2OJP:
reference: Evolution of quaternary structure in a homotetrameric enzyme., Griffin MD, Dobson RC, Pearce FG, Antonio L, Whitten AE, Liew CK, Mackay JP, Trewhella J, Jameson GB, Perugini MA, Gerrard JA, J Mol Biol. 2008 Jul 18;380(4):691-703. Epub 2008 May 22. PMID: 18556019

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