1T4Y:
reference: Structure of the N-terminal domain of the circadian clock-associated histidine kinase SasA., Vakonakis I, Klewer DA, Williams SB, Golden SS, LiWang AC, J Mol Biol 2004 Sep 3;342(1):9-17. PMID: 15313603

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