TABLE 1.

Inhibition constant IC₅₀ and transmembrane electric distance for wt-Kcv and various Leu70 mutants

Residue type and mutant	I (−60 mV)	IC50 (−60 mV)	δ (−V)	I (60 mV)	IC50 (60 mV)	δ (+V)
	pA	mM		pA	mM
Aromatic
L70Y	−15.7 ± 1.2	0.74 ± 0.09	0.06	16.3 ± 1.1	1.9 ± 0.2	0.25
L70F	−17.6 ± 0.8	0.86 ± 0.07	0.09	15.9 ± 1.2	2.0 ± 0.2	0.26
L70H	−6.51 ± 0.42	3.3 ± 0.5	0.00	12.6 ± 1.5	3.6 ± 0.7	0.16
L70W	−15.0 ± 0.9	8.6 ± 0.7	0.09	14.1 ± 0.7	22 ± 3	0.27
Nonpolar
wt (L70)	−5.43 ± 1.3	0.098 ± 0.02	0.12	12.0 ± 1.1	0.41 ± 0.03	0.29
L70M	−10.4 ± 0.6	6.8 ± 1.1	0.15	11.4 ± 0.6	19 ± 2	0.22
L70I	−9.81 ± 1.10	9.8 ± 0.7	0.06	13.7 ± 0.4	18 ± 2	0.21
L70V	−12.5 ± 0.4	17 ± 3	0.09	15.1 ± 0.9	31 ± 4	0.23
L70A	−11.3 ± 1.2	45 ± 5	0.08	13.9 ± 1.1	72 ± 18	0.22
Polar
L70C	−16.4 ± 0.6	4.9 ± 0.2	0.06	14.8 ± 0.2	12 ± 2	0.23
L70S	−13.4 ± 1.2	14 ± 2	0.00	15.8 ± 1.0	21 ± 4	0.21
L70T	−13.3 ± 0.8	23 ± 4	0.12	17.6 ± 0.7	41 ± 7	0.25
Charged
L70Ka	ND	ND	ND	4.48 ± 0.28	NS	ND
L70E	−11.5 ± 0.6	79 ± 11	ND	12.8 ± 1.1	NS	ND

The relative electrical distance δ was calculated from the voltage dependence of IC₅₀ according to the Woodhull equation I/I₀(V) = I/I₀(0)exp(−zδFV/RT), where z = 1 is the valence of TEA, F is the Faraday constant, R is the gas constant, and T is the temperature (in K).

^aThe negative current of L70K was not observed; thus, the TEA sensitivity cannot be determined.