制不同于RNA噬菌体所提出的机制，根据后者，RNA促使衣壳形成。通过比较待包装的基因组可以理解这两种不同的机制：单链fII RNA具有非常紧密的结构，螺旋含量高。它可能很容易在溶液中形成准球形结构（如Thach和Thach（1973年）在电子显微镜下所见），衣壳可以围绕该结构组装。另一方面，双链噬菌体DNA是一种刚性分子，在溶液中占据较大体积，在包装到预先形成的衣壳过程中必须浓缩15倍，由此观察到的衣壳结构变化可能提供必要的DNA浓缩能量。
