Deciphering protein complexes and protein interaction networks by tandem affinity purification and mass spectrometry:...

We employed a combination of tandem affinity purification and mass spectrometry for deciphering protein complexes and the protein interaction network in budding yeast. 53 genes were epitope-tagged, and their interaction partners were isolated by two-step immunoaffinity chromatography from whole cell lysates. 38 baits pulled down a total of 220 interaction partners, which are members of 19 functionally distinct protein complexes. We identified four proteins shared between complexes of different functionality thus charting segments of a protein interaction network. Concordance with the results of genome-wide two-hybrid screening was poor (14% of identified interactors overlapped) suggesting that the two approaches may provide complementary views on physical interactions within the proteome.