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 consists of a common heterodimeric core enzyme, composed of a 36 kDa catalytic subunit (subunit C) and a 65 kDa constant regulatory subunit (PR65 or subunit A), that associates with a variety of regulatory subunits. Proteins that associate with the core dimer include three families of regulatory subunits B (the R2/B/PR55/B55, R3/B''/PR72/PR130/PR59 and R5/B'/B56 families), the 48 kDa variable regulatory subunit, viral proteins, and cell signaling molecules. Interacts with IPO9. Interacts with SGO1. Interacts with RAF1. Each HEAT repeat appears to consist of two alpha helices joined by a hydrophilic region, the intrarepeat loop. The repeat units may be arranged laterally to form a rod-like structure. Belongs to the phosphatase 2A regulatory subunit A family. Contaminating sequence. Sequence of unknown origin in the N-terminal part.