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Structural insights into a protein-bound iron-molybdenum cofactor precursor.
Mary C Corbett1, Yilin Hu, Aaron W Fay
1Department of Chemistry, Stanford University, Stanford, CA 94305.
Summary
Researchers identified a molybdenum-free precursor for the iron-molybdenum cofactor (FeMoco) essential for biological nitrogen fixation. This finding supports a new mechanism for FeMoco biosynthesis and cofactor synthesis.
Area of Science:
- Biochemistry
- Bioinorganic Chemistry
- Microbiology
Background:
- Biological nitrogen fixation is crucial for life, primarily mediated by the nitrogenase enzyme complex.
- The iron-molybdenum cofactor (FeMoco) is the catalytic center of the MoFe protein within nitrogenase.
- FeMoco biosynthesis is a complex, multi-step process involving specific proteins and precursors.
Purpose of the Study:
- To elucidate the structure of the FeMoco precursor bound to the NifEN protein.
- To provide physical evidence supporting a proposed mechanism for FeMoco biosynthesis.
- To investigate the relationship between FeMoco precursors and alternative nitrogenase cofactors.
Main Methods:
- X-ray absorption spectroscopy (XAS) was employed to analyze the NifEN-bound FeMoco precursor.
- Comparative analysis of Azotobacter vinelandii strains with and without the nifB gene was performed.
- Biochemical characterization of FeMoco precursor structures was conducted.
Main Results:
- A molybdenum-free analog of FeMoco, bound to NifEN, was identified.
- The NifEN-bound precursor does not conform to commonly proposed [4Fe-4S] cluster architectures.
- Physical evidence supports a stepwise FeMoco assembly pathway involving NifEN and a molybdenum-free intermediate.
Conclusions:
- The NifEN-bound precursor represents a key intermediate in FeMoco biosynthesis.
- A common precursor can be utilized for synthesizing both FeMoco and alternative nitrogenase cofactors.
- This research has implications for understanding nitrogen fixation and developing biomimetic synthesis strategies.