Purification of PP2A holoenzymes by sequential immunoprecipitation with anti-peptide antibodies.

Understanding the multiple functions of protein phosphatase 2A (PP2A) rests on elucidating the enzymatic properties of over 50 different possible forms of the PP2A holoenzyme. We describe a procedure for highly purifying each one of these forms. This procedure is based on coexpressing in 293 cells one scaffolding A subunit, one regulatory B subunit, and one catalytic C subunit, each tagged with a different sequence, and purifying the trimeric holoenzyme by three consecutive immunoprecipitations with antibodies against the tags. In a few hours and from a small number of cells, sufficient enzyme can be purified for enzymatic studies. Purification of six different holoenzymes in parallel can easily be accomplished.