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去蛋白肌红蛋白折叠的基本分子机制进行定量了解。对平衡折叠中间体和动力学折叠中间体的详细结构和动力学表征是从氨基酸序列预测蛋白质结构和合理开发药物的关键步骤。这项研究将解决围绕平衡的载脂蛋白折叠途径的几个重要问题。最初的研究将集中在通过对特定位置的自旋标记衍生的距离约束进行计算建模来表征熔融球体结构系综中类自然螺旋堆积的拓扑异质性和程度。随后的工作将集中在利用弛豫色散核磁共振测量来监测沿平衡展开路径的微秒到毫秒的时间尺度动力学，重点是解决酸展开状态下的早期坍塌事件和在熔融球体形成之前协同形成的折叠核。一旦彻底研究了野生型蛋白质的松弛分散动力学，将对核心堆积发生变化的去肌红蛋白突变体进行更多的定性测量，以回答关于崩溃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.