3SJ5:
reference: Controlling Conformational Flexibility of an O(2)-Binding H-NOX Domain., Weinert EE, Phillips-Piro CM, Tran R, Mathies RA, Marletta MA, Biochemistry. 2011 Jul 15. PMID: 21721586

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