TABLE 6

The effect of the αQ241W mutation on channel activation by P4S in the absence and presence of 3α5αP: closed times

The closed-time histograms were fitted to sums of two (γβα-βα with P4S) or three exponentials. The table gives the mean durations (CT1-3) and relative contributions (fraction CT1-3) for the closed-time components. For data obtained in the presence of P4S + 3α5αP, the significance levels apply to comparison with the same type of receptor activated by P4S (t test) and to the γ2Lβ2α1Q241W-β2α1Q241W receptor activated by P4S + 3α5αP (ANOVA with Dunnett's correction). Due to lack of clusters, statistical comparison for the effect of steroid was not carried out for the wild-type concatemeric receptor.

Receptor	P4S	3α5αP	CT1	Fraction CT1	CT2	Fraction CT2	CT3	Fraction CT3
			ms		ms		ms
γβα-βα	1 mM		0.42 ± 0.34	0.10 ± 0.04	42 ± 33	0.90 ± 0.04
γβα-βα	1 mM	1 μM	0.21 ± 0.08^‡,^†	0.40 ± 0.10^‡,^*	1.2 ± 0.3^‡,^*	0.39 ± 0.07^‡,^†	9 ± 3^‡,^†	0.21 ± 0.06^‡,^*
γβαQ241W-βα	1 mM		0.14 ± 0.04	0.17 ± 0.06	3.6 ± 3.1	0.33 ± 0.23	15 ± 6	0.50 ± 0.24
γβαQ241W-βα	1 mM	1 μM	0.21 ± 0.09^†,^†	0.39 ± 0.05^**,^	1.6 ± 0.7^†,^†	0.35 ± 0.08^†,^†	13 ± 8^†,^†	0.26 ± 0.07^†,^†
γβα-βαQ241W	1 mM		0.27 ± 0.12	0.19 ± 0.10	2.9 ± 2.4	0.20 ± 0.19	29 ± 12	0.61 ± 0.19
γβα-βαQ241W	1 mM	1 μM	0.18 ± 0.03^†,^†	0.35 ± 0.04^**,^†	1.4 ± 0.4^†,^*	0.29 ± 0.07^†,^†	18 ± 7^†,^*	0.36 ± 0.07^**,^†
γβαQ241W-βαQ241W	1 mM		0.23 ± 0.10	0.24 ± 0.05	2.5 ± 0.3	0.42 ± 0.11	9 ± 3	0.34 ± 0.15
γβαQ241W-βαQ241W	1 mM	1 μM	0.27 ± 0.03^†,^‡	0.28 ± 0.06^†,^‡	2.6 ± 1.0^†,^‡	0.37 ± 0.07^†,^‡	8 ± 3^†,^‡	0.35 ± 0.09^†,^‡

↵* P < 0.05.
↵** P < 0.01.
↵*** P < 0.001.
↵† Not significant.
↵‡ Not applicable.