Date of Award:

5-2017

Document Type:

Dissertation

Degree Name:

Doctor of Philosophy (PhD)

Department:

Chemistry and Biochemistry

Committee Chair(s)

Lance C. Seefeldt

Committee

Lance C. Seefeldt

Committee

Sean Johnson

Committee

Scott A. Ensign

Committee

Edwin Antony

Committee

Korry Hintze

Abstract

Nitrogen is essential for life on earth as it is a major constituent of amino acids and nucleic acids. Nitrogen gas (N2) is the most abundant form of nitrogen in the atmosphere but the strong N≡N bond makes it unavailable for most organisms. Certain prokaryotes known as diazotrophs possess the unique ability to convert N2 to ammonia (NH3) which can be utilized by other organisms as a source of nitrogen. The diazotrophs perform this difficult reaction with the help of a complex metalloenzyme, nitrogenase. This enzyme is a major contributor of the fixed source of nitrogen in the biogeochemical nitrogen cycle other than the industrial Haber-Bosch process.

The research presented here has focused on nitrogenase isolated from a free living bacteria called Azotobacter vinelandii. Nitrogenase is composed of two components, the catalytic component with two halves known as the MoFe protein and the electron transferring protein also known as the Fe protein. These two proteins associate and dissociate multiple times to fix nitrogen. These events are coupled with transferring electrons and ATP hydrolysis. These events were studied during the course of this research and it was discovered that the two halves of the MoFe protein are negatively cooperative to each other. Apart from fixing nitrogen, nitrogenase is known to reduce other small molecules such as acetylene, nitrous oxide, nitrite etc. The other half of the research was focused on understanding the reduction mechanism of two key players of global nitrogen cycle, nitrite and nitrate by nitrogenase.

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