Figure 9.

Two-pathway model for Cvt/Apg transport to the vacuole. (1) prAPI rapidly oligomerizes into a dodecameric conformation after translation. (2) The dodecamers assemble into Cvt complexes, which are subsequently sequestered and wrapped by double-membrane Cvt vesicles and autophagosomes in a process requiring Apg5p. (3) The vesicles are then targeted to the vacuole, where subsequent docking and fusion of the outer membrane results in the release of the inner vesicle into the lumen. (4) The inner membrane is degraded within the lumen, allowing vacuolar hydrolases access to the cargo. (5) The N-terminal propeptides of the prAPI molecules are proteolytically removed in a PEP4-dependent manner to generate mature API dodecamers.