4RX2:
reference: A Triple Mutant in the Omega-loop of TEM-1 beta-lactamase Changes the Substrate Profile via a Large Conformational Change and an Altered General Base for Catalysis., Stojanoski V, Chow DC, Hu L, Sankaran B, Gilbert HF, Prasad BV, Palzkill T, J Biol Chem. 2015 Feb 20. pii: jbc.M114.633438. PMID: 25713062

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