Structure of Glycinin and Its Significance in Thermal Polymerization of Glycinin Molecule

大豆贮藏蛋白的主要成分之一的LLS球蛋白（称为大豆球蛋白）是由六个亚基组成的多亚基蛋白，其中酸性和碱性多肽通过二硫键以1：1的比例连接。大豆球蛋白具有热胶凝能力，即，大豆球蛋白分子的聚合。本研究探讨大豆球蛋白的凝胶能力与蛋白质结构的相关性。(1)大豆球蛋白的组成亚基ASI、ASII、ASIII和ASIV在聚合过程中对大豆球蛋白分子的相互作用表现出各自的特征性贡献。(2)本文<la>报道了G.最大变异数Shirotsurunoko决心。将其氨基酸序列与var. CX 635 -1-1-1和邦米诺里比较表明，这些亚基之间存在相当程度的同源性，并且同源区、可变区和半胱氨酸残基类似地位于所有亚基中的多肽序列的特定区域中。(3)大豆球蛋白分子在聚合过程中的相互作用似乎是通过疏水相互作用和二硫键交换反应发生在大豆球蛋白分子表面的特定区域。多肽序列中的可变区和游离半胱氨酸残基可能分别参与疏水相互作用和二硫键交换反应。

lls globulin (referred to as glycinin), one of the major components of the soybean storage protein, is a multisubunit protein consisting of six subunits in which the acidic and basic polypeptides are linked by disulfide bridges in 1:1 ratio. The glycinin exhibits thermal gelling ability, i.e., polymerization of glycinin molecules. In this study, the correlation between the gelling ability and the protein structure of glycinin was investigated. (1) The constituent subunits of glycinin, ASI,ASII,ASIII, and ASIV, exhibited each characteristic contribution to interactions of glycinin molecules in the course of polymerization. (2) The nucleotide and deduced amino acid sequences of ASI (A_<la>B_x) subunit from G. max var. Shirotsurunoko were determined. The amino acid sequence was compared with those from var. CX635-1-1-1 and Bonminori. The comparison indicated that a considerable degree of homology exists among those subunits, and that homologous regions, variable regions and cysteine residues are located in specific regions of the polypeptide sequence similarly in all the subunits. (3) The interactions of glycinin molecules in the course of polymerization seemed to occur at specific regions of the surface of glycinin molecule through hydrophobic interactions and disulfide exchange reactions. The variable regions and free cysteine residues in polypeptide sequence may be involved in the hydrophobic interaction and disulfide exchange reaction, respectively.