Structure, assembly, and biological activity of amyloid peptides and proteins.

淀粉样纤维是一种高度有序的丝状结构，由一系列不同的蛋白质和多肽组成。这些组件最初被描述为淀粉样变性中潜在的细胞毒性介质，并与普恩病毒疾病的传染性有关。最近，淀粉样蛋白被证明在各种生物过程中发挥着重要的功能作用，从皮肤黑色素的组装，真菌和酵母的遗传多样性，以及细菌和酵母在生物膜形成过程中对表面的黏附。尽管它们具有重要的生物学意义，但不同蛋白质自组装成具有高度不同功能的紧密相关结构的能力仍然知之甚少。同样，目前还不知道这些组件中的一些如何具有强大的细胞毒性，而另一些组件如何避免毒性来执行生物任务。这种建立在有序支架上的化学和功能多样性，也是开发新型生物材料的理想特征。了解淀粉样蛋白在生物学中的作用，以及开发其材料潜力，都需要详细了解纤维形成的分子基础，以及将序列与纤维状态的结构和功能联系起来的能力。 我们将使用固态核磁共振来确定由具有不同序列和功能的多肽和蛋白质形成的淀粉样纤维的分子结构。这种方法已经成为结构生物学的一个强大的工具，否则难以处理的系统，并使我们能够获得原子分辨结构的纤维蛋白组件。我们将集中于三个不同的系统，提供一个机会来阐明淀粉样蛋白结构变异的分子基础，并区分有毒和功能组装。具体地说，我们将：1)确定由模型淀粉样肽形成的细胞毒性低聚体杀死细胞的机制；2)确定由血清淀粉样蛋白A形成的纤维中所见独特结构多态的基础；以及3)确定淀粉样原纤维形成区域如何调节真菌生物膜中细胞与细胞及细胞表面的黏附。

Amyloid fibrils are highly ordered filamentous structures formed by a wide range of different proteins and peptides. These assemblies were originally described as potential mediators of cytotoxicity in amyloidosis, and are linked to infectivity in prion diseases. More recently, amyloids been shown to play important functional roles in diverse biological processes ranging from assembly of the skin pigment melanin, genetic diversification of fungi and yeast and adhesion of bacteria and yeast to surfaces during biofilm formation. Despite their biological importance, the ability of diverse proteins to self-assemble into closely related structures having highly divergent function remains poorly understood. Similarly, it is not known how some of these assemblies can be potently cytotoxic while others avoid toxicity to perform biological tasks. This chemical and functional diversity, built on an ordered scaffold, is also a desirable feature in the development of novel biomaterials. Understanding the roles of amyloid proteins in biology, and exploiting their materials potential, both require detailed knowledge of the molecular basis for fibril formation, and the ability to link sequence with the structure and function of the fibrillar state. We will use solid-state nuclear magnetic resonance to determine the molecular structures of amyloid fibrils formed by peptides and proteins with varied sequence and functionality. This method has emerged as a powerful tool for structural biology of otherwise intractable systems, and allows us to obtain atomic resolution structures of fibrillar protein assemblies. We will focus on three distinct systems, providing an opportunity to elucidate the molecular basis for structural variation in amyloids, and to distinguish between toxic and functional assemblies. Specifically we will: 1) Determine the mechanism through which cytotoxic oligomers formed by model amyloid peptides kill cells; 2) Define the basis for the unique structural polymorphism seen in fibrils formed by the serum amyloid A protein; and 3) Determine how amyloid fibril forming domains mediate cell-cell and cell-surface adhesion in fungal biofilms.