Immunochemical reactivity of soybean β-conglycinin subunits

The immunochemical reactivity of two polyclonal sera raised against soybean purified alpha alpha' and beta subunits was analysed. We show that anti-alpha alpha' serum mainly reacts with alpha alpha' subunits and beta' subunit, but it does not recognize beta subunit. In addition, beta subunit is not able to compete with alpha alpha' subunit for anti-alpha alpha' serum recognition sites; therefore the main immunogenic region of alpha alpha' subunits is the extension region. Both anti-alpha alpha' and anti-beta sera were able to recognize E. coli produced alpha subunit, consequently glycosylation is apparently not required for antigen - antibody interaction. Anti-beta subunit serum shows strong reactivity against soybean produced beta-subunit and recombinant alpha subunit, while it shows weak recognition of soybean purified alpha alpha' subunits. A mutant of alpha subunit with the N terminal beta barrel region and C terminal alpha helices deleted, failed to be recognized by anti-beta serum. For that reason although N and C terminal domains are structurally equivalent, their immunochemical reactivity is different.