3WXR:
reference: N-terminal alpha7 deletion of the proteasome 20S core particle substitutes for yeast PI31 function., Yashiroda H, Toda Y, Otsu S, Takagi K, Mizushima T, Murata S, Mol Cell Biol. 2015 Jan;35(1):141-52. doi: 10.1128/MCB.00582-14. Epub 2014 Oct, 20. PMID: 25332237

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