Structural comparison of NaK2CNG-Dm and NaK2CNG-E. (A) Superimposition of NaK2CNG-Dm (blue) and NaK2CNG-E (orange) at the selectivity filter region, showing the divergence of the main-chain backbones at the 65GET region. The superimposition is highlighted for the front subunit, and the other subunits of NaK2CNG-Dm are shaded in light blue in the background. (B) Comparison of the selectivity filter of one subunit from NaK2CNG-Dm and NaK2CNG-E. Dashed lines indicate the hydrogen bonds between Glu66 and surrounding residues. Residues from a neighboring subunit are marked with single quotation marks. (C) A comparison of the hydrogen-bonding network of NaK2CNG-Dm and NaK2CNG-E, viewed from the external side of the channel tetramers. Residues involved in the hydrogen bonds are displayed as yellow sticks.
