1YLS:
reference: Structural basis for Diels-Alder ribozyme-catalyzed carbon-carbon bond formation., Serganov A, Keiper S, Malinina L, Tereshko V, Skripkin E, Hobartner C, Polonskaia A, Phan AT, Wombacher R, Micura R, Dauter Z, Jaschke A, Patel DJ, Nat Struct Mol Biol 2005 Mar;12(3):218-24. Epub 2005 Feb 20. PMID: 15723077

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