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Biophysical and structural analysis of human green cone opsin
Weekie Yao1, Jonathan F Fay2, David L Farrens1
1Department of Chemical Physiology and Biochemistry, Oregon Health & Science University, Portland, Oregon.
Biophysical Journal
|March 15, 2026
Summary
Researchers developed a new method to study human green cone opsin (GCO) and its mutants. This work reveals key insights into GCO
Area of Science:
- Biochemistry
- Structural Biology
- Vision Science
Background:
- Human green cone opsin (GCO) plays a crucial role in color vision.
- Understanding GCO's structure and function is vital for vision research.
- Previous studies faced challenges in GCO purification and optimization.
Purpose of the Study:
- To develop a streamlined method for purifying and optimizing human green cone opsin (GCO).
- To investigate the biophysical and structural properties of a GCO mutant (GCOE129Q).
- To elucidate the structural basis of GCO activation and G protein signaling.
Main Methods:
- Developed a straightforward purification and optimization workflow for GCO.
- Utilized biophysical techniques to study GCOE129Q.
- Determined the cryo-electron microscopy (cryo-EM) structure of an active GCOE129Q-G protein complex.
Main Results:
- Residue E129 in dark-state GCO is critical for long-wavelength light absorption.
- GCOE129Q exhibits a lower Schiff-base pKa compared to rhodopsin.
- Light-activated GCOE129Q shows altered decay kinetics and enhanced G protein activation.
- The cryo-EM structure reveals similarities and differences between active GCO and rhodopsin architectures.
Conclusions:
- Established a generalizable and streamlined approach for cone opsin biophysical and structural studies.
- Provided novel mechanistic insights into GCO activation and signaling.
- Highlighted the distinct electrostatic environment at the retinal attachment site in GCO compared to rhodopsin.
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