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A photosensitive rhodopsin-regenerating system in the crayfish retina
Abstracts
PHOTOENERGETICS OF OCTOPUS RHODOPSIN ALAN COOPER, SHEILA F. MUNN a n d MOTOYUKI TSUDA* Chemistry Department, Glasgow University, Glasgow GI2 8QQ, Scotland Despite similarities between vertebrate and cephalopod visual pigments there are interesting differences in the photolysis sequences, especially in the later stages. Direct energy measurements of the various steps in the bleaching of bovine rhodopsin have helped to clarify some of the molecular mechanisms involved. We have now embarked on a similar comparative study of the energetics of octopus rhodopsin in microvilli membranes. Preliminary results and interpretations will be reported. *Department of Physics, Sapporo Medical College, Sapporo 060, Japan.
A PHOTOSENSITIVE RHODOPSIN-REGENERATING SYSTEM IN THE CRAYFISH RETINA T. W. CRONIN a n d T. H. GOLDSMITH Department of Biology, Yale University, New Haven, CT 06511, U.S.A. We followed the in vivo dark regeneration of rhodopsin in crayfish photoreceptors following intense light adaptation, by measuring fluorescence of metarhodopsin in samples of isolated rhabdoms. Adaptation to blue light (450 nm) causes a net conversion of 55~ rhodopsin to metarhodopsin, after which the recovery to 100~ rhodopsin requires about 36hr in the dark. In contrast, orange-light adaptation (>500 nm) produces 75~ metarhodopsin, and full recovery requires up to a week. This lengthened recovery time is not a result of damage to the photoreceptor, for if the orange-light exposure is followed with an immediate exposure to blue light, recovery time is reduced to 36 hr. However, if orange light follows blue, the lengthened recovery time characteristic of adaptation to orange alone is observed. Prolonged recovery is not caused solely by the 20~ greater content of metarhodopsin in orange-adapted receptors. Exposing the orange-adapted eye to blue light 15 hr after the orange exposure, when rhodopsin content has been restored to about 45~, causes no net change in metarhodopsin content, but it substantially shortens subsequent recovery. These results indicate that the crayfish eye possesses a photosensitive system for regenerating rhodopsin that is activated by blue light and inactivated by orange.
EXAMINATION OF RETINOCHROME A N D RHODOPSIN IN THE GASTROPOD RETINA KOICHI OZAKI, REIKO HARA a n d TOMIYUKI HARA Department of Biology, Faculty of Science, Osaka University, Toyonaka, Osaka 560, Japan Retinal location of retinochrome and rhodopsin was studied in the red-mouthed conch, Conomulex luhuanus.
Retinochrome is readily reduced by NaBH 4 into an N-retinyl protein that emits yellow-green fluorescence on irradiation with near-u.v, light. Rhodopsin is also converted to a similar fluorescent product, but only when denatured with HCHO and CH3OH before reduction. Based upon this difference, retinochrome was discriminated from rhodopsin on a frozen section of the eye. The band of yellow-green fluorescence due to reduced rhodopsin appeared along the internal side of the layer of black pigment, whereas that of reduced retinochrome was observed in the area just outside of the layer of black pigment. In this area, the photic vesicles were abundantly present, according to electron microscopy. The homogenate of the eye was suspended in 40~ sucrose and centrifuged to obtain two fractions, the rhabdomal parts floated and the debris sedimented. The isomers of retinal in each fraction were converted to retinal oxime and then analyzed by HPLC. The former mainly contained the 11-cis isomer (rhodopsin), whereas the latter contained the mixture of all-trans and 11-cis forms. After irradiation of the debris with orange light, the all-trans isomer decreased and the l l-cis increased, suggesting the presence of retinochrome.
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PHOTOENERGETICS OF OCTOPUS RHODOPSIN ALAN COOPER, SHEILA F. MUNN a n d MOTOYUKI TSUDA* Chemistry Department, Glasgow University, Glasgow GI2 8QQ, Scotland Despite similarities between vertebrate and cephalopod visual pigments there are interesting differences in the photolysis sequences, especially in the later stages. Direct energy measurements of the various steps in the bleaching of bovine rhodopsin have helped to clarify some of the molecular mechanisms involved. We have now embarked on a similar comparative study of the energetics of octopus rhodopsin in microvilli membranes. Preliminary results and interpretations will be reported. *Department of Physics, Sapporo Medical College, Sapporo 060, Japan.
A PHOTOSENSITIVE RHODOPSIN-REGENERATING SYSTEM IN THE CRAYFISH RETINA T. W. CRONIN a n d T. H. GOLDSMITH Department of Biology, Yale University, New Haven, CT 06511, U.S.A. We followed the in vivo dark regeneration of rhodopsin in crayfish photoreceptors following intense light adaptation, by measuring fluorescence of metarhodopsin in samples of isolated rhabdoms. Adaptation to blue light (450 nm) causes a net conversion of 55~ rhodopsin to metarhodopsin, after which the recovery to 100~ rhodopsin requires about 36hr in the dark. In contrast, orange-light adaptation (>500 nm) produces 75~ metarhodopsin, and full recovery requires up to a week. This lengthened recovery time is not a result of damage to the photoreceptor, for if the orange-light exposure is followed with an immediate exposure to blue light, recovery time is reduced to 36 hr. However, if orange light follows blue, the lengthened recovery time characteristic of adaptation to orange alone is observed. Prolonged recovery is not caused solely by the 20~ greater content of metarhodopsin in orange-adapted receptors. Exposing the orange-adapted eye to blue light 15 hr after the orange exposure, when rhodopsin content has been restored to about 45~, causes no net change in metarhodopsin content, but it substantially shortens subsequent recovery. These results indicate that the crayfish eye possesses a photosensitive system for regenerating rhodopsin that is activated by blue light and inactivated by orange.
EXAMINATION OF RETINOCHROME A N D RHODOPSIN IN THE GASTROPOD RETINA KOICHI OZAKI, REIKO HARA a n d TOMIYUKI HARA Department of Biology, Faculty of Science, Osaka University, Toyonaka, Osaka 560, Japan Retinal location of retinochrome and rhodopsin was studied in the red-mouthed conch, Conomulex luhuanus.
Retinochrome is readily reduced by NaBH 4 into an N-retinyl protein that emits yellow-green fluorescence on irradiation with near-u.v, light. Rhodopsin is also converted to a similar fluorescent product, but only when denatured with HCHO and CH3OH before reduction. Based upon this difference, retinochrome was discriminated from rhodopsin on a frozen section of the eye. The band of yellow-green fluorescence due to reduced rhodopsin appeared along the internal side of the layer of black pigment, whereas that of reduced retinochrome was observed in the area just outside of the layer of black pigment. In this area, the photic vesicles were abundantly present, according to electron microscopy. The homogenate of the eye was suspended in 40~ sucrose and centrifuged to obtain two fractions, the rhabdomal parts floated and the debris sedimented. The isomers of retinal in each fraction were converted to retinal oxime and then analyzed by HPLC. The former mainly contained the 11-cis isomer (rhodopsin), whereas the latter contained the mixture of all-trans and 11-cis forms. After irradiation of the debris with orange light, the all-trans isomer decreased and the l l-cis increased, suggesting the presence of retinochrome.
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