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Updated: May 29, 2026

A Rhodopsin Transport Assay by High-Content Imaging Analysis
Published on: January 16, 2019
Rhodopsin-transducin heteropentamer: three-dimensional structure and biochemical characterization
Beata Jastrzebska1, Philippe Ringler, David T Lodowski
1Department of Pharmacology, School of Medicine, Case Western Reserve University, Cleveland, OH 44106-4965, USA. bxj27@case.edu
None:
The process of vision is initiated when the G protein-coupled receptor, rhodopsin (Rho), absorbs a photon and transitions to its activated Rho(∗) form. Rho(∗) binds the heterotrimeric G protein, transducin (G(t)) inducing GDP to GTP exchange and G(t) dissociation. Using nucleotide depletion and affinity chromatography, we trapped and purified the resulting nucleotide-free Rho(∗)·G(t) complex. Quantitative SDS-PAGE suggested a 2:1 molar ratio of Rho(∗) to G(t) in the complex and its mass determined by scanning transmission electron microscopy was 221±12kDa. A 21.6Å structure was calculated from projections of negatively stained Rho(∗)·G(t) complexes. The molecular envelope thus determined accommodated two Rho molecules together with one G(t) heterotrimer, corroborating the heteropentameric structure of the Rho(∗)·G(t) complex.
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