6CEQ:
reference: THE AER2 RECEPTOR FROM VIBRIO CHOLERAE IS A DUAL PAS-HEME OXYGEN SENSOR., Greer-Phillips SE, Sukomon N, Chua TK, Johnson MS, Crane BR, Watts KJ, Mol Microbiol. 2018 May 2. doi: 10.1111/mmi.13978. PMID: 29719085

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