4E6K:
reference: The structure of the BfrB-Bfd complex reveals protein-protein interactions enabling iron release from bacterioferritin., Yao H, Wang Y, Lovell SW, Kumar R, Ruvinsky AM, Battaile KP, Vakser IA, Rivera M, J Am Chem Soc. 2012 Jul 19. PMID: 22812654

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