Biological Methane Oxidation
Rosenzweig determined the molecular structures of Nature's main methane
oxidation catalysts. Methane monooxygenases (
MMO) are metalloenzymes found in the family of
methanotrophic bacteria. These enzymes belong in the
oxidoreductase class. They activate carbon-hydrogen bonds to selectively install oxygen onto their substrate. Two major species of MMO exist—soluble MMO (sMMO) and
particulate MMO (pMMO). Despite mediating the same chemical reaction, these two enzymes' structure and mechanism are significantly different. Since the early 1990s, Rosenzweig has studied MMO enzymes in various biological systems. Her team was the first to solve the
crystal structure of particulate MMO in 1993. In the following years, she made major advances in determining the enzyme's
bioactivity and chemical constitution, including vast contributions to research on the metal-coordinated
active site. The currently proposed
mechanism for sMMO involves an
Iron (II)
coordination complex that is twice oxidized to form a
metalloperoxide species. This species then undergoes reduction in the presence of substrate
methane to afford the oxidized alkyl
methanol. The crystal structure of the sMMO protein-protein complex has been determined. Currently, there remains a mystery in the direct understanding of pMMO-substrate interaction, particularly in diagnosing a complex mechanism. According to Rosenzweig, this elusive problem remains "one of the major unsolved problems in bioinorganic chemistry." == Metal Transport ==
Works
• Walker, C. B.; de la Torre, J. R.; Klotz, M. G.; Urakawa, H.; Pinel, N.; Arp, D. J.; Brochier-Armanet, C.; Chain, P. S.; Chan, P. P.; Gollabgir, A.; Hemp, J.; Hügler, M.; Karr, E. A.; Könneke, M.; Shin, M.; Lawton, T. J.; Lowe, T.; Martens-Habbena, W.; Sayavedra-Soto, L. A.; Stahl, D. A. Nitrosopumilus maritimus Genome Reveals Unique Mechanisms for Nitrification and Autotrophy in Globally Distributed Marine Crenarchaea. Proc. Natl. Acad. Sci. U.S.A. 2010, 107 (19), 8818–8823. • Lieberman, R. L & Rosenzweig, A. C. "Crystal structure of a membrane-bound metalloenzyme that catalyses the biological oxidation of methane", Nature 2005, 434, 177-182. • Lieberman, R. L., Kondapalli, K. C., Shrestha, D. B., Hakemian, A. S., Smith, S. M., Telser, J., Kuzelka, J., Gupta, R., Borovik, A. S., Lippard, S. J., Hoffman, B. M., Rosenzweig, A. C., & Stemmler, T. L. "Characterization of the particulate methane monooxygenase metal centers in multiple redox states by X-ray absorption spectroscopy". Inorg. Chem. 2006, 45, 8372-8381. • Sazinsky, M. H., Mandal, A. L, Argüello, J. M., & Rosenzweig, A. C. "Structure of the ATP binding domain from the Archaeglobus fulgidus Cu1+-ATPase". J. Biol. Chem.. 2006, 281, 11161-11166. • Yatsunyk, L. A. & Rosenzweig, A. C. "Copper binding and transfer by the N-terminus of the Wilson disease protein", J. Biol. Chem.. 2007, 282, 8622-8631. • Rosenzweig, Lippard, "Structure and Biochemistry Methane Monooxygenase Enzyme Systems", Transition metals in microbial metabolism, Editors Günther Winkelmann, Carl J. Carrano, CRC Press, 1997, • Rosenzweig, Feng, Lippard, "Studies of Methane Monooxygenase and Alkane Oxidation Model Complexes", Applications of enzyme biotechnology, Editors Jeffery W. Kelly, Thomas O. Baldwin, Springer, 1991, ==References==