4WLW:
reference: TRANSCRIPTION. Allosteric transcriptional regulation via changes in the overall topology of the core promoter., Philips SJ, Canalizo-Hernandez M, Yildirim I, Schatz GC, Mondragon A, O'Halloran TV, Science. 2015 Aug 21;349(6250):877-81. doi: 10.1126/science.aaa9809. PMID: 26293965

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