We performed mass-spectrometry analysis of proteins co-purifying with the Pab1, the B55 regulatory subunit of the PP2A protein phosphatase complex. Pab1 was tagged with YFP at the C-terminus and expressed from its endogenous promoter at its chromosomal locus. After one hour of nitrogen starvation, Pab1-YFP was pulled down and co-purifying proteins were analysed by mass-spectrometry. Our results revealed the presence of all components of PP2A protein complexes including Paa1, the catalytic subunits Ppa1, Ppa2, and Ppa3.