Structural Biology Program, Memorial Sloan-Kettering Cancer Center, New York, New York, USA. Graduate Program in Neuroscience, Weill Medical College of Cornell University, New York, New York, USA.
Nat Struct Mol Biol. 2011 Jun;18(6):658-64. doi: 10.1038/nsmb.2069. Epub 2011 May 8.
Trax-translin heteromers, also known as C3PO, have been proposed to activate the RNA-induced silencing complex (RISC) by facilitating endonucleolytic cleavage of the siRNA passenger strand. We report on the crystal structure of hexameric Drosophila C3PO formed by truncated translin and Trax, along with electron microscopic and mass spectrometric studies on octameric C3PO formed by full-length translin and Trax. Our studies establish that Trax adopts the translin fold, possesses catalytic centers essential for C3PO's endoRNase activity and interacts extensively with translin to form an octameric assembly. The catalytic pockets of Trax subunits are located within the interior chamber of the octameric scaffold. Truncated C3PO, like full-length C3PO, shows endoRNase activity that leaves 3'-hydroxyl-cleaved ends. We have measured the catalytic activity of C3PO and shown it to cleave almost stoichiometric amounts of substrate per second.
Trax-translin 异源六聚体，也被称为 C3PO，据推测可以通过促进 siRNA 过客链的内切核酸酶切割来激活 RNA 诱导的沉默复合物（RISC）。我们报告了由截短的 translin 和 Trax 形成的六聚体果蝇 C3PO 的晶体结构，以及由全长 translin 和 Trax 形成的八聚体 C3PO 的电子显微镜和质谱研究。我们的研究确定 Trax 采用了 translin 折叠结构，具有 C3PO 的内切核糖核酸酶活性所必需的催化中心，并与 translin 广泛相互作用形成八聚体组装。Trax 亚基的催化口袋位于八聚体支架的内部腔室中。截短的 C3PO 与全长 C3PO 一样，表现出内切核糖核酸酶活性，留下 3'-羟基切割末端。我们已经测量了 C3PO 的催化活性，并表明它每秒几乎以化学计量的量切割底物。
