Structure around C6-C7 bond of the chromophore in bathorhodopsin: low-temperature spectroscopy of 6s-cis-locked bicyclic rhodopsin analogs.
To elucidate the structural changes near the beta-ionone ring region of the chromophore during the photobleaching process of rhodopsin, the photochemical and subsequent thermal reactions of rhodopsin analogs, whose retinylidene chromophores were fixed in a 6s-cis form with a five-membered ring (6,5-rhodopsin) and a seven-membered ring (6,7-rhodopsin), respectively, were investigated by low-temperature spectroscopy. Like rhodopsin, both the rhodopsin analogs convert to the respective batho-intermediates upon absorption of light at -190 degrees C. The extinction coefficient of batho-intermediate of 6,5-rhodopsin is similar to that of bathorhodopsin, while that of 6,7-rhodopsin is considerably smaller than that of bathorhodopsin. Like bathorhodopsin, the batho-intermediate of 6,5-rhodopsin directly converts to lumi-intermediate, while that of 6,7-rhodopsin first converts to a blue-shifted intermediate and then to lumi-intermediate. These results strongly suggest that the structure around the beta-ionone ring region of the bathorhodopsin chromophore resembles 6,5-retinal rather than 6,7-retinal. From the comparison of the structural features among retinal, 6,5-retinal, and 6,7-retinal, a possible conformation around C6-C7 bond of the bathorhodopsin chromophore is discussed.
Imamoto
Y
Y
Department of Biophysics, Faculty of Science, Kyoto University, Japan.
Sakai
M
M
Katsuta
Y
Y
Wada
A
A
Ito
M
M
Shichida
Y
Y
D000818:Animals; D002417:Cattle; D003080:Cold Temperature; D008968:Molecular Conformation; D015394:Molecular Structure; D010777:Photochemistry; D012172:Retinaldehyde / Q000737:chemistry; D012243:Rhodopsin / Q000031:analogs & derivatives* / Q000737:chemistry* / Q000528:radiation effects; D013053:Spectrophotometry
C015017:bathorhodopsin; D012243:Rhodopsin; D012172:Retinaldehyde