Specific Binding of Allergenic Soybean Protein<i>Gly m</i>Bd 30K with<i>α</i>′- and<i>α</i>-Subunits of Conglycinin in Soy Milk

Abstract

When defatted soy milk was ultracentrifuged, 34kDa allergenic soyabean protein Gly m Bd 30 K was more abundant in the precipitate than in the supernatant by an SDS-PAGE analysis. The addition of more than 10 mM of 2-mercaptoethanol (2-ME) to the soy milk resulted not only in further removal of the 34kDa allergenic protein to the precipitate, but also in better recovery of conglycinin in the supernatant. After a two-dimensional SDS-PAGE analysis (the first dimension, minus 2-ME; the second, plus 2-ME) of the precipitates, superimposition between the CBB-stained gel and the eletroblotted membrane stained with a monoclonal antibody specific to Gly m Bd 30 K indicated that part of Gly m Bd 30 K was preferentially bound to the alpha'- and alpha-subunits of conglycinin, and that part of them had formed the dimer through a disulfide bond.