Figure 8.

Invertase is efficiently secreted by ypt6Δ cells. Wild-type (WT, SEY6210) and ypt6Δ (GPY1700) strains expressing SUC2 from a multicopy plasmid (pRB58) were grown overnight at 30°C to midlogarithmic phase. After a 30-min incubation in low glucose media (0.1%) to induce invertase expression, cells were metabolically labeled with [³⁵S]methionine/cysteine followed by the addition of excess nonlabeled amino acids (chase). Samples were removed after 0, 10, and 30 min of chase, and invertase was immunoprecipitated from internal (I) and external (E) fractions. Invertase was resolved by SDS-PAGE and subjected to phosphorimage analysis. Cytoplasmic (cyto), core, and highly glycosylated mature forms of invertase are shown.