Efficiency of Phototransduction Cascade in Cones
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Cone photoreceptors are less light sensitive than rods, and the photoresponse of a cone is much briefer than that of a rod. In previous studies, the phototransduction cascade in cones has been shown to be essentially the same as that of rods: there are rod- and cone-version of components of the cascade. For this similarity, it has been speculated that the difference between a rod and a cone photoresponse is due to a quantitative difference in the reaction(s) of the cascade between rods and cones. However, the actual difference has not been measured yet. To understand the molecular mechanisms characterizing cone photoresponses, we compared the reactions in the phototransduction cascade between rods and cones.