Quantification of the effect on CSI caused by single- and double-point mutations in S4S5C and S6 of monomeric Kv4.2 constructs. Mutation-induced changes in apparent affinity for a transitory state (left, open bars) and steady-state inactivation (right, solid bars) are expressed as ln (Ktrans/Ktrans,wt) and ln (Ksteady/Ksteady,wt), respectively (green, S4S5C single mutations; blue, S6 single mutations; red, S4S5C/S6 double-point mutations). (A–C) Separate graphs show the data for the coupling pairs with the S4S5C residues S322 (A), E323 (B) and F326 (C). X: Double-exponential fitting was not possible, and therefore Ktrans data are not available for [326], [326:407], [326:408], and [326:412] (see Materials and Methods).