Rapid and reproducible deactivation of rhodopsin requires multiple phosphorylation sites.
Efficient single-photon detection by retinal rod photoreceptors requires timely and reproducible deactivation of rhodopsin. Like other G protein-coupled receptors, rhodopsin contains multiple sites for phosphorylation at its COOH-terminal domain. Transgenic and electrophysiological methods were used to functionally dissect the role of the multiple phosphorylation sites during deactivation of rhodopsin in intact mouse rods. Mutant rhodopsins bearing zero, one (S338), or two (S334/S338) phosphorylation sites generated single-photon responses with greatly prolonged, exponentially distributed durations. Responses from rods expressing mutant rhodopsins bearing more than two phosphorylation sites declined along smooth, reproducible time courses; the rate of recovery increased with increasing numbers of phosphorylation sites. We conclude that multiple phosphorylation of rhodopsin is necessary for rapid and reproducible deactivation.
Mendez
A
A
Department of Ophthalmology and Cell and Neurobiology, Keck School of Medicine, University of Southern California, Los Angeles 90089, USA.
Burns
M E
ME
Roca
A
A
Lem
J
J
Wu
L W
LW
Simon
M I
MI
Baylor
D A
DA
Chen
J
J
D000818:Animals; D001665:Binding Sites / Q000235:genetics; D005136:Eye Proteins; D051606:G-Protein-Coupled Receptor Kinase 1; D051379:Mice; D008822:Mice, Transgenic; D016297:Mutagenesis, Site-Directed; D010766:Phosphorylation; D017785:Photons; D011494:Protein Kinases / Q000378:metabolism; D011930:Reaction Time / Q000235:genetics; D015203:Reproducibility of Results; D017948:Retinal Rod Photoreceptor Cells / Q000378:metabolism*; D012243:Rhodopsin / Q000235:genetics* / Q000378:metabolism*
D005136:Eye Proteins; D012243:Rhodopsin; D011494:Protein Kinases; D051606:G-Protein-Coupled Receptor Kinase 1; C496762:Grk1 protein, mouse