title: Crystal structure of soybean 11S globulin: glycinin A3B4 homohexamer.
abstract: Most plant seeds contain 11S globulins as major storage proteins for their nutrition. Soybean glycinin belongs to the 11S globulin family and consists of five kinds of subunits. We determined the crystal structure of a homohexamer of the glycinin A3B4 subunit at 2.1-A resolution. The crystal structure shows that the hexamer has 32-point group symmetry formed by face-to-face stacking of two trimers. The interface buries the highly conserved interchain disulfide. Based on the structure, we propose that an ingenious face-to-face mechanism controls the hexamer formation of the 11S globulin by movement of a mobile disordered region to the side of the trimer after posttranslational processing. Electrostatic analysis of the faces suggests that the interchain disulfide-containing face has high positive potential at acidic pH, which induces dissociation of the hexamer into trimers that may be susceptible to proteinases after seed imbibition. This dissociation might result in the degradation and mobilization of 11S globulins as storage proteins in embryos during germination and seedling growth.
authors.affiliation: Laboratory of Food Quality Design and Development, Graduate School of Agriculture, Kyoto University, Uji, Kyoto 611-0011, Japan.
authors.forename: Motoyasu
authors.initials: M
authors.lastname: Adachi
authors.forename: Jiro
authors.initials: J
authors.lastname: Kanamori
authors.forename: Taro
authors.initials: T
authors.lastname: Masuda
authors.forename: Kazuhiro
authors.initials: K
authors.lastname: Yagasaki
authors.forename: Keisuke
authors.initials: K
authors.lastname: Kitamura
authors.forename: Bunzo
authors.initials: B
authors.lastname: Mikami
authors.forename: Shigeru
authors.initials: S
authors.lastname: Utsumi
mesh_terms: D000595:Amino Acid Sequence; D018360:Crystallography, X-Ray; D018525:Germination; D005916:Globulins / Q000737:chemistry* / Q000235:genetics; D008958:Models, Molecular; D008969:Molecular Sequence Data; D020836:Protein Structure, Quaternary; D017386:Sequence Homology, Amino Acid; D030262:Soybean Proteins / Q000737:chemistry* / Q000235:genetics; D013025:Glycine max / Q000737:chemistry* / Q000235:genetics / Q000254:growth & development; D055672:Static Electricity
chemical_list: D005916:Globulins; D030262:Soybean Proteins; C093157:glycinin A(3)B(4)