Access Type

Open Access Dissertation

Date of Award

January 2016

Degree Type

Dissertation

Degree Name

Ph.D.

Department

Biochemistry and Molecular Biology

First Advisor

Timothy L. Stemmler

Abstract

Disrupted iron homeostasis within the human body materializes as various disorders. Pathophysiology of many of them relates to iron induced oxidative damage to key cellular components caused by iron accumulation within the tissues. Pertaining to the growing occurrence, cost of patient care and devastating burden associated with these diseases, the call for understanding the role of iron homeostasis within these disorders becomes inevitable. Being an abundant iron containing cofactor, the role of Fe-S clusters in cellular iron homeostasis is indisputable in the case of Friedreich’s ataxia, a disease caused by a deficiency in the protein frataxin that is indispensable during Fe-S cluster assembly. Friedreich’s ataxia and similar disorders associated with defective Fe-S cluster assembly accentuate the need to unravel the structural and functional aspects of this fundamental biochemical pathway. Effective disease treatment has been hampered by the lack of a molecular level understanding of the individual roles of the key proteins in Fe-S cluster formation.

The work presented within this dissertation diminish this knowledge gap significantly by providing a comprehensive biophysical characterization of the key proteins involved in the sulfur mobilization step during the yeast mitochondrial Fe-S cluster synthesis process. The role of the accessory protein “Isd11” within the catalytic role of the cysteine desulfurase “Nfs1” in delivering sulfane sulfur for cluster assembly has been studied. The effect of Yfh1 on sulfur mobilization by the Nfs1-Isd11 complex has also been evaluated in detail. Our results suggest a possible regulatory function of Isd11 and possibly rationalize the evolutionary requirement for its role as an additional cofactor introduced in eukaryotes. Frataxin’s effect on cluster assembly was evident to materialize the most at the overall assembled complex level rather than at the individual protein level. This work, therefore, provides novel and significant insight into how the cluster assembly proteins function, and sets the groundwork for which additional experiments that need to be designed to further unravel the mechanistic details of sulfur mobilization during Fe-S cluster bioassembly. These molecular level details will assist in future drug design strategies directed at treating the diseases outlined above.

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