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Intermediate P* from soluble methane monooxygenase contains a diferrous cluster
Rahul Banerjee1, Katlyn K Meier, Eckard Münck
1Department of Biochemistry, Molecular Biology, and Biophysics and Center for Metals in Biocatalysis, University of Minnesota, Minneapolis, Minnesota 55455, United States.
Biochemistry
|May 31, 2013
Summary
Researchers investigated a key intermediate (P*) in methane monooxygenase catalysis. Unexpectedly, P* retains a reduced diiron cluster, revealing electronic structure changes rather than oxidation are responsible for altered signals during methane oxidation.
Area of Science:
- Biochemistry
- Enzymology
- Bioinorganic Chemistry
Background:
- Soluble methane monooxygenase (MMOH) catalyzes methane to methanol conversion.
- MMOH features a diiron cluster crucial for its catalytic activity.
- Intermediate P* was previously detected but poorly characterized.
Purpose of the Study:
- To spectroscopically and kinetically characterize the elusive intermediate P*.
- To elucidate the structural and electronic changes occurring during MMOH catalysis.
- To understand the role of the regulatory protein MMOB in modulating enzyme activity.
Main Methods:
- Utilized a MMOB mutant (His33Ala) to stabilize intermediate P*.
- Employed spectra-kinetic data collection for intermediate characterization.
- Applied rapid freeze-quench Mössbauer spectroscopy to determine cluster oxidation states.
Main Results:
- Intermediate P* was accumulated quantitatively and characterized.
- P* exhibits an optical spectrum similar to reduced MMOH states (Hred and O).
- Mössbauer spectroscopy revealed P* contains a Fe(II)Fe(II) cluster, contrary to previous oxidation assumptions.
Conclusions:
- The loss of the EPR signal in P* is due to electronic structure changes, not oxidation.
- Subtle alterations in the diiron cluster during P* formation are essential for O2 activation.
- This study provides critical insights into the mechanism of methane oxidation by MMOH.
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