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

大豆蛋白除了具有物理化学功能外，还具有降胆固醇的功能。此外，它们的营养价值优于植物蛋白。因此，扩大大豆蛋白的用途是很有必要的。为此，我们必须在分子水平上阐明大豆蛋白的结构与品质(理化和生理功能)之间的关系。(1)大豆球蛋白和伴大豆球蛋白组成亚基的X射线结晶学研究在2.3Å分辨率下，对伴球蛋白DNA核心的三维结构进行了解析。建立了大豆球蛋白原A2B1a和伴球蛋白α核心的结晶学基础。(2)大豆球蛋白和伴球蛋白亚基水平的结构-物理化学功能关系从含有单一亚基和限制性亚基的突变大豆品种中纯化得到了分子物种。对它们的结构特征和生理功能的分析表明它们呈现出典型的结构-理化功能关系。(3)球蛋白胆汁酸结合能力的多肽区域的鉴定我们利用大肠杆菌表达系统确定了球蛋白A1aB1b与胆汁酸结合能力最重要的区域。(4)球蛋白和伴球蛋白在分子水平上的结构-质量关系我们可以在研究(1)、(2)和(3)结果的基础上，通过蛋白质工程从分子水平上深入了解球蛋白和伴球蛋白的结构-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).