Structure and Electron Transfer Reactions of Blue Copper Proteins

Gray, Harry B.; Coyle, C. L.; Dooley, David M.; Grunthaner, P. J.; Hare, Jeffrey W.; Holwerda, Robert A.; McArdle, James V.; McMillin, David R.; Rawlings, J.; Rosenberg, Robert C.; Sailasuta, Napapon; Solomon, Edward I.; Stephens, P. J.; Wherland, Scot; Wurzbach, J. A.

doi:10.1021/ba-1977-0162.ch008

Cited by 5 publications

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“…Despite potential Cys-Cu(II) LMCT transitions could contribute to strong absorption bands in the visible region (>400 nm) in tetrahedral type-1 Cu(II) centers, − no evidence of transient formation of T1 Cu(II) complexes is observed in the EPR analysis upon Cu(II) binding to MT-3 prior to reduction (vide infra, Table ). Studies of model mononuclear Cu(II) and mixed valence Cu(I)/Cu(II) complexes containing cis -N(amine) 2 S(thiolate) 2 copper ligands indicate that, for planar tetragonal Cu(II) complexes, typical σ(S)-Cu(II) LMCT are centered below 400 nm, with few examples showing extremely weak π(S)-Cu(II) LMCT contributions extending above 400 nm. − On the other hand, σ- and π(S)-Cu(II) LMCT transitions are red-shifted in the visible region when significant distortion toward tetrahedral coordination and higher covalency in the thiolate-Cu(II) bond occur, resulting in Cu(II) complexes that mimic T1 Cu(II) centers. , Our EPR analysis of the hyperfine splitting in the parallel region observed upon rapid mixing of Cu(II) with Zn 7 MT-3 (see Table below) shows spectral parameters consistent with standard tetragonal Type-2 Cu(II) complexes.…”

Section: Resultsmentioning

confidence: 99%

Evidence for a Long-Lived, Cu-Coupled and Oxygen-Inert Disulfide Radical Anion in the Assembly of Metallothionein-3 Cu(I)₄-Thiolate Cluster

et al. 2022

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The human copper-binding protein metallothionein-3 (MT-3) can reduce Cu(II) to Cu(I) and form a polynuclear Cu(I)4-Cys5–6 cluster concomitant with intramolecular disulfide bonds formation, but the cluster is unusually inert toward O2 and redox-cycling. We utilized a combined array of rapid-mixing spectroscopic techniques to identify and characterize the transient radical intermediates formed in the reaction between Zn7MT-3 and Cu(II) to form Cu(I)4Zn(II)4MT-3. Stopped-flow electronic absorption spectroscopy reveals the rapid formation of transient species with absorption centered at 430–450 nm and consistent with the generation of disulfide radical anions (DRAs) upon reduction of Cu(II) by MT-3 cysteine thiolates. These DRAs are oxygen-stable and unusually long-lived, with lifetimes in the seconds regime. Subsequent DRAs reduction by Cu(II) leads to the formation of a redox-inert Cu(I)4-Cys5 cluster with short Cu–Cu distances (<2.8 Å), as revealed by low-temperature (77 K) luminescence spectroscopy. Rapid freeze-quench Raman and electron paramagnetic resonance (EPR) spectroscopy characterization of the intermediates confirmed the DRA nature of the sulfur-centered radicals and their subsequent oxidation to disulfide bonds upon Cu(II) reduction, generating the final Cu(I)4-thiolate cluster. EPR simulation analysis of the radical g- and A-values indicate that the DRAs are directly coupled to Cu(I), potentially explaining the observed DRA stability in the presence of O2. We thus provide evidence that the MT-3 Cu(I)4-Cys5 cluster assembly process involves the controlled formation of novel long-lived, copper-coupled, and oxygen-stable disulfide radical anion transient intermediates.

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Section: Resultsmentioning

confidence: 99%

Evidence for a Long-Lived, Cu-Coupled and Oxygen-Inert Disulfide Radical Anion in the Assembly of Metallothionein-3 Cu(I)₄-Thiolate Cluster

et al. 2022

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“…Inclusion of this T1 Cu self-exchange rate with a bimolecular rate constant of 10 5 M –1 s –1 is required to accurately model the IET behavior observed in the SF. Self-exchange rates are reported to vary from 10 3 –10 6 M –1 s –1 , largely based on the proximity of the T1 Cu to the enzyme surface. , …”

Section: Results and Analysismentioning

confidence: 99%

Rapid Decay of the Native Intermediate in the Metallooxidase Fet3p Enables Controlled Fe^II Oxidation for Efficient Metabolism

Jones

Heppner

et al. 2020

J. Am. Chem. Soc.

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The multicopper oxidases (MCOs) couple four 1e – oxidations of substrate to the 4e – reduction of O2 to H2O. These divide into two groups: those that oxidize organic substrates with high turnover frequencies (TOFs) up to 560 s–1 and those that oxidize metal ions with low TOFs, ∼1 s–1 or less. The catalytic mechanism of the organic oxidases has been elucidated, and the high TOF is achieved through rapid intramolecular electron transfer (IET) to the native intermediate (NI), which only slowly decays to the resting form. Here, we uncover the factors that govern the low TOF in Fet3p, a prototypical metallooxidase, in the context of the MCO mechanism. We determine that the NI decays rapidly under optimal turnover conditions, and the mechanism thereby becomes rate-limited by slow IET to the resting enzyme. Development of a catalytic model leads to the important conclusions that proton delivery to the NI controls the mechanism and enables the slow turnover in Fet3p that is functionally significant in Fe metabolism enabling efficient ferroxidase activity while avoiding ROS generation.

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Some Aspects of the Reactivity of Metal Ion–Sulfur Bonds

Kuehn

Isied

1980

Progress in Inorganic Chemistry

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Structure and Electron Transfer Reactions of Blue Copper Proteins

Cited by 5 publications

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Evidence for a Long-Lived, Cu-Coupled and Oxygen-Inert Disulfide Radical Anion in the Assembly of Metallothionein-3 Cu(I)₄-Thiolate Cluster

Evidence for a Long-Lived, Cu-Coupled and Oxygen-Inert Disulfide Radical Anion in the Assembly of Metallothionein-3 Cu(I)₄-Thiolate Cluster

Rapid Decay of the Native Intermediate in the Metallooxidase Fet3p Enables Controlled Fe^II Oxidation for Efficient Metabolism

Some Aspects of the Reactivity of Metal Ion–Sulfur Bonds

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Structure and Electron Transfer Reactions of Blue Copper Proteins

Cited by 5 publications

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Evidence for a Long-Lived, Cu-Coupled and Oxygen-Inert Disulfide Radical Anion in the Assembly of Metallothionein-3 Cu(I)4-Thiolate Cluster

Evidence for a Long-Lived, Cu-Coupled and Oxygen-Inert Disulfide Radical Anion in the Assembly of Metallothionein-3 Cu(I)4-Thiolate Cluster

Rapid Decay of the Native Intermediate in the Metallooxidase Fet3p Enables Controlled FeII Oxidation for Efficient Metabolism

Some Aspects of the Reactivity of Metal Ion–Sulfur Bonds

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Product

Resources

About

Evidence for a Long-Lived, Cu-Coupled and Oxygen-Inert Disulfide Radical Anion in the Assembly of Metallothionein-3 Cu(I)₄-Thiolate Cluster

Evidence for a Long-Lived, Cu-Coupled and Oxygen-Inert Disulfide Radical Anion in the Assembly of Metallothionein-3 Cu(I)₄-Thiolate Cluster

Rapid Decay of the Native Intermediate in the Metallooxidase Fet3p Enables Controlled Fe^II Oxidation for Efficient Metabolism