Figure 4.

Pulse-chase experiments of invertase secretion. Wild-type cells (YPH499, WT), integrants of wild-type ARF1 (NYY0, Δarf2), and arf1 ts mutant alleles (arf1-11–arf1-18) were grown to an early log phase at 23°C, converted to spheroplasts, induced to produce invertase, preincubated at 37°C for 30 min, and labeled with Tran³⁵S-label for 4 min. Aliquots were withdrawn at the indicated times and then separated by centrifugation into internal and external fractions. Invertase was recovered by immunoprecipitation and visualized by SDS-PAGE and fluorography.