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

蛋白质和多肽的自组装对生物学的许多方面都是至关重要的。人们越来越感兴趣的是响应局部溶液条件而形成的大分子组件，例如富含蛋白质的液滴(例如。原弹性蛋白，无膜细胞器中的RNA结合蛋白，贻贝足部蛋白)，纤维集合体(例如。淀粉样纤维、丝、胶原蛋白)和无序的交联物(例如。弹性蛋白、resilin)。每个组装体的形成和功能是基本生物过程的基础，也是开发具有受控组装、功能和物理特性的新型生物材料的机会。要充分利用这些系统，首先必须了解驱动它们的组装和结构以及定义它们的功能属性的原理。我们已经使用核磁共振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：淀粉样纤维和细胞毒性低聚物；跨膜螺旋；液滴；以及基于人弹性蛋白的交联材料。这为我们提供了一套强大的工具，可以在整个组装过程中跟踪自组装肽的结构和动力学。在前人研究的基础上，我们将确定具有兴趣弹性和表面粘附性两种特殊性质的多肽的组装和材料性质的分子基础。I.测定Resilin和Resilin多肽的原子结构。Resilin是一种昆虫弹性体，在序列上(更具极性和芳香性)和材料性质(更高的压缩性)上与脊椎动物弹性蛋白有很大不同，在分子水平上的表征很差。结构表征将使人们深入了解resilin如何在昆虫中发挥生物力学功能，并将用于设计具有明确机械性能的resilin多肽。二、确定贻贝足部蛋白自组装和表面黏附的分子基础。贻贝足部蛋白(MFP)是一种重复的、无序的、高度化学修饰的蛋白质，可以自组装形成结构未知的强大水下粘附剂。我们将确定MFP组装和黏附的分子基础，并将测试MFP在弹性生物材料表面附着的效用。三、发展对蛋白质弹性体中压缩和拉伸的分子理解。使用我们最近开发的用于监测弹性拉伸或压缩对生物聚合物的分子效应的核磁共振方法，我们将确定基于resilin的材料如何作为弹性体发挥作用，这些材料在拉伸和压缩下都表现出相似的弹性模量。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.