Joint Study on the Mechanism of Protein Folding

阐明蛋白质折叠的机制对于理解蛋白质的结构和功能至关重要。蛋白质折叠是蛋白质一级氨基酸序列中包含的遗传信息传递到其独特的三维结构中的机制。我们开展了国际科学研究计划，以澄清蛋白质折叠的各种问题，并取得了以下结果。我们表征了熔融小球的构象和稳定性，以及各种蛋白质的相关状态，包括细胞色素c、去肌红蛋白和α-乳白蛋白。特别是，我们使用了溶液X射线散射来表征它们的致密性和形状。根据溶液X射线散射得到的结构性质，描述了熔融球态的一般结构图像和概念结构图像，并与核磁共振模型进行了比较。结果表明，熔融球体可用来描述较宽范围的…更多的非天然构象，没有一个与最初的定义完全一致。β-乳球蛋白是一种主要的β-折叠蛋白，是一个有趣的例子，代表了局部和非局部二级结构偏好的不一致。我们研究了β-乳球蛋白的折叠动力学，发现部分α-螺旋中间体在形成天然的β-折叠之前是瞬时积累的。结果表明，β-乳球蛋白的折叠遵循非分级机制，其中非天然的α-螺旋结构起着重要作用。在GDN-HCl诱导的平衡去折叠转变过程中也检测到类似的α-螺旋中间体。为了了解分子伴侣GroEL底物所需的构象特征，我们研究了GroEL与马细胞色素c不同构象状态的相互作用。结果表明，底物上波动和暴露的疏水团簇是相互作用的原因，相互作用受静电相互作用的调制。这些特征类似于细胞色素c衍生物与带负电荷的磷脂膜的相互作用，表明了共同的作用机制。较少

Elucidation of the mechanisms of protein folding, by which the genetic information contained in the primary amino acid sequence of a protein is transmitted to its unique three-dimensional structure, is essential for understanding the structure and function of proteins. We carried out the International Scientific Research Program in order to clarify various problems of protein folding and obtained the following results.1. We characterized the conformation and stability of the molten globule and related states of various proteins including cytochrome c, apomyoglobin, and alpha-lactalbumin. In particular, we used solution X-ray scattering to characterize their compactness and shape. Based on the structural properties obtained by solution X-ray scattering, general and conceptual structural images for the molten globule states are described and compared with the model obtained by nuclear magnetic resonance. The results indicate that the term "molten globule" is used to describe a wide range … More of non-native conformations, none of them completely consistent with the original definition.2. beta-Lactoglobulin, a predominantly beta-sheet protein, is an interesting example representing inconsistency of the local and non-local secondary structure preference. We have studied the folding kinetics of beta-lactoglobulin and showed that a partly alpha-helical intermediate accumulates transiently before formation of the native beta-sheet. The results suggest that the folding of beta-lactoglobulin follows a non-hierarchical mechanism, in which non-native alpha-helical structures play important roles. The similar alpha-helical intermediate was also detected during the equilibrium unfolding transition induced by Gdn-HCl.3. To understand the conformational features required for the substrate of GroEL,a molecular chaperone, we studied the interactions of GroEL with various conformational states of horse cytochrome c. The results indicate that the fluctuating and exposed hydrophobic clusters of the substrates are responsible for the interaction, and that the interaction is modulated by electrostatic interaction. These characteristics are similar to those of the interaction of cychrome c derivatives with negatively charged phospholipid membranes, suggesting a common mechanism. Less