3OPP:
reference: Ligand-dependent disorder of the Omega loop observed in extended-spectrum SHV-type beta-lactamase., Sampson JM, Ke W, Bethel CR, Pagadala SR, Nottingham MD, Bonomo RA, Buynak JD, van den Akker F, Antimicrob Agents Chemother. 2011 May;55(5):2303-9. Epub 2011 Feb 28. PMID: 21357298

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