STRUCTURE AND FUNCTION OF ROD AND CONE PIGMENTS

这项提案的长期目标是了解杆和锥色素的结构和激活机制。视紫红质（视杆色素）的几种突变已被证明会导致功能的获得或丧失，并最终导致视网膜变性。然而，类似的退行性疾病还没有报道锥色素突变。两个可能的原因是缺乏关于视锥色素的信息或视锥色素结构和/或活化的固有差异。更多关于骨色素基本性质的数据将有助于阐明这两种情况。这个建议是针对确定重要的蛋白质配体的相互作用，特别是围绕9-甲基基团的11-顺式视网膜，在杆和锥色素的激活和失活。该建议有三个目的：（1）建立一种与“空间触发”机制一致的视锥色素的光依赖性活性形式，该机制涉及与其他人先前发表的氨基酸不同的氨基酸;（2）测试视锥色素中激活的“盐桥”模型;（3）确定细胞外结构域对视色素稳定性和激活的作用。将使用表达的蝾螈视色素的光谱和转导素活性测量。这些结果也将是重要的G蛋白偶联受体的更大领域的激活机制的理解。

The long-term goal of this proposal is to understand the structures and activation of mechanisms of rod and cone pigments. Several mutations in rhodopsin, the rod pigment, have been shown to result in gain or loss of function and ultimately lead to retinal degeneration. However, similar degenerative diseases have not been reported from cone pigment mutations. The dearth of information on cone pigments or inherent differences of cone pigment structure and/or activation are two possible reasons. More data on the basic properties of bone pigments will shed light on eith4r scenario. This proposal is directed at determining the important protein-ligand interactions, particularly around the 9-methyl group of 11-cis retinal, in the activation and inactivation of rod and cone pigments. There are three aims to this proposal: (1) establishment of a light-independent active form of a cone pigment consistent with a "steric trigger" mechanism involving amino acids different from those previously published by others; (2) test of the "salt bridge" model of activation in the cone pigments; (3) determination of the role of the extracellular domains on the stability and activation of visual pigments. Spectroscopic and transducin activity measurements of expressed salamander visual pigments will be used. These results will also be important in the understanding of the activation mechanisms of the larger field of G protein-coupled receptors.