Department of Biophysics and Radiation Biology, Semmelweis University, Tűzoltó u. 37-47, Budapest H-1094, Hungary.
Nanoscale. 2018 Jan 25;10(4):1898-1904. doi: 10.1039/c7nr05897g.
The foremost event of bacteriophage infection is the ejection of genomic material into the host bacterium after virus binding to surface receptor sites. How ejection is triggered is yet unknown. Here we show, in single mature T7 phage particles, that tapping the capsid wall with an oscillating atomic-force-microscope cantilever triggers rapid DNA ejection via the tail complex. The triggering rate increases exponentially as a function of force, following transition-state theory, across an activation barrier of 23 kcal mol at 1.2 nm along the reaction coordinate. The conformation of the ejected DNA molecule revealed that it had been exposed to a propulsive force. This force, arising from intra-capsid pressure, assists in initiating the ejection process and the transfer of DNA across spatial dimensions beyond that of the virion. Chemical immobilization of the tail fibers also resulted in enhanced DNA ejection, suggesting that the triggering process might involve a conformational switch that can be mechanically activated either by external forces or via the tail-fiber complex.
噬菌体感染的首要事件是病毒与表面受体结合后，基因组物质被喷射到宿主细菌中。目前尚不清楚喷射是如何触发的。在这里，我们在单个成熟的 T7 噬菌体粒子中表明，通过振动原子力显微镜悬臂敲击衣壳壁可以通过尾部复合物触发快速 DNA 喷射。触发率随着力的指数增加，符合过渡态理论，在沿着反应坐标的 1.2nm 处，跨越 23 kcal/mol 的激活能垒。喷射 DNA 分子的构象表明它已经暴露于推进力下。这种来自衣壳内的压力产生的力有助于启动喷射过程，并将 DNA 转移到病毒粒子以外的空间维度。尾部纤维的化学固定也导致 DNA 喷射增强，这表明触发过程可能涉及构象转变，该转变可以通过外部力或通过尾部纤维复合物机械激活。
