4A5U:
reference: A compact viral processing proteinase/ubiquitin hydrolase from the OTU family., Lombardi C, Ayach M, Beaurepaire L, Chenon M, Andreani J, Guerois R, Jupin I, Bressanelli S, PLoS Pathog. 2013 Aug;9(8):e1003560. doi: 10.1371/journal.ppat.1003560. Epub 2013, Aug 15. PMID: 23966860

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