ANALYSIS OF THERMAL-STABILITY OF SOYA GLOBULINS USING MONOCLONAL-ANTIBODIES

The epitopes of two monoclonal antibodies (Mabs), one raised to soya g lycinin (IFRN 0025) and one to beta-conglycinin (IFRN 0089), have been defined. The epitope of 0025 corresponds to residues 86-104 of the ac idic polypeptide of glycinin A(1a)B(1b) and lies at the C terminus of the proteolytic intermediate known as glycinin-T, whilst that of 0089 corresponds to residues 78-84 in the acidic extension present in the a lpha' subunit of beta-conglycinin. As the Mabs bind to synthetic pepti des corresponding to the epitope regions both epitopes can be consider ed as being continuous in nature. The regions recognised correspond to surface loops, which are probably flexible in nature. Both Mabs were used to investigate thermally induced conformational changes in soya g lobulins. Thermally treated glycinin was recognised more strongly than native protein, possibly due to disruption of the disulphide bond joi ning the acidic and basic polypeptides. Disruption could increase epit ope accessibility, as could the conformational changes associated with denaturation. The binding of anti-beta-conglycinin Mab 0089 was unaff ected by heating, suggesting that its epitope remains on the surface o f the aggregates formed on heating. This study demonstrates that Mabs with defined specificities can be sensitive probes for monitoring loca l conformational changes within a protein molecule during thermal dena turation. (C) 1998 Elsevier Science B.V. All rights reserved.