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A methyl group at C7 of 11-cis-retinal allows chromophore formation but affects rhodopsin activation
Laia Bosch1, Arnau Cordomí, Marta Domínguez
1Departament d'Enginyeria Química, Universitat Politècnica de Catalunya, 08222 Terrassa, Catalonia, Spain.
Abstract:
The newly synthesized 11-cis-7-methylretinal can form an artificial visual pigment with kinetic and spectroscopic properties similar to the native pigment in the dark-state. However, its photobleaching behavior is altered, showing a Meta I-like photoproduct. This behavior reflects a steric constraint imposed by the 7-methyl group that affects the conformational change in the binding pocket as a result of retinal photoisomerization. Transducin activation is reduced, when compared to the native pigment with 11-cis-retinal. Molecular dynamics simulations suggest coupling of the C7 methyl group and the beta-ionone ring with Met207 in transmembrane helix 5 in agreement with recent experimental results.
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