Multiple phosphorylation sites confer reproducibility of the rod's single-photon responses.
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.
Doan
Thuy
T
Program in Neurobiology and Behavior, University of Washington, Seattle, WA 98195, USA.
Mendez
Ana
A
Detwiler
Peter B
PB
Chen
Jeannie
J
Rieke
Fred
F
D000818:Animals; D019393:Arrestin / Q000378:metabolism; D004594:Electrophysiology; D051379:Mice; D008822:Mice, Transgenic; D008954:Models, Biological; D009154:Mutation; D018408:Patch-Clamp Techniques; D010766:Phosphorylation; D017785:Photons; D017948:Retinal Rod Photoreceptor Cells / Q000378:metabolism*; D012243:Rhodopsin / Q000235:genetics / Q000378:metabolism*; D014785:Vision, Ocular
D019393:Arrestin; D012243:Rhodopsin