Structure-function relationships of soybean proglycinins at subunit levels.
Glycinin consists of five kinds of subunits, group I (A1aB1b, A1bB2, and A2B1a) and group II (A3B4 and A5A4B3). cDNAs for individual subunits were cloned by reverse transcription-polymerase chain reaction method and expressed in Escherichia coli using pET vector. The recombinant proglycinins were purified by ammonium sulfate fractionation and column chromatography in the form of homotrimers. Physicochemical properties such as molecular dimensions, solubility, surface hydrophobicity, thermal stability, and emulsifying ability of individual proglycinins were studied. Molecular dimensions were proportional to molecular size for all proglycinins except A2B1a. Solubility was intrinsic to each proglycinin. At the ionic strength of 0.5, all proglycinins except A1aB1b showed a very low solubility at acidic pH, but A1aB1b was soluble to higher than 60%. At ionic strength 0.08, all proglycinins exhibited isoelectric precipitation, although A2B1a and A1bB2 were not completely insoluble. The order of emulsifying ability (A1bB2 < A2B1a < A5A4B3 < A3B4 < or = A1aB1b) was not of the same for surface hydrophobicity (A5A4B3 < A1aB1b < or = A3B4 < A1bB2 < A2B1a) and thermal stability (A1bB2 << A2B1a < or = A5A4B3 < A3B4 < or = A1aB1b).
Prak
Krisna
K
Laboratory of Food Quality Design and Development, Graduate School of Agriculture, Kyoto University, Uji, Kyoto 611-0011, Japan.
Nakatani
Kazuyo
K
Katsube-Tanaka
Tomoyuki
T
Adachi
Motoyasu
M
Maruyama
Nobuyuki
N
Utsumi
Shigeru
S
D002152:Calorimetry, Differential Scanning; D045703:Emulsifying Agents / Q000737:chemistry; D004926:Escherichia coli / Q000235:genetics; D015870:Gene Expression; D006863:Hydrogen-Ion Concentration; D021122:Protein Subunits / Q000737:chemistry* / Q000235:genetics; D011994:Recombinant Proteins / Q000737:chemistry; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012995:Solubility; D030262:Soybean Proteins / Q000737:chemistry* / Q000235:genetics; D013025:Glycine max / Q000737:chemistry*; D013329:Structure-Activity Relationship
D045703:Emulsifying Agents; D021122:Protein Subunits; D011994:Recombinant Proteins; D030262:Soybean Proteins; C405345:proglycinin A(1a)B(1b), soybean