Rockefeller University Press

TABLE II

Gating Parameters for α97 AChR Mutants Activated by Choline

α97	β₂	α₂	L₂	L₂-ratio  (mut/wt)
	s⁻¹	s⁻¹
I	60	2,801	0.022	0.45
L	91	2,684	0.034	0.71
D (wt)	100	2,100	0.048	—
V	161	1,974	0.082	1.71
N	268	2,379	0.113	2.37
P₁	322	2,276	0.141	2.97
G₁	421	2,105	0.200	4.20
C	531	2,172	0.244	5.13
M	835	2,255	0.370	7.78
G₂	570	942	0.605	2.37
P₂	1,396	2,276	0.613	12.88
Y	1,396	1,992	0.701	14.72
H	1,840	1,938	0.949	19.94
E	2,967	2,076	1.429	24.78
F	2,748	1,831	1.501	31.52
Q	6,006	2,016	2.979	62.56
R	10,951	1,653	6.624	139.12
A	13,793	1,719	8.023	168.50

α97	β₂	α₂	L₂	L₂-ratio  (mut/wt)
	s⁻¹	s⁻¹
I	60	2,801	0.022	0.45
L	91	2,684	0.034	0.71
D (wt)	100	2,100	0.048	—
V	161	1,974	0.082	1.71
N	268	2,379	0.113	2.37
P₁	322	2,276	0.141	2.97
G₁	421	2,105	0.200	4.20
C	531	2,172	0.244	5.13
M	835	2,255	0.370	7.78
G₂	570	942	0.605	2.37
P₂	1,396	2,276	0.613	12.88
Y	1,396	1,992	0.701	14.72
H	1,840	1,938	0.949	19.94
E	2,967	2,076	1.429	24.78
F	2,748	1,831	1.501	31.52
Q	6,006	2,016	2.979	62.56
R	10,951	1,653	6.624	139.12
A	13,793	1,719	8.023	168.50

The diliganded channel opening (β₂) and closing (α₂) rate constants were estimated from single-channel currents elicited by 20 and 0.4 mM choline, respectively. The diliganded gating equilibrium constant was calculated as the ratio β₂/α₂. Proline and glycine substitutions have two distinct kinetic modes, denoted by subscripts. The values are means from ≥3 patches. A REFER analysis of these data is shown in Fig. 8. G₂ kinetics were measured only at 20 mM choline. Because of unresolved channel block, the α₂ value shown in the table is twice the apparent closing rate constant.

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