B56 domain

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PDB 2nyl EBI.jpg
crystal structure of protein phosphatase 2a (pp2a) holoenzyme with the catalytic subunit carboxyl terminus truncated
Symbol B56
Pfam PF01603
InterPro IPR002554
SCOP 1qq3
TCDB 5.A.4

Protein phosphatase 2A (PP2A) is a major intracellular protein phosphatase that regulates multiple aspects of cell growth and metabolism. Phosphorylation enables the activation or The ability of this widely distributed heterotrimeric enzyme to act on a diverse array of substrates is largely controlled by the nature of its regulatory B subunit. There are multiple families of B subunits, this family is called the B56 family.[1]


Protein phosphatase 2A (PP2A) is a major intracellular protein phosphatase that regulates multiple aspects of cell growth and metabolism such as DNA replication, transcription, translation, cell cycle, development, and apoptosis.

In order to exhibit specificity control over catalysis, hetero-oligomers are formed so the catalytic subunits are complexed with regulatory subunits. This helps direct their action towards the cellular substrate. This is the function of the B56 domain.[2]

B56 alpha, is additionally thought to play a role in nuclear export.[3]


Regulatory B subunit is a heterotrimer.

Subcellular Localization[edit]

Mainly found in the cytoplasm, however various isoforms can be found in the nucleus.[3]

Isoforms of B56 protein family[edit]

  • B56alpha
  • B56beta
  • B56delta
  • B56epsilon
  • B56gamma[3]


  1. ^ McCright B, Virshup DM (November 1995). "Identification of a new family of protein phosphatase 2A regulatory subunits". J. Biol. Chem. 270 (44): 26123–8. doi:10.1074/jbc.270.44.26123. PMID 7592815. 
  2. ^ Magnusdottir A, Stenmark P, Flodin S, Nyman T, Kotenyova T, Gräslund S, et al. (2009). "The structure of the PP2A regulatory subunit B56 gamma: the remaining piece of the PP2A jigsaw puzzle". Proteins. 74 (1): 212–21. doi:10.1002/prot.22150. PMID 18618707. 
  3. ^ a b c Flegg CP, Sharma M, Medina-Palazon C, Jamieson C, Galea M, Brocardo MG, et al. (2010). "Nuclear export and centrosome targeting of the protein phosphatase 2A subunit B56alpha: role of B56alpha in nuclear export of the catalytic subunit". J Biol Chem. 285 (24): 18144–54. doi:10.1074/jbc.M109.093294. PMC 2881738Freely accessible. PMID 20378546. 

This article incorporates text from the public domain Pfam and InterPro IPR002554

External links[edit]