Alignment of the outer vestibules of hERG channel and other potassium channels. (A) Primary sequence alignment for hERG channel and other potassium channels. Black shading shows the selectively filter, whereas gray background indicates pore region of potassium channels, respectively. Red letters highlight the residues selected for alanine-scanning mutagenesis. These residues are H578, D580, R582, I583, W585, L586, H587, N588, L589, D591, Q592, K595, P596, Y597, N598, S600, K608, D609, K610, T613, N629 and S631. (B) Diagram of hERG channel subunit containing six transmembrane domains and possible helix structure in channel turret.