Specific photoisomerization of retinal in squid rhodopsin and metarhodopsin.
The composition of retinal isomers in the photosteady-state mixtures formed from squid rhodopsin and metarhodopsin was determined by high-pressure liquid chromatography. A large amount of 9-cis-retinal was obtained at liquid N2 temperature when rhodopsin was irradiated with orange light, but only small quantities of 9-cis-retinal were obtained at 15 degrees C. Scarcely any 9-cis-retinal was produced from metarhodopsin by irradiation at liquid N2 temperature. A large quantity of 7-cis-retinal was found in the photoproduct of rhodopsin irradiated at solid carbon dioxide temperature, but not at 15 degrees C and liquid N2 temperature. 7-cis-Retinal was not produced from metarhodopsin at any temperatures. These results indicate that the photoisomerization of retinal is regulated by the structure of the retinal-binding site of this protein. The formation of 9-cis- and 7-cis-retinals is forbidden in the metarhodopsin protein.
D000818:Animals; D049832:Decapodiformes / Q000032:analysis*; D008027:Light; D011487:Protein Conformation; D012168:Retinal Pigments / Q000528:radiation effects*; D012172:Retinaldehyde / Q000528:radiation effects*; D012243:Rhodopsin / Q000031:analogs & derivatives / Q000528:radiation effects*; D013057:Spectrum Analysis; D013237:Stereoisomerism; D013696:Temperature; D014801:Vitamin A / Q000031:analogs & derivatives*
D012168:Retinal Pigments; D014801:Vitamin A; C013110:metarhodopsins; D012243:Rhodopsin; D012172:Retinaldehyde