Altering Protein Functional Properties Through Terminal Fusions

Abstract

The invention provides isolated terminal fusion glycinin and proglycinin polypeptides that when expressed alter the functional properties of the protein in comparison with wild type. Also provided are nucleic acid sequences that encode the terminal fusion polypeptides, and methods of modifying the functional properties of glycinin proteins.

1 . An isolated terminal fusion polypeptide comprising: a first soybean glycinin or proglycinin polypeptide operably linked to at least a second polypeptide wherein the resulting terminal fusion polypeptide exhibits modified functional properties.  
     
     
         2 . A transformed soybean plant comprising the terminal fusion polypeptide of  claim 1 .  
     
     
         3 . A soybean protein product comprising the terminal fusion polypeptide of  claim 1 .  
     
     
         4 . The fusion polypeptide of  claim 1  wherein the second polypeptide is acidic.  
     
     
         5 . The fusion polypeptide of  claim 4  wherein the calculated pI of the fusion polypeptide is from 0.4 to 1.1 pH units less than the pI of the wild type proglycinin or glycinin polypeptide.  
     
     
         6 . The fusion polypeptide of  claim 1  wherein the second polypeptide is basic.  
     
     
         7 . The fusion polypeptide of  claim 6  wherein the calculated pI of the fusion polypeptide is from 0.2 to 2.8 pH units greater than the pI of the wild type proglycinin or glycinin polypeptide.  
     
     
         8 . The second polypeptide of  claim 1  comprising a polypeptide selected from the group consisting of: SEQ ID NOS: 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, and 18.  
     
     
         9 . The second polypeptide of  claim 1  comprising a polypeptide selected from the group consisting of: soybean thioredoxin, LEA, BHL-8, BHL-9, soybean glycinin 1, and alpha-conglycinin.  
     
     
         10 . An expression cassette comprising a promoter operably linked to a first soybean glycinin or proglycinin polynucleotide operably linked at either terminus to at least a second polynucleotide wherein the resulting fusion polypeptide exhibits modified functional properties.  
     
     
         11 . The expression cassette of  claim 10  wherein the first and at least second polynucleotide are operably linked to a third polynucleotide at the opposite terminus; wherein the resulting fusion polypeptide exhibits modified functional properties.  
     
     
         12 . The expression cassette of  claim 10  wherein the at least second polynucleotide encodes a polypeptide selected from the group consisting of: 
 SEQ ID NOS: 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, and 18.    
     
     
         13 . The host cell of  claim 12  that is a plant cell.  
     
     
         14 . A transgenic plant comprising at least one expression cassette of  claim 10 .  
     
     
         15 . A transgenic seed from the plant of  claim 14 .  
     
     
         16 . A soybean protein product derived from the processing of soybean seeds expressing a soybean glycinin or proglycinin protein with modified functional properties, the method comprising: 
 a) introducing into a non-human host cell an expression cassette comprising a promoter operably linked to a first soybean glycinin or proglycinin polynucleotide operably linked at either terminus to at least a second polynucleotide; wherein the resulting fusion polypeptide exhibits modified functional properties;    b) growing the plant cell under plant-forming conditions to express the protein with modified properties in the seed; and    c) processing the seed to obtain a soybean protein product with modified properties.    
     
     
         17 . The soybean protein product of  claim 16  wherein the fusion polypeptide is further operably linked to a polypeptide at the opposite terminus, wherein the resulting fusion polypeptide exhibits modified functional properties.  
     
     
         18 . The soybean protein product of  claim 16  wherein the modified property is a change in solubility of the protein as compared to wild-type.  
     
     
         19 . The soybean protein product of  claim 16  wherein the modified property is a change in gel-forming ability of the protein as compared to wild-type.  
     
     
         20 . The soybean protein product of  claim 16  wherein the modified property is a change in emulsifying ability of the protein as compared to wild-type.