1WAS:
reference: The three-dimensional structure of the ligand-binding domain of a wild-type bacterial chemotaxis receptor. Structural comparison to the cross-linked mutant forms and conformational changes upon ligand binding., Yeh JI, Biemann HP, Pandit J, Koshland DE, Kim SH, J Biol Chem 1993 May 5;268(13):9787-92. PMID: 8486661

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