Identification of the acidic and basic subunit complexes of glycinin

Abstract

Five complexes consisting of one acidic and one basic subunit that were linked via disulfide bonds were purified from unreduced S-alkylated glycinin. The acidic and basic subunits were identified unambiguously using NH2-terminal sequence analysis, sodium dodecyl sulfate (SDS)-electrophoresis, and analytical isoelectric focusing. The subunit pairings are A1aB2, A1bB1b, A2B1a, A3B4, and F2(2)B3. Polypeptide A4 was not linked to a corresponding basic subunit via a disulfide bond. The study shows that pairing between subunits is nonrandom, which is consistent with evidence that glycinin is synthesized as a Mr = 60,000 precursor that undergoes post-translational modification to form the individual linked subunits.