The PR65 subunit of protein phosphatase 2A serves as a scaffolding molecule to coordinate the assembly of the catalytic subunit and a variable regulatory B subunit. PP2A exists in several trimeric forms, all of which consist of a core composed of a catalytic subunit associated with a 65 kDa regulatory subunit (PR65) (subunit A). The core complex associates with a third, variable subunit (subunit B), which confers distinct properties to the holoenzyme. Belongs to the phosphatase 2A regulatory subunit A family.