4GZK:
reference: Structure of the RNA-directed RNA Polymerase from the cystovirus varphi12., Ren Z, C Franklin M, Ghose R, Proteins. 2013 Aug;81(8):1479-84. doi: 10.1002/prot.24297. Epub 2013 Jun 1. PMID: 23568335

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