Structure-quality relationships at molecular level of soybean major storage proteins

大豆蛋白具有降胆固醇和理化功能。其营养价值在植物蛋白中具有优势。因此，希望扩大大豆蛋白的利用。为此，我们必须在分子水平上阐明大豆蛋白的结构-质量（理化和生理功能）关系。我们是这样来解释它们的。(1)甘氨酸和conglycin组成亚基的x射线晶体学在2.3Å分辨率下对conglycin α′核的三维结构进行了解析。建立了原甘氨酸A2B1a和甘氨酸α核的结晶学基础。(2) glycine和conglycine在亚基水平上的结构-理化功能关系从含有该亚基的大豆突变品种中纯化出由单个亚基和受限亚基组成的分子种。对其结构特征和生理功能的分析表明，它们具有典型的结构-理化功能关系。(3)确定与甘氨酸胆汁酸结合能力相关的肽区我们利用大肠杆菌表达系统确定了与甘氨酸A1aB1b胆汁酸结合能力相关的最重要区域。基于(1)、(2)和(3)的研究结果，我们可以通过蛋白质工程技术深入了解甘氨酸和甘氨酸在分子水平上的结构-质量关系。

Soybean proteins have cholesterol-lowering ability as well as physicochemical functions. Moreover, their nutritional value is superior among those of plant proteins. Therefore, it is desired to enlarge the usage of soybean proteins. For this, we have to elucidate the structure-quality (physicochemical and physiological functions) relationships at molecular level of soybean proteins. We approached to the elucidation of them as follows.(1) X-ray crystallography of the constituent subunits of glycinin and conglycininThe three dimensional structure of conglycinin α'core was solved at 2.3Å resolution. Bases for crystallography of proglycinin A2B1a and conglycinin αcore were established.(2) Structure-physicochemical function relationships at subunit level of glycinin and conglycininMolecular species composed of a single subunit and restricted subunits were purified from mutant soybean cultivars containing such species. Analyses of their structural features and physiological functions demonstrated that they exhibit the characteristic structure-physicochemical function relationships.(3) Identification of peptide regions contributing bile acid-binding ability of glycininWe identified the most important region responsible for bile acid binding ability of glycinin A1aB1b by using E. coli expression system.(4) Structure-quality relationships at molecular level of glycinin and conglycininWe could understand deeply structure-quality relationships at molecular level of glycinin and conglycinin by protein engineering based on the results obtained by the investigations (1), (2) and (3).