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Cyclic GMP and photoreceptor function
Author(s) -
Lolley Richard N.,
Lee Rehwa H.
Publication year - 1990
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.4.12.1697545
Subject(s) - transducin , visual phototransduction , rhodopsin , biophysics , phosphodiesterase , chemistry , photoreceptor cell , hyperpolarization (physics) , heterotrimeric g protein , g protein , biology , biochemistry , retinal , signal transduction , stereochemistry , nuclear magnetic resonance spectroscopy , enzyme
A single photon can be detected by a rod photoreceptor cell. The absorption of light by rhodopsin triggers a cascade of reactions that amplifies the photon signal and results in ion channel closure with hyperpolarization of the rod photoreceptor cell. Light‐induced conformational changes in rhodopsin facilitate the binding of a guanosine nucleotide‐binding protein, transducin, which then undergoes aGTP‐GDP exchange reaction and dissociation of the transducin complex. A subunit of transducin then activates a phosphodiesterase complex that hydrolyzes cyclic GMP. In darkness, cyclic GMP binds to cation channels of the photoreceptor plasma membrane, maintaining them in an open configuration. The light‐induced reduction in cyclic GMP concentration dissociates the bound cyclic GMP, resulting in channel closure and hyperpolarization. Down‐regulation of the cascade involves other proteins that block the interaction of transducin with rhodopsin and another protein that may interfere with transducin recycling. Cone photoreceptors possess a light‐activated cascade that follows the rod format, but it is composed of proteins that are homologous to those of rod photoreceptors. Phototransduction in invertebrate photoreceptors uses rhodopsin to activate a cascade that uses phosphoinositides and calcium ion to regulate membrane polarization.— L olley , R. N.; L ee , R. H. Cyclic GMP and photoreceptor function. FASEB J. 4: 3001‐3008; 1990.