Methane monooxygenase cluster

Methylococcus capsulatus, methane monooxygenase, diferric iron cluster, 43 362-363 2-(l-Methylpyridinium-4-yl)-4,4,5,5,-... 

C. pasteurianum ferredoxin, 38 85, 87 4Fe-4S] cluster, 38 358 fuscoredoxin, 47 380 methane monooxygenase, 43 383-384 "prismane protein, 47 230-231, 246 Rieske and Rieske-type proteins, 47 119-121... 

The multiprotein complex methane monooxygenase (MMO) serves meth-anotrophs to convert methane to methanol. It can be either soluble (sMMO) or membrane bound ( particulate , pMMO) and it typically consists of three components, a reductase (MMOR), a component termed protein B (MMOB) and a hydroxylase denoted MMOH. The nature of the metal cofactors in the latter component are reasonably well understood for sMMO as will be discussed in the non-heme iron section. For the pMMO of Methylococcus capsulatus an obligate requirement for copper was shown. As reported in reference 1 a trinuclear Cu(II) cluster was discussed128 but the number and coordination of coppers still is a matter of continuing investigation since then. 

It seems probable that other redox centres contain this binuclear iron structure, but that this has not yet been recognized. For example, a non-heme iron protein of the methane monooxygenase from Methylococcus capsulatus (Bath), which functions as the oxygenase in equation (28), has been described as having a novel iron centre which is not an iron-sulfur cluster. This may well be an oxo-bridged system. Analysis suggests 2.3 Fe per molecule of protein. 

Lieberman, R. L. Shrestha, D. B. Doan, P. E. Hoffman, B. M. Stemmier, T. L. Rosenzweig, A. C. Purified particulate methane monooxygenase from Methylococcus capsulatus (Bath) is a dimer with both mononuclear copper and a copper-containing cluster. Proc. Natl. Acad. Sci. USA 2003, 100(1), 3820-3825. 

Chan SI, Yu SSF. Controlled oxidation of hydrocarbons by the membrane-bound methane monooxygenase the case for a tricopper cluster. Acc Chem Res. 2008 41 969-79. 

Cardy, D. L., Laidler, V., Salmond, G. P., and Murrell, J. C., 1991a, The methane monooxygenase gene cluster of Methylosinus trichosporium cloning and sequencing of the mmoC gene, Arch. Microbiol. 156 477n483. 

Davydov, A., Davydov, R., Gr%oslund, A., Lipscomb, J. D., and Andersson, K. K., 1997, Radiolytic reduction of methane monooxygenase dinuclear iron cluster At 77K6EPR evidence for conformational change upon reduction or binding of component B to the diferric state, J. Biol. Chem. 272 702267026. 

Fox, B. G., Surerus, K. K., M,nck, E., and Lipscomb, J. D., 1988, Evidence for a p-oxo-bridged binuclear iron cluster in Oie hych oxylase component of methane monooxygenase. MYs-bauer and EPR studies, J. Biol. Chem. 263 10553nl0556. 

The cluster size of the transition metal in zeolites was determined for a number of different preparations. In the mesoporous MCM-41 materials [48, 49] isolated clusters were observed, whereas for some solid-state exchanged and chemical vapor deposition samples dimeric species similar to methane monooxygenase were suggested [50, 51]. To date the discussion centers on clustered versus isolated species present in the various zeoHtes. 

Various iron salts and mononuclear Fe or binuclear Fe complexes with a N,0 environment, biomimetic to methane monooxygenase complexes, have been applied to the oxidation of cyclohexane with various oxidants [6u,v,7a-g], but their catalytic activity is usually modest, with the exception of a hexanuclear Fe(III) compound derived from p-nitrobenzoic acid, which gives the highest total yield to Ol/One of about 30% [7a]. Moreover, most of these complexes are often unstable and very expensive. A hexanuclear heterotrimetallic Fe/Cu/Co complex bearing two Cu(p-0)2Co(p-0)2Fe cores, prepared by self-assembly, oxidizes cyclohexane with aqueous HP, with a maximum yield to Ol/One of 45%, virtually total selectivity to the two compounds, and preferred formation of cyclohexanol [7hj. The remarkable activity of the Fe/Cu/Co cluster was associated with the synergic effect of the three metals. 

Structure of the Iron Center Formation of the Iron Center and Tyrosyl Radical Spectroscopy of the Diferric Iron Center Spectroscopy of the Tyrosyl Radical Redox Properties of the Iron Center Mixed-Valent Form of the Iron Center Diferrous Form of the Iron Center Inhibitors to Iron-Containing Ribonucleotide Reductase Methane Monooxygenase A. Spectroscopy of the MMOH Cluster X-Ray Structure of MMOH... 

Fig. 2. Diferric iron clusters from ribonucleotide reductase R2 subunit and methane monooxygenase hydroxylase. The drawings are based on (18, 19) for RNR-R2 and (15) for MMOH.

Fig. 1. Diferric iron clusters form hemer3fthrin, ribonucleotide reductase R2 subunit, and methane monooxygenase hydroxylase. The figure was made with the RasMol 2.0 program, and the protein coordinates as PDB files were obtained from Brookhaven Protein Data Bank. Only the amino acids (histidines, green carboxylates, black oxygen, red nitrogen, yellow acetate, blue iron, violet) coordinated to the iron cluster are shown, coordinated waters are not indicated. The first subunit containing the cluster is shown. Diferric Hr is from sipunculid worm Themiste dyscritra). The RNR-R2 is from E. coli. The MMOH is from Methvlococcus caosulatus (Bath).

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