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</td></tr><tr id='ligand'><td class="sblockLbl"><b>[[Ligand|Ligands:]]</b></td><td class="sblockDat" id="ligandDat"><scene name='pdbligand=CA:CALCIUM+ION'>CA</scene>, <scene name='pdbligand=EPE:4-(2-HYDROXYETHYL)-1-PIPERAZINE+ETHANESULFONIC+ACID'>EPE</scene>, <scene name='pdbligand=K:POTASSIUM+ION'>K</scene>, <scene name='pdbligand=SPM:SPERMINE'>SPM</scene></td></tr>

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== Publication Abstract from PubMed ==

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.

Visualizing Group II Intron Catalysis through the Stages of Splicing.,Marcia M, Pyle AM Cell. 2012 Oct 26;151(3):497-507. doi: 10.1016/j.cell.2012.09.033. PMID:23101623<ref>PMID:23101623</ref>

From MEDLINE&reg;/PubMed&reg;, a database of the U.S. National Library of Medicine.<br>

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== References ==

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