2BR2:
reference: The archaeal exosome core is a hexameric ring structure with three catalytic subunits., Lorentzen E, Walter P, Fribourg S, Evguenieva-Hackenberg E, Klug G, Conti E, Nat Struct Mol Biol. 2005 Jul;12(7):575-81. Epub 2005 Jun 12. PMID: 15951817

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