4OZ6:
reference: Structure of the branched intermediate in protein splicing., Liu Z, Frutos S, Bick MJ, Vila-Perello M, Debelouchina GT, Darst SA, Muir TW, Proc Natl Acad Sci U S A. 2014 Apr 28. PMID: 24778214

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