Two conserved domains in regulatory B subunits mediate binding to the A subunit of protein phosphatase 2A

Eur J Biochem. 2002 Jan;269(2):546-52. doi: 10.1046/j.0014-2956.2001.02680.x.


Protein phosphatase 2A (PP2A) is an abundant heterotrimeric serine/threonine phosphatase containing highly conserved structural (A) and catalytic (C) subunits. Its diverse functions in the cell are determined by its association with a highly variable regulatory and targeting B subunit. At least three distinct gene families encoding B subunits are known: B/B55/CDC55, B'/B56/RTS1 and B"/PR72/130. No homology has been identified among the B families, and little is known about how these B subunits interact with the PP2A A and C subunits. In vitro expression of a series of B56alpha fragments identified two distinct domains that bound independently to the A subunit. Sequence alignment of these A subunit binding domains (ASBD) identified conserved residues in B/B55 and PR72 family members. The alignment successfully predicted domains in B55 and PR72 subunits that similarly bound to the PP2A A subunit. These results suggest that these B subunits share a common core structure and mode of interaction with the PP2A holoenzyme.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Amino Acid Sequence
  • Conserved Sequence*
  • Glutathione Transferase / metabolism
  • Molecular Sequence Data
  • Phosphoprotein Phosphatases / chemistry
  • Phosphoprotein Phosphatases / metabolism*
  • Protein Phosphatase 2
  • Recombinant Fusion Proteins / metabolism
  • Sequence Homology, Amino Acid
  • Substrate Specificity


  • Recombinant Fusion Proteins
  • Glutathione Transferase
  • Phosphoprotein Phosphatases
  • Protein Phosphatase 2