4XJR:
reference: The catalytic mechanism of human parainfluenza virus type 3 haemagglutinin-neuraminidase revealed., Dirr L, El-Deeb IM, Guillon P, Carroux CJ, Chavas LM, von Itzstein M, Angew Chem Int Ed Engl. 2015 Mar 2;54(10):2936-40. doi: 10.1002/anie.201412243., Epub 2015 Feb 10. PMID: 25676091

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