6GIS:
reference: Structural basis of human PCNA sliding on DNA., De March M, Merino N, Barrera-Vilarmau S, Crehuet R, Onesti S, Blanco FJ, De Biasio A, Nat Commun. 2017 Jan 10;8:13935. doi: 10.1038/ncomms13935. PMID: 28071730

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