K. D. Schwenke

Secondary structure of globulins from plant seeds: a re-evaluation from circular dichroism measurements

Abstract The secondary structure parameters of plant seed globulins (11S from Brassica napus L, 11S from Helianthus annuus L, IIS from Vicia faba , 7S from Phaseolus vulgaris L) have been determined from their circular dichroism spectra by the method of Provencher and Glockner. According to this method, the proteins contain 40–50% β-sheet structure and only about 10% helical structure. We conclude, therefore, that the plant seed globulins belong to the class of β-sheet proteins. Their overall secondary structure is homologous. It is shown that the method of Provencher and Glockner provides reasonable secondary structure parameters for proteins which are rich in β-sheet structure even if the spectral range utilized for analysis is restricted to 210–240 nm.

Effect of dissociation and conformational changes on the surface behavior of pea legumin

Abstract In order to improve knowledge of the influence of dissociation of pea legumin on the surface behavior, the influence of pH and the effect of succinylation on the kinetics of adsorption have been studied at the air/water interface. Ultracentrifugation and the Wilhemy plate method were used, respectively, for the characterization of the protein and the interfacial tension measurements. Dissociation results in an improvement in the ability of the protein to diffuse to the interface whereas the charge of the molecule influences the kinetic parameters of anchorage and conformational rearrangement in the occupied interfacial layer. These effects are discussed in relation first to the dissociation of the oligomeric 12S globulin into subunits, then to the unfolding of these subunits, and finally to the charge variations and location along the primary sequence of legumin.

Structural Studies on the Native and Chemically Modified Low-Molecular Mass Basic Storage Protein (Napin) from Rapeseed (Brassica napusL.)

Summary The low-molecular mass basic napin fraction from rapeseed represents helical proteins (40–45 α-helix) the secondary structure of which is stabilized by interchain and intrachain disulfide bridges. Succinylation or acetylation did not change the secondary structure which was dissolved after splitting the disulfide bonds. The secondary structure prediction based on the napin amino acid sequence in α-helix and β-contents which are in good correspondence with the values determined by means of circular dichroism spectroscopy. The predicted position of flexible and exposed (antigenic determinants) regions is dicussed with regard to protein functionality and reactivity in food systems.