6ATK:
reference: Receptor-binding loops in alphacoronavirus adaptation and evolution., Wong AHM, Tomlinson ACA, Zhou D, Satkunarajah M, Chen K, Sharon C, Desforges M, Talbot PJ, Rini JM, Nat Commun. 2017 Nov 23;8(1):1735. doi: 10.1038/s41467-017-01706-x. PMID: 29170370

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