3BUS:
reference: Structure and mechanism of the rebeccamycin sugar 4'-O-methyltransferase RebM., Singh S, McCoy JG, Zhang C, Bingman CA, Phillips GN Jr, Thorson JS, J Biol Chem. 2008 Aug 15;283(33):22628-36. Epub 2008 May 23. PMID: 18502766

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