Probing Conformational Change in a Cl-/H+ Antiporter of Known Structure

所有的生物体都是由细胞组成的，这些细胞被一层薄膜与环境隔开。虽然这层膜形成了一个重要的保护屏障，但它也包含了一个重要的细胞成分屏障。为了克服这个问题，细胞膜包含了各种各样的蛋白质，每种蛋白质都专门用于运输特定的货物。这些膜蛋白是动态的分子机器，它们经历构象变化（形状和结构的变化）来吸收和释放膜两侧的货物。理解膜蛋白如何工作的一个主要挑战是定义这些构象变化。CLC蛋白是一类膜蛋白，它能以相反的方向运输氯离子和质子（两种小而带相反电荷的离子）。这个项目的目标是了解CLC蛋白是如何完成这一壮举的：具体地说，是定义蛋白质以如此精细的特异性拾取和脱落每个底物离子的构象变化。这将通过在CLC蛋白中定位小（19F）探针并使用核磁共振（NMR）检测它们的运动来完成。通过将这些信息与x射线晶体学中已知的静态分子分辨率结构相结合，将创建CLC蛋白质功能的动态模型。更广泛的影响本研究项目中描述的实验将包括在生化和生物物理方法和分析方面培训研究生和博士后科学家，这将为学术界或生物技术部门的职业生涯提供良好的准备。这项研究还将包括对本科生暑期学生的培训（继续包括女性和少数民族），这将有两个目的：(1)为年轻的、潜在的未来科学家提供研究经验；(2)为领导实验的研究生和博士后提供指导经验。该项目的PI将继续招募和指导女性和少数族裔，参与生物物理学会的女性职业机会委员会，并为斯坦福大学的学生制定指导计划。此外，她将扩大她的角色，包括与当地学校的联系。

All living organisms are composed of cells that are separated from their environment by a thin membrane. Although this membrane forms an important protective barrier, it also comprises a significant barrier to essential cellular components. To overcome this problem, cell membranes contain a broad assortment of proteins that are each specialized to transport specific cargo. These membrane proteins are dynamic molecular machines that undergo conformational change (change in shape and structure) to pick up and release cargo on either side of the membrane. A major challenge to understanding how membrane proteins work is to define these conformational changes. The CLC proteins are a class of membrane proteins that specifically transport chloride and protons (two small and oppositely-charged ions) in opposite directions. The goal of this project is to understand how the CLC proteins accomplish this feat: specifically, to define the conformational changes by which the protein pick up and drops off each substrate ion with such exquisite specificity. This will be accomplished by positioning small (19F) probes throughout the CLC protein and detecting their motion using nuclear magnetic resonance (NMR). By combining this information with the static molecular-resolution structure that is known from X-ray crystallography, a dynamic model of CLC protein function will be created.Broader ImpactsThe experiments described in this research project will involve training a graduate student and a postdoctoral scientist in biochemical and biophysical methods and analysis that will provide excellent preparation for a career in academia or in the biotechnology sector. This research will also involve the training of undergraduate summer students (with continued inclusion of women and minorities), which will serve a twofold purpose of (1) providing research experiences to young, potential future scientists and (2) providing mentoring experience to the graduate student and post-doc who are leading the experiments. The PI of this project will continue to recruit and mentor women and minorities, to participate in the Biophysical Society's Committee for Professional Opportunities for Women, and to develop mentoring programs for students at Stanford. In addition, she will broaden her role to include outreach to the local schools.