3GS3:
reference: Crystal structure of the HEAT domain from the Pre-mRNA processing factor Symplekin., Kennedy SA, Frazier ML, Steiniger M, Mast AM, Marzluff WF, Redinbo MR, J Mol Biol. 2009 Sep 11;392(1):115-28. Epub 2009 Jul 1. PMID: 19576221

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