title: Homogeneous TR-FRET high-throughput screening assay for calcium-dependent multimerization of sorcin.
abstract: A homogeneous high-throughput screening method based on time-resolved fluorescence resonance energy transfer (TR-FRET) for the measurement of calcium-dependent multimerization of an EF-hand protein, sorcin, is described. The assay is based on a specific sorcin binding peptide conjugated either with an intrinsically highly fluorescent europium chelate (donor) or an Alexa Fluor 700 fluorophore (acceptor). Addition of calcium results in multimerization of sorcin, allowing several peptides to bind simultaneously to the epitopes of the multimeric protein complex, and the proximity of peptides labeled either with donor or acceptor label results in fluorescence resonance energy transfer between the 2 labels. When no calcium is present, the protein remains in a monomer form, and thus no FRET can take place. In the optimized assay construct, the assay was performed in 45 min, and a more than 20-fold signal-to-background ratio was achieved. The reversibility of sorcin multimerization was shown by chelating free calcium with ethylenediamine tetraacetic acid (EDTA). The developed homogeneous assay can be used in screening molecules that either inhibit or enhance multimerization of sorcin, and the assay format is applicable to various noncompetitive high-throughput screening assays detecting protein multimerization reactions.
authors.affiliation: University of Turku, Department of Biotechnology, Finland. heidi.appelblom@utu.fi
authors.forename: Heidi
authors.initials: H
authors.lastname: Appelblom
authors.forename: Jussi
authors.initials: J
authors.lastname: Nurmi
authors.forename: Tero
authors.initials: T
authors.lastname: Soukka
authors.forename: Michael
authors.initials: M
authors.lastname: Pasternack
authors.forename: Kai E
authors.initials: KE
authors.lastname: Penttilä
authors.forename: Timo
authors.initials: T
authors.lastname: Lövgren
authors.forename: Pauliina
authors.initials: P
authors.lastname: Niemelä
mesh_terms: D002118:Calcium / Q000494:pharmacology*; D002135:Calcium-Binding Proteins / Q000737:chemistry / Q000378:metabolism*; D019281:Dimerization; D004353:Drug Evaluation, Preclinical / Q000379:methods*; D031541:Fluorescence Resonance Energy Transfer / Q000379:methods*; D008954:Models, Biological; D010446:Peptide Fragments / Q000378:metabolism / Q000494:pharmacology; D011485:Protein Binding / Q000187:drug effects
chemical_list: D002135:Calcium-Binding Proteins; D010446:Peptide Fragments; C503113:SRI protein, human; D002118:Calcium