Membrane protein retention in the yeast Golgi apparatus: dipeptidyl aminopeptidase A is retained by a cytoplasmic signal containing aromatic residues

The existence of a prevacuolar compartment in yeast has not been firmly established. However, recently our laboratory has demonstrated that a subset of the vps mutants, which are defective in vacuolar protein sorting, accumulates a vacuolar-like organelle adjacent to the vacuole (Raymond et al., 1992) . This organelle shares similarity with the vacuole in that it contains the V-ATPase and soluble vacuolar hydrolases such as carboxypeptidase Y and protease A. However, the organelle also contains a significant pool of A-ALP, with the rest being located in the Golgi. Therefore, it is possible that wild-type cells contain a prevacuolar compartment and DPAP A passes through it as part of its retrieval system. An exciting possibility is that retrograde trafficking of vesicles (containing DPAP A) from this compartment back to the Golgi is partially blocked in these mutants.