Acetylation of faba bean legumin: conformational changes and aggregation

The effect of progressive acetylation upon the conformation of the 11S globulin legumin from faba bean has been studied using chemical analysis, UV, fluorescence and CD spectroscopy, viscometry and analytical ultracentrifugation. The modification did not induce complete dissociation of the oligomeric protein. Only 30% of the protein was found to be a dissociated 3S subunit after excessive acetylation, whereas 70% was a dimeric legumin aggregate with a molecular mass of about 700 kDa. The aggregation of the highly modified legumin in high-ionic-strength buffer solution leads to soluble higher legumin oligomers. The acetylation resulted in a moderate molecular expansion of legumin due to a changed tertiary structure, whereas the far-UV circular dichroism spectra did not provide definitive evidence of a decrease in domain-stabilizing β-sheet conformations in their secondary structure. © 2000 Society of Chemical Industry