Quantitative Proteomics of Yeast Post-Golgi Vesicles Reveals a Discriminating Role for Sro7p in Protein Secretion

We here report the first comparative proteomics of purified yeast post-Golgi vesicles (PGVs). Vesicle samples isolated from PGV-accumulating sec6-4 mutants were treated with isobaric tags (iTRAQ) for subsequent quantitative tandem mass spectrometric analysis of protein content. After background subtraction, a total of 66 vesicle-associated proteins were identified, including known or assumed vesicle residents as well as a fraction not previously known to be PGV associated. Vesicles isolated from cells lacking the polarity protein Sro7p contained essentially the same catalogue of proteins but showed a reduced content of a subset of cargo proteins, in agreement with a previously shown selective role for Sro7p in cargo sorting.