TABLE I.

Comparison of MTSET Modification of S4 Residues in KCNQ1

	KCNQ1		KCNQ1/KCNE1		KCNQ1/KCNE3
Construct	kopen	kclosed	kopen	kclosed	kopen	kclosed
A226C	153 ± 10	21 ± 7a	11 ± 2	5.2 ± 0.3a	64 ± 5	23 ± 2a
I227C	161 ± 31	60 ± 3a	12 ± 3	13 ± 1	29 ± 3	26 ± 4
R228C	20 ± 1	∼1	15 ± 1	∼1	28 ± 3	19 ± 2a
G229C	1.5 ± 0.2	∼0.1	0.49 ± 0.06	<0.05	8.5 ± 1.0	5.3 ± 0.6a
I230C	9.4 ± 1.1	∼0.5	1.2 ± 0.1	<0.05	19 ± 2	15 ± 1

Data from individual exponential fits in ND96, obtained from three to seven oocytes. All MTSET modifications were fit to a single exponential, except for Q1(A226C) in the open protocol, which required a biexponential fit to extract the fast component of the reaction, as described in the Materials and methods. k_open and k_closed are the second order modification rate constants (M⁻¹·s⁻¹) determined using the open and closed pulse protocols. Measured values are mean ± SEM. Approximate values were calculated based on the extent of modification in the closed protocol, as described in the Materials and methods. Statistical comparison is between k_open and k_closed for each mutant K⁺ channel complex.

^aP < 0.05.