1I6H:
reference: Structural basis of transcription: an RNA polymerase II elongation complex at 3.3 A resolution., Gnatt AL, Cramer P, Fu J, Bushnell DA, Kornberg RD, Science 2001 Jun 8;292(5523):1876-82. PMID: 11313499

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