Nakagawa M, Kikkawa S, Tominaga K, Tsugi N, Tsuda M
Department of Life Science, Himeji Institute of Technology, Harima Science Garden City, Hyogo, Japan.
FEBS Lett. 1998 Oct 2;436(2):259-62. doi: 10.1016/s0014-5793(98)01138-7.
The photointermediate of octopus rhodopsin responsible for G-protein activation was examined by a GTPgammaS-binding assay in a reconstituted system with purified rhodopsin and photoreceptor G-protein. When octopus rhodopsin alone was incubated in the dark after illumination, its ability to stimulate GTPgammaS-binding by the G-protein decreased in a time-dependent manner. We associate this decay with the decay of a novel photointermediate, transient acid metarhodopsin, which lies between mesorhodopsin and acid metarhodopsin. Spectroscopic evidence for its existence was suggested by its effects on the turbidity of the vesicles. These results suggest that the transient acid metarhodopsin, not the stable final photoproduct, acid metarhodopsin, activates a G-protein in octopus photoreceptors.
在由纯化的视紫红质和光感受器G蛋白组成的重构系统中，通过GTPγS结合试验检测了负责激活G蛋白的章鱼视紫红质的光中间体。光照后在黑暗中单独孵育章鱼视紫红质时，其刺激G蛋白结合GTPγS的能力随时间呈下降趋势。我们将这种衰减与一种新型光中间体——瞬态酸性视紫红质的衰减联系起来，瞬态酸性视紫红质介于中视紫红质和酸性视紫红质之间。其对囊泡浊度的影响提示了其存在的光谱学证据。这些结果表明，在章鱼光感受器中，激活G蛋白的是瞬态酸性视紫红质，而非稳定的最终光产物酸性视紫红质。
