THEORY OF FOLDING TRANSITION IN A-HELICAL PROTEIN

拟议工作的目标是发展统计 旨在剥离自然和相关事物的机械模型 短、中、长距离相互作用的重要性以及 占优的折叠跃迁的拓扑约束 α-螺旋蛋白质。最初，拟议的工作重点是 平衡理论和动力学理论的进一步发展 在阿尔法螺旋、双链、盘绕线圈中的螺旋-线圈转变 原肌球蛋白作为重要的肌肉调节蛋白。这些 体系结构简单的系统不仅具有强大的内在 生化兴趣(例如，原肌球蛋白在 肌肉收缩)，但也具有许多定性方面的 球状蛋白质折叠过程；从这些过程中获得的见解 研究将被用来检查折叠转变在 球状蛋白质。具体地说，关于盘绕线圈的拟议工作 和球状蛋白质模型包括以下内容：(1) 均衡理论的进一步发展和应用 盘绕线圈中的螺旋-线圈过渡提供了一种半 现有的所有实验数据的量化理论 非交联型、单交联型和双交联型兔α-和 β-原肌球蛋白。(2)交联剂效应的研究 在盘绕线圈结构上通过 用ECEPP/2构建原肌球蛋白片段 Scheraga等人的程序，随后是势能 最小化。(3)采用动态蒙特卡罗模拟 和解析模型，对螺旋线圈的运动理论进行了分析。 随机卷曲变换将被扩展以包括环路熵 (构型熵的减少，当 随机卷曲相对于它们的自由时间被约束，一个 对均衡的至关重要的影响)和 非交联性分子，链的解离和交换 在两个链的寄存器外状态之间。尝试 将进行识别实验签名，以指示 存在各种松弛机制。(4)一个 天然到变性的平衡和动力学理论 多重构成的模型球状蛋白的跃迁 通过环或弯连接在一起的相互作用的螺旋将是 发展起来的。这些研究旨在检验这些猜想 循环熵在很大程度上决定了 单结构域球状蛋白的平衡二态模型 折叠和本征状态的动力学稳定。(5)至 阐明看似合理的新生折叠路径、布朗动力学 给出了原理图模型的仿真结果。

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.