Doctor of Philosophy (PhD)
We investigate the regulation of an E.coli iron-sulfur protein DNA damage inducible DNA helicase (DinG) by single-stranded DNA binding protein (SSB). We find that SSB can form a stable protein complex with DinG and stimulate the DinG DNA helicase activity. On the other hand, SSB mutant that retains the single-stranded DNA binding activity but fails to form a protein complex with DinG becomes a potent inhibitor for the DinG DNA helicase. The results indicate SSB stimulates the DinG DNA helicase activity via direct protein-protein interaction. The results from these studies suggest that iron-sulfur proteins are regulated not only by intracellular metal homeostasis but also by specific protein factors in cells. We also describe a novel iron binding protein YrdD in E.coli cell. YrdD is a homolog of the C-terminal zinc-binding region of E.coli topoisomerase I. Purified YrdD contains both zinc and iron. Supplement of exogenous zinc in the growth medium abolishes the iron binding of YrdD in E. coli cells, indicating that iron and zinc may compete for the same metal binding sites in the protein. While the zinc-bound YrdD is able to bind single-stranded (ss) DNA and protect ssDNA from the DNase I digestion in vitro, the iron-bound YrdD has very little or no binding activity for ssDNA, suggesting that the zinc-bound YrdD may have an important role in DNA repair by interacting with ssDNA in cells.
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Cheng, Zishuo, "Stimulation of Escherichia coli DNA Damage Inducible DNA Helicase DinG by the Single-stranded DNA Binding Protein SSB" (2015). LSU Doctoral Dissertations. 3413.