Native top-down mass spectrometry provides insights into the copper centers of membrane-bound methane monooxygenase

Aerobic methane oxidation is catalyzed by particulate methane monooxygenase (pMMO), a copper-dependent, membrane metalloenzyme composed of subunits PmoA, PmoB, and PmoC. Characterization of the copper active site has been limited by challenges in spectroscopic analysis stemming from the presence of...

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Bibliographic Details
Published in:	Nature communications 2019-06, Vol.10 (1), p.2675-12, Article 2675
Main Authors:	Ro, Soo Y, Schachner, Luis F, Koo, Christopher W, Purohit, Rahul, Remis, Jonathan P, Kenney, Grace E, Liauw, Brandon W, Thomas, Paul M, Patrie, Steven M, Kelleher, Neil L, Rosenzweig, Amy C
Format:	Article
Language:	eng
Subjects:	Bacterial Proteins - chemistry Bacterial Proteins - metabolism Bacterial Proteins - ultrastructure Binding Sites Biocatalysis Catalytic Domain Copper Copper - chemistry Copper - metabolism Cryoelectron Microscopy Crystal structure Mass spectrometry Mass Spectrometry - methods Mass spectroscopy Methane Methane - metabolism Methane monooxygenase Methanol - metabolism Methylococcaceae - chemistry Methylococcaceae - metabolism Methylococcaceae - ultrastructure Models, Molecular Oxidation Oxidation-Reduction Oxygenases - chemistry Oxygenases - metabolism Oxygenases - ultrastructure Post-translation Protein Processing, Post-Translational Scientific imaging Solubilization Stoichiometry
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Summary:	Aerobic methane oxidation is catalyzed by particulate methane monooxygenase (pMMO), a copper-dependent, membrane metalloenzyme composed of subunits PmoA, PmoB, and PmoC. Characterization of the copper active site has been limited by challenges in spectroscopic analysis stemming from the presence of multiple copper binding sites, effects of detergent solubilization on activity and crystal structures, and the lack of a heterologous expression system. Here we utilize nanodiscs coupled with native top-down mass spectrometry (nTDMS) to determine the copper stoichiometry in each pMMO subunit and to detect post-translational modifications (PTMs). These results indicate the presence of a mononuclear copper center in both PmoB and PmoC. pMMO-nanodisc complexes with a higher stoichiometry of copper-bound PmoC exhibit increased activity, suggesting that the PmoC copper site plays a role in methane oxidation activity. These results provide key insights into the pMMO copper centers and demonstrate the ability of nTDMS to characterize complex membrane-bound metalloenzymes.
ISSN:	2041-1723 2041-1723