3UX4:
reference: Structure of the proton-gated urea channel from the gastric pathogen Helicobacter pylori., Strugatsky D, McNulty R, Munson K, Chen CK, Soltis SM, Sachs G, Luecke H, Nature. 2012 Dec 9. doi: 10.1038/nature11684. PMID: 23222544

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