Molecular strategies to improve the nutritional quality of legume proteins

Legume proteins are relatively deficient in the sulfur amino acids. Among the different strategies to increase the sulfur amino acid contents of legumes, we have chosen to increase the biosynthesis of endogenous, non-abundant sulfur-rich proteins we have identified in soybean seed. We identified and isolated an 8 kDa sulfur-rich protein from the albumin fraction of soybean seed. Subsequently, a cDNA designated Gm2S-1, has been isolated and characterized. The Gm2S-1 cDNA encodes a pre-proprotein that contains a signal peptide and a precursor protein that undergoes post-translational processing to yield the mature 8 kDa protein containing 7.8% methionine and 7.8% cysteine. The Gm2S-1 gene is an ideal candidate for overexpression to improve the nutritional quality of soybean and other legumes.