Structural Origins of Cooperativity in Molten Globule Formation

描述（由申请人提供）：指导当前提案的长期目标是对驱动无肌红蛋白折叠的基本分子机制的定量理解。平衡折叠和动力学折叠中间体的详细结构和动力学表征是根据氨基酸序列预测蛋白质结构和合理开发药物的关键步骤。本研究将解决围绕平衡失肌红蛋白折叠途径的几个重要问题。最初的研究将集中在通过特定位置的自旋标签衍生的距离约束的计算模型来表征熔融球结构系综中天然螺旋堆积的拓扑异质性和程度。后续工作将侧重于利用弛豫色散核磁共振测量来监测平衡展开途径的微秒到毫秒时间尺度动力学，重点是解决酸展开状态的早期坍塌事件，以及在熔融球形成之前协同形成折叠核。一旦对野生型蛋白的弛豫分散动力学进行了彻底的探索，将对表现出核心包装改变的无肌红蛋白突变体进行更多的定性测量，以回答有关崩塌过程中的可塑性和适应性的基本问题。

DESCRIPTION (provided by applicant): The long-term objective guiding the current proposal is a quantitative understanding of the fundamental molecular mechanisms driving apomyoglobin folding. Detailed structural and dynamical characterization of equilibrium and kinetic folding intermediates is a critical step toward the prediction of protein structures from amino acid sequence and the rational development of drugs. This research will address several important questions surrounding the equilibrium apomyoglobin folding pathway. Initial studies will focus on characterizing the topological heterogeneity and extent of native-like helical packing in the molten globule structural ensemble through computational modeling of site-specific spin label derived distance constraints. Subsequent work will focus on utilizing relaxation dispersion NMR measurements to monitor microsecond to millisecond timescale dynamics along the equilibrium unfolding pathway with emphasis on resolving early collapse events in the acid-unfolded state and cooperatively formed folding nuclei preceding molten globule formation. Once the relaxation dispersion kinetics have been thoroughly explored in the wild type protein, more qualitative measurements will be made on apomyoglobin mutants which exhibit altered core packing to answer fundamental questions about plasticity and adaptability in the collapse process.