4WFX:
reference: Structure-Function Relationships Underlying the Replication Fidelity of Viral RNA-dependent RNA Polymerases., Campagnola G, McDonald S, Beaucourt S, Vignuzzi M, Peersen OB, J Virol. 2014 Oct 15. pii: JVI.01574-14. PMID: 25320316

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