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Báo cáo khoa học: Two conserved domains in regulatory B subunits mediate binding to the A subunit of protein phosphatase 2A

Protein phosphatase 2A (PP2A) is an abundant heterotri-meric serine/threonine phosphatase containing highly con-served 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 homologyhasbeen identi®edamong theBfamilies, and little is knownabout howtheseBsubunits interactwith the PP2A A and C subunits | Eur. J. Biochem. 269 546-552 2002 FEBS 2002 Two conserved domains in regulatory B subunits mediate binding to the A subunit of protein phosphatase 2A Xinghai Li1 and David M. Virshup1 2 1 Department of Oncological Sciences Center for Children Huntsman Cancer Institute and 2Department of Pediatrics University of Utah Salt Lake City UT USA 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 B56a fragments identified two distinct domains that bound inde pendently to the A subunit. Sequence alignment of these A subunit binding domains ASBD identifed 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. Keywords phosphoprotein phosphatase PP2A subunit interactions phosphorylation. Protein phosphatase 2A PP2A is an abundant cellular serine threonine-specifc phosphatase that regulates a significant array of cellular events. The PP2A holoenzyme is a heterotrimer containing a 65-kDa regulatory A subunit A PR65 a 36-kDa catalytic C subunit and one of a variety of regulatory B subunits. These diverse B subunits in the PP2A heterotrimer allow the phosphatase to localize to distinct regions of the cell and to dephosphorylate specifc substrates thereby allowing PP2A to regulate diverse processes in the cell such as DNA replication Wnt signaling