Milieu-induced, selective aggregation of regulated secretory proteins in the trans-Golgi network

In some experiments, the standard procedure was modified in that various concentrations of saponin were used ; 1% (wt/vol) of Triton X-100 was used instead of saponin, or the pH and calcium concentration was varied (see text and figure legends) . In the latter case, the ionic strength was kept constant using KC1 . In other experiments, 05S]sulfate-labeled TGN vesicles were resuspended in 100 Al of buffer containing 0.5 mg/ml saponin and 2 mM MES, pH 7.4, incubated for 15 min at 0°C, centrifuged (110,000 g for 15 min), and the supernatant containing released CgB and SgII was supplemented with 10 pl of 10-fold concentrated aggregative milieu .