title: Mapping the Ca2+ -dependent binding of an invertebrate homolog of protein phosphatase 4 regulatory subunit 2 to the small EF-hand protein, calsensin.
abstract: The EF-hand family of calcium-binding proteins regulates cellular signal transduction events via calcium-dependent interactions with target proteins. Here, we show that the COOH-terminal tail of the leech homolog of protein phosphatase 4 regulatory subunit 2 (PP4-R2) interacts with the small neuronal EF-hand calcium-binding protein, Calsensin, in a calcium-dependent manner. Using two-dimensional NMR spectroscopy and chemical shift perturbations we have identified and mapped the residues of Calsensin that form a binding surface for PP4-R2. We show that the binding groove is formed primarily of discontinuous hydrophobic residues located in helix 1, the hinge region, and helix 4 of the unicornate-type four helix structure of Calsensin. The findings suggest the possibility that calcium-dependent modulation of phosphatase complexes through interactions with small calcium-binding proteins may be a general mechanism for regulation of signal transduction pathways.
authors.affiliation: Department of Biochemistry, Biophysics, and Molecular Biology, 3156 Molecular Biology Building, Iowa State University Ames, IO 50011, USA.
authors.forename: Deepa V
authors.initials: DV
authors.lastname: Venkitaramani
authors.forename: D Bruce
authors.initials: DB
authors.lastname: Fulton
authors.forename: Amy H
authors.initials: AH
authors.lastname: Andreotti
authors.forename: Kristen M
authors.initials: KM
authors.lastname: Johansen
authors.forename: Jørgen
authors.initials: J
authors.lastname: Johansen
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D002118:Calcium / Q000378:metabolism* / Q000494:pharmacology; D002135:Calcium-Binding Proteins / Q000737:chemistry* / Q000378:metabolism*; D020832:EF Hand Motifs; D007865:Leeches / Q000201:enzymology*; D008958:Models, Molecular; D008969:Molecular Sequence Data; D009419:Nerve Tissue Proteins / Q000737:chemistry* / Q000378:metabolism*; D019906:Nuclear Magnetic Resonance, Biomolecular; D010749:Phosphoprotein Phosphatases / Q000737:chemistry / Q000378:metabolism*; D010802:Phylogeny; D011485:Protein Binding / Q000187:drug effects; D025941:Protein Interaction Mapping
chemical_list: D002135:Calcium-Binding Proteins; D009419:Nerve Tissue Proteins; C093964:calsensin protein, Hirudinea; D010749:Phosphoprotein Phosphatases; D002118:Calcium