title: Role of noncovalent binding of 11-cis-retinal to opsin in dark adaptation of rod and cone photoreceptors.
abstract: Regeneration of visual pigments of vertebrate rod and cone photoreceptors occurs by the initial noncovalent binding of 11-cis-retinal to opsin, followed by the formation of a covalent bond between the ligand and the protein. Here, we show that the noncovalent interaction between 11-cis-retinal and opsin affects the rate of dark adaptation. In rods, 11-cis-retinal produces a transient activation of the phototransduction cascade that precedes sensitivity recovery, thus slowing dark adaptation. In cones, 11-cis-retinal immediately deactivates phototransduction. Thus, the initial binding of the same ligand to two very similar G protein receptors, the rod and cone opsins, activates one and deactivates the other, contributing to the remarkable difference in the rates of rod and cone dark adaptation.
authors: Department of Physiology, Boston University School of Medicine, 715 Albany Street, Boston, MA 02118, USA. vkefalov@jhmi.edu
authors: V J
authors: VJ
authors: Kefalov
authors: R K
authors: RK
authors: Crouch
authors: M C
authors: MC
authors: Cornwall
mesh_terms: D015106:3',5'-Cyclic-GMP Phosphodiesterases / Q000378:metabolism; D000557:Ambystoma; D000818:Animals; D003623:Dark Adaptation / Q000502:physiology*; D004789:Enzyme Activation / Q000187:drug effects; D006162:Guanylate Cyclase / Q000378:metabolism; D007700:Kinetics; D010786:Photoreceptor Cells / Q000187:drug effects / Q000502:physiology*; D020419:Photoreceptor Cells, Vertebrate / Q000187:drug effects / Q000502:physiology*; D012172:Retinaldehyde / Q000378:metabolism* / Q000494:pharmacology; D017299:Rod Opsins / Q000378:metabolism*; D014785:Vision, Ocular
chemical_list: D017299:Rod Opsins; D015106:3',5'-Cyclic-GMP Phosphodiesterases; D006162:Guanylate Cyclase; D012172:Retinaldehyde