7,8-Dihydro Retinals Outperform the Native Retinals in Conferring Photosensitivity to Visual Opsin

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• 作者：Willem J. DeGrip ; Petra H.M. Bovee-Geurts ; Ineke van der Hoef ; Johan Lugtenburg
• 刊名：Journal of the American Chemical Society
• 出版年：2007
• 出版时间：October 31, 2007
• 年：2007
• 卷：129
• 期：43
• 页码：13265 - 13269
• 全文大小：153K
• 年卷期：v.129,no.43(October 31, 2007)
• ISSN：1520-5126

文摘

The visual pigment rhodopsin presents an astonishing photochemical performance. It exhibitsan unprecedented quantum yield (0.67) in a highly defined and ultrafast photoisomerization process. Thistriggers the conformational changes leading to the active state Meta II of this G protein-coupled receptor.The responsible ligand, retinal, is covalently bound to Lys-296 of the protein in a protonated Schiff base.The resulting positive charge delocalization over the terminal part of the polyene chain of retinal creates aconjugation defect that upon photoexcitation moves to the opposite end of the polyene. Shortening thepolyene as in 5,6-dihydro- or 7,8-dihydro analogues might facilitate photoisomerization of a 9-Z and an11-Z bond. Here we describe pigment analogues generated with bovine opsin and 11-Z 7,8-dihydro retinalor 9-Z 7,8-dihydro retinal. Both isomers readily generate photosensitive pigments that differ remarkably inspectral properties from the native pigments. In addition, in spite of the more flexible 7,8 single bond, bothanalogue pigments exhibit strikingly efficient photoisomerization while largely maintaining the activity towardthe G-protein. These results bear upon the activation of ligand-gated signal transducers such as G protein-coupled receptors.