Diiron Oxidation State Control of Substrate Access to the Active Site of Soluble Methane Monooxygenase Mediated by the Regulatory Component
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Lippard_Diiron oxidation.pdf
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Author(s)
Wang, Weixue
Lippard, Stephen J.
Date Issued
January 2014
Journal
Journal of the American Chemical Society
Publisher
American Chemical Society (ACS)
Citation
Wang, Weixue, and Stephen J. Lippard. “Diiron Oxidation State Control of Substrate Access to the Active Site of Soluble Methane Monooxygenase Mediated by the Regulatory Component.” Journal of the American Chemical Society 136, no. 6 (February 12, 2014): 2244–2247. © 2014 American Chemical Society
Version
Final published version
Abstract
The regulatory component (MMOB) of soluble methane monooxygenase (sMMO) has a unique N-terminal tail not found in regulatory proteins of other bacterial multicomponent monooxygenases. This N-terminal tail is indispensable for proper function, yet its solution structure and role in catalysis remain elusive. Here, by using double electron–electron resonance (DEER) spectroscopy, we show that the oxidation state of the hydroxylase component, MMOH, modulates the conformation of the N-terminal tail in the MMOH–2MMOB complex, which in turn facilitates catalysis. The results reveal that the N-terminal tail switches from a relaxed, flexible conformational state to an ordered state upon MMOH reduction from the diiron(III) to the diiron(II) state. This observation suggests that some of the crystallographically observed allosteric effects that result in the connection of substrate ingress cavities in the MMOH–2MMOB complex may not occur in solution in the diiron(III) state. Thus, O[subscript 2] may not have easy access to the active site until after reduction of the diiron center. The observed conformational change is also consistent with a higher binding affinity of MMOB to MMOH in the diiron(II) state, which may allow MMOB to displace more readily the reductase component (MMOR) from MMOH following reduction.
MIT Department
Massachusetts Institute of Technology. Department of Chemistry
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DOI of Published Version
https://doi.org/10.1021/ja412351b
