Mecahnism of the Conformational Change in E1E2-Type Transport Atpases

E1E2型转运Atpases构象变化的机制

• 批准号: 9106338
• 负责人: Larry Faller
• 金额: $ 14.4万
• 依托单位: University of California-Los Angeles
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 1992
• 资助国家: 美国
• 起止时间: 1992-02-15 至 1995-01-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=9106338&HistoricalAwards=false
• 关键词: Mecahnism; Conformational; Change; E1E2; Type

A variety of life processes, ranging from muscle contraction to nutrient absorption, are either triggered or driven by the selective transport of ions across cell membranes. The working hypothesis in virtually all models of mammalian active ion transport is that the carrier can assume different conformations in which the ion binding sites are alternately exposed to opposite sides of the membrane. The mechanism of the conformational change is unknown. Does the conformational change gate a channel, or is extensive rearrangement of the protein structure involved? The principal objective of the research proposed in this application is to obtain physicochemical data on the conformational transition step in the reaction mechanism to permit discrimination among alternative proposals for active ion transport. The forward and reverse rates of the conformational change reported by fluorescent labeling of E1E2-pumps will be measured as a function of temperature. Analysis of the results by absolute reaction rate theory places contraints on the types of molecular chemical events that are occurring by resolving the enery which determines the rate and extent of reaction into heat changes resulting from formation, or cleavage, of chemical bonds and into changes in the organization of the system that increase, or decrease, the number of molecular degrees of freedom. The transport enzyme, the monovalent cation and the solvent structure will be empirically varied to learn which reactants are important and how they affect the conformational change in E1E2-enyzmes.

从肌肉收缩到营养吸收的各种生命过程都是由离子跨细胞膜的选择性运输触发或驱动的。 几乎所有哺乳动物活性离子运输模型的工作假设是载体可以呈现不同的构象，其中离子结合位点交替暴露于膜的相对侧。 构象变化的机制尚不清楚。 构象变化是否会影响通道，或者是否涉及蛋白质结构的广泛重排？ 本申请提出的研究的主要目的是获得反应机制中构象转变步骤的物理化学数据，以允许区分活性离子传输的替代方案。 E1E2 泵荧光标记报告的构象变化的正向和反向速率将作为温度的函数进行测量。 通过绝对反应速率理论对结果的分析对分子化学事件的类型进行了限制，这些分子化学事件的类型通过将决定反应速率和程度的能量解析为由化学键的形成或断裂引起的热变化以及增加或减少分子自由度数量的系统组织变化来实现。 转运酶、单价阳离子和溶剂结构将根据经验进行变化，以了解哪些反应物是重要的以及它们如何影响 E1E2 酶的构象变化。