Purification, characterization, and crystallization of single molecular species of β-conglycinin from soybean seeds

Abstract

Four major molecular species of β-conglycinin, α3, α2β αβ2, and β3, were isolated and purified from seeds of an α' subunit-deficient strain of soybeans (Glycine max). All components were found to be homogeneous by high pressure liquid chromatography, SDS-polyacrylamide gel electrophoresis, and amino acid and amino terminal sequence analyses. The amino acid compositions of the α3 and β3 components agreed fairly well with the compositions deduced from the cDNA sequences, and all of the components were highly glycosylated. The α3 and β3 components were compared regarding their secondary structures. The secondary structure of the α3 component deduced from CD measurements showed a higher α-helix content than that of the β3 component. The β3 component was crystallized by decreasing the ionic strength from 0.5 to 0.14 in phosphate buffer, pH 7.3, and the crystals grew to a size (1.0 mm × 0.2 mm × 0.2 mm) suitable for X-ray crystallographic analysis. A preliminary X-ray analysis showed that the crystal belonged to an orthorhombic crystal system having the space group P212121 and unit cell dimensions of a = 185.1 Å, b = 107.9 Å, and c = 97.6 Å. © 1996, Taylor & Francis Group, LLC. All rights reserved.