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EPR-Derived Structure of a Paramagnetic Intermediate Generated by Biotin Synthase BioB.
Lizhi Tao1, Troy A Stich1, Corey J Fugate2
1Department of Chemistry , University of California , Davis , California 95616 , United States.
Journal of the American Chemical Society
|September 18, 2018
Summary
Researchers used advanced EPR spectroscopy to study a key intermediate in biotin synthesis. This reveals the precise positioning of atoms, clarifying how biotin synthase forms the final C-S bond for vitamin B7 production.
Area of Science:
- Biochemistry
- Molecular Biology
- Structural Biology
Background:
- Biotin (vitamin B7) is essential for numerous metabolic processes.
- Biotin biosynthesis occurs only in microbes and plants, involving the enzyme biotin synthase (BioB).
- Previous studies identified a key intermediate in biotin synthesis involving a [2Fe-2S] cluster.
Purpose of the Study:
- To elucidate the structure of a semistable intermediate in biotin biosynthesis.
- To understand the mechanism of the second C-S bond formation by biotin synthase.
- To provide atomic-level insights into the final steps of vitamin B7 production.
Main Methods:
- Site-specific isotopic labeling of the biotin intermediate.
- Orientation-selected pulse electron paramagnetic resonance (EPR) spectroscopy.
- Quantum chemical modeling and computational analysis.
Main Results:
- Detailed hyperfine interactions between the [2Fe-2S] cluster and labeled nuclei (57Fe, 15N, 13C, 2H) were observed.
- A structural model of the intermediate was generated, showing specific atomic proximity.
- The C6 atom was found to be positioned near the thioether sulfur, ready for the second C-S bond formation.
Conclusions:
- The study provides unprecedented structural detail of a crucial intermediate in biotin biosynthesis.
- The findings clarify the mechanism by which biotin synthase catalyzes the final C-S bond formation.
- This work advances our understanding of essential vitamin production in microorganisms.
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