Abstract
Rod photoreceptors generate measurable responses to single-photon activation of individual molecules of the G-protein-coupled receptor, rhodopsin. Timely rhodopsin desensitization depends on phosphorylation and arrestin binding, which quenches G-protein activation. Rhodopsin phosphorylation has been measured biochemically at C-terminal serine residues, suggesting that these residues are critical for producing fast, low noise responses. The role of native threonine residues is unclear. We compared single-photon responses from rhodopsin lacking native serine or threonine phosphorylation sites. Contrary to expectation, serine-only rhodopsin generated prolonged step-like single-photon responses that terminated abruptly and randomly, whereas threonine-only rhodopsin generated responses that were only modestly slower than normal. We show that the step-like responses of serine-only rhodopsin reflect slow and stochastic arrestin binding. Thus, threonine sites play a privileged role in promoting timely arrestin binding and rhodopsin desensitization. Similar coordination of phosphorylation and arrestin binding may more generally permit tight control of the duration of G-protein-coupled receptor activity.
Original language | English (US) |
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Article number | e05981 |
Pages (from-to) | 1-57 |
Number of pages | 57 |
Journal | eLife |
Volume | 2015 |
Issue number | 4 |
DOIs | |
State | Published - Apr 24 2015 |
ASJC Scopus subject areas
- General Neuroscience
- General Biochemistry, Genetics and Molecular Biology
- General Immunology and Microbiology