STRUCTURE AND FUNCTION OF ROD AND CONE PIGMENTS

这项提议的长期目标是了解杆状和锥状颜料的结构和激活机制。视紫红质是一种杆状色素，它的几个突变已被证明会导致功能的增加或丧失，并最终导致视网膜退化。然而，锥体色素突变引起的类似退行性疾病尚未见报道。缺乏关于锥体色素的信息或锥体色素结构和/或激活的固有差异是两个可能的原因。更多关于骨色素基本性质的数据将为这两种情况提供线索。这项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9-甲基周围，在视杆细胞和视锥细胞色素的激活和失活过程中。这项提议有三个目的：(1)建立一种与“立体触发”机制一致的锥体色素的光不依赖活性形式，涉及不同于其他人之前发表的氨基酸；(2)测试锥体色素中的“盐桥”激活模型；(3)确定细胞外域对视觉色素的稳定和激活的作用。将使用表达的火蜥蜴视觉色素的光谱和转导活性测量。这些结果对于理解更大范围的G蛋白偶联受体的激活机制也将是重要的。

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.