Could perform a substrate recognition function or could be responsible for targeting the enzyme complex to the appropriate subcellular compartment. 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 B family. It is uncertain whether Met-1, Met-18, Met-33 or Met-44 is the initiator.