Acetylation of faba bean legumin: conformational changes and aggregation

The effect of progressive acetylation upon the conformation of the 11S glob ulin legumin from faba bean has been studied using chemical analysis, UV, f luorescence and CD spectroscopy, viscometry and analytical ultracentrifugat ion. The modification did not induce complete dissociation of the oligomeri c protein. Only 30% of the protein was found to be a dissociated 3S subunit after excessive acetylation, whereas 70% was a dimeric legumin aggregate w ith a molecular mass of about 700kDa. The aggregation of the highly modifie d legumin in high-ionic-strcngth buffer solution leads to soluble higher le gumin oligomers. The acetylation resulted in a moderate molecular expansion of legumin due to a changed tertiary structure, whereas the far-UV circula r dichroism spectra did not provide definitive evidence of a decrease in do main-stabilizing beta -sheet conformations in their secondary structure. (C ) 2000 Society of Chemical Industry.