Figure 4.

Effects of substitution of μ1-Y401 with other amino acids on external QX222 block. Actions of externally applied 500 μM QX222 were studied for μ1-Y401F (▪), μ1-Y401A (▴), and μ1-Y401D (▾). For comparison, the mean values of block for μ1-WT (○) and μ1-Y401C (•) shown in Fig. 2C were represented. The bar indicates the period of exposure to 500 μM QX222 in the bath solution. The protocol was the same as that in Fig. 2, and peak currents were normalized to that in control. Data represent the means ± SEM from four oocytes for μ1-Y401F, seven for μ1-Y401A, and five for μ1-Y401D.