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Conformational Changes in Calcium‐Sensor Proteins under Molecular Crowding Conditions
Authors:Stefan Sulmann  Dr Daniele Dell'Orco  Valerio Marino  Dr Petra Behnen  Prof?Dr Karl‐Wilhelm Koch
Institution:1. Department of Neurosciences, Biochemistry Group, University of Oldenburg, 26111 Oldenburg (Germany);2. Department of Life Sciences and Reproduction, Section of Biological Chemistry and Center for BioMedical Computing (CBMC), University of Verona, Verona (Italy);3. Department of Biomedical Sciences, University of Modena, Modena (Italy)
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 Ca2+ sensors, which undergo conformational changes in response to oscillating intracellular Ca2+ 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 Ca2+‐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 Ca2+‐sensor protein a fingerprint profile that reflects different hydrodynamic properties under changing Ca2+ 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 Ca2+‐occupied functional state under crowding conditions.
Keywords:calcium sensor  conformational change  protein crowding  protein folding  surface plasmon resonance
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