ACh concentration–response data for muscle-type single-subunit mutants before and after MTSEA treatment. Oocytes were stimulated alternately with control applications of 30 µM ACh and ACh at increasing concentrations: 1 µM, 10 µM, 100 µM, and 1 mM (i.e., the sequence of applications was 30, 1, 30, 10, 30, 100, 30, 1,000, and 30). Next, the oocytes were treated with 2 mM MTSEA for 60 s before being tested with the same sequence of ACh applications. All of the data were normalized to the individual oocytes’ average responses to the five 30-µM ACh applications given before the MTSEA treatment. Therefore, the 30-µM point in the pretreatment data is fixed at 1, and the SEM plotted for that point is the average SEM of the five 30-µM responses obtained from each cell. The 30-µM point in the post-MTSEA curve is based on the responses to 30 µM ACh obtained between the posttreatment 10-µM ACh and 100-µM ACh applications. The plots on the right represent the repeated 30-µM ACh responses obtained through the course of the entire experiments, normalized to the average pre-MTSEA 30-µM ACh responses from each cell. The arrowhead indicates the point at which MTSEA was applied. The values plotted are the means ± SEM of five, three, and eight oocytes for α1β1γδL121C, α1β1εL119Cδ, and α1β1εδL121C, respectively. Fit parameters are listed in Table II.