4OW4:
reference: Evolution and design of protein structure by folding nucleus symmetric expansion., Longo LM, Kumru OS, Middaugh CR, Blaber M, Structure. 2014 Oct 7;22(10):1377-84. doi: 10.1016/j.str.2014.08.008. Epub 2014, Sep 18. PMID: 25242458

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