3O1J:
reference: An asymmetry-to-symmetry switch in signal transmission by the histidine kinase receptor for TMAO., Moore JO, Hendrickson WA, Structure. 2012 Apr 4;20(4):729-41. Epub 2012 Apr 3. PMID: 22483119

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