THEORY OF FOLDING TRANSITION IN A-HELICAL PROTEIN

拟议工作的目标是发展统计 机械模型旨在区分自然和相对 短期、中期和长期相互作用的重要性， 拓扑约束的折叠过渡占主导地位 α-螺旋蛋白。 最初，拟议的工作重点是 平衡和动力学理论的进一步发展 α-螺旋、双链、卷曲螺旋中螺旋-卷曲转变， 作为重要的肌肉调节蛋白原肌球蛋白。 这些 架构简单的系统不仅具有很好的内在 生物化学兴趣（例如，原肌球蛋白在 肌肉收缩），但也具有许多定性方面， 球状蛋白质折叠过程;从中获得的见解 研究将被用来检查折叠过渡， 球状蛋白质 具体来说，拟议的工作对盘绕线圈 和球状蛋白模型包括以下（1） 平衡理论的进一步发展和应用 螺旋线圈中的螺旋-线圈过渡以提供半- 所有现存实验数据的定量理论 非交联、单交联和双交联兔α-和 β-原肌球蛋白 (2)交联作用的研究 通过螺旋线圈结构上的感应应力 使用ECEPP/2构建原肌球蛋白片段 Scheraga等人的方法，其次是势能 最小化 (3)采用动态蒙特卡罗模拟 和分析模型，卷曲螺旋的动力学理论， 无规卷曲跃迁将被扩展到包括环熵 (the当结构的末端 无规卷曲相对于自由时受到约束， 平衡时至关重要的影响）和 非交联分子，链离解和交换 两个链的寄存器外状态之间的关系。 尝试 将确定实验签名指示 各种松弛机制的存在。 (4)一个 变性的平衡和动力学理论 由多个蛋白质组成的模型球状蛋白质的转变 通过环或弯曲连接在一起的相互作用的螺旋将 开发 这些研究的目的是检验 循环熵在很大程度上决定了 单结构域球状蛋白质平衡双态模型 折叠和天然状态的动力学稳定。 (5)到 阐明合理的新生折叠途径，布朗动力学 提出了示意性模型的仿真。

The goal of the proposed work is the development of statistical mechanical models designed to disect the nature and relative importance of short, medium and long range interactions and topological constraints on the folding transition of predominantly alpha-helical proteins. Initially the proposed work focuses on the further development of the equilibrium and kinetic theory of the helix-coil transition in alpha-helical, two-chain, coiled coils such as the important muscle regulatory protein tropomyosin. These architecturally simple systems are not only of great intrinsic Biochemical interest (e.g. tropomyosin plays an important role in muscle contraction) but also possess many qualitative aspects of the globular protein folding process; insights gained from these studies will be employed to examine the folding transition in globular proteins. Specifically, the proposed work on coiled coils and globular protein models comprises the following (1) the further development and application of the equilibrium theory of the helix-coil transition in coiled coils to provide a semi- quantitative theory of all extant experimental data on noncrosslinked, singly and doubly crosslinked rabbit alpha-and beta-tropomyosin. (2) The investigation of the effect of crosslink induced stress on the coiled coil structure through the construction of tropomyosin fragments using the ECEPP/2 procedure of Scheraga et al., followed by potential energy minimization. (3) Employing dynamic Monte Carlo simulations and analytic models, the kinetic theory of the coiled coil helix-to- random coil transition will be extended to include loop entropy (the reduction in configurational entropy when the ends of a random coil are constrained relative to when they are free, an effect of crucial importance at equilibrium) and for noncrosslinked molecules, chain dissociation an interchange between the out-of-register states of the two chains. Attempts will be made to identify experimental signatures indicative of the presence of the various relaxation mechanisms. (4) An equilibrium and kinetic theory of the native to denatured transition in model globular proteins composed of multiply interacting helices joined together by loops or bends will be developed. These studies are designed to test the conjectures that loop entropy is largely responsible for the validity of the equilibrium two state model of single domain globular protein folding and for the kinetic stabilization of the native state. (5) To elucidate plausible nascent folding pathways, Brownian dynamics simulations of schematic models are proposed.