STRUCTURE AND FUNCTION OF ROD AND CONE PIGMENTS

本研究的长期目标是了解视杆色素和视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，类似的退行性疾病尚未报道由锥体色素突变引起。缺乏关于视锥色素的信息或视锥色素结构和/或激活的内在差异是两个可能的原因。更多关于骨色素基本特性的数据将阐明这两种情况。该建议旨在确定重要的蛋白质-配体相互作用，特别是在11-顺式视网膜的9-甲基周围，在杆状色素和锥体色素的激活和失活中。这一建议有三个目的：(1)建立一种与“立体触发”机制相一致的不依赖光的锥体色素活性形式，该机制涉及的氨基酸与之前发表的氨基酸不同；(2)锥体色素活化的“盐桥”模型检验；(3)确定细胞外结构域对视觉色素的稳定性和活化的作用。表达的蝾螈视觉色素的光谱和转导活性测量将被使用。这些结果对于理解G蛋白偶联受体更大范围的激活机制也具有重要意义。

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.