Structure and stability of 3-alpha vs alpha/beta folds

描述(由申请人提供)：本提案的目标是给出一种蛋白质折叠(和功能)如何转变为另一种蛋白质的遗传、热力学和结构描述。这是基于我们的能力：1)创建具有不同折叠(异形对)的高度同源蛋白质；2)在异形对的每个成员中设计双重功能，使得一个结合功能在一个折叠中明显，而在另一个折叠中隐藏；3)使用折叠和结合之间的热力学联系来确定折叠倾向；4)使用核磁共振来确定异形对的结构。我们从整体稳定性代码中解析折叠特定折叠代码的能力使我们能够研究两个折叠之间的构象转换代码。 具体目标如下：1.确定从一个折叠和功能到另一个折叠的有效进化路径；2.建立分隔两个功能折叠的最小序列间隙；3.为结构和热力学研究生成具有最大同一性的异形对。我们将研究小分子氨基酸如何决定两种不同的天然折叠。这将通过完全检查分隔两个折叠的功能序列空间，测量少量突变对折叠倾向的影响，并确定结构来评估有限的一组相互作用如何确定折叠来实现这一点。理解一小部分突变如何导致两个稳定的单体折叠和两个不同功能之间的切换，将对我们理解蛋白质折叠、生物信息学以及新折叠和功能的自然进化具有深远的意义。这一建议的目的是更好地了解氨基酸序列如何指定独特的三级折叠，方法是将折叠问题减少到那些包含最多信息的氨基酸，从而指定一个折叠而不是另一个折叠。这项工作对理解蛋白质折叠密码和新折叠的进化具有直接的意义，将对蛋白质工程、蛋白质结构预测和从头蛋白质设计领域有很大的帮助。在继续开发新的生物医学有用疗法以改善人类健康方面，将需要在这些领域取得进展。

DESCRIPTION (provided by applicant): The goal of this proposal is to give a genetic, thermodynamic and structural description of how one protein fold (and function) changes into another. This is based on our ability to: 1) Create highly homologous proteins with different folds (heteromorphic pairs); 2) Engineer dual functional capacity within each member of the heteromorphic pair such that one binding function is manifest in one fold and cryptic in the other fold; 3) Use the thermodynamic linkage between folding and binding to determine folding propensity; 4) Use NMR to determine structures of heteromorphic pairs. Our ability to parse the fold-specific folding code from the overall stability code allows us to study a code for conformational switching between two folds. The specific goals are as follows: 1. Determine an efficient evolutionary path from one fold and function to another; 2. Establish the minimum sequence gap separating two functional folds; 3. Generate heteromorphic pairs of maximum identity for structural and thermodynamic study. We will study how small sets of amino acids determine two different native folds. This will be done by completely examining the functional sequence space separating the two folds, measuring the effects of small numbers of mutations on folding propensity, and determining structures to assess how a limited set of interactions can determine fold. Understanding how a small set of mutations can cause a switch between two stable, monomeric folds and two different functions will have profound implications on our understanding of protein folding, bioinformatics and the natural evolution of new folds and functions. The aim of this proposal is to better understand how amino acid sequence specifies unique tertiary folds by reducing the folding problem to those amino acids that contain the most information toward specifying one fold versus another. This work has direct implications for understanding the protein folding code and the evolution of new folds and will greatly benefit the fields of protein engineering, protein structure prediction, and de novo protein design. Advances in these areas will be needed in the continuing development of new biomedically useful therapeutics to improve human health.