An Fe
 2
 IV
 O
 2
 Diamond Core Structure for the Key Intermediate Q of Methane Monooxygenase

Shu, Lei; Nesheim, Jeremy C.; Kauffmann, Karl; Münck, Eckard; Lipscomb, John D.; Que, Lawrence

doi:10.1126/science.275.5299.515

Cited by 578 publications

(646 citation statements)

References 29 publications

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“…A detailed analysis of EXAFS and Mössbauer spectroscopic data revealed that Q is best described as a strongly exchange-coupled S = 2 diiron(IV) species with an Fe-Fe distance of 2.46 Å and pairs of short and long Fe-O bonds of 1.77 and 2.05 Å, respectively, consistent with an Fe 2 IV (µ-O) 2 -diamond core structure 70 . Xue et al 71 (Fig.…”

Section: Dinuclear Bis(µ-oxo)diiron(iv) Model Complexesmentioning

confidence: 99%

The biology and chemistry of high-valent iron–oxo and iron–nitrido complexes

2012

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selective functionalization of unactivated c-H bonds and ammonia production are extremely important industrial processes. a range of metalloenyzmes achieve these challenging tasks in biology by activating dioxygen and dinitrogen using cheap and abundant transition metals, such as iron, copper and manganese. High-valent iron-oxo and -nitrido complexes act as active intermediates in many of these processes. the generation of well-described model compounds can provide vital insights into the mechanism of such enzymatic reactions. advances in the chemistry of model high-valent iron-oxo and -nitrido systems can be related to our understanding of the biological systems.H igh-valent oxoiron(IV) and formally oxoiron(V) species have been spectroscopically identified as active intermediates in the catalytic cycles of a number of enzymatic systems 1-10 . Haem and non-haem proteins use these reactive intermediates to couple the activation of dioxygen to the oxidation of their substrates. In most cases, an oxygen atom is inserted into an unactivated C-H bond of the substrate; for example, in hydroxylation reactions [1][2][3][4][5][6][7][8][9][10] . However, many other reactions, including halogenation, desaturation, cyclization, epoxidation and decarboxylation, are also known to involve oxoiron species 1,3 . Superoxidized iron complexes with (valence) isoelectronic imido and nitrido ligands, as well as 'surface nitrides' , have also been implicated as key intermediates in the nitrogen atom transfer reactions 11 , the biological synthesis of ammonia by the nitrogenase enzyme 12-16 and the industrial Haber-Bosch process 17 .The generation of well-described model compounds can provide vital insights into the mechanism of such enzymatic reactions. Consequently, considerable effort has been made by synthetic chemists to prepare viable models for the putative reaction intermediates in the catalytic cycles of O 2 and N 2 activating enzymes. In this review, we provide an overview of all high-valent oxoiron and nitridoiron species that have been either identified or proposed as reactive intermediates in biology. Subsequently, we summarize some of the recent advances in bioinorganic chemistry that have led to the identification and isolation of iron complexes in unusually high formal oxidation states, containing iron-oxygen or iron-nitrogen multiple bonds. The spectroscopic characterization and the reactivity studies of these model complexes provide vital insights into the mechanism that nature uses to induce the reductive cleavage of dioxygen or dinitrogen in carrying out a number of important biochemical oxidative transformations. Moreover, the comparative review of the electronic structures of the isoelectronic oxoiron and nitridoiron functionalities reveals that the Fe-N bonds are intrinsically more covalent than the Fe-O bonds.

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Section: Dinuclear Bis(µ-oxo)diiron(iv) Model Complexesmentioning

confidence: 99%

The biology and chemistry of high-valent iron–oxo and iron–nitrido complexes

2012

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“…P and Q have been trapped, allowing the oxidation state of their diiron cluster and their overall structure ( Figure 10) to be studied using spectroscopic approaches. 29,32,35 Each has an optical chromophore that allows their reaction with substrates to be monitored.…”

Section: Kinetic Approaches To the Identification Of Intermediatesmentioning

confidence: 99%

Finding Intermediates in the O₂ Activation Pathways of Non-Heme Iron Oxygenases

et al. 2007

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Intermediates in the reaction cycle of an oxygenase are usually very informative of the chemical mechanism of O 2 activation and insertion. However, detection of these intermediates is often complicated by their short lifetime and the regulatory mechanism of the enzyme designed to ensure specificity. Here, the methods used to detect the intermediates in an extradiol dioxygenase, a Rieske cis-dihydrodiol dioxygenase, and soluble methane monooxygenase are discussed. The methods include the use of alternative, chromophoric substrates, mutagenesis of active site catalytic residues, forced changes in substrate binding order, control of reaction rates using regulatory proteins, and initialization of catalysis in crystallo.

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“…These intermediates range from the proposed peroxo-bridged compound P, which may require an Fe-Fe distance of up to 4 8, (Kim & Lippard, 1996), to the proposed diamond core bridged compound Q, in which the Fe-Fe distance is 2.47 8, (Shu et al, 1996b).…”

Section: Superposition Of the Two Protomers Of Mmoh Bath Found In Itsmentioning

confidence: 99%

Crystal structure of the hydroxylase component of methane monooxygenase fromMethylosinus trichosporiumOB3b

et al. 1997

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Methane monooxygenase (MMO), found in aerobic methanotrophic bacteria, catalyzes the 02-dependent conversion of methane to methanol. The soluble form of the enzyme (sMMO) consists of three components: a reductase, a regulatory "B" component (MMOB), and a hydroxylase component (MMOH), which contains a hydroxo-bridged dinuclear iron cluster. Two genera of methanotrophs, termed Type X and Type 11, which differ markedly in cellular and metabolic characteristics, are known to produce the sMMO. The structure of MMOH from the Type X methanotroph Methylococcus capsulatus Bath (MMO Bath) has been reported recently. Two different structures were found for the essential diiron cluster, depending upon the temperature at which the diffraction data were collected. In order to extend the structural studies to the Type I1 methanotrophs and to determine whether one of the two known MMOH structures is generally applicable to the MMOH family, we have determined the crystal structure of the MMOH from Type I1 Methylosinus trichosporium OB3b (MMO OB3b) in two crystal forms to 2.0 A and 2.7 8, resolution, respectively, both determined at 18 "C. The crystal forms differ in that MMOB was present during crystallization of the second form. Both crystal forms, however, yielded very similar results for the structure of the MMOH. Most of the major structural features of the MMOH Bath were also maintained with high fidelity. The two irons of the active site cluster of MMOH OB3b are bridged by two OH (or one OH and one H20), as well as both carboxylate oxygens of Glu a144. This bis-yhydroxo-bridged "diamond core" structure, with a short Fe-Fe distance of 2.99 A, is unique for the resting state of proteins containing analogous diiron clusters, and is very similar to the structure reported for the cluster from flash frozen (-160 "C) crystals of MMOH Bath, suggesting a common active site structure for the soluble MMOHs. The high-resolution structure of MMOH OB3b indicates 26 consecutive amino acid sequence differences in the p chain when compared to the previously reported sequence inferred from the cloned gene. Fifteen additional sequence differences distributed randomly over the three chains were also observed, including Da209E, a ligand of one of the irons.

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An Fe ₂ ^IV O ₂ Diamond Core Structure for the Key Intermediate Q of Methane Monooxygenase

Cited by 578 publications

References 29 publications

The biology and chemistry of high-valent iron–oxo and iron–nitrido complexes

The biology and chemistry of high-valent iron–oxo and iron–nitrido complexes

Finding Intermediates in the O₂ Activation Pathways of Non-Heme Iron Oxygenases

Crystal structure of the hydroxylase component of methane monooxygenase fromMethylosinus trichosporiumOB3b

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An Fe 2 IV O 2 Diamond Core Structure for the Key Intermediate Q of Methane Monooxygenase

Cited by 578 publications

References 29 publications

The biology and chemistry of high-valent iron–oxo and iron–nitrido complexes

The biology and chemistry of high-valent iron–oxo and iron–nitrido complexes

Finding Intermediates in the O2 Activation Pathways of Non-Heme Iron Oxygenases

Crystal structure of the hydroxylase component of methane monooxygenase fromMethylosinus trichosporiumOB3b

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An Fe ₂ ^IV O ₂ Diamond Core Structure for the Key Intermediate Q of Methane Monooxygenase

Finding Intermediates in the O₂ Activation Pathways of Non-Heme Iron Oxygenases