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The Many Roles of the Nitrogenase Iron Protein


Wenke, Belinda B. (2019) The Many Roles of the Nitrogenase Iron Protein. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/8RB1-HC30.


Nitrogenase is the only known enzyme capable of reducing atmospheric nitrogen (N2) into ammonia (NH3) for incorporation into cellular material. N2 reduction by nitrogenase is accomplished by sequential electron transfer between two component proteins: the substrate reductase (the MoFe-protein), and a specialized low-potential electron donor (the Fe-protein). The MoFe-protein contains the active site for nitrogen reduction, the FeMocofactor (FeMo-co). During nitrogen reduction, each Fe-protein dimer docks onto the MoFe-protein, transferring electrons to an intermediate cluster (P-cluster), and ultimately to the FeMo-co.

Strikingly, the Fe-protein has another critical role in nitrogen fixation. The Fe-protein is required for the biosynthesis of the two unique metalloclusters of the MoFe-protein: the Pcluster [8Fe:7S] and the active site FeMo-co ([Mo:7Fe:9S:C]-R-homocitrate) cluster. During FeMo-co-cluster maturation, the Fe-protein forms a complex with NifEN, a scaffolding protein homologous to the MoFe-protein, catalyzing the final step in the FeMoco biosynthesis. Studies indicate that the Fe-protein catalyzes insertion of molybdenum and R-homocitrate into an all-iron FeMo-co precursor in a reductant and nucleotide dependent manner. The remaining questions about the cellular functions of the Fe-protein include how the Fe-protein interacts with other maturation proteins in distinct (or similar) ways compared to the MoFe-protein, and how the Fe-protein contributes to the activation and insertion of molybdenum into the FeMo-co.

Item Type:Thesis (Dissertation (Ph.D.))
Subject Keywords:Nitrogen fixation, nitrogenase, iron sulfur protein, X-ray crystallography, electron microscopy
Degree Grantor:California Institute of Technology
Division:Chemistry and Chemical Engineering
Major Option:Biochemistry and Molecular Biophysics
Thesis Availability:Public (worldwide access)
Research Advisor(s):
  • Rees, Douglas C.
Thesis Committee:
  • Leadbetter, Jared R. (chair)
  • Bjorkman, Pamela J.
  • Gray, Harry B.
  • Rees, Douglas C.
Defense Date:18 January 2019
Record Number:CaltechTHESIS:04222019-175445561
Persistent URL:
Related URLs:
URLURL TypeDescription adapted for Ch.1 adapted for Ch.1 adapted for Ch.3
Wenke, Belinda B.0000-0003-3214-6197
Default Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:11482
Deposited By: Belinda Wenke
Deposited On:02 May 2019 00:56
Last Modified:20 Dec 2019 18:07

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