1L9U:
reference: Structural basis of transcription initiation: RNA polymerase holoenzyme at 4 A resolution., Murakami KS, Masuda S, Darst SA, Science 2002 May 17;296(5571):1280-4. PMID: 12016306

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