Figure 6.

Functional-coupling analysis for S4S5/S6 amino acid pairs based on monomeric Kv4.2 constructs. (A and B) Coupling coefficients for all S4S5/S6 pairings studied were determined by double-mutant cycle analysis based on K_trans and K_steady values and plotted as lnΩ_trans (A) and lnΩ_steady (B), respectively (see Materials and Methods). The three-dimensional plots in (A) and (B) show the native S4S5 amino acid residues on the left x axis and the native S6 amino acid residues on the right x axis. The mean lnΩ_trans and lnΩ_steady values are shown as vertical cuboids (common y axis, error bars omitted). Note the homogeneous and strong functional coupling during steady-state inactivation for pairings with the S6 residues V404 and I412. (C) The ratio Ω_steady/Ω_trans shows how functional coupling may change when the channel goes from transitory to steady-state inactivation (dotted line: Ω_steady/Ω_trans = 1, no change).