High-level expression, purification and functional properties of soybean proglycinin from Escherichia coli.

Abstract

The proglycinin synthesized in E. coli JM105 comprised approximately 20 % of the total bacterial proteins, with a yield of 39 mg per liter of culture under the optimum cultivation conditions. The proglycinin was purified to homogeneity by salt precipitation, ion-exchange chromatography, and cryoprecipitation. The purified proglycinin self-assembled to a trimer with a secondary structure similar to that of the glycinin half-molecule from soybean seeds, and had properties of gel formation by heating and precipitation with calcium salt as the native glycinin and glycinin half-molecule do. This indicated that the E. coli expression system of glycinin cDNA may be used for the evaluation of the self-assembly and the food qualities of protein-engineered soybean proteins.