4I44:
reference: HAMP Domain Conformers That Propagate Opposite Signals in Bacterial Chemoreceptors., Airola MV, Sukomon N, Samanta D, Borbat PP, Freed JH, Watts KJ, Crane BR, PLoS Biol. 2013 Feb;11(2):e1001479. doi: 10.1371/journal.pbio.1001479. Epub 2013 , Feb 12. PMID: 23424282

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