Scheme of API transport pathways to the vacuole. As described in the text, proAPI forms a complex in the cytosol. This Cvt complex is then targeted to the vacuole by two pathways depending upon the nutrient conditions. In growing conditions, a double membrane vesicle of ∼140 to 160 nm forms around the Cvt complex and excludes cytosol. In contrast, when cells are starved for nitrogen, the Cvt complex is taken up into larger autophagosomes (300-900 nm) together with cytosolic components. Vacuolar delivery is achieved by fusion of the outer membrane of the Cvt vesicle or autophagosome with the vacuolar membrane. Finally, the resulting Cvt bodies or autophagic bodies are broken down by vacuolar hydrolases to release proAPI into the vacuole lumen. The precursor form of the protein is then processed into the mature hydrolase. 