3KA6:
reference: Moving metal ions through ferritin-protein nanocages from three-fold pores to catalytic sites., Tosha T, Ng HL, Bhattasali O, Alber T, Theil EC, J Am Chem Soc. 2010 Oct 20;132(41):14562-9. PMID: 20866049

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