Activation of the G-Protein-Coupled Receptor Rhodopsin by Water.

Udeep Chawla, Suchithranga M D C Perera, Steven D E Fried, Anna R Eitel, Blake Mertz, Nipuna Weerasinghe, Michael C Pitman, Andrey V Struts, Michael F Brown

Angewandte Chemie (International ed. in English) 2021 Feb 01

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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. © 2020 Wiley-VCH GmbH.

Citation

Udeep Chawla, Suchithranga M D C Perera, Steven D E Fried, Anna R Eitel, Blake Mertz, Nipuna Weerasinghe, Michael C Pitman, Andrey V Struts, Michael F Brown. Activation of the G-Protein-Coupled Receptor Rhodopsin by Water. Angewandte Chemie (International ed. in English). 2021 Feb 01;60(5):2288-2295