X-RAY CRYSTALLOGRAPHIC STUDIES OF METHANE MONOOXYGENASE

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This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Soluble methane monooxygenase (sMMO) is a four-component enzyme system that catalyzes the oxidation of methane to methanol in methanotrophic bacteria. Catalysis occurs at a carboxylate-bridged dinuclear iron center in the a subunit of the hydroxylase (MMOH) component. Kinetic and spectroscopic studies have shown that the docking of the coupling protein (MMOB) with MMOH enhances the reaction rate and alters the spectroscopic properties of the diiron center. The reasons for these changes are unknown. MMOD, a newly discovered protein encoded in the sMMO operon, alters the spectroscopic properties of the MMOH diiron center, cross-links to the a subunit, and inhibits hydroxylase activity by competing with MMOB for binding. It is unknown how MMOD alters the properties of the diiron center or inhibits activity. Current studies are aimed at determining the structures of the MMOH-MMOB and MMOH-MMOD complexes and probing structural details of the diiron site of MMOH under various conditions.