Fernandez-Leiro Rafael, Conrad Julian, Scheres Sjors Hw, Lamers Meindert H
MRC Laboratory of Molecular Biology, Cambridge, United Kingdom.
Elife. 2015 Oct 24;4:e11134. doi: 10.7554/eLife.11134.
The replicative DNA polymerase PolIIIα from is a uniquely fast and processive enzyme. For its activity it relies on the DNA sliding clamp β, the proofreading exonuclease ε and the C-terminal domain of the clamp loader subunit τ. Due to the dynamic nature of the four-protein complex it has long been refractory to structural characterization. Here we present the 8 Å resolution cryo-electron microscopy structures of DNA-bound and DNA-free states of the PolIII-clamp-exonuclease-τ complex. The structures show how the polymerase is tethered to the DNA through multiple contacts with the clamp and exonuclease. A novel contact between the polymerase and clamp is made in the DNA bound state, facilitated by a large movement of the polymerase tail domain and τ. These structures provide crucial insights into the organization of the catalytic core of the replisome and form an important step towards determining the structure of the complete holoenzyme.
来自[具体来源未提及]的复制性DNA聚合酶PolIIIα是一种独特的快速且持续合成的酶。它的活性依赖于DNA滑动夹β、校对核酸外切酶ε以及夹装载亚基τ的C末端结构域。由于这种四蛋白复合物的动态性质，长期以来它一直难以进行结构表征。在此，我们展示了PolIII - 夹 - 核酸外切酶 - τ复合物结合DNA和未结合DNA状态的8埃分辨率冷冻电子显微镜结构。这些结构展示了聚合酶如何通过与夹和核酸外切酶的多重接触与DNA相连。在结合DNA的状态下，聚合酶与夹之间形成了一种新的接触，这是由聚合酶尾部结构域和τ的大幅移动促成的。这些结构为复制体催化核心的组织提供了关键见解，并朝着确定完整全酶的结构迈出了重要一步。
