3H9V:
reference: Crystal structure of the ATP-gated P2X(4) ion channel in the closed state., Kawate T, Michel JC, Birdsong WT, Gouaux E, Nature. 2009 Jul 30;460(7255):592-8. PMID: 19641588

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