Abstract
PP1 (protein phosphatase 1) is among the most conserved enzymes known, with one or more isoforms present in all sequenced eukaryotic genomes. PP1 dephosphorylates specific serine/threonine phosphoproteins as defined by associated regulatory or targeting subunits. In the present study we performed a PP1-binding screen to find putative PP1 interactors in Arabidopsis thaliana and uncovered a homologue of the ancient PP1 interactor, I-2 (inhibitor-2). Bioinformatic analysis revealed remarkable conservation of three regions of plant I-2 that play key roles in binding to PP1 and regulating its function. The sequence-related properties of plant I-2 were compared across eukaryotes, indicating a lack of I-2 in some species and the emergence points from key motifs during the evolution of this ancient regulator. Biochemical characterization of AtI-2 (Arabidopsis I-2) revealed its ability to inhibit all plant PP1 isoforms and inhibitory dependence requiring the primary interaction motif known as RVXF. Arabidopsis I-2 was shown to be a phosphoprotein in vivo that was enriched in the nucleus. TAP (tandem affinity purification)-tag experiments with plant I-2 showed in vivo association with several Arabidopsis PP1 isoforms and identified other potential I-2 binding proteins.
Publication types
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Research Support, Non-U.S. Gov't
MeSH terms
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Amino Acid Sequence
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Arabidopsis / genetics
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Arabidopsis / metabolism*
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Arabidopsis Proteins / chemistry*
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Arabidopsis Proteins / genetics
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Arabidopsis Proteins / isolation & purification
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Arabidopsis Proteins / metabolism
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Cell Line
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Cell Nucleus / metabolism
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Computational Biology / methods
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Databases, Protein
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Molecular Sequence Data
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Phosphoproteins / chemistry
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Phosphoproteins / genetics
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Phosphoproteins / isolation & purification
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Phosphoproteins / metabolism
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Phylogeny
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Plant Epidermis / cytology
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Plant Epidermis / metabolism
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Plant Leaves / cytology
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Plant Leaves / metabolism
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Plant Structures / metabolism
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Protein Isoforms / genetics
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Protein Isoforms / isolation & purification
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Protein Isoforms / metabolism
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Protein Phosphatase 1 / chemistry*
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Protein Phosphatase 1 / genetics
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Protein Phosphatase 1 / isolation & purification
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Protein Phosphatase 1 / metabolism
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Protein Subunits / chemistry
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Protein Subunits / genetics
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Protein Subunits / isolation & purification
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Protein Subunits / metabolism
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Protein Transport
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Recombinant Fusion Proteins / metabolism
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Sequence Alignment
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Sequence Homology, Amino Acid
Substances
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Arabidopsis Proteins
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Phosphoproteins
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Protein Isoforms
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Protein Subunits
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Recombinant Fusion Proteins
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AtI-2 protein, Arabidopsis
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Protein Phosphatase 1