3MKR:
reference: Structure of coatomer cage proteins and the relationship among COPI, COPII, and clathrin vesicle coats., Lee C, Goldberg J, Cell. 2010 Jul 9;142(1):123-32. Epub 2010 Jun 24. PMID: 20579721

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