Author
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NIELSEN, NIELS |
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HERMAN, ELIOT |
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Submitted to: Proceedings of the Royal Society of London B
Publication Type: Proceedings Publication Acceptance Date: 10/5/2001 Publication Date: N/A Citation: N/A Interpretive Summary: Technical Abstract: Seven glycinin genes encode the 11S storage globulin gene family in soybean. Six are functional genes expressed in varying amounts in seeds, while the seventh lacks the 3'-end of its coding region and is nonfunctional. The initial translation products from the glycinin genes are preproproteins. After co-translational removal of a signal peptide, and chaperon-mediated subunit folding in rough endoplasmic reticulum, the 3S proglycinin monomers assemble into 9S trimers. The trimers are transported via the endomembrane system to storage vacuoles where they undergo post-translational modification by a specific asparaginyl endopeptidase. Cleavage transforms them into the stored 11S hexamer oligomer. Soybeans and legumes in general are deficient in sulfur amino acids. Attempts to increase methionine content by expressing high-methionine engineered glycinin in tobacco seeds have resulted in post-translational instability, which indicates there are hurdles to engineering improved variants of glycinin. One solution may be found in soybean knockouts of conglycinin, the 7S storage protein. These result in up-regulation of one of the glycinin genes, and these seeds produce compensating levels of total seed protein in transgenic soybeans. The glycinin that is induced is sequestered in ER-derived protein bodies that may prove useful as a storage site for not only modified glycinin but also as a means to produce novel proteins in transgenic soybeans. |
