DNA-PK 全酶的冷冻电镜结构。
Cryo-EM structure of the DNA-PK holoenzyme.
机构信息
Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, MA 02115.
Program in Cellular and Molecular Medicine, Boston Children's Hospital, Boston, MA 02115.
出版信息
Proc Natl Acad Sci U S A. 2017 Jul 11;114(28):7367-7372. doi: 10.1073/pnas.1707386114. Epub 2017 Jun 26.
DNA-dependent protein kinase (DNA-PK) is a large protein complex central to the nonhomologous end joining (NHEJ) DNA-repair pathway. It comprises the DNA-PK catalytic subunit (DNA-PKcs) and the heterodimer of DNA-binding proteins Ku70 and Ku80. Here, we report the cryo-electron microscopy (cryo-EM) structures of human DNA-PKcs at 4.4-Å resolution and the DNA-PK holoenzyme at 5.8-Å resolution. The DNA-PKcs structure contains three distinct segments: the N-terminal region with an arm and a bridge, the circular cradle, and the head that includes the kinase domain. Two perpendicular apertures exist in the structure, which are sufficiently large for the passage of dsDNA. The DNA-PK holoenzyme cryo-EM map reveals density for the C-terminal globular domain of Ku80 that interacts with the arm of DNA-PKcs. The Ku80-binding site is adjacent to the previously identified density for the DNA-binding region of the Ku70/Ku80 complex, suggesting concerted DNA interaction by DNA-PKcs and the Ku complex.
DNA 依赖性蛋白激酶（DNA-PK）是一种大型蛋白复合物，是非同源末端连接（NHEJ）DNA 修复途径的核心。它由 DNA-PK 催化亚基（DNA-PKcs）和 DNA 结合蛋白 Ku70 和 Ku80 的异二聚体组成。在这里，我们报告了人源 DNA-PKcs 在 4.4-Å 分辨率和 DNA-PK 全酶在 5.8-Å 分辨率的冷冻电镜（cryo-EM）结构。DNA-PKcs 结构包含三个不同的片段：带有臂和桥的 N 端区域、圆形摇篮和包含激酶结构域的头部。结构中存在两个垂直的孔，其大小足以容纳双链 DNA 通过。DNA-PK 全酶的 cryo-EM 图谱揭示了 Ku80 的 C 端球状结构域的密度，该结构域与 DNA-PKcs 的臂相互作用。Ku80 的结合位点与先前鉴定的 Ku70/Ku80 复合物的 DNA 结合区域的密度相邻，表明 DNA-PKcs 和 Ku 复合物协同进行 DNA 相互作用。
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