Most vertebrate retinas contain a single type of rod for scotopic vision and multiple types of cones for photopic and color vision. The retinas of certain amphibian species uniquely contain two types of rods: red rods, which express rhodopsin, and green rods, which express a blue-sensitive cone pigment (M1/SWS2 group). Spontaneous activation of rhodopsin induced by thermal isomerization of the ...

Phototransduction in cones differs significantly from that in rods in sensitivity, kinetics, and recovery following exposure to light. The contribution that the visual pigment makes in determining the cone response was investigated biochemically by expressing a Xenopus violet cone opsin (VCOP) cDNA in COS1 cells and assaying the light-dependent activation of transducin. Light-exposed VCOP stimu...

The bleaching and regeneration of rhodopsin in the living cat retina was studied by means of fundus reflectometry. Bleaching was effected by continuous light exposures of 1 min or 20 min, and the changes in retinal absorbance were measured at 29 wavelengths. For all of the conditions studied (fractional bleaches of from 65 to 100%), the regeneration of rhodopsin to its prebleach levels required...

The composition of the lipid matrix is critical for function of membrane proteins. Perhaps one of the best studied examples is the function of the G-protein-coupled membrane receptor (GPCR) rhodopsin which is located in membranes with high content of phospholipids with polyunsaturated docosahexaenoic acid chains (DHA, 22:6n-3). Technological advances enabled a more detailed study of structure a...

Upon absorption of light, the retinal chromophore in rhodopsin isomerizes from the 11-cis to the trans configuration, initiating a photoreaction cycle. The primary photoreaction state, bathorhodopsin (BATHO), relaxes thermally through lumirhodopsin (LUMI) into a photoactive state, metarhodopsin (META), which stimulates the conjugated G-protein. Previous crystallographic studies of squid and bov...

Rhodopsins are the major photopigments in the fruit fly Drosophila melanogaster. Drosophila express six well-characterized Rhodopsins (Rh1-Rh6) with distinct absorption maxima and expression pattern. In 2000, when the Drosophila genome was published, a novel Rhodopsin gene was discovered: Rhodopsin 7 (Rh7). Rh7 is highly conserved among the Drosophila genus and is also found in other arthropods...

TAT rhodopsin extracted from the marine bacterium SAR11 HIMB114 has a characteristic Thr-Ala-Thr motif and contains both protonated deprotonated states of Schiff base at physiological pH conditions due to low pKa. Here, using solid-state NMR spectroscopy, we investigated 13C 15N signals retinal in only state 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphoethanolamine/1-palmitoyl-2-oleoyl-sn-glycero-3...

We have recently described the synthesis of rhodopsin in a solution containing four components: vitamin A, the precursor of the rhodopsin chromophore; opsin, the protein of rhodopsin; and liver alcohol dehydrogenase and cozymase, the enzyme and coenzyme which oxidize vitamin A to retinene (Hubbard and Wald, 1951). 1 This experiment was first performed with a fish liver 0il concentrate as the so...

PURPOSE The goal of this study was to evaluate the effect of oxygen deprivation on rhodopsin regeneration in the excised mouse eye. METHODS A new preparation for studying rhodopsin regeneration with a superfused excised albino mouse eye was developed. The preparation exhibits multiple regenerations after moderate bleaches (15%-20%) and is sensitive to the composition of the perfusate, allowin...

The effect of cholesterol on rod outer segment disk membrane structure and rhodopsin activation was investigated. Disk membranes with varying cholesterol concentrations were prepared using methyl-beta-cyclodextrin as a cholesterol donor or acceptor. Cholesterol exchange followed a simple equilibrium partitioning model with a partition coefficient of 5.2 +/- 0.8 in favor of the disk membrane. Re...