An ATP-powered DNA translocation machine encapsidates the viral genome in the large dsDNA bacteriophages. The essential components include the empty shell, prohead, and the packaging enzyme, terminase. During translocation, terminase is docked on the prohead's portal protein. The translocation ATPase and the concatemer-cutting endonuclease reside in terminase. Remarkably, terminases, portal proteins, and shells of tailed bacteriophages and herpes viruses show conserved features. These DNA viruses may have descended from a common ancestor. Terminase's ATPase consists of a classic nucleotide binding fold, most closely resembling that of monomeric helicases. Intriguing models have been proposed for the mechanism of dsDNA translocation, invoking ATP hydrolysis-driven conformational changes of portal or terminase powering DNA motion. Single-molecule studies show that the packaging motor is fast and powerful. Recent advances permit experiments that can critically test the packaging models. The viral genome translocation mechanism is of general interest, given the parallels between terminases, helicases, and other motor proteins.

中文翻译：

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噬菌体DNA包装马达。

由 ATP 驱动的 DNA 易位机器将病毒基因组包裹在大型 dsDNA 噬菌体中。基本成分包括空壳、前头和包装酶、终止酶。在易位期间，终止酶停靠在前头的门户蛋白上。易位 ATP 酶和串联体切割核酸内切酶位于终止酶中。值得注意的是，末端酶、门户蛋白和有尾噬菌体和疱疹病毒的外壳显示出保守的特征。这些 DNA 病毒可能来自一个共同的祖先。Terminase 的 ATPase 由经典的核苷酸结合折叠组成，与单体解旋酶最相似。对于 dsDNA 易位的机制，已经提出了有趣的模型，调用了入口或终止酶的 ATP 水解驱动的构象变化，为 DNA 运动提供动力。单分子研究表明，包装电机速度快，功率大。最近的进展允许可以批判性地测试包装模型的实验。鉴于终止酶、解旋酶和其他运动蛋白之间的相似性，病毒基因组易位机制受到普遍关注。