1BRN:
reference: Subsite binding in an RNase: structure of a barnase-tetranucleotide complex at 1.76-A resolution., Buckle AM, Fersht AR, Biochemistry 1994 Feb 22;33(7):1644-53. PMID: 8110767

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