Molecular species of glycinin in some soybean cultivars

A(4) polypeptide-containing (Shirotsurunoko and York) and A(4) polypeptide-lacking (Raiden and Suzuyutaka) soybean cultivars were used to investigate the heterogeneity of glycinin molecular species. Purification of glycinin by DEAE-Toyopearl column chromatography afforded molecular species eluting before the glycinin fraction. Analysis of this fraction by SDS-polyacrylamide gel electrophoresis (SDS-PAGE) and sucrose density gradient centrifugation indicated that this protein consisted of A(1) and A(2) polypeptides. The A(4)-containing soybean cultivars contained less of this protein than the A(4)-lacking soybean cultivars, as exhibited by the size of the early peak appearing during column chromatography. Alkaline PAGE and N-terminal amino acid sequence analysis confirmed that the A(1)- and A(2)-rich molecular species in the A(4) polypeptide-lacking cultivars consisted of the A(1a) and A(2) polypeptides. Estimation of the molecular mass by gel permeation chromatography and multi-angle laser light scattering (GPC-MALLS) indicated that the A(1a)- and A(2)-rich molecular species were similar to a monomer of glycinin.