5YZG:
reference: Structure of a human catalytic step I spliceosome., Zhan X, Yan C, Zhang X, Lei J, Shi Y, Science. 2018 Feb 2;359(6375):537-545. doi: 10.1126/science.aar6401. Epub 2018, Jan 4. PMID: 29301961

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