InterPro domain: IPR000009

Protein phosphatase 2A (PP2A) is a serine/threonine phosphatase implicated in many cellular processes, including the regulation of metabolic enzymes and proteins involved in signal transduction [ 1 , 2 ]. PP2A is a trimercomposed of a 36kDa catalytic subunit, a 65kDa regulatory subunit (subunit A) and a variable third subunit (subunit B) [ 3 , 3 ]. Subunits B can be classified into three subfamilies, the R2/B/PR55/B55, the R3/B''/PR72/PR130/PR59 and the R5/B'/B56 families.

This entry represent the R2/B/PR55/B55 family, which exists inDrosophila melanogaster and yeast, and has up to three isoforms in mammals (alpha/beta/gamma) [ 3 , 3 ]. PR55 may act as a substrate recognition unit, or may help to target the enzyme to thecorrect subcellular location [ 3 ]. In budding yeasts, it is also known as Cdc55, which is essential for the spindle assembly checkpoint (SAC) [ 3 ]. In flies, it is also known as PP2A-twins, which collaborates with polo kinase for cell cycle progression and centrosome attachment to nuclei in Drosophila embryos [ 4 ].

1. Structure of the 55-kDa regulatory subunit of protein phosphatase 2A: evidence for a neuronal-specific isoform. Biochemistry 30, 3589-97
2. The third subunit of protein phosphatase 2A (PP2A), a 55-kilodalton protein which is apparently substituted for by T antigens in complexes with the 36- and 63-kilodalton PP2A subunits, bears little resemblance to T antigens. J. Virol. 66, 886-93
3. Nuclear PP2A-Cdc55 prevents APC-Cdc20 activation during the spindle assembly checkpoint. J. Cell. Sci. 126, 4396-405
4. PP2A-twins is antagonized by greatwall and collaborates with polo for cell cycle progression and centrosome attachment to nuclei in drosophila embryos. PLoS Genet. 7, e1002227