Fig. 3.
DHβE and NBT sensitivity of receptors formed by chimeric β subunits. A, DHβE sensitivity of receptors formed by each of a series of chimeric subunits in which increasingly larger portions of the N-terminal end of β2 were replaced by the corresponding portion of β4. Current in response to an EC20 concentration of ACh in the presence of 3 μm DHβE is presented as a percent of the response to ACh alone (mean ± SD of 3–4 separate oocytes).B, NBT sensitivity of receptors formed by the chimeras inA. Current in response to an ACh concentration at or below the EC50 after 30 min incubation with 100 nm NBT is presented as a percentage of the response to ACh alone (mean ± SD of 3–4 separate oocytes, except for β4, which is mean ± SEM of 3 separate sets of oocytes, each set consisting of 3–4 separate oocytes). C, DHβE sensitivity of receptors formed by each of a series of chimeric subunits in which increasingly larger portions of β4 were replaced by the corresponding portion of β2. Current in response to an EC20concentration of ACh in the presence of 3 μmDHβE is presented as a percent of the response to ACh alone (mean ± SD of 3–4 separate oocytes). D, NBT sensitivity of receptors formed by the chimeras in C. Current in response to an ACh concentration at or below the EC50after 30 min incubation with 100 nm NBT is presented as a percentage of the response to ACh alone (mean ± SD of 3–4 separate oocytes, except for β2-54-β4, which is mean ± SEM of 3 separate sets of oocytes, each set consisting of 3–4 separate oocytes). Significant differences from β2 are denoted byasterisks (*p < 0.05; **p < 0.01; ***p < 0.001). Significant differences from β4 are denoted by daggers (†p < 0.05;†††p < 0.001). Some error bars are too small to appear.