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

描述（由申请人提供）：在破译的主要困难， 蛋白质折叠密码是折叠信息是分散的。的目的 建议是更好地了解氨基酸序列如何指定独特的 三级折叠通过将折叠问题减少到那些 包含指定一个折叠与另一个折叠的最多信息。做 为此，Orban博士建议生成和研究具有高表达的蛋白质对。 序列相同但三级结构不同。他将学习转换 α/β结构和三个α-螺旋束结构（3-a）之间的关系， 氨基酸序列的功能，并表征分离两者的能量 构象的各种生物物理方法。的igg结合结构域 链球菌蛋白G（GB）和葡萄球菌蛋白A（AB）将用作 一双。蛋白G（GA）和GB的白蛋白结合结构域将被用作 第二对。所有三个结构域具有相似的大小（45-58个氨基酸）。AB GA具有3-α折叠，GB具有α/β折叠。噬菌体展示 选择方法将用于诱导构象之间的转换， 3-a结构和α/β结构，同时保持最高的 序列同一性的可行水平。PI将使用热力学 折叠与IgG或白蛋白结合之间的连接，以定量折叠 在同源对中不同的每个氨基酸的信息含量。一 将使用多种生物物理技术，包括多维NMR 探索序列空间的结构和能量特性， 同源蛋白质对。更全面地了解初级 序列决定了稳定的、独特的蛋白质折叠， 蛋白质工程、蛋白质结构预测和从头蛋白质领域 设计这项技术也可能应用于创造分子 基于蛋白质的特性的开关， 一个微妙的外部刺激。

DESCRIPTION (provided by applicant): The major difficulty in deciphering the protein folding code is that folding information is diffuse. 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 which contain the most information toward specifying one fold versus another. To do this, Dr. Orban proposes to generate and study pairs of proteins with high sequence identity but different tertiary structures. He will study switching between alpha/beta structure and three a-helix bundle structure (3-a) as a function of amino acid sequence and characterize the energy separating the two conformations by a variety of biophysical methods. The IgG-binding domains of streptococcal protein G (GB) and staphylococcal protein A (AB) will be used as one pair. The albumin binding domain of protein G (GA) and GB will be used as the second pair. All three domains are of similar size (45-58 amino acids). AB and GA have 3-alpha folds and GB has an alpha/beta fold. Phage display selection methods will be used to induce a conformational switch between the 3-a structure and the alpha/beta structure, while maintaining the highest practicable level of sequence identity. The PI will then use the thermodynamic linkage between folding and IgG- or albumin-binding to quantitate the folding information content of each amino acid which differs in homologous pairs. A variety of biophysical techniques including, multidimensional NMR, will be used to explore structural and energetic properties of the sequence space between the homologous protein pairs. More complete knowledge concerning how primary sequence determines stable, unique protein folds should greatly advance the fields of protein engineering, protein structure prediction and de novo protein design. There also may be applications of this technology to create molecular switches based on the property of a protein to change conformations in response to a subtle external stimulus.