3PM1:
reference: A single acidic residue can guide binding site selection but does not govern QacR cationic-drug affinity., Peters KM, Brooks BE, Schumacher MA, Skurray RA, Brennan RG, Brown MH, PLoS One. 2011 Jan 17;6(1):e15974. PMID: 21264225

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