Internal DNA pressure modifies stability of WT phage
Internal DNA pressure modifies stability of WT phage
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DOI：
10.1073/pnas.0703166104
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发表时间：
2007-06-05
影响因子：
11.1
通讯作者：
Evilevitch, Alex
中科院分区：
文献类型：
--
作者：
Ivanovska, Irena;Wuite, Gijs;Evilevitch, Alex
噬菌体中的双链DNA受到高度应力，并在衣壳壁上施加许多大气压（1 atm = 101.3 kPa）的内压。我们通过使用原子力显微镜压痕技术研究了A噬菌体中包装的DNA长度（WT DNA的78-100%）与衣壳强度之间的相关性。我们表明，与WT DNA的双链是两倍强的较短的基因组突变体，表现得像空衣壳，不管高的内部压力。我们的分析模型的DNA填充的衣壳变形表明，由于DNA水合水分子，渗透压存在于衣壳内，呈指数增加时，包装的DNA密度接近WT噬菌体。该渗透压提高WT衣壳强度，并且大约等于空壳的最大断裂力。这一结果表明，壳的强度限制了最大包装的基因组长度。此外，这意味着WT的进化优化，使它们能够在自然界中承受更大的外部机械应力。
dsDNA in bacteriophages is highly stressed and exerts internal pressures of many atmospheres (1 atm = 101.3 kPa) on the capsid walls. We investigate the correlation between packaged DNA length in A phage (78-100% of WT DNA) and capsid strength by using an atomic force microscope indentation technique. We show that phages with WT DNA are twice as strong as shorter genome mutants, which behave like empty capsids, regardless of high internal pressure. Our analytical model of DNA-filled capsid deformation shows that, because of DNA-hydrating water molecules, an osmotic pressure exists inside capsids that increases exponentially when the packaged DNA density is close to WT phage. This osmotic pressure raises the WT capsid strength and is approximately equal to the maximum breaking force of empty shells. This result suggests that the strength of the shells limits the maximal packaged genome length. Moreover, it implies an evolutionary optimization of WT phages allowing them to survive greater external mechanical stresses in nature.