2YOI:
reference: Conservation of Protein Structure over Four Billion Years., Ingles-Prieto A, Ibarra-Molero B, Delgado-Delgado A, Perez-Jimenez R, Fernandez JM, Gaucher EA, Sanchez-Ruiz JM, Gavira JA, Structure. 2013 Aug 6. pii: S0969-2126(13)00244-X. doi:, 10.1016/j.str.2013.06.020. PMID: 23932589

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