Figure 4

Structural models of KCNQ4 and Tyr270His. (A) Stereoview of the KCNQ4 α-carbon frame model (yellow) superimposed onto that of Kv1.2 (cyan). The position of Tyr270 is indicated with a yellow arrow. The α-helices, the PH, and the P-loop are also identified. (B) Part of the wild-type KCNQ4 model, and (C) the Tyr270His model overlaid with their corresponding electrostatic surface potentials. The side chains of Tyr270 (B) and His270 (C) are indicated by arrows. Negatively and positively charged residues are depicted respectively in red and blue in the electrostatic potential surface representations. (D) Stereoview of a portion of the ribbon model of the Tyr270His pore region. Residues that are negatively charged or that can form a hydrogen bond and surround His270 are identified and shown in red. (E, F) The Tyr270His ribbon model was superimposed onto (E) a horizontal view of the plasma membrane and (F) an extracellular view with the four rotational axes of the Kv1.2 crystal structure shown as hydrophobicity surface. Hydrophobic and hydrophilic residues are depicted respectively in red and blue in the hydrophobicity surface representations. His270 is shown in yellow. (A-F) K⁺ in the central pore is shown as a purple sphere and indicated by an arrow in (F).