Studies on a Missing Reaction in the Visual Cycle


DEVELOPMENT in the biochemistry of vision during the past twenty-five years can be summarized by equations (1) and (2) in Fig. 1, which envisage1 that 11-cis-retinal combines with the visual protein opsin in a dark reaction to form the photolabile complex rhodopsin, λmax 497 nm. When rhodopsin absorbs light it stimulates, through a process whose mechanism is not understood, the transmission of impulses, which are responsible for the visual sensation, although much is known about the biochemical changes accompanying the absorption of light by rhodopsin. These changes culminate in the formation of all-trans-retinal (λmax 385 nm) and opsin (equation (2), Fig. 1), through a number of intermediates2, and for the completion of the cycle one needs a molecular process which may regenerate 11-cis-retinal from all-trans-retinal (equation (3), Fig. 1).

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AMER, S., AKHTAR, M. Studies on a Missing Reaction in the Visual Cycle. Nature New Biology 237, 266–267 (1972).

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