Heterogeneity of beta-conglycinin

Abstract

Beta-conglycinin, a major 7 S soybean globulin, purified by ion-exchange and gel chromatography was fractionated into six distinct components on columns of DEAE-Sephadex. The six components (designated B1 to B6-conglycinins) were characterized by disc electrophoresis. Gel electrophoresis and gel electrofocusing in dissociating buffers indicate that the six conglycinins are isomers containing varying proportions of three kinds of subunits (alpha, alpha' and beta). The subunit structures of these isomers are alpha' beta (B1-), alpha beta (B2-), alpha alpha' beta (B3-), alpha beta (B4-), alpha alpha' (B5-), and alpha (B6-conglycinin). Beta subunit is a major constitutent of B1- and B2-conglycinins, whereas B3- to B6-conglycinins are composed predominantly of alpha subunit. The six beta-conglycinins are all glycoproteins containing mannose and glucosamine. They differ in the N-terminal amino acid composition. The isolated B1- to B4-conglycinins are immunologically identical with one another and with the total beta-conglycinin. B5- and Bl-conglycinins which comprise no beta subunit are partially identical with the total protein. Some antigenic determinants that are lacking in the B5- and B6-conglycinins are expected to be located on the beta subunit.