1RCN:
reference: Crystal structure of ribonuclease A.d(ApTpApApG) complex. Direct evidence for extended substrate recognition., Fontecilla-Camps JC, de Llorens R, le Du MH, Cuchillo CM, J Biol Chem 1994 Aug 26;269(34):21526-31. PMID: 8063789

This OCA Structure page
uses Jmol, developed by the Jmol Development Team (documentation).