5KHH:
reference: Cyclic Purine and Pyrimidine Nucleotides Bind to the HCN2 Ion Channel and Variably Promote C-Terminal Domain Interactions and Opening., Ng LC, Putrenko I, Baronas V, Van Petegem F, Accili EA, Structure. 2016 Aug 23. pii: S0969-2126(16)30193-9. doi:, 10.1016/j.str.2016.06.024. PMID: 27568927

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