1Y6W:
reference: Structure of a Trapped Intermediate of Calmodulin: Calcium Regulation of EF-hand Proteins from a New Perspective., Grabarek Z, J Mol Biol 2005 Mar 11;346(5):1351-66. Epub 2005 Jan 19. PMID: 15713486

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