Oxygen Capture by Sulfur in Nickel Thiolates

Grapperhaus, Craig A.; Darensbourg, Marcetta Y.

doi:10.1021/ar950048v

Cited by 323 publications

(360 citation statements)

References 57 publications

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“…27,39,68,[70][71][72][73][74] DFT calculations described earlier indicated that the S-O bond of 5 is single and significantly polarized. This is supported by the X-ray structure.…”

Section: Structural and Reactivity Properties Of The Metal-bound Sulfmentioning

confidence: 90%

How Does Single Oxygen Atom Addition Affect the Properties of an Fe−Nitrile Hydratase Analogue? The Compensatory Role of the Unmodified Thiolate

et al. 2006

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Nitrile hydratase (NHase) is one of a growing number of enzymes shown to contain posttranslationally modified cysteine sulfenic acids (Cys-SOH). Cysteine sulfenic acids have been shown to play diverse roles in cellular processes, including transcriptional regulation, signal transduction, and the regulation of oxygen metabolism and oxidative stress responses. The function of the cysteine sulfenic acid coordinated to the iron active site of NHase is unknown. Herein we report the first example of a sulfenate-ligated iron complex, [Fe III (ADIT)(ADIT-O)] + (5), and compare its electronic and magnetic properties with those of structurally related complexes in which the sulfur oxidation state and protonation state have been systematically altered. Oxygen atom addition was found to decrease the unmodified thiolate Fe-S bond length and blue-shift the ligand-to-metal charge-transfer band (without loss of intensity). S K-edge X-ray absorption spectroscopy and density functional theory calculations show that, although the modified RS-O − fragment is incapable of forming a π bond with the Fe III center, the unmodified thiolate compensates for this loss of π bonding by increasing its covalent bond strength. The redox potential shifts only slightly (75 mV), and the magnetic properties are not affected (the S = ½ spin state is maintained). The coordinated sulfenate S-O bond is activated and fairly polarized (S + -O − ). Addition of strong acids at low temperatures results in the reversible protonation of sulfenateligated 5. An X-ray structure demonstrates that Zn 2+ binds to the sulfenate oxygen to afford [Fe III HHS Public Access Author Manuscript Author ManuscriptAuthor ManuscriptAuthor Manuscript unmodified NHase thiolate, involving its ability to "tune" the electronics in response to protonation of the sulfenate (RS-O − ) oxygen and/or substrate binding, is discussed.Nitrile hydratases (NHases) are non-heme iron enzymes that convert nitriles to less toxic amides cleanly, and rapidly, under mild conditions. [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16] It is unusual for a hydrolytic metalloenzyme to incorporate iron, as opposed to zinc, 17,18 presumably because, unlike other metal ions, Zn 2+ is not complicated by redox chemistry. Iron, on the other hand, can promote unwanted side reactions with dioxygen (i.e., Fenton chemistry involving OH · radicals) upon reduction to the Fe 2+ oxidation state. 19,20 The NHase iron site is, however, redox inactive and stabilized in the 3+ oxidation state. The stabilization of Fe 3+ is accomplished by placing the iron in an electron-rich environment consisting of five anionic ligands-two deprotonated peptide amides and three cysteinates (Figure 1). Two of the three coordinated cysteinate sulfurs are oxidized (post-translationally modified) in NHase -one to a sulfenic acid ( 114 Cys-S-(OH)) and the other to a sulfinate 112 CysSO 2 −.3,21 The third cysteinate sulfur, which is trans to the inhibitor/substrate binding site and less accessible to solvent, remains unmodifie...

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“…27,39,68,[70][71][72][73][74] DFT calculations described earlier indicated that the S-O bond of 5 is single and significantly polarized. This is supported by the X-ray structure.…”

Section: Structural and Reactivity Properties Of The Metal-bound Sulfmentioning

confidence: 90%

How Does Single Oxygen Atom Addition Affect the Properties of an Fe−Nitrile Hydratase Analogue? The Compensatory Role of the Unmodified Thiolate

et al. 2006

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“…4b). The oxygenation step might be copperdependent, because metal-induced oxygenation of thiolates is a well-known reaction (41). Cysteine-sulfenic acid is known to function as a redox center in NADH oxidases and peroxidases, and in some peroxiredoxins and transcription regulators (42).…”

Section: Discussionmentioning

confidence: 99%

Crystal structure of the precursor of galactose oxidase: An unusual self-processing enzyme

Firbank

Rogers

Wilmot

et al. 2001

Proc. Natl. Acad. Sci. U.S.A.

109

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Galactose oxidase (EC 1.1.3.9) is a monomeric enzyme that contains a single copper ion and catalyses the stereospecific oxidation of primary alcohols to their corresponding aldehydes. The protein contains an unusual covalent thioether bond between a tyrosine, which acts as a radical center during the two-electron reaction, and a cysteine. The enzyme is produced in a precursor form lacking the thioether bond and also possessing an additional 17-aa prosequence at the N terminus. Previous work has shown that the aerobic addition of Cu 2؉ to the precursor is sufficient to generate fully processed mature enzyme. The structure of the precursor protein has been determined to 1.4 Å, revealing the location of the pro-sequence and identifying structural differences between the precursor and the mature protein. Structural alignment of the precursor and mature forms of galactose oxidase shows that five regions of main chain and some key residues of the active site differ significantly between the two forms. The precursor structure provides a starting point for modeling the chemistry of thioether bond formation and pro-sequence cleavage.

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“…In spite of this, the Ni-CO I isoform is more stable than the Ni-CO II in presence of air, as shown in the results section. We may speculate that in the Ni-CO II conformation the terminal cysteine ligand is more protected from oxidation by O 2 than in the Ni-CO I conformation, because it is well known that thiolate ligands of many Ni complexes [36] and cysteine side-chains of some proteins [37] react with O 2 forming sulfenates or sulfinates, and a sulfinate group is present in the oxidized active site of this hydrogenase (Scheme 1). It has been recently shown with biomimetic compounds of hydrogenases that sulfenates can be easily deoxygenated electrochemically [38], although the same has not been reported for metal complexes with sulfinate ligands.…”

Section: Methodsmentioning

confidence: 99%

Interaction of the active site of the Ni–Fe–Se hydrogenase from Desulfovibrio vulgaris Hildenborough with carbon monoxide and oxygen inhibitors

et al. 2010

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The study of Ni-Fe-Se hydrogenases is interesting from the basic research point of view because their active site is a clear example of how nature regulates the catalytic function of an enzyme by the change of a single residue, in this case a cysteine that is replaced by a selenocysteine. Most hydrogenases are inhibited by carbon monoxide and oxygen. In this work we study these inhibition processes for the Ni-Fe-Se hydrogenase from Desulfovibrio vulgaris Hildenborough by combining catalytic activity measurements, followed by mass

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Oxygen Capture by Sulfur in Nickel Thiolates

Cited by 323 publications

References 57 publications

How Does Single Oxygen Atom Addition Affect the Properties of an Fe−Nitrile Hydratase Analogue? The Compensatory Role of the Unmodified Thiolate

How Does Single Oxygen Atom Addition Affect the Properties of an Fe−Nitrile Hydratase Analogue? The Compensatory Role of the Unmodified Thiolate

Crystal structure of the precursor of galactose oxidase: An unusual self-processing enzyme

Interaction of the active site of the Ni–Fe–Se hydrogenase from Desulfovibrio vulgaris Hildenborough with carbon monoxide and oxygen inhibitors

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