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. Author manuscript; available in PMC: 2016 Nov 9.
Published in final edited form as: Angew Chem Int Ed Engl. 2015 Sep 18;54(46):13555–13560. doi: 10.1002/anie.201505798

Figure 1.

Figure 1

Mammalian visual cycle. The concentration of all-trans-retinal (ATR) is dependent on two processes: i) retinal release during the photocycle in the rod outer segment (ROS) and ii) retinal removal by a regeneration pathway in the retinal pigment epithelium (RPE) as schematically shown on the left. Continuous exposure to light leads to the accumulation of ATR (right, top), which initiates rhodopsin deactivation by arrestin (arr). Arrestin binding slows down the retinal release, which gives ample time to retinal dehydrogenase (RDH) to remove excess ATR by converting it to all-trans-retinol (right, bottom).