Lo Yu-Hua, Tsai Kuang-Lei, Sun Yuh-Ju, Chen Wei-Ti, Huang Cheng-Yang, Hsiao Chwan-Deng
Institute of Molecular Biology, Academia Sinica, Taipei, 115, Taiwan.
Nucleic Acids Res. 2009 Feb;37(3):804-14. doi: 10.1093/nar/gkn999. Epub 2008 Dec 15.
DNA helicases are motor proteins that play essential roles in DNA replication, repair and recombination. In the replicative hexameric helicase, the fundamental reaction is the unwinding of duplex DNA; however, our understanding of this function remains vague due to insufficient structural information. Here, we report two crystal structures of the DnaB-family replicative helicase from Geobacillus kaustophilus HTA426 (GkDnaC) in the apo-form and bound to single-stranded DNA (ssDNA). The GkDnaC-ssDNA complex structure reveals that three symmetrical basic grooves on the interior surface of the hexamer individually encircle ssDNA. The ssDNA-binding pockets in this structure are directed toward the N-terminal domain collar of the hexameric ring, thus orienting the ssDNA toward the DnaG primase to facilitate the synthesis of short RNA primers. These findings provide insight into the mechanism of ssDNA binding and provide a working model to establish a novel mechanism for DNA translocation at the replication fork.
DNA解旋酶是一种驱动蛋白，在DNA复制、修复和重组过程中发挥着至关重要的作用。在复制性六聚体解旋酶中，其基本反应是双链DNA的解旋；然而，由于结构信息不足，我们对这一功能的理解仍然模糊不清。在此，我们报告了嗜热栖热放线菌HTA426（GkDnaC）的DnaB家族复制性解旋酶的两种晶体结构，一种为无配体形式，另一种与单链DNA（ssDNA）结合。GkDnaC-ssDNA复合物结构显示，六聚体内表面上的三个对称碱性凹槽分别环绕着ssDNA。该结构中的ssDNA结合口袋朝向六聚体环的N端结构域环，从而使ssDNA朝向DnaG引发酶，以促进短RNA引物的合成。这些发现为ssDNA结合机制提供了见解，并为建立复制叉处DNA易位的新机制提供了一个工作模型。
