Role of visual pigment properties in rod and cone phototransduction
Role of visual pigment properties in rod and cone phototransduction
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DOI：
10.1038/nature01992
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发表时间：
2003-10-02
期刊：
影响因子：
64.8
通讯作者：
Yau, KW
中科院分区：
文献类型：
--
作者：
Kefalov, V;Fu, YB;Yau, KW
视网膜视杆细胞和视锥细胞共享一个涉及环GMP的光转导途径（1）。视锥细胞的光敏性通常比视杆细胞低100倍，它们的反应动力学快几倍（2），但其潜在机制在很大程度上仍不清楚。几乎所有参与光转导的蛋白质都具有不同的视杆和视锥变体。已经描述了视杆和视锥色素之间的性质差异，例如视锥色素的间-II状态（活性构象）的寿命短10倍（3-6），并且其自发异构化的速率更高（7，8），但是它们对视杆和视锥之间的功能差异的贡献仍然是推测性的。我们已经解决了这个问题，通过表达人类或蝾螈红锥色素在非洲爪蟾杆，和人类杆色素在非洲爪蟾锥。在这里，我们表明，杆和锥色素时，存在于同一个细胞产生相同的放大和动力学的光响应，从而排除任何差异，其信号传导特性。然而，红锥色素自发异构化的频率比杆状色素高10，000倍。这种高自发性活动即使在黑暗中也能适应原生视锥细胞，使它们比视杆细胞更不敏感和运动更快。然而，这些差异可能还涉及其他因素。
Retinal rods and cones share a phototransduction pathway involving cyclic GMP(1). Cones are typically 100 times less photosensitive than rods and their response kinetics are several times faster(2),but the underlying mechanisms remain largely unknown. Almost all proteins involved in phototransduction have distinct rod and cone variants. Differences in properties between rod and cone pigments have been described, such as a 10-fold shorter lifetime of the meta-II state (active conformation) of cone pigment(3-6) and its higher rate of spontaneous isomerization(7,8), but their contributions to the functional differences between rods and cones remain speculative. We have addressed this question by expressing human or salamander red cone pigment in Xenopus rods, and human rod pigment in Xenopus cones. Here we show that rod and cone pigments when present in the same cell produce light responses with identical amplification and kinetics, thereby ruling out any difference in their signalling properties. However, red cone pigment isomerizes spontaneously 10,000 times more frequently than rod pigment. This high spontaneous activity adapts the native cones even in darkness, making them less sensitive and kinetically faster than rods. Nevertheless, additional factors are probably involved in these differences.