Figure 1.

HCN4 structure and its comparison with that of HCN1

(A) Structure of the HCN4 channel tetramer in cAMP-bound state (holo), in a cross-membrane view. For clarity, only two subunits are shown in full (tan and blue), while for the other two subunits (black and green), only the cytosolic C-linker/CNBD domains are presented.

(B) Protomer of HCN4 holo with structural elements indicated.

(C) HCN4 comparison with HCN1. Only two subunits in the tetramer are shown in full, while for the other two subunits the cytosolic C-linker/CNBD domains are shown. HCN4 structure color-coded (gray-to-red) according to the local deviations observed for the Cα atoms of HCN4 versus HCN1 holo (PDB: 5U6P). Gray color represents 0.5-Å displacements, and red color represents displacements up to 5 Å, as shown by the bar.