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4e8v; DSSR-derived features in text and JSON formats
X-ray (3.995 Å)
Structure of oceanobacillus iheyensis group ii intron in a ligand-free state in the presence of k+ and ba2+
Marcia M, Pyle AM (2012): "Visualizing Group II Intron Catalysis through the Stages of Splicing." Cell(Cambridge,Mass.), 151, 497-507. doi: 10.1016/j.cell.2012.09.033.
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.

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