Physicochemical properties of native adzuki bean (Vigna angularis) 7S globulin and the molecular cloning of its cDNA isoforms.

7S globulin (vicilin), the major seed storage protein in adzuki bean [Vigna angularis], was purified by ammonium sulfate fractionation, gel filtration column chromatography, and anion-exchange column chromatography that resulted in two fractions. On SDS-PAGE, both fractions gave two major and some minor bands, but there was a difference in the minor band compositions between the two fractions. Thermal stability, solubility, surface hydrophobicity, and emulsifying ability of these three samples were analyzed. Although there was no difference in solubility and emulsifying ability among the samples, thermal stability and surface hydrophobicity were different. These differences might be due to the differences in subunit compositions. cDNAs were cloned by reverse transcription-polymerase chain reaction (RT-PCR) using primers designed on the basis of the determined N-terminal sequences of the major bands. We obtained three isoforms of cDNAs, which had highest homology with the mung bean 8Salpha globulin (7S globulin), and then soybean beta-conglycinin (7S globulin) beta subunit among legume plants. Adzuki bean 7S globulin isoforms contain more methionine and tryptophan than mung bean 8Salpha globulin and soybean beta-conglycinin beta subunit. In addition, high mannose types of glycans were attached to two or one N-glycosylation sites of adzuki bean 7S globulins.