Deactivation of Rhodopsin in the Transition from the Signaling State Meta II to Meta III Involves a Thermal Isomerization of the Retinal Chromophore CN Double Bond

• DOI: 10.1021/bi034684+
• Publication Date: 2003-08-19T05:01:05Z
• Authors: Reiner Vogel; Friedrich Siebert; Gerald Mathias; Paul Tavan; Guibao Fan; Mordechai Sheves
• Keywords: Chromophore; Opsin

Light-induced isomerization of rhodopsin's retinal chromophore to the activating all-trans geometry initializes formation active receptor state, Meta II. In absence peripheral regulatory proteins, activity II is switched off spontaneously by two independent pathways: either hydrolysis Schiff base and dissociation light into apoprotein opsin plus free or III, an inactive species with intact protonated absorbing at 470 nm. By FTIR spectroscopy on rhodopsin reconstituted isotopically labeled chromophores in combination quantum mechanical DFT calculations, we show that deactivating step during III involves a thermal C[double bond]N, such all-trans-15-syn. This catalyzed protein environment proceeds via I, as suggested its dependence pH properties lipid/detergent protein. long term, decays likewise slow base.