Opportunistic complexation and mesoscopic aggregates in protein solutions

蛋白质溶液中的机会络合和介观聚集体

• 批准号: 1518204
• 负责人: Vassiliy Lubchenko
• 金额: $ 63.18万
• 依托单位: University of Houston
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2015
• 资助国家: 美国
• 起止时间: 2015-07-15 至 2020-06-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1518204&HistoricalAwards=false
• 关键词: Opportunistic; complexation; mesoscopic; aggregates; protein

Title: Opportunistic complexation and mesoscopic aggregates in protein solutionProtein aggregation is a central problem of biophysics and other life sciences. This investigation focuses on a particularly puzzling type of protein aggregation during which protein-rich inclusions form in protein solutions. These inclusions are a micron or less in size and have been called the "mesoscopic clusters". Despite their small volume, the clusters are essential nucleation sites for ordered protein solids such as crystals and sickle cell anemia fibers. The mesoscopic clusters are also at odds with standard notions of thermodynamics, which dictates that such clusters should be either much larger or should not exist at all. Understanding the molecular origin of the mesoscopic clusters will resolve a major fundamental question of thermodynamics. This research will test the hypothesis that the mesoscopic clusters are caused by formation of long-lived complexes made up of individual protein molecules. A combination of advanced experimental techniques, theoretical modeling, and computer simulations will be employed to test this hypothesis. Understanding protein aggregation has implications in all facets of biology as well as on biotechnology and health. At the core of the broader impact activities is training of graduate, undergraduate, and, in particular, high school students. The project is a multidisciplinary study that spans many topics in physics, chemistry, and biology and represents a great platform for further academic endeavors of the involved students.The microscopic hypothesis underlying the proposed work is that the mesoscopic clusters stem from the formation of transient protein-containing complexes. The complexes are stabilized at high protein densities. In contrast with the bulk solution, the complexes are the dominant protein-containing species inside the clusters. In a steady-state cluster, the influx of protein in the form of monomers is exactly balanced by the outflow of protein in the form of complexes. The nature of the complex depends on whether the protein is monomeric, as is lysozyme, or oligomeric, as is hemoglobin, ordinarily a tetrameric protein. The investigators in this study hypothesize that for typically monomeric proteins, complex formation is accompanied by partial protein unfolding and, possibly, domain swapping. In the case of oligomeric proteins, the complexes are oligomers that contain an untypical number of individual monomers. A core aspect of the hypothesis is that the complexes are opportunistic; they represent untypical ways to transiently bind individual protein molecules together. The research team will establish the identity and mechanisms of the complexation using a combination of physicochemical and biochemical experimental techniques (dynamic light scattering, Brownian microscopy, mass spectroscopy, amide exchange NMR, sheer flow) and theoretical tools (molecular modeling employing coarse-grained energy functions and the classical density functional theory). They will test whether the clusters are truly steady-state objects and explore the possibility that cluster formation has a slow, irreversible component. This part of the proposed study may answer the question whether clusters ripen according to an Ostwald-like scenario, or a different mechanism is involved.

职务名称：蛋白质溶液中的介观聚集体与络合作用蛋白质聚集是生物物理学和其他生命科学的核心问题。这项调查的重点是一个特别令人费解的类型的蛋白质聚集过程中，蛋白质溶液中形成的富含蛋白质的夹杂物。 这些夹杂物的尺寸为微米或更小，被称为“介观团簇”。尽管它们体积小，但这些簇是有序蛋白质固体如晶体和镰状细胞贫血纤维的基本成核位点。介观团簇也与热力学的标准概念不一致，热力学的标准概念要求这样的团簇要么大得多，要么根本不存在。 理解介观团簇的分子起源将解决热力学的一个主要基本问题。这项研究将测试介观簇是由单个蛋白质分子组成的长寿命复合物形成引起的假设。先进的实验技术，理论建模和计算机模拟相结合，将被用来测试这一假设。 了解蛋白质聚集对生物学的各个方面以及生物技术和健康都有影响。更广泛的影响活动的核心是培训研究生、本科生，特别是高中生。 该项目是一项跨学科的研究，涉及物理、化学和生物学的多个主题，为参与研究的学生提供了一个很好的学术平台。该项目的微观假设是，介观团簇起源于瞬时含蛋白质复合物的形成。 复合物在高蛋白质密度下稳定。 与本体溶液相比，复合物是簇内占主导地位的含蛋白质的物种。在稳态簇中，单体形式的蛋白质流入与复合物形式的蛋白质流出完全平衡。 复合物的性质取决于蛋白质是单体的，如溶菌酶，还是寡聚的，如血红蛋白，通常是四聚体蛋白。 在这项研究中，研究人员假设，对于典型的单体蛋白质，复合物的形成伴随着部分蛋白质解折叠，并可能，结构域交换。 在寡聚蛋白质的情况下，复合物是含有非典型数量的单个单体的寡聚物。 该假说的一个核心方面是复合物是机会主义的;它们代表了将单个蛋白质分子瞬时结合在一起的非典型方式。 研究小组将使用物理化学和生物化学实验技术（动态光散射，布朗显微镜，质谱，酰胺交换NMR，剪切流）和理论工具（采用粗粒能量函数和经典密度泛函理论的分子建模）的组合来确定络合的身份和机制。 他们将测试这些星团是否是真正的稳态天体，并探索星团形成有一个缓慢、不可逆的组成部分的可能性。 这部分研究可能会回答这样一个问题，即集群是否根据Ostwald类似的场景成熟，或者涉及不同的机制。

项目成果

Anomalous Dense Liquid Condensates Host the Nucleation of Tumor Suppressor p53 Fibrils

异常致密液体凝结物承载肿瘤抑制因子 p53 原纤维的成核

• DOI: 10.1016/j.isci.2019.01.027
• 发表时间: 2019
• 期刊: iScience
• 影响因子: 5.8
• 作者: Safari, Mohammad S.;Wang, Zhiqing;Tailor, Kunaal;Kolomeisky, Anatoly B.;Conrad, Jacinta C.;Vekilov, Peter G.
• 通讯作者: Vekilov, Peter G.