 | A Mechanism of Photo-Activation of Rhodopsin
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| | Masaji Ishiguro1), Takahiro Hirano2), In Tek Lim1), Don Moon Kim1), Kazuo Yoshihara1) and Yoshinori Shichida2) |
| 1) Suntory Institute for Bioorganic Research
2) Department of Biophysics, Kyoto University |
| | The photo-isomerization of the retinylidene chromophore and the process of thermal relaxation of its strained conformation were examined by restrained molecular dynamic simulations in the transmembrane model of rhodopsin. This model was constructed based on the crystal structure of rhodopsin. The photo-conversion process from the 11-cis-retinylidene chromophore to the all-trans chromophore was traced by simultaneous rotation of the adjacent C12-C13 bond, leading to an all-trans chromophore having a twisted conformation at the C11-C12 and C12-C13 bonds for the bathorhodopsin chromophore. In accord with the characteristic CD signals at 500 and 540 nm, the retinylidene chromophore of rhodopsin and bathorhodopsin showed characteristic right-handed and left-handed helical conformations, respectively. The photo-isomerization of the 9-cis-retinylidene chromophores with a trans C11-C12 double bond-locked structure and an s-trans C12-C13 bond-locked structure suggested an importance of the structural change of opsin in the formation of pigments. |
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