Structure-physicochemical function relationships of soybean beta-conglycinin constituent subunits

beta-Conglycinin, one of the dominant storage proteins of soybean, has a tr imeric structure, being composed of three subunits alpha, alpha', and beta. The alpha and alpha' subunits contain the extension regions in addition to the core regions common to all subunits, which are N-glycosylated. Physico chemical functions of recombinant nonglycosylated individual subunits and d eletion mutants (alpha(c) and alpha'(c)) lacking the extension regions of t he alpha and alpha' subunits were examined at pH 7.6 and 3.7 at low (mu = 0 .08) and high (mu = 0.5) ionic strengths. Although individual recombinant s ubunits exhibited different properties at all conditions, there were some c onsistencies. Surface hydrophobicities and thermal stabilities of the indiv idual subunits were likely to be conferred by their core regions, and the c arbohydrate moieties did not contribute to these properties at any conditio ns examined here. Solubility at mu = 0.08, heat-induced association, and em ulsifying ability remarkably depended on the extension regions and the carb ohydrate moieties in addition to the structural features of the core region s. These findings indicate that various end products could be produced by t he selection of soybean varieties containing beta-conglycinin with differen t subunit compositions and suggest a direction for a principle of soybean b reeding.