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ARS Home » Midwest Area » West Lafayette, Indiana » Crop Production and Pest Control Research » Research » Publications at this Location » Publication #126538
Title: PROCESSING AND ASSEMBLY IN VITRO OF ENGINEERED SOYBEAN BETA-CONGLYCININ SUBUNITS WITH THE ASPARAGINES-GLYCINE PROTEOLYTIC CLEAVAGE SITE OF 11S GLOBULINS

Author
item OLIVEIRA, LUIZ - PURDUE UNIVERSITY AGRY
item NAM, YOUNG-WOO - PURDUE UNIVERSITY AGRY
item JUNG, RUDOLPH - PIONEER
item Nielsen, Niels

Submitted to: Molecular Cell
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/28/2002
Publication Date: N/A
Citation: N/A

Interpretive Summary: The modification of soybean composition to improve food and feed quality is an important objective. To achieve this objective, it is necessary to understand what proteins are stored in the seed, how they are made, and how they interact with one another. The two seed storage proteins in soybean seeds, glycinin and beta-conglycinin, account for more than 70 percent of the total seed protein. These two proteins are composed of subunits that share similar 3D structures and are located in the same storage compartment in seeds. Because of their structural similarity, we asked if their subunits would assemble with one another, and demonstrated that they do not. We also modified beta-conglycinin so that it could undergo the same assembly process as glycinin, and even under these conditions the proteins did not co-assemble. Therefore, subtle but important differences between the two proteins exist despite their high degree of structural similarity. These results provide insight about the relationship of glycinin to beta-conglycinin that will be useful in efforts of molecular biologists and geneticists to improve seed quality. The information also will be used primarily by scientists studying the packaging of seed storage protein.

Technical Abstract: A short interdomain sequence between the N- and C-terminal domains of beta-conglycinin, the major 7S seed storage protein of soybean, was selected as a target for insertion of amino acid residues specifically cleaved by an asparaginyl endopeptidase that processes 11S globulins into acidic and basic chains. Modified beta-conglycinin subunits containing the proteolytic cleavage site self-assembled into trimers in vitro at an efficiency similar to that of the unmodified subunit. In contrast to the absence of cleavage of the unmodified subunits, however, the modified B-conglycinin trimers were processed by purified soybean asparaginyl endopeptidase into two polypeptides, each the size expected for the beta-conglycinin N- and C-terminal domains, respectively. The cleavage did not alter the assembly of mutant beta-conglycinins and the cleaved mutant trimers remained stable to further proteolytic attack. To examine the possibility of coassembly between the cleaved 11S and 7S subunits, in vitro processed mutant beta-conglycinin subunits were mixed with native dissociated 11S globulin preparations. Reassembly at a high ionic condition did not induce the 7S subunits to interact with 11S subunits to form hexameric complexes. Thus, cleavage of 7S globulin subunits into acidic and basic domains may not be sufficient to cause for hexamer assembly to occur. Biotechnological implications of the engineered proteins are discussed.