Rod and cone opsin families differ in spectral tuning domains but not signal transducing domains as judged by saturated evolutionary trace analysis
Rod and cone opsin families differ in spectral tuning domains but not signal transducing domains as judged by saturated evolutionary trace analysis
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DOI：
10.1007/s00239-004-0289-z
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发表时间：
2005-07-01
影响因子：
3.9
通讯作者：
Cote, RH
中科院分区：
文献类型：
--
作者：
Carleton, KL;Spady, TC;Cote, RH
视杆细胞和视锥细胞的视觉感受器是脱辅基蛋白、视蛋白和光敏发色团11-顺式-视网膜的共价复合物。这种色素必须履行许多功能，包括光活化，光谱调谐，信号传输，失活和发色团再生。视杆和视锥光感受器使用不同的视蛋白家族。虽然众所周知，这些视蛋白家族提供独特的光谱灵敏度范围，但尚不清楚这些家族是否具有额外的功能差异。在这项研究中，我们使用进化痕迹（ET）分析188脊椎动物视蛋白序列，以确定在每个视蛋白家族的功能重要的网站。我们证明了以下结果。(1)可用的脊椎动物视蛋白序列产生所有五种脊椎动物视蛋白家族的明确描述。这是在ET分析之前的序列饱和的第一个证明，我们称之为饱和ET（SET）。(2)视锥视蛋白类与视杆视蛋白类相比具有类特异性位点。这些位点位于跨膜区，并将每个视蛋白类的光谱灵敏度调节到其特征波长范围。(3)细胞质环，主要负责信号传递和失活，基本上是不变的视杆视蛋白与视锥。这表明视杆细胞和视锥细胞之间的电生理差异不能归因于视蛋白的蛋白质相互作用区域的差异。SET显示，发色团结合和再生是视蛋白结构的唯一方面，视杆细胞和视锥细胞之间可能具有功能上的显著差异，而视蛋白家族的兴奋性和适应性似乎在功能上是不变的。
The visual receptor of rods and cones is a covalent complex of the apoprotein, opsin, and the light-sensitive chromophore, 11-cis-retinal. This pigment must fulfill many functions including photoactivation, spectral tuning, signal transmission, inactivation, and chromophore regeneration. Rod and cone photoreceptors employ distinct families of opsins. Although it is well known that these opsin families provide unique ranges in spectral sensitivity, it is unclear whether the families have additional functional differences. In this study, we use evolutionary trace (ET) analysis of 188 vertebrate opsin sequences to identify functionally important sites in each opsin family. We demonstrate the following results. (1) The available vertebrate opsin sequences produce a definitive description of all five vertebrate opsin families. This is the first demonstration of sequence saturation prior to ET analysis, which we term saturated ET (SET). (2) The cone opsin classes have class-specific sites compared to the rod opsin class. These sites reside in the transmembrane region and tune the spectral sensitivity of each opsin class to its characteristic wavelength range. (3) The cytoplasmic loops, primarily responsible for signal transmission and inactivation, are essentially invariant in rod versus cone opsins. This indicates that the electrophysiological differences between rod and cone photoreceptors cannot be ascribed to differences in the protein interaction regions of the opsins. SET shows that chromophore binding and regeneration are the only aspects of opsin structure likely to have functionally significant differences between rods and cones, whereas excitatory and adaptational properties of the opsin families appear to be functionally invariant.