Toor Navtej, Keating Kevin S, Taylor Sean D, Pyle Anna Marie
Department of Molecular Biophysics and Biochemistry, Yale University, 266 Whitney Avenue, Bass Building, New Haven, CT 06511, USA.
Science. 2008 Apr 4;320(5872):77-82. doi: 10.1126/science.1153803.
Group II introns are self-splicing ribozymes that catalyze their own excision from precursor transcripts and insertion into new genetic locations. Here we report the crystal structure of an intact, self-spliced group II intron from Oceanobacillus iheyensis at 3.1 angstrom resolution. An extensive network of tertiary interactions facilitates the ordered packing of intron subdomains around a ribozyme core that includes catalytic domain V. The bulge of domain V adopts an unusual helical structure that is located adjacent to a major groove triple helix (catalytic triplex). The bulge and catalytic triplex jointly coordinate two divalent metal ions in a configuration that is consistent with a two-metal ion mechanism for catalysis. Structural and functional analogies support the hypothesis that group II introns and the spliceosome share a common ancestor.
II 组内含子是自我剪接核酶，可催化自身从前体转录本中切除并插入到新的基因位置。在此，我们报告了来自伊贺海洋芽孢杆菌（Oceanobacillus iheyensis）的完整、自我剪接的 II 组内含子的晶体结构，分辨率为 3.1 埃。广泛的三级相互作用网络促进了内含子亚结构域围绕包含催化结构域 V 的核酶核心的有序堆积。结构域 V 的凸起采用了一种不寻常的螺旋结构，该结构位于一个大沟三链螺旋（催化三链体）附近。凸起和催化三链体共同以与双金属离子催化机制一致的构型配位两个二价金属离子。结构和功能类比支持了 II 组内含子和剪接体具有共同祖先的假说。
