STRUCTURE/FUNCTION OF COLOR VISION PIGMENTS

视觉科学的中心问题之一是光谱的机制 在视觉色素之间进行调节。 为什么最大吸收 当吸收的实际分子在380 nm到600 nm之间时， 光，11-顺式-视网膜发色团，在所有的色素中是相同的？ 显然，视网膜发色团与氨基酸之间存在相互作用， 蛋白质中改变光谱特性的侧链， 发色团 这些研究的目的就是要解开这些机制 对于一个非常明确的实验系统：人类的色觉， 颜料. 这项工作将集中在这些蛋白质中已知的三组氨基酸 为了深刻地影响发色团的光谱性质：1） 7种氨基酸导致红色和绿色之间的光谱差异 颜料; 2）发色团的质子化席夫碱和席夫碱 3）红色和绿色颜料的氯离子结合位点。 该方法将使用定点诱变，化学 蛋白质的修饰和发色团类似物与 纯化色素的体外表征。 由于最近的技术突破， 共振拉曼光谱的研究，这些色素，这强大的 光谱工具将被广泛用于探测的结构， 视网膜发色团在这项工作的各个方面。 的巨大潜力 该应用从以下认识中是显而易见的： 色素的拉曼研究将是一个超过150个突变体的图书馆， 蓝色、绿色和红色的视觉色素， 补助期。

One of the central problems in visual science is the mechanism of spectral tuning among the visual pigments. How is it that the absorption maxima can range from 380 nm to over 600 nm when the actual molecule that absorbs light, the 11-cis-retinal chromophore, is identical in all of the pigments? Clearly, there are interactions of the retinal chromophore with amino acid sidechains in the proteins that modify the spectral properties the chromophore. It is the purpose these studies to unravel these mechanisms for one extremely well defined experimental system: the human color vision pigments. This work will focus on three groups of amino acids in these proteins known to profoundly affect the spectral properties of the chromophore: 1) the 7 amino acids that cause the spectral difference between the red and green pigments; 2) the protonated Schiff base of the chromophore and Schiff base counterion; and 3) the chloride binding site of the red and green pigments. The approach will be to use site-directed mutagenesis, chemical modification of the proteins, and chromophore analogs in combination with in vitro characterization of the purified pigments. As a result of a recent technical breakthrough in the application of resonance Raman spectroscopy to the study of these pigments, this powerful spectroscopic tool will be used extensively to probe the structure of the retinal chromophore in all aspects of this work. The enormous potential of this application is apparent from a realization that the source of visual pigment for the Raman studies will be a library of over 150 mutants in the blue, green and red visual pigments that was constructed over the original grant period.