小柯机器人

德国汉堡大学Thomas C. Marlovits等研究人员合作揭示AAA+ATP酶介导的RuvAB-霍利迪连结体分支迁移的机制。相关论文于2022年8月24日在线发表在《自然》杂志上。

利用时间分辨的冷冻电镜，研究人员获得了ATP-水解RuvAB复合物在七个不同的构象状态下的结构，这些结构是在组装和处理霍利迪连结体时捕获的。五个结构共同解析了完整的核苷酸循环，并揭示了ATP水解、核苷酸交换和RuvB的特定构象变化之间的时空关系。由脱离DNA的RuvB亚单位形成的转换器中的协调运动刺激了水解和核苷酸交换。转换器的固定化使RuvB能够将含有ATP的能量转化为杠杆运动，从而产生驱动分支迁移的拉力。

结果表明，RuvB马达与DNA底物一起旋转，这与不断进步的核苷酸循环一起，构成了通过连续分支迁移进行DNA重组的机制基础。总之，这些数据破译了RuvAB复合体同源重组的分子原理，阐明了六聚体AAA+马达的化学-机械耦合的离散和顺序过渡状态的中间体，并为设计针对AAA+马达的状态特异性化合物提供了一个蓝图。

据介绍，霍利迪连结体是在所有生命王国的DNA重组过程中形成的一个关键中间环节。在细菌中，霍利迪连结体由两个同源六聚体AAA+ATP酶RuvB马达处理，它们与RuvA-霍利迪连结体复合物一起组装，为链式交换反应提供能量。尽管它对染色体的维护很重要，但这种复合体促进分支迁移的结构和机制尚不清楚。

附：英文原文

Title: Mechanism of AAA+ ATPase-mediated RuvAB–Holliday junction branch migration

Author: Wald, Jiri, Fahrenkamp, Dirk, Goessweiner-Mohr, Nikolaus, Lugmayr, Wolfgang, Ciccarelli, Luciano, Vesper, Oliver, Marlovits, Thomas C.

Issue&Volume: 2022-08-24

Abstract: The Holliday junction is a key intermediate formed during DNA recombination across all kingdoms of life1. In bacteria, the Holliday junction is processed by two homo-hexameric AAA+ ATPase RuvB motors, which assemble together with the RuvA–Holliday junction complex to energize the strand-exchange reaction2. Despite its importance for chromosome maintenance, the structure and mechanism by which this complex facilitates branch migration are unknown. Here, using time-resolved cryo-electron microscopy, we obtained structures of the ATP-hydrolysing RuvAB complex in seven distinct conformational states, captured during assembly and processing of a Holliday junction. Five structures together resolve the complete nucleotide cycle and reveal the spatiotemporal relationship between ATP hydrolysis, nucleotide exchange and context-specific conformational changes in RuvB. Coordinated motions in a converter formed by DNA-disengaged RuvB subunits stimulate hydrolysis and nucleotide exchange. Immobilization of the converter enables RuvB to convert the ATP-contained energy into a lever motion, which generates the pulling force driving the branch migration. We show that RuvB motors rotate together with the DNA substrate, which, together with a progressing nucleotide cycle, forms the mechanistic basis for DNA recombination by continuous branch migration. Together, our data decipher the molecular principles of homologous recombination by the RuvAB complex, elucidate discrete and sequential transition-state intermediates for chemo-mechanical coupling of hexameric AAA+ motors and provide a blueprint for the design of state-specific compounds targeting AAA+ motors.

DOI: 10.1038/s41586-022-05121-1

Source: https://www.nature.com/articles/s41586-022-05121-1

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