Table 3.

Ion selectivity of MEC-4 Cys mutants near the selectivity filter

Benzamil-sensitive whole-cell currents were measured for the MEC-4 A713T (MEC-4d) channel or individual Cys mutant channels by perfusing the oocytes with TEV solutions containing 100 mm Na⁺, Li⁺, or K⁺ as major carrying cations (see “Experimental procedures”). The average whole-cell Na⁺ current of oocytes expressing MEC-4 A713T was −5.1 ± 4.4 μA. Experiments were repeated in four batches of oocytes. n indicates the number of oocytes measured for each group. Statistical significance was determined with one-way ANOVA followed by a Bonferroni test (*, p < 0.05).

Mutation	ILi+/INa+	IK+/INa+	n
A713T	0.75 ± 0.15	0.16 ± 0.08	17
A713T/L721C	0.67 ± 0.20	0.18 ± 0.06	24
A713T/I725C	0.68 ± 0.24	0.24 ± 0.06*	22
A713T/F727C	0.72 ± 0.14	0.16 ± 0.07	30
A713T/L728C	0.59 ± 0.24*	0.10 ± 0.02*	18