Date of Award

5-16-2008

Degree Type

Thesis

Degree Name

M.S.

Degree Program

Biological Sciences

Department

Biological Sciences

Major Professor

Clancy, Mary; Burt-Utley, Kathleen

Second Advisor

Dyer, John

Third Advisor

Schluchter, Wendy

Abstract

Differences have been shown in the steady-state accumulation and half-lives between Brassica FAD3 (BF3) and tung FAD3 (TF3) proteins expressed in yeast cells cultured at 30°C. TF3 has a greater steady-state accumulation and longer half-life than BF3. These differences are attributed to post-translational modification and have been shown to be controlled by an Nterminal element. I attempted to determine specific amino acids important for regulation, and further characterize the mechanism contributing to the differences. Through site-directed mutagenesis, it was shown that replacing lysine residues with asparagines in the BF3 and TF3 Ntermini increased protein stability, while replacing an asparagine with lysine in the TF3 Nterminus decreased its stability. Furthermore, I showed that the TF3 polyglutamic region (six consecutive glutamic acid residues) is primarily responsible for the higher steady-state amount of TF3 in comparison to BF3. This negatively charged region likely acts as an electrostatic shield protecting the protein from degradation.

Rights

The University of New Orleans and its agents retain the non-exclusive license to archive and make accessible this dissertation or thesis in whole or in part in all forms of media, now or hereafter known. The author retains all other ownership rights to the copyright of the thesis or dissertation.

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