Characterization of structural and functional properties of soybean 11S globulin during the renaturation after the guanidine hydrochloride denaturation

Abstract

In this study, we explored how 11S globulin undergoes the renaturation with the decrease of guanidine hydrochloride (GuHCl) concentration. To analyze the changes in the structural and functional properties of 11S globulin, circular dichroism spectroscopy (CD), intrinsic fluorescence, particle size, foaming capacity (FC), foam stability (FS), emulsifying activity index (EAI) and emulsion stability index (ESI) at different GuHCl concentrations (8.0 mol/L, 4.0 mol/L, 2.0 mol/L, 0.8 mol/L, and 0.4 mol/L) were performed. 11S globulin was completely denatured after being treated with 8.0 mol/L of GuHCl. The CD spectra and particle size analyses showed that the α-helix and β-sheet contents and particle size of the renaturation process for 11S globulin were gradually close to those of native state protein and the protein structure became more orderly. The α-helix content increased from 0.2 ± 0.1% to 7.8 ± 0.3% and the hydrophobic groups inside the 11S globulin were exposed, which increased the surface hydrophobicity of the 11S globulin and changed its conformation. Regarding the functional properties, when the GuHCl concentration was diluted to 2.0 mol/L, some functional properties were improved compared with those of native state protein. The FC and FS of 11S globulin were increased by 5 and 2.2 times respectively and the EAI and ESI were increased by 1.25 times respectively. This study will provide guidance for the control of renaturation degree during 11S globulin production process to improve functional properties.