Studies of bacterial topoisomerases I and III at the single-molecule level.
Studies of bacterial topoisomerases I and III at the single-molecule level.
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DOI：
10.1042/bst20120297
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发表时间：
2013-04
影响因子：
3.9
通讯作者：
Mondragón A
中科院分区：
文献类型：
--
作者：
Terekhova K;Marko JF;Mondragón A
拓扑异构酶是负责维持细胞中DNA的超卷曲状态的酶，也是许多其他DNA拓扑相关反应的酶。IA型酶通过破坏一条DNA链并使另一条或多条DNA链通过断裂来改变DNA的拓扑结构。虽然所有IA型拓扑异构酶在序列、结构和机制水平上都是相关的，但不同类型的IA酶参与的细胞过程并不相同。我们利用单分子技术研究了大肠杆菌拓扑异构酶I和III的DNA弛豫机制，以了解它们的不同之处。我们的实验在单分子水平上显示了重要的差异，同时也恢复了大量实验的结果。总的来说，拓扑异构酶III通过快速的过程运行和长时间的停顿来放松DNA，而拓扑异构酶I通过缓慢的过程运行和短时间的停顿来放松DNA。这两种性质结合在一起产生了总体松弛速率，正如许多生化观察所预期的那样，拓扑异构酶I比拓扑异构酶III更快。这些结果有助于更好地理解这两种拓扑异构酶在细胞中的作用，也有助于强调单分子实验在揭示生物分子新功能特征方面的力量。
Topoisomerases are the enzymes responsible for maintaining the supercoiled state of DNA in the cell and also for many other DNA topology-associated reactions. Type IA enzymes alter DNA topology by breaking one DNA strand and passing another strand or strands through the break. Although all type IA topoisomerases are related at the sequence, structure, and mechanism level, different type IA enzymes do not participate in the same cellular processes. We have studied the mechanism of DNA relaxation by E. coli topoisomerases I and III using single-molecule techniques to understand their dissimilarities. Our experiments show important differences at the single molecule-level, while also recovering the results from bulk experiments. Overall, topoisomerase III relaxes DNA using fast processive runs followed by long pauses, whereas topoisomerase I relaxes DNA through slow processive runs followed by short pauses. These two properties combined give rise to the overall relaxation rate, which is faster for topoisomerase I than for topoisomerase III, as expected from many biochemical observations. The results help understand better the role of these two topoisomerases in the cell and also serve to emphasize the power of single-molecule experiments to uncover new functional characteristics of biological molecules.