Molecular Mechanisms of Topological Rearrangements in Integral Membrane Proteins

该项目研究了膜蛋白（即，存在于细胞膜内的蛋白质）在蛋白质合成后获得相对于膜的正确取向。膜蛋白对于细胞功能包括运输、信号传导和酶活性是至关重要的。为了正常发挥功能，膜蛋白必须折叠成正确的拓扑结构，这需要蛋白质的所有结构元件相对于膜获得特定的方向。未能获得正确拓扑结构的膜蛋白在细胞中迅速降解。该项目使用分子模拟技术来解决如何建立膜蛋白拓扑结构的知识空白。这些知识将为工程方法提供信息，以最大限度地提高正确的蛋白质生产。该研究团队将吸收本科生，包括来自代表性不足群体的学生，在跨学科研究环境中培养下一代研究人员。将根据这一项目开发学习模块，用于针对中学生的外联活动，以激励青年学生从事研究工作。该项目的成果也将纳入研究生和高级本科课程。 该项目将使用分子动力学模拟来研究实验表征的一系列代表性膜蛋白的拓扑重排。最近的实验结果表明，某些膜蛋白进行拓扑重排，其中亲水性蛋白质元素直接穿过膜，即使这个过程应该面临一个大的能量障碍。原子和粗粒度的模拟，加速增强的采样技术，将进行表征亲水性蛋白质元素穿过膜的途径。这些模拟将阐明蛋白质，脂质和水的相互作用，促进生物相关的时间尺度上的拓扑重排的相互作用。基于模拟洞察，将对每个模型系统测试序列突变，以生成实验可验证的预测。该项目中开发和应用的模拟方法对于研究与脂质翻转、膜蛋白构象变化或药物载体向细胞输送相关的类似双层移位过程也具有价值。该奖项反映了NSF的法定使命，并且通过使用基金会的智力价值和更广泛的影响审查标准进行评估，被认为值得支持。

This project investigates the mechanisms by which membrane proteins (i.e., proteins that reside within the cell membrane) obtain correct orientations with respect to the membrane after protein synthesis. Membrane proteins are critical for cellular functions including transport, signaling, and enzymatic activity. To function properly, a membrane protein must fold into its correct topology, which requires all structural elements of the protein to obtain specific orientations with respect to the membrane. Membrane proteins that fail to obtain a correct topology are rapidly degraded in the cell. This project uses molecular simulation techniques to address gaps in the knowledge of how membrane protein topology is established. This knowledge will inform engineering approaches to maximize correct protein production. The research team will incorporate undergraduate students, including students from underrepresented groups, to train the next generation of researchers in an interdisciplinary research environment. Learning modules based on this project will be developed for outreach initiatives targeted at middle-school students to inspire young students to pursue research careers. Results from this project will also be incorporated into graduate and advanced undergraduate courses. This project will use molecular dynamics simulations to study experimentally characterized topological rearrangements in a series of representative membrane proteins. Recent experimental results have indicated that certain membrane proteins undergo topological rearrangements in which hydrophilic protein elements directly cross the membrane, even though this process should face a large energy barrier. Atomistic and coarse-grained simulations, accelerated by enhanced sampling techniques, will be performed to characterize the pathways by which hydrophilic protein elements cross the membrane. These simulations will elucidate the interplay of protein, lipid, and water interactions that facilitate topological rearrangements on biologically relevant timescales. Based on simulation insight, sequence mutations will be tested for each of the model systems to generate experimentally verifiable predictions. The simulation methods developed and applied in this project will also be of value for studying similar bilayer translocation processes relevant to lipid flip-flop, membrane protein conformational changes, or the delivery of drug carriers to cells.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.