Intracellular pH measurements. Traces are intracellular pH measurements of representative oocytes expressing GPA and wt (A) or mutated hAE1 (B: S731P: C: H734R) as a function of time and extracellular medium composition. The graph bars (D) illustrate the initial speed of pH recovery after intracellular acidification for control oocytes (noninjected) or oocytes expressing GPA and wt hAE1 or GPA and the 4 different point mutations of hAE1. Data are mean (± SEM) of 5 (NI), 10 (L687P), 7 (D705Y), 10 (S731P), 8 (H734R), or 16 (wt hAE1) oocytes coming from different xenopus.