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== Publication Abstract from PubMed ==

Protein phosphatase 2A (PP2A) regulates many essential aspects of cellular physiology. Members of the regulatory B/B55/PR55 family are thought to play a key role in the dephosphorylation of Tau, whose hyperphosphorylation contributes to Alzheimer's disease. The underlying mechanisms of the PP2A-Tau connection remain largely enigmatic. Here, we report the complete reconstitution of a Tau dephosphorylation assay and the crystal structure of a heterotrimeric PP2A holoenzyme involving the regulatory subunit Balpha. We show that Balpha specifically and markedly facilitates dephosphorylation of the phosphorylated Tau in our reconstituted assay. The Balpha subunit comprises a seven-bladed beta propeller, with an acidic, substrate-binding groove located in the center of the propeller. The beta propeller latches onto the ridge of the PP2A scaffold subunit with the help of a protruding beta hairpin arm. Structure-guided mutagenesis studies revealed the underpinnings of PP2A-mediated dephosphorylation of Tau.

Structure of a protein phosphatase 2A holoenzyme: insights into B55-mediated Tau dephosphorylation.,Xu Y, Chen Y, Zhang P, Jeffrey PD, Shi Y Mol Cell. 2008 Sep 26;31(6):873-85. PMID:18922469<ref>PMID:18922469</ref>

From MEDLINE&reg;/PubMed&reg;, a database of the U.S. National Library of Medicine.<br>

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