Mendez A, Burns M E, Roca A, Lem J, Wu L W, Simon M I, Baylor D A, Chen J
Department of Ophthalmology and Cell and Neurobiology, Keck School of Medicine, University of Southern California, Los Angeles 90089, USA.
Neuron. 2000 Oct;28(1):153-64. doi: 10.1016/s0896-6273(00)00093-3.
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.
视网膜视杆光感受器实现高效单光子检测需要视紫红质及时且可重复地失活。与其他G蛋白偶联受体一样，视紫红质在其COOH末端结构域含有多个磷酸化位点。采用转基因和电生理方法，在完整的小鼠视杆中对视紫红质失活过程中多个磷酸化位点的作用进行功能剖析。具有零个、一个（S338）或两个（S334/S338）磷酸化位点的突变型视紫红质产生的单光子反应持续时间大大延长，呈指数分布。表达具有两个以上磷酸化位点的突变型视紫红质的视杆产生的反应沿着平滑、可重复的时间进程下降；恢复速率随着磷酸化位点数量的增加而增加。我们得出结论，视紫红质的多重磷酸化对于快速且可重复的失活是必要的。
