Kinase activation by Trg (5Q), Trg (3E-2Q), and Trg (5E). Assays were performed as described in the legend to Fig. 1, using 1 μM receptor. The data are averages from three independent experiments, including one with several replicates. Prior to averaging, the average values from independent experiments were normalized by using the value for Trg (3E-2Q). For this reason there are no error bars for that value. The error bars represent standard errors.