Decaging of middle sites in the R domain yield fast, diverse functional effects. (A) Western blot showing the specific rescue of S700TAG, S737TAG, and S768TAG-CFTR with caged serine via pCAGEDSER (pCS) synthetase. The WT CFTR lysate was diluted 1:8 to compare with rescued samples. (B–D) Representative traces of HEK cells expressing CFTR channels with caged serine encoded at S700, S737, or S768, with decaging occurring at plateau (purple arrowhead). n = 3 experimental replicates for each variant; quantification in Fig. 6 and Table 1. (E) IV curves for the individual cells in C–E: gray = initial, black = plateau of forskolin, magenta = after light pulse. Source data are available for this figure: SourceData F4.