BIOCHEMISTRY AND BIOPHYSICS OF BPTI FOLDING MUTANTS

这项工作的广泛、长期目标是阐明 管理蛋白质折叠。牛胰酶抑制物(BPTI) 被选为模型系统是因为它是一种简单的球状多肽和 大量的结构、生物物理和理论数据已经 可用于野生型蛋白质。BPTI也是最被理解的 库尼茨类蛋白酶抑制剂的一员，该家族包括 一些与人类生理和疾病有关的成员，包括 脂蛋白相关凝血抑制物及其选择性剪接 阿尔茨海默病淀粉样β蛋白前体的结构域。 这项研究的总体基本主旨是使 具有干扰折叠特性的BPTI的转基因形式， 大量表达这些蛋白质，并对它们进行生物物理特性鉴定。 这笔赠款的具体研究重点是： 1)通过制作BPTI来解决“设计出”二硫键的问题 缺失两个或两个以上天然二硫化物的突变体； 2)对所有稳定相互作用进行量化调查 通过系统地将每个非丙氨酸残基突变为丙氨酸和 表征得到的突变体的稳定自由能； 3)测试蛋白质折叠的“纸板箱”模型 静电对5-55二硫键形成的贡献 全球多肽稳定性； 4)促进合作者实验室正在进行的工作，旨在 研究选定的BPTI突变体的结构和动力学。 据推测，这种遗传和生物物理相结合的方法 剖析一个非常简单的模型蛋白质的折叠机制 阐明目前仍知之甚少的蛋白质折叠过程 将军。

The broad, long-term objective of this work is to elucidate the rules that govern protein folding. Bovine pancreatic trypsin inhibitor (BPTI) was chosen as a model system because it is a simple globular polypeptide and a large amount of structural, biophysical, and theoretical data is already available for the wild type protein. BPTI is also the best understood member of the Kunitz class of protease inhibitors, a family that includes several members relevant to human physiology and disease including the lipoprotein-associated coagulation inhibitor and the alternatively-spliced domain of the Alzheimer's amyloid beta protein precursor. The overall basic thrust of the research has been to make genetically-modified forms of BPTI that have perturbed folding properties, express these proteins in quantity, and characterize them biophysically. The specific research priorities for this grant are: 1) Address the problem of "designing out" disulfide bonds by making BPTI mutants missing two or more of the native disulfides; 2) Conduct a quantitative survey of all stabilizing interactions in the molecule by systematically mutating each non-alanine residue to alanine and characterizing the stabilization free energies of the resulting mutants; 3) Test the "cardboard box" model of protein folding by measuring the contribution of electrostatics to 5-55 disulfide bond formation and to global polypeptide stability; 4) Facilitate ongoing work in collaborators' laboratories aimed at investigating the structure and dynamics of selected BPTI mutants. Presumably, this combined genetic and biophysical approach to the dissection of the folding mechanism of a very simple model protein will illuminate the still poorly-understood process of protein folding in general.