Multiple phosphorylation sites confer reproducibility of the rod's single-photon responses |
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Authors: | Doan Thuy Mendez Ana Detwiler Peter B Chen Jeannie Rieke Fred |
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Affiliation: | Program in Neurobiology and Behavior, University of Washington, Seattle, WA 98195, USA. |
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Abstract: | Although signals controlled by single molecules are expected to be inherently variable, rod photoreceptors generate reproducible responses to single absorbed photons. We show that this unexpected reproducibility-the consistency of amplitude and duration of rhodopsin activity-varies in a graded and systematic manner with the number but not the identity of phosphorylation sites on rhodopsin's C terminus. These results indicate that each phosphorylation site provides an independent step in rhodopsin deactivation and that collectively these steps tightly control rhodopsin's active lifetime. Other G protein cascades may exploit a similar mechanism to encode accurately the timing and number of receptor activation. |
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