Visualizing group II intron catalysis through the stages of splicing.
Publication Type:Journal Article
Source:Cell, Volume 151, Issue 3, p.497-507 (2012)
Keywords:Bacillaceae, Catalytic Domain, Crystallography, X-Ray, Introns, Models, Biological, Mutation, Retroelements, RNA Precursors, RNA Splice Sites, RNA Splicing, RNA, Bacterial
<p>Group II introns are self-splicing ribozymes that share a reaction mechanism and a common ancestor with the eukaryotic spliceosome, thereby providing a model system for understanding the chemistry of pre-mRNA splicing. Here we report 14 crystal structures of a group II intron at different stages of catalysis. We provide a detailed mechanism for the first step of splicing, we describe a reversible conformational change between the first and the second steps of splicing, and we present the ligand-free intron structure after splicing in an active state that corresponds to the retrotransposable form of the intron. During each reaction, the reactants are aligned and activated by a heteronuclear four-metal-ion center that contains a metal cluster and obligate monovalent cations, and they adopt a structural arrangement similar to that of protein endonucleases. Based on our data, we propose a model for the splicing cycle and show that it is applicable to the eukaryotic spliceosome.</p>