4PZ8:
reference: How an mRNA capping enzyme reads distinct RNA polymerase II and Spt5 CTD phosphorylation codes., Doamekpor SK, Sanchez AM, Schwer B, Shuman S, Lima CD, Genes Dev. 2014 Jun 15;28(12):1323-36. doi: 10.1101/gad.242768.114. PMID: 24939935

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