title: Differential Nanosecond Protein Dynamics in Homologous Calcium Sensors.
abstract: Shaping the temporal response of photoreceptors is facilitated by a well-balanced second messenger cascade, in which two neuronal Ca(2+)-sensor proteins operate in a sequential relay mechanism. Although they share structurally similar sensing units, they differentially activate the same target protein. Here, as a prototypical case in Ca(2+)-mediated signal processing, we investigate differential cellular responsiveness in protein conformational dynamics on a nanosecond time scale. For this, we have site-specifically labeled cysteine residues in guanylate cyclase-activating protein GCAP1 by the fluorescent dye Alexa647 and probed its local environment via time-resolved fluorescence spectroscopy. Fluorescence lifetime and rotational anisotropy measurements reveal a distinct structural movement of the polypeptide chain around position 106 upon release of Ca(2+). This is supported by analyzing the diffusional dye motion in a wobbling-in-a-cone model and by molecular dynamics simulations. We conclude that GCAP1 and its cellular cognate GCAP2 operate by distinctly different switching mechanisms despite their high structural homology.
authors.affiliation: Ultrafast Nano-Optics, Institute of Physics, Faculty V, University of Oldenburg , D-26111 Oldenburg, Germany.|Center of Interface Science, University of Oldenburg , D-26111 Oldenburg, Germany.
authors.forename: Jörg
authors.initials: J
authors.lastname: Robin
authors.affiliation: Ultrafast Nano-Optics, Institute of Physics, Faculty V, University of Oldenburg , D-26111 Oldenburg, Germany.|Center of Interface Science, University of Oldenburg , D-26111 Oldenburg, Germany.
authors.forename: Jens
authors.initials: J
authors.lastname: Brauer
authors.affiliation: Biochemistry, Department of Neurosciences, Faculty VI, University of Oldenburg , D-26111 Oldenburg, Germany.
authors.forename: Stefan
authors.initials: S
authors.lastname: Sulmann
authors.affiliation: Department of Life Sciences and Reproduction, Section of Biological Chemistry, University of Verona , Verona, Italy.
authors.forename: Valerio
authors.initials: V
authors.lastname: Marino
authors.affiliation: Department of Life Sciences and Reproduction, Section of Biological Chemistry, University of Verona , Verona, Italy.|Center for BioMedical Computing (CBMC), University of Verona , Verona, Italy.
authors.forename: Daniele
authors.initials: D
authors.lastname: Dell'Orco
authors.affiliation: Ultrafast Nano-Optics, Institute of Physics, Faculty V, University of Oldenburg , D-26111 Oldenburg, Germany.|Center of Interface Science, University of Oldenburg , D-26111 Oldenburg, Germany.
authors.forename: Christoph
authors.initials: C
authors.lastname: Lienau
authors.affiliation: Center of Interface Science, University of Oldenburg , D-26111 Oldenburg, Germany.|Biochemistry, Department of Neurosciences, Faculty VI, University of Oldenburg , D-26111 Oldenburg, Germany.
authors.forename: Karl-Wilhelm
authors.initials: KW
authors.lastname: Koch
mesh_terms: D002118:Calcium / Q000032:analysis* / Q000737:chemistry*; D002232:Carbocyanines / Q000032:analysis; D005456:Fluorescent Dyes / Q000032:analysis; D051604:Guanylate Cyclase-Activating Proteins / Q000737:chemistry*; D056004:Molecular Dynamics Simulation; D011487:Protein Conformation; D017434:Protein Structure, Tertiary; D013050:Spectrometry, Fluorescence
chemical_list: C569686:Alexa Fluor 647; D002232:Carbocyanines; D005456:Fluorescent Dyes; D051604:Guanylate Cyclase-Activating Proteins; D002118:Calcium