2O8K:
reference: Structural basis of DNA recognition by the alternative sigma-factor, sigma54., Doucleff M, Pelton JG, Lee PS, Nixon BT, Wemmer DE, J Mol Biol. 2007 Jun 15;369(4):1070-8. Epub 2007 Apr 12. PMID: 17481658

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