The A subunit of protein phosphatase 2A serves as a scaffolding molecule to coordinate the assembly of the catalytic subunit and a variable regulatory B subunit. Involved during developmental process such as seedling and floral developments. Seems to act as a negative regulator of PP2A catalytic activity. PP2A consists of a common heterodimeric core enzyme, composed of a 36 kDa catalytic subunit (subunit C) and a 65 kDa constant regulatory subunit (subunit A), that associates with a variety of regulatory subunits such as subunits B (the R2/B/PR55/B55, R3/B''/PR72/PR130/PR59 and R5/B'/B56 families) (By similarity). Interacts with CHIP (PubMed:16640601). Interacts with SRK2E/OST1 (PubMed:26175513). A number of isoforms are produced. According to EST sequences. Expressed ubiquitously at stable levels. However, higher protein levels in roots and flowers (at protein level). 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 (By similarity). Ubiquitinated. CHIP-mediated ubiquitination enhances phosphatase activity after an abiotic stress such as low temperature or darkness. Due to the stability of its transcription, PubMed:16166256 proposed this gene as a reference gene for transcript normalization. Belongs to the phosphatase 2A regulatory subunit A family.