4K2X:
reference: Uncovering the Enzymes that Catalyze the Final Steps in Oxytetracycline Biosynthesis., Wang P, Bashiri G, Gao X, Sawaya MR, Tang Y, J Am Chem Soc. 2013 May 15;135(19):7138-7141. Epub 2013 May 1. PMID: 23621493

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