Schiffer Jamie M, Malmstrom Robert D, Parnell Jonathan, Ramirez-Sarmiento Cesar, Reyes Javiera, Amaro Rommie E, Komives Elizabeth A
Department of Chemistry and Biochemistry, University of California, San Diego, 9500 Gilman Drive, La Jolla, CA 92093-0378, USA.
Department of Chemistry and Biochemistry, University of California, San Diego, 9500 Gilman Drive, La Jolla, CA 92093-0378, USA; National Biomedical Computation Resource, University of California, San Diego, 9500 Gilman Drive, La Jolla, CA 92093-0608, USA.
Structure. 2016 Aug 2;24(8):1248-1256. doi: 10.1016/j.str.2016.05.016. Epub 2016 Jul 7.
Cullin-RING E3 ligases (CRLs) are elongated and bowed protein complexes that transfer ubiquitin over 60 Å to proteins targeted for proteasome degradation. One such CRL contains the ankyrin repeat and SOCS box protein 9 (ASB9), which binds to and partially inhibits creatine kinase (CK). While current models for the ASB9-CK complex contain some known interface residues, the overall structure and precise interface of the ASB9-CK complex remains unknown. Through an integrative modeling approach, we report a third-generation model that reveals precisely the interface interactions and also fits the shape of the ASB9-CK complex as determined by small-angle X-ray scattering. We constructed an atomic model for the entire CK-targeting CRL to uncover dominant modes of motion that could permit ubiquitin transfer. Remarkably, only the correctly docked CK-containing E3 ligase and not incorrectly docked structures permitted close approach of ubiquitin to the CK substrate.
Cullin-RING E3 连接酶（CRLs）是一种细长且呈弓形的蛋白质复合物，它能将泛素转移超过60埃至靶向蛋白酶体降解的蛋白质上。其中一种这样的CRL包含锚蛋白重复序列和SOCS盒蛋白9（ASB9），它能与肌酸激酶（CK）结合并部分抑制肌酸激酶。虽然目前关于ASB9-CK复合物的模型包含一些已知的界面残基，但ASB9-CK复合物的整体结构和精确界面仍不清楚。通过一种整合建模方法，我们报告了一个第三代模型，该模型精确揭示了界面相互作用，并且与小角X射线散射所确定的ASB9-CK复合物形状相契合。我们构建了整个靶向CK的CRL的原子模型，以揭示可能允许泛素转移的主要运动模式。值得注意的是，只有正确对接的含CK的E3连接酶，而不是错误对接的结构，才允许泛素接近CK底物。
