4C3O:
reference: How the structure of the large subunit controls function in an oxygen-tolerant [NiFe]-hydrogenase., Bowman L, Flanagan L, Fyfe PK, Parkin A, Hunter WN, Sargent F, Biochem J. 2014 Jan 16. PMID: 24428762

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