Here we review the application of modern spectral methods for the study of G-protein-coupled receptors (GPCRs) using rhodopsin as a prototype. Because X-ray analysis gives us immobile snapshots of protein conformations, it is imperative to apply spectroscopic methods for elucidating their function: vibrational (Raman, FTIR), electronic (UV-visible absorption, fluorescence) spectroscopies, and magnetic resonance (electron paramagnetic resonance, EPR), and nuclear magnetic resonance (NMR). In the first of the two companion articles, we discuss the application of optical spectroscopy for studying rhodopsin in a membrane environment. Information is obtained regarding the time-ordered sequence of events in rhodopsin activation. Isomerization of the chromophore and deprotonation of the retinal Schiff base leads to a structural change of the protein involving the motion of helices H5 and H6 in a pH-dependent process. Information is obtained that is unavailable from X-ray crystallography, which can be combined with spectroscopic studies to achieve a more complete understanding of GPCR function.

中文翻译：

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用于研究G蛋白偶联受体视紫红质的光谱方法。I.振动和电子光谱。

在这里，我们回顾了使用视紫红质为原型的现代光谱方法在研究G蛋白偶联受体（GPCR）方面的应用。由于X射线分析为我们提供了蛋白质构象的固定快照，因此必须使用光谱学方法阐明其功能：振动（拉曼光谱，FTIR），电子（紫外可见吸收，荧光）光谱学和磁共振（电子顺磁共振） ，EPR）和核磁共振（NMR）。在这两篇配套文章的第一篇中，我们讨论了光谱技术在膜环境中研究视紫红质的应用。获得关于视紫红质激活中事件的时间顺序的信息。发色团的异构化和视网膜席夫碱的去质子化导致蛋白质的结构变化，涉及在依赖pH的过程中螺旋H5和H6的运动。获得的信息是X射线晶体学无法获得的，可以将其与光谱研究相结合以获得对GPCR功能的更完整的了解。