Void space behind the SF of Kir2 channels. (a) Y146 residue is shown in white sticks in the starting crystal structure (left) and after MD simulations without restraints (right). Void volumes near the Y146 side chain are detected in the surface rendering and marked by dotted lines. The increased distance between the hydroxyl groups of Y146 and T140 indicates the anticlockwise rotation of the Y146 side chain. (b) Void volume behind the SF is present in Kir2.2 but absent in Kir3.2 crystal structures. (c) Discrepant residues surrounding the void volume between Kir2.2 and Kir3.2 channels are shown in sticks.