Identifier

etd-04062016-121004

Degree

Master of Science (MS)

Department

Biological Sciences

Document Type

Thesis

Abstract

Iron-sulfur ([Fe-S]) proteins are widely distributed in the biological systems. These proteins are involved in diverse fundamental life processes such as photosynthesis, respiration, ribosome biogenesis, DNA synthesis, and repair. Dysfunction of these proteins or their biogenesis has been implicated in causing cardiovascular diseases, neurodegenerative diseases, and various cancers. Iron-sulfur proteins are highly sensitive to nitric oxide (NO) and readily form dinitrosyl iron complexes (DNICs) upon exposure. Restoration of the iron-sulfur cluster in the NO-modified protein requires a two-step repair process. The first step is to remove DNICs from proteins. The second step is to re-assemble the iron-sulfur cluster in proteins. In this work, we report that protein-bound DNICs can be transferred to thioredoxin (TrxA) under reducing conditions in the presence of a reducing mediator. DNICs formed in two [4Fe-4S] proteins, aconitase B (AcnB) and dihydroxyacid dehydratase (IlvD) were used as DNIC donors to explore DNICs transfer to TrxA. AcnB is an enzyme involved in the citric acid cycle in Escherichia coli. IlvD is required for the branched-chain amino acid biosynthesis. To be functional, both proteins require an intact [4Fe-4S] cluster. In the first experiment, IlvD-DNICs or AcnB-DNICs and TrxA were incubated in the presence of dithiothreitol (DTT) to monitor the DNICs transfer from these protein-bound DNICs to TrxA. Experiment results suggest that DNICs may be partially transferred from IlvD-DNICs or AcnB-DNICs to TrxA under reducing conditions. We also utilized the TrxAB/NADPH system which is responsible for maintaining reducing conditions in cells to mediate the DNIC transfer, and found that the TrxAB/NADPH system can also promote the DNICs transfer from AcnB-DNICs to TrxA. The results from this study may provide a new pathway of DNIC removal for the repair of the NO-modified iron-sulfur proteins.

Date

2016

Document Availability at the Time of Submission

Release the entire work immediately for access worldwide.

Committee Chair

Ding, Huangen

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