Molecular underpinnings of elasticity and adhesion in self-assembling protein biopolymers

蛋白质和肽的自组装对生物学的许多方面都至关重要。越来越感兴趣的是响应于局部溶液条件而形成的大分子组装体，例如富含蛋白质的液滴（例如，弹性蛋白原、无膜细胞器中的RNA结合蛋白、贻贝足蛋白）、纤维组装体（例如，淀粉样纤维、丝、胶原）和无序交联材料（例如，弹性蛋白、弹性蛋白）。每个组合的形成和功能是基本生物过程的基础，也代表了开发具有受控组装、功能和物理性质的新型生物材料的机会。为了充分利用这些系统，首先重要的是要了解驱动其组装和结构的原理，以及定义其功能特性的原理。我们已经使用核磁共振（NMR）和广泛的生物物理方法来阐明几种类型的自组装多肽的结构和组装机制：淀粉样蛋白原纤维和细胞毒性低聚物;跨膜螺旋;液滴;和基于人类弹性蛋白的交联材料。这为我们提供了一套强大的工具，用于跟踪自组装肽在整个组装过程中的结构和动力学。建立在这些以前的研究，我们将确定的分子基础的组装和材料特性的多肽表现出两个特定的属性的兴趣弹性和表面粘附。 I.确定节枝弹性蛋白和基于节枝弹性蛋白的多肽的原子结构。树脂蛋白是一种昆虫弹性体，其在序列（更极性和芳香性）和材料性质（更高的可压缩性）上与脊椎动物弹性蛋白显著不同，并且在分子水平上表征较差。结构表征将提供深入了解节枝弹性蛋白如何在昆虫中执行生物力学功能，并将用于设计基于节枝弹性蛋白的肽与定义的机械性能。二.确定贻贝足蛋白自组装和表面粘附的分子基础。贻贝足蛋白（Mfps）是一种重复的、无序的、高度化学修饰的蛋白质，能够自组装形成结构未知的强水下粘合剂。我们将确定MFP组装和粘附的分子基础，并将测试弹性生物材料表面附着的MFPS的效用。三.发展蛋白质弹性体中压缩与延伸的分子理解。使用我们最近开发的NMR方法来监测弹性拉伸或压缩对生物聚合物的分子效应，我们将确定如何基于弹性蛋白的材料，其在拉伸和压缩下表现出相似的弹性模量，作为弹性体。这将为弹性组织生物学和生物材料设计提供重要的见解。

The self-assembly of proteins and peptides is critical to many aspects of biology. Of increasing interest are large macromolecular assemblies that form in response to local solution conditions, such as protein-rich droplets (eg. tropoelastin, RNA binding proteins in membraneless organelles, mussel foot proteins), fibrous assemblies (eg. amyloid fibrils, silk, collagen), and disordered cross-linked materials (eg. elastin, resilin). The formation and function of each assemblage underlies fundamental biological processes, and also represents an opportunity to develop novel biomaterials with controlled assembly, functionality, and physical properties. To make full use of these systems it is first important to understand the principles that drive their assembly and structure, and which define their functional properties. We have used nuclear magnetic resonance (NMR) and extensive biophysical methods to elucidate the structures and assembly mechanisms of several types of self-assembling polypeptides: amyloid fibrils and cytotoxic oligomers; transmembrane helices; fluid droplets; and crosslinked materials based on human elastin. This has provided us with a robust set of tools for tracking the structure and dynamics of self-assembling peptides through their entire assembly process. Building on these previous studies, we will determine the molecular basis for the assembly and material properties of polypeptides exhibiting two specific properties of interest elasticity and surface adhesion. i. Determine the atomistic structures of resilin and resilin-based polypeptides. Resilin is an insect elastomer that differs significantly from vertebrate elastin in sequence (more polar and aromatic) and material properties (higher compressibility), and is poorly characterized at the molecular level. Structural characterization will provide insight into how resilin performs biomechanical functions in insects, and will be used to design resilin-based peptides with defined mechanical properties. ii. Determine the molecular basis for self-assembly and surface adhesion of mussel foot proteins. Mussel foot proteins (Mfps) are repetitive, disordered and highly chemically modified proteins which self-assemble to form strong underwater adhesives of unknown structure. We will determine the molecular basis for Mfp assembly and adhesion, and will test the utility of Mfps for surface attachment of elastic biomaterials. iii. Develop a molecular understanding of compression versus extension in protein elastomers. Using NMR methods we recently developed to monitor the molecular effects of elastic extension or compression on biopolymers, we will determine how resilin-based materials, which exhibit similar elastic moduli under both extension and compression, function as elastomers. This will provide important insights for both elastic tissue biology and biomaterials design.