5A0Q:
reference: Cryo-EM reveals the conformation of a substrate analogue in the human 20S proteasome core., da Fonseca PC, Morris EP, Nat Commun. 2015 Jul 2;6:7573. doi: 10.1038/ncomms8573. PMID: 26133119

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