3U9F:
reference: The structural basis for substrate versatility of chloramphenicol acetyltransferase CAT(I)., Biswas T, Houghton JL, Garneau-Tsodikova S, Tsodikov OV, Protein Sci. 2012 Jan 31. doi: 10.1002/pro.2036. PMID: 22294317

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