1RPH:
reference: The structures of RNase A complexed with 3'-CMP and d(CpA): active site conformation and conserved water molecules., Zegers I, Maes D, Dao-Thi MH, Poortmans F, Palmer R, Wyns L, Protein Sci 1994 Dec;3(12):2322-39. PMID: 7756988

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