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Updated: Jul 17, 2025
12:08
Monitoring the Reductive and Oxidative Half-Reactions of a Flavin-Dependent Monooxygenase using Stopped-Flow Spectrophotometry
Published on: March 18, 2012
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Oligomeric Changes Regulate Flavin Transfer in Two-Component FMN Reductases Involved in Sulfur Metabolism.
Chioma H Aloh1, Tonya N Zeczycki1, Holly R Ellis1
1Department of Biochemistry and Molecular Biology, Brody School of Medicine at East Carolina University, Greenville, North Carolina 27834, United States.
Biochemistry
|August 31, 2023
Summary
Flavin reductases SsuE and MsuE regulate flavin reduction and transfer by changing their oligomeric states. FMN binding stabilizes both enzymes, but substrate-induced shifts differ, impacting their roles in desulfonation.
Area of Science:
- Biochemistry
- Enzymology
- Structural Biology
Background:
- FMN reductases SsuE and MsuE are key components of alkanesulfonate monooxygenase systems.
- These enzymes supply reduced flavin to partner monooxygenases for desulfonation reactions.
- Regulation of flavin reduction and transfer is crucial for the function of two-component flavin reductase systems.
Purpose of the Study:
- To investigate the role of oligomeric state changes in the regulation of SsuE and MsuE activity.
- To compare the substrate-induced structural dynamics of SsuE and MsuE.
- To understand how enzyme oligomerization impacts flavin binding and stability.
Main Methods:
- Analytical ultracentrifugation to determine oligomeric states.
- Hydrogen-deuterium exchange mass spectrometry (H/D-X MS) to probe structural dynamics.
- Differential scanning fluorimetry (DSF) to assess protein stability (melting temperature).
Main Results:
- SsuE transitions from a tetramer to a dimer/tetramer equilibrium upon FMN or NADPH binding.
- MsuE shifts from a dimer to a tetrameric state with FMN, but not with NADPH.
- FMN binding significantly increases the stability of both SsuE and MsuE, indicated by higher melting temperatures.
Conclusions:
- Oligomeric state changes are a key regulatory mechanism for SsuE and MsuE.
- Differential substrate-induced structural shifts suggest distinct functional roles in delivering reduced flavin.
- FMN binding confers conformational stability, essential for enzyme function in desulfonation pathways.
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