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Conformation changes of cuttlefish (Euprymna morsei) rhodopsin following photoconversion
K Hiraki1, T Hamanaka, M Seidou
1Department of Biology, Faculty of Science, Osaka University, Japan.
Biochimica Et Biophysica Acta
|April 29, 1991
Summary
Cuttlefish rhodopsin undergoes conformational changes upon light exposure, indicated by increased radius of gyration and altered charge distribution. These findings reveal structural shifts in the visual pigment after photoconversion.
Area of Science:
- Biochemistry
- Structural Biology
- Vision Science
Background:
- Cuttlefish rhodopsin is a visual pigment crucial for light detection.
- Photoconversion of rhodopsin to its metarhodopsin form involves significant structural alterations.
Purpose of the Study:
- To investigate conformational changes in Euprymna morsei rhodopsin after photoconversion to acid metarhodopsin.
- To compare the structural and charge properties of rhodopsin and its photoproduct.
Main Methods:
- Small-angle X-ray scattering (SAXS) was used to analyze structural changes.
- Chromatofocusing determined changes in isoelectric points (pI).
- Spectroscopic studies confirmed high conversion rates to the meta form.
Main Results:
- A 1.5% increase in the radius of gyration was observed from rhodopsin to acid metarhodopsin.
- Significant changes in the distribution function and secondary peak intensities were detected.
- Acid metarhodopsin showed a lower pI (5.06) compared to rhodopsin (5.32), indicating carboxyl group dissociation.
Conclusions:
- Photoconversion induces monomeric conformational changes in the cuttlefish rhodopsin-detergent complex.
- Charge redistribution and altered protein mass distribution occur following illumination.
- These structural shifts are key to understanding visual pigment function.