4X2Z:
reference: Structural View and Substrate Specificity of Papain-like Protease from Avian Infectious Bronchitis Virus., Kong L, Shaw N, Yan L, Lou Z, Rao Z, J Biol Chem. 2015 Mar 13;290(11):7160-8. doi: 10.1074/jbc.M114.628636. Epub 2015 , Jan 21. PMID: 25609249

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