Raspaud Eric, Forth Thomas, São-José Carlos, Tavares Paulo, de Frutos Marta
Laboratoire de Physique des Solides, Université Paris-Sud, CNRS, UMR 8502, F-91405 Orsay cedex, France.
Biophys J. 2007 Dec 1;93(11):3999-4005. doi: 10.1529/biophysj.107.111435. Epub 2007 Aug 3.
All tailed bacteriophages follow the same general scheme of infection: they bind to their specific host receptor and then transfer their genome into the bacterium. DNA translocation is thought to be initiated by the strong pressure due to DNA packing inside the capsid. However, the exact mechanism by which each phage controls its DNA ejection remains unknown. Using light scattering, we analyzed the kinetics of in vitro DNA release from phages SPP1 and lambda (Siphoviridae family) and found a simple exponential decay. The ejection characteristic time was studied as a function of the temperature and found to follow an Arrhenius law, allowing us to determine the activation energy that governs DNA ejection. A value of 25-30 kcal/mol is obtained for SPP1 and lambda, comparable to the one measured in vitro for T5 (Siphoviridae) and in vivo for T7 (Podoviridae). This suggests similar mechanisms of DNA ejection control. In all tailed phages, the opening of the connector-tail channel is needed for DNA release and could constitute the limiting step. The common value of the activation energy likely reflects the existence for all phages of an optimum value, ensuring a compromise between efficient DNA delivery and high stability of the virus.
它们与特定的宿主受体结合，然后将其基因组转移到细菌中。DNA易位被认为是由衣壳内DNA包装产生的强大压力引发的。然而，每种噬菌体控制其DNA喷射的确切机制仍然未知。我们利用光散射分析了噬菌体SPP1和λ（长尾噬菌体科）体外DNA释放的动力学，发现其呈简单的指数衰减。研究了喷射特征时间与温度的函数关系，发现其遵循阿累尼乌斯定律，这使我们能够确定控制DNA喷射的活化能。SPP1和λ的活化能值为25 - 30千卡/摩尔，与体外测量的T5（长尾噬菌体科）和体内测量的T7（短尾噬菌体科）的值相当。这表明DNA喷射控制机制相似。在所有有尾噬菌体中，连接体 - 尾通道的开放是DNA释放所必需的，并且可能是限制步骤。活化能的共同值可能反映了所有噬菌体都存在一个最佳值，确保在高效DNA传递和病毒高稳定性之间达成妥协。
