Fig. 1.

The Kv channel gating pore and mutants characterization. (A) Refined X-ray structure of the Kv1.2 VSD (21) showing the S1–S4 helices, the gating charges R1–R4 (blue, licorice representation), and 10 gating pore residues in licorice representation: V236 (orange), I237 (green), S240 (cyan), I241 (green), and F244 (purple) in S1; C286 (cyan), I287 (green), and F290 (purple) in S2; A319 (brown) and I320 (green) in S3. Residue numbering is from Shaker. (B) Sequence alignment (T-Coffee) of gating pore residues in several VSDs (Shaker, GI: 13432103; Kv1.1, GI: 223590092; Kv1.2, GI: 4826782; Kv2.1, GI: 4826784; Kv3.1, GI: 76825377; Kv4.1, GI: 27436981; Kv5.1, GI: 24418476; Kv6.4, GI: 26006803; Kv7.1, GI: 32479527; KvAP, GI: 38605092; Nav1.1^DIV, GI: 12644229; Nav1.4^DI, GI: 292495096; Nav1.5^DIII, GI: 215273881; Nav1.7^DII, GI: 327478559; Ci-VSP, GI: 76253898; and Hv1, GI: 74751810). Coloring method is identical to A. Boxed residues indicate the position of mutations linked to human diseases. (C) Activation (blue; Left) and deactivation (red; Right) gating current recordings for V236F. (D) Activation (blue) and deactivation (red) gating current kinetics and relative charge Q (black) are plotted as a function of the pulse voltage (V) for V236F. T^A and T^D represent the slowest time constant for activation and deactivation, respectively, whereas V_1/2 represents the midpoint voltage of the Q–V curve. (E) The gating parameters T^A, T^D, and V_1/2 are plotted as a function of the side chain present at position V236, where amino acids are ordered according to a monotonic increase of the V_1/2 value. The native residue is indicated by an asterisk.