6B6H:
reference: Structural basis of bacterial transcription activation., Liu B, Hong C, Huang RK, Yu Z, Steitz TA, Science. 2017 Nov 17;358(6365):947-951. doi: 10.1126/science.aao1923. PMID: 29146813

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