Photobiology of Rhodopsin and the Cone Pigments

视紫红质和视锥细胞色素的光生物学

• 批准号: 7769862
• 负责人: ROBERT Richards BIRGE
• 金额: $ 22.72万
• 依托单位: UNIVERSITY OF CONNECTICUT STORRS
• 依托单位国家: 美国
• 财政年份: 1988
• 资助国家: 美国
• 起止时间: 1988-08-01 至 2013-02-28
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/7769862
• 关键词: Address; Adopted; Adoption; Belief; Binding; Binding Sites; Biochemical; Biological; Budgets; Cells; Charge; Code; Communities; Comparative Study; Complex; Computer software; Development; Electronics; Electrostatics; Eye diseases; Funding; G Protein-Coupled Receptor Genes; Goals; Grant; Homology Modeling; Human; Individual; Instruction; Light; Linux; Mechanics; Methods; Modeling; Molecular; Molecular Conformation; Motion; Nature; Nerve; Noise; Organic Chemistry; Photobiology; Photobleaching; Photoreceptors; Pigments; Procedures; Process; Property; Protein Binding; Proteins; Quantum Mechanics; Quantum Theory; Recovery; Relative (related person); Research; Research Personnel; Rest; Retinal; Retinal Cone; Retinal Photoreceptors; Retinal Pigments; Rhodopsin; Site-Directed Mutagenesis; Spectrum Analysis; Staging; Structure; Structure-Activity Relationship; Temperature; Time; Transducin; United States National Institutes of Health; Vision; Vision research; absorption; base; chromophore; disorder of macula of retina; experience; graphical user interface; improved; interest; light intensity; molecular orbital; neglect; photoactivation; programs; public health relevance; quantum; receptor; theories; tool; vibration; vision blue pigment; visual process; visual processing

DESCRIPTION (provided by applicant): Cone cells are responsible for photopic vision, the visual process under normal light conditions. The cone receptors must operate over a wide range of light intensities and cover the full range of the visible spectrum. The ability to function under these diverse conditions is due primarily to the highly optimized GPCR light-transducing proteins informally called cone pigments. These proteins have absorption maxima that range from 350 to 660 nm, and upon the absorption of light, undergo an efficient photobleaching sequence to produce an activated protein. Subsequent binding of transducin to the activated protein results in a nerve impulse and vision. A key observation made during the previous NIH funded study was that cone pigments undergo a counterion switch during photoactivation. A key aim of this study is to explore whether a counterion switch mechanism is also active in the red and blue cone pigments, and if so, to characterize the molecular details. To achieve this goal, we will use vibrational and electronic spectroscopy at temperatures from 10K to ambient to trap and characterize the photobleaching intermediates. Site directed mutagenesis will be used to identify the key residues responsible for wavelength selection and the nature of the counterion switch. It is clear from homology studies that many of the red cones differ from the green, blue and UV cones in nature and implementation of the counterion switch. Indeed, it is possible that the red cones lack this mechanistic feature entirely. An additional aim of this study is to systematically identify the mechanisms of wavelength selection in the UV, blue, green and red cones. Although our research identified key features of wavelength selection in the blue and UV cones, much remains to be understood. Our inclusion of the red cones in this study is new, and our enthusiasm for this topic rests in part on our belief that the red cones are fundamentally different. We have preliminary evidence, presented in our preliminary studies discussion, that the deep red cones use at least one new mechanism for wavelength selection involving manipulation of the chromophore ring conformation. The combination of unique wavelength selection and a significantly different (or absent) counterion switching mechanism make the red cones an important target. Our studies will include the use of molecular orbital theory to probe structure-function relationships in the cone pigments, and to calculate the spectroscopic properties of the bound chromophores. We will refactor our MNDO-PSDCI code and improve the interface to make these procedures more useful to the scientific community. As before, we will provide these procedures to interested researchers without charge. PUBLIC HEALTH RELEVANCE: There is a growing need to understand the photobleaching and recovery mechanisms associated with light exposure in cone photoreceptors. Because these cells are essential for human photopic vision, it is important to understand the structure and function relationships in the associated light transducing pigments. The project goals of this research may help understand macular disease, which involves loss of cone cells, cone dystrophy, and other eye diseases, which involve damage or diminished function of retinal photoreceptors.

描述（由申请人提供）：视锥细胞负责明视觉，即正常光照条件下的视觉过程。视锥细胞受体必须在较宽的光强度范围内工作并覆盖整个可见光谱范围。在这些不同条件下发挥作用的能力主要归功于高度优化的 GPCR 光转导蛋白，非正式地称为锥体色素。这些蛋白质的最大吸收范围为 350 至 660 nm，并且在吸收光后，经过有效的光漂白序列以产生活化的蛋白质。随后转导蛋白与激活的蛋白质结合导致神经冲动和视觉。在之前的美国国立卫生研究院资助的研究中进行的一个关键观察是，锥体色素在光激活过程中经历了抗衡离子转换。这项研究的一个主要目的是探索抗衡离子开关机制在红色和蓝色锥体颜料中是否也活跃，如果是的话，表征分子细节。为了实现这一目标，我们将在 10K 至环境温度下使用振动和电子光谱来捕获和表征光漂白中间体。定点诱变将用于识别负责波长选择和抗衡离子开关性质的关键残基。从同源性研究可以清楚地看出，许多红色视锥细胞在性质和抗衡离子开关的实现上与绿色、蓝色和紫外线视锥细胞不同。事实上，红色视锥细胞可能完全缺乏这种机械特征。这项研究的另一个目的是系统地确定紫外线、蓝色、绿色和红色视锥细胞中波长选择的机制。尽管我们的研究确定了蓝色和紫外线锥体中波长选择的关键特征，但仍有许多问题有待了解。我们将红锥体纳入这项研究是新的，我们对这个主题的热情部分取决于我们相信红锥体是根本不同的。我们在初步研究讨论中提出了初步证据，表明深红色视锥细胞至少使用一种新的波长选择机制，涉及发色团环构象的操纵。独特的波长选择和显着不同（或不存在）的抗衡离子切换机制相结合，使红色视锥细胞成为重要目标。我们的研究将包括使用分子轨道理论来探测锥体色素中的结构-功能关系，并计算结合发色团的光谱特性。我们将重构 MNDO-PSDCI 代码并改进界面，使这些程序对科学界更有用。和以前一样，我们将免费向感兴趣的研究人员提供这些程序。公共健康相关性：越来越需要了解与锥体光感受器曝光相关的光漂白和恢复机制。由于这些细胞对于人类明视觉至关重要，因此了解相关光传导色素的结构和功能关系非常重要。这项研究的项目目标可能有助于了解黄斑疾病，其中涉及视锥细胞损失、视锥细胞营养不良和其他眼部疾病，这些疾病涉及视网膜感光细胞的损伤或功能减弱。