Mechanism of the sliding beta-clamp of DNA polymerase III holoenzyme.
Mechanism of the sliding beta-clamp of DNA polymerase III holoenzyme.
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DOI：
10.1016/s0021-9258(18)99166-0
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发表时间：
1991-06
期刊：
影响因子：
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通讯作者：
P. Stukenberg;P. S. Studwell-Vaughan;M. O’Donnell
中科院分区：
文献类型：
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作者：
P. Stukenberg;P. S. Studwell-Vaughan;M. O’Donnell
DNA聚合酶III全酶（holo酶）是大肠杆菌的多蛋白复制酶，在DNA合成过程中基本上是无限的。过程性活动可以由两个组成部分重构。其中一种成分是-起始前复合物，是夹在引物DNA上的-二聚体。预起始复合物是由五蛋白复合物形成的，它水解ATP，使β蛋白与引物DNA结合。另一个成分是聚合酶。- epsilon聚合酶本身不具有进程性，但在与-起始前复合物组装时具有极高的进程活性。在这里，我们研究了β预起始复合物赋予α epsilon聚合酶加工能力的机制。我们发现-起始前复合物在DNA上是可移动的。DNA上的扩散是双链DNA特有的，是双向的，不需要ATP，并且沿着双链呈线性扩散。此外，β通过与DNA聚合酶亚基α的接触直接结合α ε聚合酶。因此，全酶的高加工性源于DNA上的“滑动钳”，它将聚合酶与引物模板连接在一起。讨论了转录和翻译的意义。
DNA polymerase III holoenzyme (holoenzyme), the multiprotein replicase of Escherichia coli, is essentially unlimited in processive DNA synthesis. Processive activity can be reconstituted from two components. One component, the beta preinitiation complex, is a beta dimer clamped onto primed DNA. The beta preinitiation complex is formed by the five-protein gamma complex, which hydrolyzes ATP to chaperone beta onto primed DNA. The other component is the alpha epsilon polymerase. The alpha epsilon polymerase itself is not processive, but is endowed with extremely high processive activity upon assembly with the beta preinitiation complex. Here we examine the mechanism by which the beta preinitiation complex confers processivity onto the alpha epsilon polymerase. We find the beta preinitiation complex to be mobile on DNA. Diffusion of beta on DNA is specific to duplex DNA, is bidirectional, does not require ATP, and appears to diffuse linearly along the duplex. Furthermore, beta directly binds the alpha epsilon polymerase through contact with alpha, the DNA polymerase subunit. Hence, the high processivity of the holoenzyme is rooted in a “sliding clamp” of beta on DNA that tethers the polymerase to the primed template. Implications for transcription and translation are discussed.