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A novel photointermediate of octopus rhodopsin activates its G‐protein
Author(s) -
Nakagawa Masashi,
Kikkawa Satoshi,
Tominaga Kayo,
Tsugi Naoko,
Tsuda Motoyuki
Publication year - 1998
Publication title -
febs letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.593
H-Index - 257
eISSN - 1873-3468
pISSN - 0014-5793
DOI - 10.1016/s0014-5793(98)01138-7
Subject(s) - rhodopsin , octopus (software) , gtp' , biophysics , g protein , chemistry , biochemistry , microbiology and biotechnology , biology , signal transduction , retinal , enzyme , computational chemistry
The photointermediate of octopus rhodopsin responsible for G‐protein activation was examined by a GTPγS‐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 GTPγS‐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.