Ordered ATP hydrolysis in the γ complex clamp loader AAA plus machine
Ordered ATP hydrolysis in the γ complex clamp loader AAA plus machine
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DOI：
10.1074/jbc.m212708200
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发表时间：
2003-04-18
影响因子：
4.8
通讯作者：
O'Donnell, M
中科院分区：
文献类型：
--
作者：
Johnson, A;O'Donnell, M
γ 复合物将 ATP 水解与 DNA 上的 β 滑动夹加载相结合，以进行持续复制。伽马复合物结构表明夹子装载机亚基排列为圆形异五聚体。三个伽马运动亚基结合 ATP，δ 扳手打开 β 环，δ' 定子调节 δ-β 相互作用。 Delta 和 Delta' 都不结合 ATP。该报告表明，δ' 定子提供催化精氨酸，用于水解与相邻 gamma(1) 亚基结合的 ATP。因此，δ'定子有助于伽马三聚体的运动功能。 γ 精氨酸 169 的突变仅从 γ(2) 和 γ3 ATP 位点去除催化精氨酸，从而消除了 ATP 酶活性，即使 ATP 位点 1 完好无损且所有三个位点均已填充。该结果意味着三个 ATP 分子的水解以特定顺序发生，与 ATP 结合相反，其中位点 1 中的 ATP 直到位点 2 和/或 3 中的 ATP 被水解后才被水解。讨论了这些结果对其他系统的夹具装载机的影响。
The gamma complex couples ATP hydrolysis to the loading of beta sliding clamps onto DNA for processive replication. The gamma complex structure shows that the clamp loader subunits are arranged as a circular heteropentamer. The three gamma motor subunits bind ATP, the delta wrench opens the beta ring, and the delta' stator modulates the delta-beta interaction. Neither delta nor delta' bind ATP. This report demonstrates that the delta' stator contributes a catalytic arginine for hydrolysis of ATP bound to the adjacent gamma(1) subunit. Thus, the delta' stator contributes to the motor function of the gamma trimer. Mutation of arginine 169 of gamma, which removes the catalytic arginines from only the gamma(2) and gamma3 ATP sites, abolishes ATPase activity even though ATP site 1 is intact and all three sites are filled. This result implies that hydrolysis of the three ATP molecules occurs in a particular order, the reverse of ATP binding, where ATP in site 1 is not hydrolyzed until ATP in sites 2 and/or 3 is hydrolyzed. Implications of these results to clamp loaders of other systems are discussed.