Essential Role of Water and Lipids in G-Protein-Coupled Receptor Chemistry

视紫红质是一种视觉蛋白，存在于眼睛的视网膜杆中，是被称为G蛋白偶联受体(GPCRs)的一大类膜蛋白的原型。通过这一奖项，化学部的生命过程化学计划资助亚利桑那大学的Michael Brown博士探索这种蛋白质与膜中的脂质以及与水的相互作用如何控制视觉信号过程。虽然包括视紫红质在内的蛋白质的原子结构已为人所知，但它们在脂膜中的作用的对应关系仍然是一个悬而未决的问题。该项目将实验和理论相结合，研究水流入蛋白质如何影响细胞膜环境中视紫红质的激活。此外，该项目还为研究生和博士后研究员以及本科生和高中生提供膜蛋白和脂类化学方面的专门培训。新的基础知识不仅通过出版的科学文献传播，还通过与亚利桑那州佛兰多科学中心共同举办的讲习班传播。该项目进一步与涉及亚利桑那州科学、工程和数学学者计划的外展计划相结合，重点关注家庭中第一个进入大学的有前途的学生、来自低收入家庭的学生以及妇女和少数族裔。这项工作涉及国际合作，并提供了旨在整合和促进人类合作和全球教育的机会。这项研究项目描述了涉及膜脂和水的重要相互作用，这些相互作用在视觉信号的催化G蛋白周期中控制视紫红质的光激活。因为活化是一个依赖于pH的过程，所以水进入或离开蛋白质对反应机理的实际化学至关重要。该项目通过实验和理论的协同作用，将分子光谱学与散射方法相结合。本研究旨在阐明视紫红质的水化激活机制，并探索由脂质和水组成的膜软物质如何影响这一过程。用低特异性的亲水性聚合物渗透膜结合重量法来定量水进入蛋白质的量，揭示水对视紫红质激活的影响及其与同源G蛋白转导蛋白的相互作用。该项目进一步阐述了膜脂如何通过双层性质和相互作用来调控细胞环境中的视紫红质功能。这项研究的信息旨在为在细胞水平上管理G-蛋白质介导的生物信号的膜组件的基本化学提供新的见解。这一奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

Rhodopsin is a visual protein found in the rods of the eye's retina, and is an archetype for the broad class of membrane proteins known as G-protein-coupled receptors (GPCRs). With this award, the Chemistry of Life Processes Program in the Chemistry Division is funding Dr. Michael Brown from the University of Arizona to explore how the interactions of this protein with lipids in membranes and with water control the visual signaling process. Although the atomic structures of proteins, including rhodopsin, are now known, the correspondence to their actions in lipid membranes remains an open question. This project combines experiment and theory to study how the flow of water into the protein affects the activation of rhodopsin within a cellular membrane environment. In addition, the project provides specialized training in the chemistry of membrane proteins and lipids to graduate students and postdoctoral fellows as well as undergraduate and high-school students. The new fundamental knowledge is disseminated not only through the published scientific literature, but also through workshops developed with the Arizona Flandreau Science Center. The project is further integrated with an outreach program involving Arizona's Science, Engineering, and Math Scholars program, focusing on promising students who are first in their family to attend college, from low-income households, and women and minorities. The work involves international collaborations and affords opportunities aimed at integrating and promoting human cooperation and global education. This research project characterizes important interactions involving membrane lipids and water that control the light activation of rhodopsin in the catalytic G-protein cycle of visual signaling. Because activation is a pH-dependent process, whether water goes into or out of the protein is crucial to the actual chemistry of the reaction mechanism. The project combines molecular spectroscopy with scattering methods through a synergetic interplay of experiment and theory. The research is intended to illuminate the hydration-mediated activation mechanism of rhodopsin, and explores how the membrane soft matter comprising lipids and water affects the process. Hydrophilic polymer osmolytes of low specificity are used to quantify the influx of water into the protein together with gravimetric methods, and reveal the influences of water on the activation of rhodopsin and its interactions with the cognate G-protein transducin. The project further addresses how the membrane lipids govern rhodopsin function in the cellular environment through the bilayer properties and interactions. The information from this study is intended to contribute new insights into the fundamental chemistry of the membrane components that are likely to govern G-protein-mediated biological signaling at the cellular level.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.