Soluble methane monooxygenase protein

STUDIES OF THE SOLUBLE METHANE MONOOXYGENASE PROTEIN SYSTEM STRUCTURE, COMPONENT INTERACTIONS, AND HYDROXYLATION MECHANISM... 

Solid-state supramolecular complexes, see Su-pramolecular copper(l)/silver(I) complexes Solubility products, 17 215 Soluble methane monooxygenase protein system, 42 263-286 hydroxylation... 

Studies of the Soluble Methane Monooxygenase Protein System Structure, Component Interactions, and Hydroxylation Mechanism Katherine E. Liu and Stephen J. Lippard... 

Green, J. Dalton, H. Protein B of soluble methane monooxygenase from Methylococcus capsulatus (Bath). A novel regulatory protein of enzyme activity. J. Biol. Chem. 1985, 260(29), 15795-15801. 

Merkx, M., Kopp, D. A., Sazinsky, M. H., Blazyk, J. L., Muller, J., and Lippard, S.J. (2001) Dioxygen activation and methane hydroxylation by soluble methane monooxygenase a tale of two irons and three proteins. Angew. Chem., Int. Ed. 40, 2782-2807. 

Woodland, M. P., Patil, D. S., Cammack, R., and Dalton, H., 1986, ESR studies of protein A of the soluble methane monooxygenase from Methylococcus capsulatus (Bath), Biochim. Biophys. Acta 873 237n242. 

Figure 3 Illustration of possible partial reaction cycles of some oxygenase enzymes. Water molecules and protein ligands have sometimes been omitted for clarity, (a) P450 (18) (b) intradiol dioxygenase (7) (c) lipoxygenase (7) (d) a-KG-dependent non-heme Iron enzymes (14) (e) soluble methane monooxygenase (15) (f) uncoupled blnuclear copper (16) (g) coupled blnuclear copper (h) flavin monooxygenases (17).

A structural module comprising tetra(carboxylato)di-iron(II) centers with two additional A-donor groups has been identified at the active sites of the hydroxylase component (MMOH) of soluble methane monooxygenase, the R2 subunit of class I ribonucleotide reductase (RNR-R2), " " and stearoyl-acyl carrier protein (AGP) A desaturase (A9D). d8 structural comparisons of these enzymes reveal striking architectural similarities involving an approximately 18 A segment of a pseudo-222-symmetric four-helix bundle that encapsulates their di-iron active... 

Trivelli et and Ubbink have reviewed NMR studies of the interactions among proteins of the photosynthetic electron transfer chain. Mueller et report the NMR structure of the [2Fe-2S] ferredoxin domain from soluble methane monooxygenase reductase. 

Dioxygen activation and methane hydroxylation by soluble methane monooxygenase a tale of two irons and three proteins. Angew. Chem. Int Ed.,... 

Sazinsky MH, Lippard SJ. 2005. Product hound structures of the soluble methane monooxygenase hydroxylase from Methylococcus capsulatus (Bath) protein motion in the alpha-subunit. J Am Chem Soc 127 5814-5825. 

Walters KJ, Gassner GT, Lippard SJ, Wagner G. 1999. Structure of the soluble methane monooxygenase regulatory protein B. Proc Natl Acad Sci USA 96 7877-7882. 

Proteins with dinuclear iron centres comprise some prominent and well studied representatives like ribonucleotide reductase (RNR), purple acid phosphatase (PAP), methane monooxygenase hydroxylase (MMOH), ruberythrin and hemerythrin. The last of these is an oxygen carrier in some sea worms it has been well characterized within this group and has thus laid the foundation to this class of iron coordination motif. Ruberythrin is found in anaerobic sulfate-reducing bacteria. Its name implies that, in addition to a hemerythrin-related diiron site another iron is coordinated in a mononuclear fashion relating to rubredoxin, which is an iron-sulfur centre. The latter will not be treated here. The hydroxylase component of methane monooxygenase is one of the three components in soluble methane monooxygenase (MMO) and contains the active diiron site it is found in methanotropic bacteria. Purple add phosphatase (PAP) occurs mainly in plants and animals, and catalyses the hydrolysis of monophosphate esters. Finally, ribonucleotide reductase reduces ribonucleotides to deoxyribonucleotides and thus has a key position in DNA synthesis. 

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. 

FIGURE 1. Reaction and protein components of the soluble form of methane monooxygenase. 

The presentation in 1993 of the structure of the hydroxylase component of methane monooxygenase (MMOH) by Rosenzweig et al. (15) is the third published three-dimensional structure of a diiron-oxygen protein (Fig. 1). The previous two are from hemerythrin (Hr) (16,17) and protein R2 of E. coli ribonucleotide reductase (RNR-R2) (18, 19). Some other dinuclear iron proteins with known fi-oxo or p.-hydroxo bridges are purple acid phosphatases (PAP) [(e.g., uteroferrin (Uf)] (20, 21), ferritins (in early stages of nucleation) (22), rubrerythrin (Rr) (23-26), nigerythrin (26), and soluble stearoyl-acyl carrier protein A desaturase (A-AGP) (27, 28). 

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