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Updated: Dec 17, 2025

Strategic Screening and Characterization of the Visual GPCR-mini-G Protein Signaling Complex for Successful Crystallization
Published on: March 16, 2020
Activation of the G-Protein-Coupled Receptor Rhodopsin by Water
Udeep Chawla1, Suchithranga M D C Perera1, Steven D E Fried1
1Department of Chemistry and Biochemistry, University of Arizona, Tucson, AZ, 85721, USA.
Abstract:
Visual rhodopsin is an important archetype for G-protein-coupled receptors, which are membrane proteins implicated in cellular signal transduction. Herein, we show experimentally that approximately 80 water molecules flood rhodopsin upon light absorption to form a solvent-swollen active state. An influx of mobile water is necessary for activating the photoreceptor, and this finding is supported by molecular dynamics (MD) simulations. Combined force-based measurements involving osmotic and hydrostatic pressure indicate the expansion occurs by changes in cavity volumes, together with greater hydration in the active metarhodopsin-II state. Moreover, we discovered that binding and release of the C-terminal helix of transducin is coupled to hydration changes as may occur in visual signal amplification. Hydration-dehydration explains signaling by a dynamic allosteric mechanism, in which the soft membrane matter (lipids and water) has a pivotal role in the catalytic G-protein cycle.
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