USE OF DESIGNED PEPTIDES TO PROBE BETA-SHEET FOLDING

我们建议使用肽模型系统来阐明β-折叠构象稳定性的起源。 这项工作将利用我们实验室的最新进展，并从其他人已经确定了诱导小肽在水溶液中采用反平行β-折叠构象的一般策略。 这种方法的重点是β-发夹折叠单元，其中两条链由一个短环连接。我们将使用基于发夹的实验设计来实现四个具体目标。(1)我们将使用模型系统来探测反平行β折叠二级结构，包括协同性和链间侧链-侧链相互作用对构象稳定性的贡献。(2)我们将研究平行β折叠稳定性的起源与模型系统开发的扩展，从我们的反平行β折叠的工作和其他工作者的结果。(3)我们将从我们的β折叠二级结构模型中构建一个新的三级结构基序，其中聚脯氨酸II（PPII）螺旋包装在双链β折叠的一个面上。 该基序可能以相对较少的残基显示高构象稳定性。 拟议的betabetaPPII基序将提供一个独特的机会，以确定在三级结构水平的协同性的起源。(4)我们将使用发夹结构来评估肽链和非肽寡聚体之间的相互作用。 最终，我们希望鉴定出能够以β折叠样方式与延伸的肽链结合的非天然寡聚体，从而破坏有害的蛋白质聚集过程。拟议的β-折叠模型研究将提高我们对蛋白质折叠偏好的理解，为许多实验室报道的广泛的α-螺旋模型研究提供补充。 我们的研究结果也有助于蛋白质设计和工程的努力，并为淀粉样疾病的化学疗法的发展。

We propose to use peptide model systems to elucidate the origins of beta-sheet conformational stability. This effort will take advantage of recent advances from our laboratory and from others that have identified a general strategy for inducing small peptides to adopt antiparallel beta-sheet conformations in aqueous solution. This approach focuses on the beta-hairpin folding unit, in which two strands are connected by a short loop. We will use hairpin-based experimental designs to achieve four specific aims. (1) We will use model systems to probe antiparallel beta-sheet secondary structure, including the contributions of cooperativity and interstrand sidechain-sidechain interactions to conformational stability. (2) We will examine the origins of parallel beta-sheet stability with model systems developed by extention from our antiparallel beta-sheet work and from results of other workers. (3) We will build from our beta-sheet secondary structure models to create a new tertiary structural motif, in which a polyproline II (PPII) helix packs against one face of a two-stranded beta-sheet. This motif is likely to display high conformational stability with relatively few residues. The proposed betabetaPPII motif will provide a unique opportunity to determine the origins of cooperativity at the tertiary structure level. (4) We will use the hairpin architecture to evaluate interactions between peptide strands and non-peptide oligomers. Ultimately, we would like to identify unnatural oligomers that can bind in beta-sheet-like fashion to an extended peptide strand, and thereby disrupt deleterious protein aggregation processes. The proposed beta-sheet model studies will enhance our understanding of protein folding preferences by providing a complement to the extensive alpha-helix model studies that have been reported from many laboratories. Our results should also contribute to protein design and engineering efforts, and to the development of chemotherapies for amyloid diseases.