RecBCD enzyme is a bipolar DNA helicase
RecBCD enzyme is a bipolar DNA helicase
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DOI：
10.1038/nature01673
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发表时间：
2003-06-19
期刊：
影响因子：
64.8
通讯作者：
Kowalczykowski, SC
中科院分区：
文献类型：
--
作者：
Dillingham, MS;Spies, M;Kowalczykowski, SC
大肠杆菌RecBCD是一种异源三聚体解旋酶/核酸酶，催化一种复杂的反应，其中DNA中的双链断裂通过同源重组进行修复（1）。一段时间以来，已经清楚RecB亚基具有3 '->5' DNA解旋酶活性（2-4），其被认为驱动RecBCD全酶中的DNA易位和解旋。在这里，我们表明，纯化的RecD蛋白也是一种DNA解旋酶，但具有5 '->3'极性。我们还表明，RecB和RecD解旋酶在完整的RecBCD中都有活性，因为当这些亚基中的任何一个被突变灭活时，酶仍然能够进行DNA解旋。这些发现指向RecBCD的双极易位模型，其中两个DNA解旋酶是互补的，在反平行DNA双链体的每条链上以相反的极性但以相同的方向行进。这种双极运动组织有助于解释RecBCD的各种生化特性，特别是其异常高的速度和持续合成能力，并为RecBCD功能的各个方面提供了一个机制性的见解。
Escherichia coli RecBCD is a heterotrimeric helicase/nuclease that catalyses a complex reaction in which double-strand breaks in DNA are processed for repair by homologous recombination(1). For some time it has been clear that the RecB subunit possesses a 3'-->5' DNA helicase activity(2-4), which was thought to drive DNA translocation and unwinding in the RecBCD holoenzyme. Here we show that purified RecD protein is also a DNA helicase, but one that possesses a 5'-->3' polarity. We also show that the RecB and RecD helicases are both active in intact RecBCD, because the enzyme remains capable of processive DNA unwinding when either of these subunits is inactivated by mutation. These findings point to a bipolar translocation model for RecBCD in which the two DNA helicases are complementary, travelling with opposite polarities, but in the same direction, on each strand of the antiparallel DNA duplex. This bipolar motor organization helps to explain various biochemical properties of RecBCD, notably its exceptionally high speed and processivity, and offers a mechanistic insight into aspects of RecBCD function.