Figure 4.

Effect of ammonium chloride and hypertonic medium on the posttranslational processing of newly synthesized AE1. Erythroid cells from a 10-d-old chicken embryo were pulsed and chased as described in the legend of Figure 1. AE1 immunoprecipitates were prepared from the detergent-soluble (S) and -insoluble (I) fractions of cells that had been detergent lysed after 0 h (A, lanes 1 and 2), 1 h (A, lanes 3 and 4), 2 h (A, lanes 5–10), and 4 h (A, lanes 11–16) of chase. Each precipitate was digested with endo F before analysis on a 6% SDS polyacrylamide gel. For some of the cells, 25 mM ammonium chloride (A, lanes 7, 8, 13, and 14), or 0.4 M sucrose (A, lanes 9, 10, 15, and 16) was added to media after 45 min of chase and was present for the remainder of the chase period. Autoradiograms from three separate experiments identical to the one shown in panel A were scanned, and the abundance of the individual anion exchanger species after endo F digestion was determined using NIH image. The values shown in panel B reflect the ratio of the 105-kDa AE1 species to the 95-kDa AE1 species at each time point. The values shown in panel C reflect the percentage of newly synthesized AE1 that was detergent insoluble at each time point. Error bars in panels B and C reflect the SD from the three experiments.