Quality-structure relationships of soybean storage proteins

本项目的目的是阐明大豆贮藏蛋白、大豆球蛋白和伴大豆球蛋白的质量结构关系。我们从三个角度对此进行了研究。(1)球蛋白的构效关系：我们在本研究之前揭示的构效关系的基础上，对球蛋白进行了修饰，以改善其功能性质。大多数修饰后的球蛋白具有比天然球蛋白更好的功能性质，说明我们揭示的构效关系是合理的。(2)共球蛋白的结构-功能关系：构建了共球蛋白的α、α‘和β亚基组成亚基的大肠杆菌表达系统。所有重组亚基都形成了具有正确构象的同源三聚体。对这些重组亚基的功能性质的分析揭示了决定其溶解性、表面疏水性、热稳定性、乳化能力和热诱导缔合的结构因素。(3)对重组和天然大豆球蛋白和伴球蛋白进行了X射线结晶学研究：利用大肠杆菌表达系统制备了重组球蛋白A1aB1b、A3B4和伴球蛋白β，从含有球蛋白或伴球蛋白的突变大豆中制备了天然球蛋白A3B4和伴球蛋白β。在2.1-2.8*水平上对其三维结构进行了求解。这些研究有助于在分子水平上研究大豆球蛋白和伴大豆球蛋白的质量-结构关系。

Object of this project is to elucidate quality-structure relationships of soybean storage proteins glycinin and conglycinin. We approached to investigate these from three viewpoints.(1) Structure-function relationships of glycinin : We modified glycinin to improve its functional properties based on the structure-function relationships revealed by us prior to this study. Most of the modified glycinins exhibited better functional properties than those of the native glycinin, indicating that the structure-function relationships revealed by us are reasonable.(2) Structure-function relationships of conglycinin : F.coli expression systems for the constituent subunits alpha, alpha' and beta of conglycinin were constructed. All recombinant subunits formed homotrimers having the proper conformation. Analyses of functional properties of these recombinant subunits revealed structural factors determining their solubilities, surface hydrophobicities, heat-stabilities, emulsifying abilities and heat-induced association.(3) X-ray crystallography of recombinant and native glycinin and conglycinin : Recombinant proglycinin A1aB1b, A3B4 and conglycinin beta prepared using B.coli expression systems, and native glycinin A3B4 and conglycinin beta prepared from mutant soybeans containing glycinin or conglycinin composed of a kind of subunit were crystallized for X-ray crystallography. Their three dimensional structures were solved at 2.1-2.8 * levels. These elucidation surely contribute to investigate quality-structure relationships of glycinin and conglycinin at a molecular level.