Phosphatidylcholine (PC) was associated with soybean 7S globulin. The amount of bound PC depended on the amount of PC in an incubation mixture. Trinitrobenzenesulfonic acid (TNBS), 2-methoxy-5-nitrotropone (MNT), 2-hydroxy-5-nitrobenzylbromide (HNBB) and 8-anilino-1-naphthalene sulfonic acid (ANS) were used to investigate the reactivity of amino acid residues of PC-bound 7S globulin, and the interaction of PC with the modified 7S globulin was also studied with these reagents. It was found that PC was not bound to the specific amino acid residues in 7S globulin, while the fluorescence intensity of the ANS-modified 7S globulin associated with PC was decreased by increasing PC. This suggests that PC is bound to the hydrophobic region of 7S globulin.
PC affected the conformation of the protein and decreased the β-structure content by its binding to the protein.