Miyata Tomoko, Suzuki Hirofumi, Oyama Takuji, Mayanagi Kouta, Ishino Yoshizumi, Morikawa Kosuke
Department of Structural Biology, Biomolecular Engineering Research Institute, 6-2-3 Furuedai, Suita, Osaka 565-0874, Japan.
Proc Natl Acad Sci U S A. 2005 Sep 27;102(39):13795-800. doi: 10.1073/pnas.0506447102. Epub 2005 Sep 16.
Ring-shaped sliding clamps and clamp loader ATPases are essential factors for rapid and accurate DNA replication. The clamp ring is opened and resealed at the primer-template junctions by the ATP-fueled clamp loader function. The processivity of the DNA polymerase is conferred by its attachment to the clamp loaded onto the DNA. In eukarya and archaea, the replication factor C (RFC) and the proliferating cell nuclear antigen (PCNA) play crucial roles as the clamp loader and the clamp, respectively. Here, we report the electron microscopic structure of an archaeal RFC-PCNA-DNA complex at 12-A resolution. This complex exhibits excellent fitting of each atomic structure of RFC, PCNA, and the primed DNA. The PCNA ring retains an open conformation by extensive interactions with RFC, with a distorted spring washer-like conformation. The complex appears to represent the intermediate, where the PCNA ring is kept open before ATP hydrolysis by RFC.
环形滑动夹钳和夹钳装载ATP酶是DNA快速准确复制的关键因素。夹钳环通过由ATP驱动的夹钳装载功能在引物-模板连接处打开并重新封闭。DNA聚合酶的持续合成能力是通过其与装载到DNA上的夹钳的附着来赋予的。在真核生物和古细菌中，复制因子C（RFC）和增殖细胞核抗原（PCNA）分别作为夹钳装载器和夹钳发挥关键作用。在此，我们报告了分辨率为12埃的古细菌RFC-PCNA-DNA复合物的电子显微镜结构。该复合物展示了RFC、PCNA和引发DNA的每个原子结构的极佳契合。PCNA环通过与RFC的广泛相互作用保持开放构象，呈扭曲的弹簧垫圈状构象。该复合物似乎代表了这样一种中间体，即PCNA环在被RFC进行ATP水解之前保持开放状态。
