Synthesis of a Photoaffinity-Labeled (11Z)-Retinal: Identification of Retinal/Rhodopsin Cross-Linked Sites along the Visual-Transduction Path
                                
                                    
                                        作者:Maria L. Souto、Joann Um、Babak Borhan、Koji Nakanishi                                    
                                    
                                        DOI:10.1002/1522-2675(20000906)83:9<2617::aid-hlca2617>3.0.co;2-9
                                    
                                    
                                        日期:2000.9.6
                                    
                                    The retinal chromophore (11Z)-3-diazo-4-oxoretinal (1) with two photo-labile moieties has been synthesized by semi-hydrogenation of an 11-yne precursor with activated Zn in aqueous media. Incorporation of 1 into opsin yielded diazoketo rhodopsin (DK-Rh), which, upon bleaching, gave rise to intermediates batho-Rh, lumi-Rh, meta-Rh, and meta-II-Rh corresponding to those of native Rh but at lower temperatures. Photoaffinity labeling of DK-Rh and these bleaching intermediates showed that the ionone ring cross-linked to Trp265 of helix F in DK-Rh and bathe intermediate, and to Ala169 of helix D in lumi, meta-I, and meta-II intermediates. These results demonstrate the occurrence of large conformational changes along the visual transduction path, which, in turn, is responsible for activation of the G-protein.