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Activation of the G‐Protein‐Coupled Receptor Rhodopsin by Water

Authors
  • Chawla, Udeep1
  • Perera, Suchithranga M. D. C.1
  • Fried, Steven D. E.1
  • Eitel, Anna R.1
  • Mertz, Blake1
  • Nipuna Weerasinghe1
  • Pitman, Michael C.1
  • Struts, Andrey V.1, 2
  • Brown, Michael F.1, 3
Type
Published Article
Journal
Angewandte Chemie International Edition
Publisher
Wiley
Publication Date
Dec 01, 2020
Volume
60
Identifiers
DOI: 10.1002/anie.202003342
Source
MyScienceWork
Funders
  • National Science Foundation
  • National Institutes of Health
License
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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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