Activities of gyrase and topoisomerase IV on positively supercoiled DNA.
Activities of gyrase and topoisomerase IV on positively supercoiled DNA.
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DOI：
10.1093/nar/gkx649
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发表时间：
2017-09-19
影响因子：
14.9
通讯作者：
Osheroff N
中科院分区：
文献类型：
--
作者：
Ashley RE;Dittmore A;McPherson SA;Turnbough CL Jr;Neuman KC;Osheroff N
虽然细菌旋切酶和拓扑异构酶IV与正超旋DNA有关键的相互作用，但对这些酶在过旋底物上的作用知之甚少。因此，我们分析了炭疽芽孢杆菌和大肠杆菌的旋切酶和拓扑异构酶IV松弛和切割正超旋DNA的能力。Gyrase去除正超线圈的速度和过程比将负超线圈引入松弛DNA的速度和过程快10倍。在时间分辨的单分子测量中，gyrase以每秒约100个超级线圈的爆发速率放松过度缠绕的DNA（平均爆发大小为6.2个超级线圈）。高效的正超级线圈去除需要GyrA-box，这是DNA包裹所必需的。拓扑异构酶IV还能够在链传递过程中区分DNA的几何形状，并且放松正超卷曲底物的速度比负超卷曲分子快3倍。Gyrase与正超卷DNA（与负超卷DNA相比）保持较低的切割复合物水平，而拓扑异构酶IV与两种底物产生相似的水平。结果表明，回转酶比拓扑异构酶IV更适合安全地去除在复制叉前积累的正超级线圈。他们还认为，螺旋酶的缠绕机制可能已经进化到促进正超级线圈的快速去除，而不是诱导负超级线圈。
Although bacterial gyrase and topoisomerase IV have critical interactions with positively supercoiled DNA, little is known about the actions of these enzymes on overwound substrates. Therefore, the abilities of Bacillus anthracis and Escherichia coli gyrase and topoisomerase IV to relax and cleave positively supercoiled DNA were analyzed. Gyrase removed positive supercoils ∼10-fold more rapidly and more processively than it introduced negative supercoils into relaxed DNA. In time-resolved single-molecule measurements, gyrase relaxed overwound DNA with burst rates of ∼100 supercoils per second (average burst size was 6.2 supercoils). Efficient positive supercoil removal required the GyrA-box, which is necessary for DNA wrapping. Topoisomerase IV also was able to distinguish DNA geometry during strand passage and relaxed positively supercoiled substrates ∼3-fold faster than negatively supercoiled molecules. Gyrase maintained lower levels of cleavage complexes with positively supercoiled (compared with negatively supercoiled) DNA, whereas topoisomerase IV generated similar levels with both substrates. Results indicate that gyrase is better suited than topoisomerase IV to safely remove positive supercoils that accumulate ahead of replication forks. They also suggest that the wrapping mechanism of gyrase may have evolved to promote rapid removal of positive supercoils, rather than induction of negative supercoils.
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影响因子：
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作者：
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