解析：CryoEM structures of open dimers of gyrase A in complex with DNA illuminate mechanism of strand passage. 这是一个包含了复杂医学词汇的句子，需要对关键词进行解析，如下： - CryoEM structures（冷冻电镜结构） - open dimers of gyrase A（A 拓扑异构酶的开放二聚体） - in complex with DNA（与 DNA 结合） - illuminate（阐明） - mechanism of strand passage（链穿越机制） 译文：A 拓扑异构酶的开放二聚体与 DNA 复合物的冷冻电镜结构阐明了链穿越机制。
CryoEM structures of open dimers of gyrase A in complex with DNA illuminate mechanism of strand passage.
机构信息
Department of Molecular Biosciences, Northwestern University, Evanston, United States.
Division of Physical Biochemistry, MRC National Institute for Medical Research, London, United Kingdom.
出版信息
Elife. 2018 Nov 20;7:e41215. doi: 10.7554/eLife.41215.
Gyrase is a unique type IIA topoisomerase that uses ATP hydrolysis to maintain the negatively supercoiled state of bacterial DNA. In order to perform its function, gyrase undergoes a sequence of conformational changes that consist of concerted gate openings, DNA cleavage, and DNA strand passage events. Structures where the transported DNA molecule (T-segment) is trapped by the A subunit have not been observed. Here we present the cryoEM structures of two oligomeric complexes of open gyrase A dimers and DNA. The protein subunits in these complexes were solved to 4 Å and 5.2 Å resolution. One of the complexes traps a linear DNA molecule, a putative T-segment, which interacts with the open gyrase A dimers in two states, representing steps either prior to or after passage through the DNA-gate. The structures locate the T-segment in important intermediate conformations of the catalytic cycle and provide insights into gyrase-DNA interactions and mechanism.
回旋酶是一种独特的 IIA 拓扑异构酶，利用 ATP 水解来维持细菌 DNA 的负超螺旋状态。为了发挥其功能，回旋酶经历了一系列构象变化，包括协同门的打开、DNA 切割和 DNA 链通过事件。尚未观察到被 A 亚基捕获的转运 DNA 分子（T 片段）的结构。在这里，我们展示了两个开放回旋酶 A 二聚体和 DNA 的寡聚复合物的 cryoEM 结构。这些复合物中的蛋白质亚基分别解析到 4 Å 和 5.2 Å 的分辨率。其中一个复合物捕获了一个线性 DNA 分子，即一个假定的 T 片段，该片段与开放的回旋酶 A 二聚体以两种状态相互作用，分别代表穿过 DNA 门之前或之后的步骤。这些结构将 T 片段定位在催化循环的重要中间构象中，并提供了对回旋酶-DNA 相互作用和机制的深入了解。
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