title: Conformational changes in calcium-sensor proteins under molecular crowding conditions.
abstract: Fundamental components of signaling pathways are switch modes in key proteins that control start, duration, and ending of diverse signal transduction events. A large group of switch proteins are Ca(2+) sensors, which undergo conformational changes in response to oscillating intracellular Ca(2+) concentrations. Here we use dynamic light scattering and a recently developed approach based on surface plasmon resonance to compare the protein dynamics of a diverse set of prototypical Ca(2+)-binding proteins including calmodulin, troponin C, recoverin, and guanylate cyclase-activating protein. Surface plasmon resonance biosensor technology allows monitoring conformational changes under molecular crowding conditions, yielding for each Ca(2+)-sensor protein a fingerprint profile that reflects different hydrodynamic properties under changing Ca(2+) conditions and is extremely sensitive to even fine alterations induced by point mutations. We see, for example, a correlation between surface plasmon resonance, dynamic light scattering, and size-exclusion chromatography data. Thus, changes in protein conformation correlate not only with the hydrodynamic size, but also with a rearrangement of the protein hydration shell and a change of the dielectric constant of water or of the protein-water interface. Our study provides insight into how rather small signaling proteins that have very similar three-dimensional folding patterns differ in their Ca(2+)-occupied functional state under crowding conditions.
authors.affiliation: Department of Neurosciences, Biochemistry Group, University of Oldenburg, 26111 Oldenburg (Germany).
authors.forename: Stefan
authors.initials: S
authors.lastname: Sulmann
authors.forename: Daniele
authors.initials: D
authors.lastname: Dell'Orco
authors.forename: Valerio
authors.initials: V
authors.lastname: Marino
authors.forename: Petra
authors.initials: P
authors.lastname: Behnen
authors.forename: Karl-Wilhelm
authors.initials: KW
authors.lastname: Koch
mesh_terms: D015374:Biosensing Techniques; D002118:Calcium / Q000737:chemistry / Q000378:metabolism*; D051604:Guanylate Cyclase-Activating Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D052139:Intracellular Calcium-Sensing Proteins / Q000032:analysis* / Q000378:metabolism; D008027:Light; D017354:Point Mutation; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D012542:Scattering, Radiation; D020349:Surface Plasmon Resonance
chemical_list: D051604:Guanylate Cyclase-Activating Proteins; D052139:Intracellular Calcium-Sensing Proteins; D002118:Calcium
keywords: calcium sensor; conformational change; protein crowding; protein folding; surface plasmon resonance