The Transitory Complexes Between Photoexcited Rhodopsin and Transducin. Biochemical and Spectroscopic Studies
In the first step of the visual transduction cascade, photoexcited rhodopsin (R*ret) binds to a GDP-carrying transducin (TGDP), allowing the release of the GDP from its site on T. We obtained a R*ret-Te complex (ret for retinal present, e for nucleotide site empty), undissociable almost indefinitely in a medium with physiological ionic strength. In this complex, rhodopsin is totally locked in the Meta-II conformation (R*ret). Incubation in a low ionic strength medium partially dissociates Te (probably a denatured form of transducin). In the presence of GDP, a R*ret-TGDP complex is obtained. TGDP appears to have a high binding affinity to R*ret in physiological ionic conditions. We show that the binding of Te or TGDP on cytoplasmic loops of rhodopsin induces different retroactions on the retinal site in rhodopsin.
KeywordsSedimentation Trypsin Turbidity Hepes Bleached
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- Bruckert,F. (1989) Thesis, University of GrenobleGoogle Scholar