Table 2. The influence of upper interface single-, double- and triple-mutations on activation gating of the tandem-dimer Shaker Kv channel^a .

Channel proteinb	V1/2 (mV)	Z	ΔG open (kcal/mol)
Wild type (AWTBWT)	−23.7±0.2	3.10±0.12	−1.70±0.06
T248A (AWTBT248A)	−10.3±0.7	2.32±0.15	−0.55±0.05
Y415A (AY415ABWT)	−13.3±0.3	2.04±0.05	−0.63±0.02
S428A (AS428ABWT)	−14.5±0.8	2.18±0.10	−0.73±0.05
I429A (AI429ABWT)	−11.0±0.1	2.55±0.08	−0.65±0.02
Y415A, T248A (AY415ABT248A)	−11.2±0.1	2.42±0.05	−0.62±0.01
S428A, T248A (AS428ABT248A)	−10.8±0.3	2.43±0.15	−0.60±0.04
I429A, T248A (AI429ABT248A)	−6.7±0.3	1.86±0.10	−0.29±0.02
Y415A,S428A (AY415A;S428ABWT)	−13.8±0.3	2.43±0.08	−0.77±0.03
Y415A,S428A,T248A (AY415A;S428ABT248A)	−10.3±0.4	2.19±0.08	−0.52±0.03

Figs. 4 and 5 .^a The table displays the gating parameters of all single-, double- and triple-mutants used to calculate the coupling free energies presented in

^b Mutants were generated using the tandem-dimer gene construct. Any mutation is thus present in only two diagonal channel subunits.