1WCM:
reference: Structures of complete RNA polymerase II and its subcomplex, Rpb4/7., Armache KJ, Mitterweger S, Meinhart A, Cramer P, J Biol Chem. 2005 Feb 25;280(8):7131-4. Epub 2004 Dec 9. PMID: 15591044

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