Transient thiyl radicals in yeast copper(I) thionein

Deters, Dirk; Hartmann, Hans-Jürgen; Weser, Ulrich

doi:10.1016/0167-4838(94)90123-6

Cited by 17 publications

(8 citation statements)

References 25 publications

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“…This is in accord with (~RSSR'-l~a~x O2"-RS~/-"-RS-CuI ~ RS -/ RS-CuI "SR + 02"-<RS-Cu'-SR ~O2 Scheme 1. Main reactions of the intermediate path of copper catalysed cysteine oxidation the finding of the metal remaining in the reduced form in the course of the oxidation and is in accord with other reports where sulfur is proposed as the electron donor in the case of the oxidation of copper complexes with penicillamine (Younes et al, 1977) and with the cysteine-rich metallothioneins (Deters et al, 1994).…”

Section: Discussionsupporting

confidence: 85%

Novel findings on the copper catalysed oxidation of cysteine

et al. 1997

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The oxidation of cysteine (RSH) has been studied by using O-2, ferricytochrome c (Cyt c) and nitro blue tetrazolium (NET) as electron accepters. The addition of 200 mu M Cu-II to a solution of 2 mM cysteine, pH 7.4, produces an absorbance with a peak at 260 nm and a shoulder at 300 nm. Generation of a cuprous bis-cysteine complex (RS-CuI-SR) is responsible for this absorbance. In the absence of O-2 the absorbance is stable for long time while in the presence of air it vanishes slowly only when the cysteine excess is consumed. The neocuproine assay and the EPR analysis show that the metal remains reduced in the course of the oxidation of cysteine returning to the oxidised form at the end of reaction when all RSH has been oxidised to RSSR. Addition of Cu-II enhances the reduction rate of Cyt c and of NET by cysteine also under anaerobiosis indicating the occurrence of a direct reduction of the acceptor by the complex. It is concluded that the cuprous bis-cysteine complex (RS-CuI-SR) is the catalytic species involved in the oxidation of cysteine. The novel finding of the stability of the complex together with the metal remaining in the reduced form during the oxidation suggest sulfur as the electron donor in the place of the metal ion

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Section: Discussionsupporting

confidence: 85%

Novel findings on the copper catalysed oxidation of cysteine

et al. 1997

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“…Protein thiyl radicals exhibit broad EPR signals that extend over the range g ϳ 2.03-2.30 (46). The observation that the second radical detected after decay of Trp-OO ⅐ is shifted to g ϭ 2.036 is consistent with the formation of a sulfur-centered radical.…”

Section: Discussionsupporting

confidence: 55%

Reaction of Human Myoglobin and H2O2

Witting¹,

Douglas²,

Mauk³

2000

Journal of Biological Chemistry

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The human myoglobin (Mb) sequence is similar to other mammalian Mb sequences, except for a unique cysteine at position 110. Reaction of wild-type recombinant human Mb, the C110A variant of human Mb, or horse heart Mb with H 2 O 2 (protein/H 2 O 2 ‫؍‬ 1:1.2 mol/mol) resulted in formation of tryptophan peroxyl (Trp-OO ⅐ ) and tyrosine phenoxyl radicals as detected by EPR spectroscopy at 77 K. For wild-type human Mb, a second radical (g ϳ 2.036) was detected after decay of Trp-OO ⅐ that was not observed for the C110A variant or horse heart Mb. When the spin trap 5,5-dimethyl-1-pyrroline N-oxide (DMPO) was included in the reaction mixture at protein/DMPO ratios <1:10 mol/mol, a DMPO adduct exhibiting broad absorptions was detected. Hyperfine couplings of this radical indicated a DMPO-thiyl radical. Incubation of wild-type human Mb with thiol-blocking reagents prior to reaction with peroxide inhibited DMPO adduct formation, whereas at protein/DMPO ratios >1:25 mol/mol, DMPO-tyrosyl radical adducts were detected. Mass spectrometry of wild-type human Mb following reaction with H 2 O 2 demonstrated the formation of a homodimer (mass of 34,107 ؎ 5 atomic mass units) sensitive to reducing conditions. The human Mb C110A variant afforded no dimer under identical conditions. Together, these data indicate that reaction of wild-type human Mb and H 2 O 2 differs from the corresponding reaction of other myoglobin species by formation of thiyl radicals that lead to a homodimer through intermolecular disulfide bond formation.

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“…Recently, Wieghardt et al and others have reported a growing number of stabilized thiyl radicals thus greatly enhancing knowledge in this field. 12, [23][24][25][26][27][28][29][30][43][44][45][46][47][48][49] As many of these examples involve amino-thiophenol chelates, we decided to investigate the electrochemical oxidation of the phosphine-thiophenol ruthenium complexes we had been previously investigating due to their rich S-centered reactivity.…”

Section: Discussionmentioning

confidence: 99%

“…In this regard, assignment of redox events as metal-based or ligand-based is difficult and often tentatively made on the basis of the reversibility of the redox couple in the cyclic voltammogram. Recently, Wieghardt et al and others have reported a growing number of stabilized thiyl radicals thus greatly enhancing knowledge in this field. ,− ,− As many of these examples involve amino−thiophenol chelates, we decided to investigate the electrochemical oxidation of the phosphine−thiophenol ruthenium complexes we had been previously investigating due to their rich S-centered reactivity.…”

Section: Discussionmentioning

confidence: 99%

Electrochemical Investigations of the [Tris(2-(diphenylphosphino)thiaphenolato)ruthenate(II)] Monoanion Reveal Metal- and Ligand-Centered Events: Radical, Reactivity, and Rate

Grapperhaus

Poturovic

2004

Inorg. Chem.

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Electrochemical investigations of [bis(triphenylphosphoranylidene)ammonium)][tris(2-(diphenylphosphino)thiaphenolato)ruthenate(II)], PPN[Ru(DPPBT)(3)] (1), and [(bis(2-(diphenylphosphino)thiaphenolato)methane)(2-(diphenylphosphino)thiaphenolato)ruthenium(II)] chloride, [Ru((DPPBT)(2)CH(2))(DPPBT)]Cl (2) are reported. Complex 1 is oxidized reversibly in a metal-centered event by one electron at a potential of +455 mV (vs Ag/AgCl) to the ruthenium(III) derivative [tris(2-(diphenylphosphino)thiaphenolato)ruthenium(III)], 3. Complex 3 can also be prepared by iodine oxidation of 1 in acetonitrile. Oxidation of 3 in acetonitrile is reversible on a cyclic voltammetry time scale but irreversible upon bulk oxidation yielding Ru-X. Monitoring the oxidation of 3 by UV-visible spectroscopy reveals a proposed metal-coordinated thiyl radical intermediate with a maximum absorbance at 850 nm. This intermediate decays at a temperature of -20 degrees C with a rate constant of (5.82 +/- 0.73) x 10(-)(3) s(-)(1) with a small, positive deltaH and a large, negative deltaS. Ru-X can be oxidized reversibly to Ru-Y at a potential of +806 mV but cannot be reduced. Complex 2 is reversibly oxidized by one electron in a metal-centered event to 4 at a potential of +767 mV.

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Transient thiyl radicals in yeast copper(I) thionein

Cited by 17 publications

References 25 publications

Novel findings on the copper catalysed oxidation of cysteine

Novel findings on the copper catalysed oxidation of cysteine

Reaction of Human Myoglobin and H2O2

Electrochemical Investigations of the [Tris(2-(diphenylphosphino)thiaphenolato)ruthenate(II)] Monoanion Reveal Metal- and Ligand-Centered Events: Radical, Reactivity, and Rate

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