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

Our data point toward an eight residue sequence in the DPAP A cytoplasmic domain containing two phenylalanine residues as being a Golgi retention signal. Mutagenesis of the A-ALP fusion protein was a viable approach for this analysis since: (a) A-ALP was localized to the Golgi apparatus as shown by its colocalization with Kex2p, (b) A-ALP was membrane bound and mutants processed in a PEP4-dependent manner were enzymatically active, indicating correct folding, (c) A-ALP could be easily detected at low expression levels, (d) localization could be assessed by both indirect immunofluorescence and by PEP4-dependent processing, and (e) regions of the DPAP A cytoplasmic domain identified as being necessary for Golgi retention of A-ALP were also shown to be necessary for DPAP A retention.