1B2M:
reference: Three-dimensional structure of ribonuclease T1 complexed with an isosteric phosphonate substrate analogue of GpU: alternate substrate binding modes and catalysis., Arni RK, Watanabe L, Ward RJ, Kreitman RJ, Kumar K, Walz FG Jr, Biochemistry. 1999 Feb 23;38(8):2452-61. PMID: 10029539

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