Conformational dynamics of activation for the pentameric complex of dimeric G protein-coupled receptor and heterotrimeric G protein
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Updated: May 22, 2026

Visualizing the Conformational Dynamics of Membrane Receptors Using Single-Molecule FRET
Published on: August 17, 2022
Tivadar Orban1, Beata Jastrzebska, Sayan Gupta
1Department of Pharmacology, School of Medicine, Case Western Reserve University, Cleveland, OH 44106-4988, USA.
Abstract:
Photoactivation of rhodopsin (Rho), a G protein-coupled receptor, causes conformational changes that provide a specific binding site for the rod G protein, G(t). In this work we employed structural mass spectrometry techniques to elucidate the structural changes accompanying transition of ground state Rho to photoactivated Rho (Rho(∗)) and in the pentameric complex between dimeric Rho(∗) and heterotrimeric G(t). Observed differences in hydroxyl radical labeling and deuterium uptake between Rho(∗) and the (Rho(∗))(2)-G(t) complex suggest that photoactivation causes structural relaxation of Rho following its initial tightening upon G(t) coupling. In contrast, nucleotide-free G(t) in the complex is significantly more accessible to deuterium uptake allowing it to accept GTP and mediating complex dissociation. Thus, we provide direct evidence that in the critical step of signal amplification, Rho(∗) and G(t) exhibit dissimilar conformational changes when they are coupled in the (Rho(∗))(2)-G(t) complex.
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