Chen J, Makino C L, Peachey N S, Baylor D A, Simon M I
Division of Biology, California Institute of Technology, Pasadena, CA 91125.
Science. 1995 Jan 20;267(5196):374-7. doi: 10.1126/science.7824934.
Although biochemical experiments suggest that rhodopsin and other receptors coupled to heterotrimeric guanosine triphosphate-binding proteins (G proteins) are inactivated by phosphorylation near the carboxyl (COOH)-terminus and the subsequent binding of a capping protein, little is known about the quenching process in vivo. Flash responses were recorded from rods of transgenic mice in which a fraction of the rhodopsin molecules lacked the COOH-terminal phosphorylation sites. In the single photon regime, abnormally prolonged responses, attributed to activation of individual truncated rhodopsins, occurred interspersed with normal responses. The occurrence of the prolonged responses suggests that phosphorylation is required for normal shutoff. Comparison of normal and prolonged single photon responses indicated that rhodopsin begins to be quenched before the peak of the electrical response and that quenching limits the response amplitude.
尽管生化实验表明，视紫红质和其他与异源三聚体鸟苷三磷酸结合蛋白（G蛋白）偶联的受体通过羧基（COOH）末端附近的磷酸化以及随后一种封端蛋白的结合而失活，但对于体内的淬灭过程却知之甚少。从视紫红质分子一部分缺乏COOH末端磷酸化位点的转基因小鼠的视杆细胞中记录了闪光反应。在单光子状态下，归因于单个截短视紫红质激活的异常延长反应夹杂着正常反应出现。延长反应的发生表明磷酸化是正常关闭所必需的。正常和延长的单光子反应的比较表明，视紫红质在电反应峰值之前就开始被淬灭，并且淬灭限制了反应幅度。
