3SQG:
reference: Structure of a methyl-coenzyme M reductase from Black Sea mats that oxidize methane anaerobically., Shima S, Krueger M, Weinert T, Demmer U, Kahnt J, Thauer RK, Ermler U, Nature. 2011 Nov 27. doi: 10.1038/nature10663. PMID: 22121022

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