Effect of Interaction between EGCG and Soy β-Conglycinin/Glycinin on Protein Structure

The interaction between β-conglycinin (7S)/glycinin (11S) and (–)-epigallocatechin-3-gallate (EGCG) under neutral conditions was characterized by fluorescence spectroscopy, ultraviolet-visible (UV-Vis) absorption spectroscopy, Fourier transform infrared (FTIR) spectroscopy and molecular docking. The results showed that EGCG and 7S/11S could interact with each other at pH 7.0, which induced a change in the microenvironment of amino acid residues. EGCG could quench the intrinsic fluorescence of 7S/11S in dynamic and static manners. EGCG had higher affinity to 11S than to 7S. The reaction between EGCG and 7S/11S was a spontaneous binding process, resulting in the formation of a complex at 1:1 molar ratio by hydrogen bonding and van der Waals force. EGCG could reduce the surface hydrophobicity of 7S/11S. With increasing EGCG concentration, 11S showed a greater change in surface hydrophobicity. FTIR and molecular docking studies suggested that in addition to hydrogen bonds, hydrophobic interactions were also involved in the formation of complexes. Binding to EGCG could cause different changes in the secondary structure of 7S/11S subsequently resulting in protein unfolding.