2v0p
From Proteopedia
The Structure of Tap42 Alpha4 Subunit
Structural highlights
FunctionTAP42_YEAST Involved in negative regulation of the TOR signaling pathway in response to type of available nitrogen source. Inhibitor of PP2A phosphatase SIT4, which results in inhibition of nuclear export of MSN2, due to lack of dephosphorylation by SIT4. Also required for rapamycin induced activation of expression of many nitrogen discrimination pathway (NDP) genes. In complex with PPH21, required for organization of the actin cytoskeletom during the cell cycle via a Rho GTPase-dependent mechanism.[1] [2] [3] [4] Evolutionary Conservation Check, as determined by ConSurfDB. You may read the explanation of the method and the full data available from ConSurf. Publication Abstract from PubMedPhysiological functions of protein phosphatase 2A (PP2A) are determined via the association of its catalytic subunit (PP2Ac) with diverse regulatory subunits. The predominant form of PP2Ac assembles into a heterotrimer comprising the scaffolding PR65/A subunit together with a variable regulatory B subunit. A distinct population of PP2Ac associates with the Tap42/alpha4 subunit, an interaction mutually exclusive with that of PR65/A. Tap42/alpha4 is also an interacting subunit of the PP2Ac-related phosphatases, PP4 and PP6. Tap42/alpha4, an essential protein in yeast and suppressor of apoptosis in mammals, contributes to critical cellular functions including the Tor signaling pathway. Here, we describe the crystal structure of the PP2Ac-interaction domain of Saccharomyces cerevisiae Tap42. The structure reveals an all alpha-helical protein with striking similarity to 14-3-3 and tetratricopeptide repeat (TPR) proteins. Mutational analyses of structurally conserved regions of Tap42/alpha4 identified a positively charged region critical for its interactions with PP2Ac. We propose a scaffolding function for Tap42/alpha4 whereby the interaction of PP2Ac at its N-terminus promotes the dephosphorylation of substrates recruited to the C-terminal region of the molecule. The structure of Tap42/alpha4 reveals a tetratricopeptide repeat-like fold and provides insights into PP2A regulation.,Yang J, Roe SM, Prickett TD, Brautigan DL, Barford D Biochemistry. 2007 Jul 31;46(30):8807-15. Epub 2007 Jul 6. PMID:17616149[5] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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