3TPZ:
reference: Control of Substrate Specificity by a Single Active Site Residue of the KsgA Methyltransferase., O'Farrell HC, Musayev FN, Scarsdale JN, Rife JP, Biochemistry. 2012 Jan 10;51(1):466-74. Epub 2011 Dec 22. PMID: 22142337

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