Overexpression, purification, and in vitro refolding of the 11S globulin from amaranth seed in Escherichia coli

An amarantin 11S globulin cDNA encoding one of the most important storage proteins of amaranth seeds, with a high content of essential amino acids, was expressed in Escherichia coli. A good level of expression of recombinant amarantin with a molecular weight of 59 kDa was obtained. The recombinant protein was extracted by ammonium sulfate precipitation and purified to homogeneity using ion-exchange chromatography and reversed phase high-performance liquid chromatography. The expressed protein exhibited electrophoretic, immunochemical, and surface hydrophobicity properties similar to those of native amarantin from amaranth seed. Also, the recombinant protein was refolded in vitro using two different methods.