A second divalent metal ion in the group II intron reaction center
A second divalent metal ion in the group II intron reaction center
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DOI：
10.1016/j.chembiol.2007.05.008
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发表时间：
2007-06-01
影响因子：
--
通讯作者：
Piccirilli, Joseph A.
中科院分区：
文献类型：
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作者：
Gordon, Peter M.;Fong, Robert;Piccirilli, Joseph A.
第二组内含子是移动的遗传元件，被认为是遗传多样性的因素，并作为研究RNA催化和前mRNA剪接的重要模型系统。在没有内含子的原子分辨率结构的情况下，对其催化机制的详细理解仍然是难以捉摸的。先前鉴定的二价金属离子稳定在两个剪接步骤中的离去基团表明，第II组内含子可能采用“双金属离子”机制，一种催化策略，由许多蛋白质磷酸酯转移酶使用。使用金属救援实验，我们现在揭示了第二个金属离子的存在下，所需的亲核试剂激活的外显子连接步骤的第二组内含子剪接。再加上生化和结构的证据，至少有两个金属离子在第一组内含子反应中心，这些结果表明一个机械的范式来描述催化大核酶。
Group II introns are mobile genetic elements that have been implicated as agents of genetic diversity, and serve as important model systems for investigating RNA catalysis and pre-mRNA splicing. In the absence of an atomic-resolution structure of the intron, detailed understanding of its catalytic mechanism has remained elusive. Previous identification of a divalent metal ion stabilizing the leaving group in both splicing steps suggested that the group II intron may employ a "two-metal ion" mechanism, a catalytic strategy used by a number of protein phosphoester transfer enzymes. Using metal rescue experiments, we now reveal the presence of a second metal ion required for nucleophile activation in the exon-ligation step of group II intron splicing. Coupled with biochemical and structural evidence of at least two metal ions at the group I intron reaction center, these results suggest a mechanistic paradigm for describing catalysis by large ribozymes.