The comparison for the sequence, conformation, and functional role of the outer vestibules of the IK
and Kv1.2 channels. (A) Sequence alignment for the outer vestibule of the IKCa and Kv1.2 channels. The conserved residues are grey-shaded, acidic residues red-shaded, basic residues blue-shaded. (B) Left and right are, respectively, the side and top views of the ribbon structures of the outer vestibules of the IKCa and the Kv1.2 channels, respectively. The IKCa channel is pink-colored, and the Kv1.2 channel is green-colored. For clarity, only two chains of the channels are shown in the side view. (C), (D) Functional roles for the turrets of the IKCa and Kv1.2 channels, respectively, in associating with MTX, respectively. All the toxin-interacting residues within a contact distance of 5Å are labeled on the turret of the IKCa and Kv1.2 channels. (E), (F) Stereoview displaying the molecular surfaces of the IKCa and Kv1.2 channels, respectively. The molecular surfaces are colored according to their electrostatic potentials, with basic residues in blue, acidic residues in red, and neutral residues in white.