Double-stranded DNA viruses package their genomes into pre-assembled capsids using virally-encoded ASCE ATPase ring motors. We present the first atomic-resolution crystal structure of a multimeric ring form of a viral dsDNA packaging motor and characterize its atomic-level dynamics via long timescale molecular dynamics simulations. Based on the results, we deduce an overall packaging mechanism that is driven by helical-to-planar transitions of the ring motor. These transitions are coordinated by inter-subunit interactions that regulate catalytic and force-generating events. Stepwise ATP binding to individual subunits increase their affinity for the helical DNA phosphate backbone, resulting in distortion away from the planar ring towards a helical configuration, inducing mechanical strain. Subsequent sequential hydrolysis events alleviate the accumulated mechanical strain, allowing a stepwise return of the motor to the planar conformation, translocating DNA in the process. This type of helical-to-planar mechanism could serve as a general framework for ring ATPases that exhibit burst-dwell dynamics.

中文翻译：

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病毒基因组包装电机中力产生，易位和协调的原子基础

双链DNA病毒使用病毒编码的ASCE ATPase环马达将其基因组包装到预先组装的衣壳中。我们介绍了病毒dsDNA包装电机的多聚环形式的第一个原子分辨率晶体结构，并通过长时间分子动力学模拟来表征其原子级动力学。根据结果​​，我们推导出了一种整体包装机制，该机制由环形电机的螺旋向平面过渡驱动。这些转变通过调节催化和力产生事件的亚基间相互作用来协调。逐步结合到单个亚基的ATP增加了它们对螺旋DNA磷酸骨架的亲和力，导致从平面环向螺旋构型的扭曲变形，从而引起机械应变。随后发生的顺序水解事件减轻了累积的机械应变，从而使电机逐步返回到平面构象，从而在此过程中转移了DNA。这种类型的螺旋到平面机制可以用作展示突发驻留动态的环状ATPase的通用框架。