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

Comparison of the Golgi retention signal of DPAP A with the signals directing plasma membrane receptors and lysosomal membrane proteins into clathrin-coated pits of animal cells also reveals some interesting similarities. Recent structural and mutagenesis studies suggest that these coated pit signals consist of short (4-6 amino acid) sequences that invariably contain one or more Tyr or Phe residues and appear to be in a turn conformation (for review see Trowbridge, 1991) . Beyond the aromatic residue requirement, most of the coated signals reveal little if any primary sequence similarity to each other or to the Phe-X-Phe-X-Asp retention motif of DPAP A. An exception is the internalization signal of bovine cation-independent mannose-6-phosphate receptor, which was demonstrated by Canfield et al. (1991) to include a Tyr-X-Tyr motif as an important dement. The similarity of the Golgi retention signal of DPAP A to signals that sort membrane proteins into clathrin-coated pits suggests that the retention of DPAP A may involve clustering into clathrincoated pits.