4YLP:
reference: Crystal Structures of the E. coli Transcription Initiation Complexes with a Complete Bubble., Zuo Y, Steitz TA, Mol Cell. 2015 Apr 8. pii: S1097-2765(15)00175-6. doi:, 10.1016/j.molcel.2015.03.010. PMID: 25866247

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