2RUP:
reference: Solution structure of the rat P2X4 receptor head domain involved in inhibitory metal binding., Igawa T, Abe Y, Tsuda M, Inoue K, Ueda T, FEBS Lett. 2015 Mar 12;589(6):680-6. doi: 10.1016/j.febslet.2015.01.034. Epub, 2015 Feb 4. PMID: 25662851

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