Department of Chemistry and Biochemistry, University of California, San Diego, La Jolla, CA, 92093, USA.
Department of Biochemistry, West Virginia University, Morgantown, WV, 26506, USA.
Nat Commun. 2018 Nov 8;9(1):4676. doi: 10.1038/s41467-018-06678-0.
The group II intron and the spliceosome share a common active site architecture and are thought to be evolutionarily related. Here we report the 3.7 Å crystal structure of a eukaryotic group II intron in the lariat-3' exon form, immediately preceding the second step of splicing, analogous to the spliceosomal P complex. This structure reveals the location of the intact 3' splice site within the catalytic core of the group II intron. The 3'-OH of the 5' exon is positioned in close proximity to the 3' splice site for nucleophilic attack and exon ligation. The active site undergoes conformational rearrangements with the catalytic triplex having different configurations before and after the second step of splicing. We describe a complete model for the second step of group II intron splicing that incorporates a dynamic catalytic triplex being responsible for creating the binding pocket for 3' splice site capture.
内含子 II 类和剪接体具有共同的活性位点结构，被认为是进化相关的。在这里，我们报告了一个真核细胞内含子 II 类在套索-3' 外显子形式的 3.7Å 晶体结构，这立即发生在剪接的第二步之前，类似于剪接体 P 复合物。该结构揭示了完整的 3' 剪接位点在内含子 II 类催化核心内的位置。5' 外显子的 3'-OH 被定位在接近 3' 剪接位点的位置，以便进行亲核攻击和外显子连接。在剪接的第二步前后，活性位点发生构象重排，催化三联体具有不同的构型。我们描述了一个完整的内含子 II 类剪接第二步模型，其中包括一个动态催化三联体，负责创建 3' 剪接位点捕获的结合口袋。
