5ZYN:
reference: Molecular basis of maintaining an oxidizing environment under anaerobiosis by soluble fumarate reductase., Kim S, Kim CM, Son YJ, Choi JY, Siegenthaler RK, Lee Y, Jang TH, Song J, Kang H, Kaiser CA, Park HH, Nat Commun. 2018 Nov 19;9(1):4867. doi: 10.1038/s41467-018-07285-9. PMID: 30451826

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