Click here to close
Hello! We notice that you are using Internet Explorer, which is not supported by Xenbase and may cause the site to display incorrectly.
We suggest using a current version of Chrome,
FireFox, or Safari.
???displayArticle.abstract???
Retinal rods and cones share a phototransduction pathway involving cyclic GMP. Cones are typically 100 times less photosensitive than rods and their response kinetics are several times faster, but the underlying mechanisms remain largely unknown. Almost all proteins involved in phototransduction have distinct rod and cone variants. Differences in properties between rod and cone pigments have been described, such as a 10-fold shorter lifetime of the meta-II state (active conformation) of cone pigment and its higher rate of spontaneous isomerization, but their contributions to the functional differences between rods and cones remain speculative. We have addressed this question by expressing human or salamander red cone pigment in Xenopus rods, and human rod pigment in Xenopus cones. Here we show that rod and cone pigments when present in the same cell produce light responses with identical amplification and kinetics, thereby ruling out any difference in their signalling properties. However, red cone pigment isomerizes spontaneously 10,000 times more frequently than rod pigment. This high spontaneous activity adapts the native cones even in darkness, making them less sensitive and kinetically faster than rods. Nevertheless, additional factors are probably involved in these differences.
Baylor,
Photoreceptor signals and vision. Proctor lecture.
1987, Pubmed
Baylor,
Photoreceptor signals and vision. Proctor lecture.
1987,
Pubmed Baylor,
Two components of electrical dark noise in toad retinal rod outer segments.
1980,
Pubmed Bowmaker,
Visual pigments of rods and cones in a human retina.
1980,
Pubmed Govardovskii,
In search of the visual pigment template.
2000,
Pubmed
,
Xenbase Hárosi,
An analysis of two spectral properties of vertebrate visual pigments.
1994,
Pubmed Hárosi,
Absorption spectra and linear dichroism of some amphibian photoreceptors.
1975,
Pubmed Imai,
Difference in molecular properties between chicken green and rhodopsin as related to the functional difference between cone and rod photoreceptor cells.
1995,
Pubmed Imai,
Photochemical and biochemical properties of chicken blue-sensitive cone visual pigment.
1997,
Pubmed Katz,
The statistical nature of the acetycholine potential and its molecular components.
1972,
Pubmed Kroll,
Transgenic Xenopus embryos from sperm nuclear transplantations reveal FGF signaling requirements during gastrulation.
1996,
Pubmed
,
Xenbase Lyubarsky,
Mice lacking G-protein receptor kinase 1 have profoundly slowed recovery of cone-driven retinal responses.
2000,
Pubmed Ma,
A visual pigment expressed in both rod and cone photoreceptors.
2001,
Pubmed Makino,
Spectral tuning in salamander visual pigments studied with dihydroretinal chromophores.
1999,
Pubmed Merbs,
Absorption spectra of human cone pigments.
1992,
Pubmed Miller,
Differences in transduction between rod and cone photoreceptors: an exploration of the role of calcium homeostasis.
1994,
Pubmed Miller,
Phototransduction and adaptation in rods, single cones, and twin cones of the striped bass retina: a comparative study.
1993,
Pubmed Moritz,
A functional rhodopsin-green fluorescent protein fusion protein localizes correctly in transgenic Xenopus laevis retinal rods and is expressed in a time-dependent pattern.
2001,
Pubmed
,
Xenbase Nakatani,
Sodium-dependent calcium extrusion and sensitivity regulation in retinal cones of the salamander.
1989,
Pubmed Okada,
Circular dichroism of metaiodopsin II and its binding to transducin: a comparative study between meta II intermediates of iodopsin and rhodopsin.
1994,
Pubmed Palacios,
Spectral and polarization sensitivity of photocurrents of amphibian rods in the visible and ultraviolet.
1998,
Pubmed
,
Xenbase Rieke,
Origin and functional impact of dark noise in retinal cones.
2000,
Pubmed Rieke,
Molecular origin of continuous dark noise in rod photoreceptors.
1996,
Pubmed Sampath,
Molecular mechanism of spontaneous pigment activation in retinal cones.
2002,
Pubmed Starace,
Activation of transducin by a Xenopus short wavelength visual pigment.
1997,
Pubmed
,
Xenbase Tachibanaki,
Low amplification and fast visual pigment phosphorylation as mechanisms characterizing cone photoresponses.
2001,
Pubmed Wang,
A locus control region adjacent to the human red and green visual pigment genes.
1992,
Pubmed Witkovsky,
A microspectrophotometric study of normal and artificial visual pigments in the photoreceptors of Xenopus laevis.
1981,
Pubmed
,
Xenbase Yau,
Phototransduction mechanism in retinal rods and cones. The Friedenwald Lecture.
1994,
Pubmed
