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

The data presented in this paper address fundamental issues in membrane protein sorting in the yeast secretory pathway. We present experiments that further test and support the validity of the vacuolar default model, which states that the vacuole is the default destination for membrane proteins of the yeast secretory pathway. In addition, a detailed characterization of the Golgi retention signal of DPAP A led to the conclusion that certain aromatic amino acid residues within the cytoplasmic domain constitute a signal that is responsible for retention. This observation, which contrasts with studies in mammalian cells demonstrating that several Golgi membrane proteins are retained via their transmembrane domains (Machamer, 1991) , indicates that Golgi retention signals can reside in cytoplasmic or transmembrane domains. Genetic approaches available with yeast should soon allow identification of components of the retention machinery that retain DPAP A in the Golgi apparatus.