LIGHT DAMAGING ACTION OF ALL-m4WS-RETINAL AND ITS DERIVATIVES TO THE RHODOPSIN MOLECULE WITHIN THE PHOTORECEPTOR MEMBRANE
The last stage of rhodopsin photolysis culminates in hydrolysis of the aldimine bond of the Schiff base to release all-trans retinal into the lipid membrane phase. In membrane, all-trans-retinal reacts with accessible amino groups of rhodopsin and phospholipids forming derivatives such as A2-rhodopsin, NR-PE (N-retinylidene-phosphatidylethanolamine), A2-PE (N-bis-retinylidene-phosphatidylethanolamine) and ATR-dimer-PE (Fishkin, N. et al (2003) Org. Biomol. Chem., 1, 1101-1105.; Fishkin, N. et al (2005) PNAS, 102, 7091-7096.) Following the first of these papers, we have reproduced the same model system containing these products, in order to study photosensitized damage to rhodopsin within photoreceptor membranes of rod outer segments. We have demonstrated that irradiation of such a system with visible light (400-700 nm) distorts the most important functional property of native visual pigment - its ability to regenerate after adding 11-cis-retinal in the dark. We have also shown that all-ftww-retinal bound to membrane phospholipids and rhodopsin exerts less photosensitizing activity than that of free all-trans-retinal.