Enhanced proteins and methods for their use

Abstract

The present invention generally relates to the field of plant genetics and protein biochemistry. More specifically, the present invention relates to modified proteins having an increased number of essential amino acids. The present invention provides proteins modified to have an increased number of essential amino acids, nucleic acid sequences encoding the enhanced proteins, and methods of designing, producing, and using the same. The present invention also includes compositions, transformed host cells, transgenic plants, and seeds containing the enhanced proteins, and methods for preparing and using the same.

1. A modified polypeptide comprising a substitution of one or more amino acids selected from the group consisting of lysine, methionine, isoleucine, and tryptophan into SEQ ID NO: 1. 
     
     
       2. The modified polypeptide of  claim 1 , wherein said modified polypeptide is capable of accumulating in a biological expression system. 
     
     
       3. The modified polypeptide of  claim 2 , wherein the biological expression system is a seed. 
     
     
       4. The modified polypeptide of  claim 1 , wherein the substitution is of two or more of said amino acids. 
     
     
       5. The modified polypeptide of  claim 1 , wherein said polypeptide comprises greater than about a 0.25% (weight per weight) increase of any one of said amino acids, or any combination thereof, relative to SEQ ID NO; 1. 
     
     
       6. A recombinant nucleic acid molecule encoding a modified glycinin polypeptide comprising a substitution of one or more amino acids selected from the group consisting of threonine, isoleucine, tryptophan, valine, arginine, lysine, methionine, and histidine into SEQ ID NO: 1. 
     
     
       7. The recombinant nucleic acid molecule of  claim 6 , wherein said modified glycinin polypeptide is capable of accumulating in a cell. 
     
     
       8. The recombinant nucleic acid molecule of  claim 7 , further comprising, in the 5′ to 3′ direction, a heterologous promoter operably linked to said recombinant nucleic acid molecule. 
     
     
       9. A cell containing, in the 5′ to 3′ direction, a heterologous promoter operably linked to a recombinant nucleic acid molecule encoding a modified glycinin polypeptide comprising a substitution of one or more amino acids selected from the group consisting of threonine, isoleucine, tryptophan, valine, arginine, lysine, methionine, and histidine into SEQ ID NO: 1. 
     
     
       10. The cell of  claim 9 , wherein said modified glycinin polypeptide is capable of accumulating in a seed. 
     
     
       11. The cell according to  claim 9 , wherein said cell is selected from the group consisting of a bacterial cell, a mammalian cell, an insect cell, a plant cell, and a fungal cell.