Figure 6.

S6 mutations and voltage gating. (A) Partial crystal structure model of the Kv1.2-Kv2.1 chimeric channel (PDB 2R9R) featuring the selectivity filter, the pore helix, and the external part of S6 in two diagonally opposite subunits. Residue numbers are those of the corresponding residues in CNGA1. Mutations at red- and gray-colored S6 residues produce voltage-gated and non-voltage–gated channels, respectively, whereas those at blue-colored ones produce nonconductive channels. (B–F) Macroscopic currents in 2 mM cGMP (left) and corresponding G-V curves (right; mean ± SEM; n = 3–7) for various CNGA1 mutants. The normalized conductance values were calculated from the current/electrochemical driving force ratio, except for those indicated by open circles in B, which were determined from isochronal tail current measurements.