Soybean glycinin A1aB1b subunit has a molecular chaperone-like function to assist folding of the other subunit having low folding ability.
Soybean (Glycine max L.) glycinin is composed of five subunits which are classified into two groups (group I: A1aB1b, A1bB2, and A2B1a; group II: A3B4 and A5A4B3). All the common soybean cultivars contain both group I and II subunits (Maruyama, N. et al., Phytochemistry, 64, 701-708 (2003)). The biosynthesis of group I starts earlier compared with that of the A3B4 subunit during seed development (Meinke, D.W. et al., Planta, 153, 130-139 (1981)). We have revealed that group I A1aB1b was mostly expressed as a soluble protein, but that A3B4 was expressed mainly as an insoluble protein in Escherichia coli under the same expression conditions; namely, A1aB1b had higher folding ability than A3B4. We therefore assumed that A1aB1b assists folding of group II subunits like a molecular chaperone does. In order to ascertain this, A1aB1b and A3B4 were co-expressed in E. coli. All of the expressed proteins of A3B4 were recovered in a soluble fraction. To confirm this result, we also co-expressed A1aB1b with modified A3B4 versions having extremely low folding ability. All expressed modified A3B4 versions were soluble. These results clearly suggest that A1aB1b has a molecular chaperone-like function in their folding.
Choi
Seon-kang
SK
Laboratory of Food Quality Design and Development, Graduate School of Agriculture, Kyoto University, Uji, Japan.
Adachi
Motoyasu
M
Yoshikawa
Masaaki
M
Maruyama
Nobuyuki
N
Utsumi
Shigeru
S
D003001:Cloning, Molecular; D004926:Escherichia coli / Q000235:genetics; D005916:Globulins / Q000235:genetics / Q000502:physiology*; D018832:Molecular Chaperones / Q000235:genetics / Q000502:physiology*; D017510:Protein Folding; D021122:Protein Subunits / Q000235:genetics / Q000502:physiology; D012995:Solubility; D030262:Soybean Proteins / Q000235:genetics / Q000502:physiology; D013025:Glycine max / Q000737:chemistry*
D005916:Globulins; D018832:Molecular Chaperones; D021122:Protein Subunits; D030262:Soybean Proteins; C093157:glycinin A(3)B(4); C011474:glycinin