Figure 4.

Time course of receptor dephosphorylation. After 100 nM AVP promoted phosphorylation, excess hormone was removed by acid wash, and the cells were allowed to recover. The amount of radioactive phosphate present in each receptor protein was quantified at the indicated times by immunoprecipitating receptors from detergent cell extracts. Results obtained for wild-type and S363A mutant receptors are shown. The values for each construct are expressed as the mean ± SEM of the percent phosphate incorporated in the immunoprecipitated receptor before the recovery. Number of experiments were n = 7 for −20 min (untreated) and time 0, n = 3 for 30 min, n = 4 for 60 min, and n = 5 for 120 min of recycling.