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Characterization of G Protein-coupled Receptors by a Fluorescence-based Calcium Mobilization Assay
Published on: July 28, 2014
Ca2+ differently affects hydrophobic properties of guanylyl cyclase-activating proteins (GCAPs) and recoverin
Wojciech A Gorczyca1, Marcin Kobiałka, Marianna Kuropatwa
1Laboratory of Signaling Proteins, L. Hirszfeld Institute of Immunology and Experimental Therapy, Polish Academy of Sciences, R. Weigla 12, 53-114 Wrocław, Poland. gorczyca@immuno.iitd.pan.wroc.pl
Abstract:
Guanylyl cyclase-activating proteins (GCAPs) and recoverin are retina-specific Ca(2+)-binding proteins involved in phototransduction. We provide here evidence that in spite of structural similarities GCAPs and recoverin differently change their overall hydrophobic properties in response to Ca(2+). Using native bovine GCAP1, GCAP2 and recoverin we show that: i) the Ca(2+)-dependent binding of recoverin to Phenyl-Sepharose is distinct from such interactions of GCAPs; ii) fluorescence intensity of 1-anilinonaphthalene-8-sulfonate (ANS) is markedly higher at high [Ca(2+)](free) (10 microM) than at low [Ca(2+)](free) (10 nM) in the presence of recoverin, while an opposing effect is observed in the presence of GCAPs; iii) fluorescence resonance energy transfer from tryptophane residues to ANS is more efficient at high [Ca(2+)](free) in recoverin and at low [Ca(2+)](free) in GCAP2. Such different changes of hydrophobicity evoked by Ca(2+) appear to be the precondition for possible mechanisms by which GCAPs and recoverin control the activities of their target enzymes.
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