Copper(III) Complexes of Tripeptides with Histidine and Histamine as the Third Residue

McDonald, Michael R.; Scheper, William M.; Lee, Hsiupu D.; Margerum, Dale W.

doi:10.1021/ic00105a038

Cited by 53 publications

(61 citation statements)

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“…A third potential source of the additional reducing equivalent is Cu B , which could be oxidized to the ϩ3 valence state. The occurrence of trivalent copper has been demonstrated in model compounds (27,28) but has not been observed in copper-containing proteins. Thus, oxidation of an amino acid residue to a radical, as in cytochrome c peroxidase (9) and prostaglandin H synthase (29), is the most likely possibility.…”

Section: Discussionmentioning

confidence: 99%

Dioxygen activation and bond cleavage by mixed-valence cytochrome c oxidase

Proshlyakov

Pressler

Babcock

1998

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

323

374

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Elucidating the structures of intermediates in the reduction of O 2 to water by cytochrome c oxidase is crucial to understanding both oxygen activation and proton pumping by the enzyme. In the work here, the reaction of O 2 with the mixed-valence enzyme, in which only heme a 3 and Cu B in the binuclear center are reduced, has been followed by time-resolved resonance Raman spectroscopy. The results show that OAO bond cleavage occurs within the first 200 s after reaction initiation; the presence of a uniquely stable FeOOOO(H) peroxy species is not detected. The product of this rapid reaction is a heme a 3 oxoferryl (Fe IV AO) species, which requires that an electron donor in addition to heme a 3 and Cu B must be involved. The available evidence suggests that the additional donor is an amino acid side chain. Recent crystallographic data [Yoshikawa, S., Shinzawa-Itoh, K., Nakashima, R., Yaono, R., Yamashita, E. OOH؊ , and the tyrosyl radical. This mechanism provides molecular structures for two key intermediates that drive the proton pump in oxidase; moreover, it has clear analogies to the proposed OOO bond forming chemistry that occurs during O 2 evolution in photosynthesis.The molecular mechanism of dioxygen activation and reduction by the terminal respiratory enzyme, cytochrome c oxidase (CcO), is accessible because of its unique kinetic properties. Elucidation of this mechanism is of fundamental importance in understanding O 2 chemistry in biological systems and necessary for insight into the function of the protein as a redox-linked proton pump. CcO uses four redox-active metal centers, Cu A , heme a, and the heme a 3 ͞Cu B binuclear center, to sustain mitochondrial electron transport by reducing molecular oxygen to water. This reaction ensures a constant flow of electrons through the respiratory chain and the coupled generation of a proton gradient across the mitochondrial membrane, which is required for ATP synthesis. The oxygen chemistry catalyzed by CcO contributes directly to the build-up of the proton gradient because of its redox-linked proton pumping function (1). Thus, the overall reaction catalyzed by CcO may be written aswhere H in ϩ and H out ϩ indicate protons on the matrix (in) and cytosolic (out) sides of the membrane. Because its reaction kinetics is controlled by its proton-pumping function, unique insights into oxygen activation mechanisms are possible (2, 3).A number of reaction intermediates in dioxygen reduction have been identified recently (3, 4). Nonetheless, the timing and mechanism of the critical OAO bond cleavage process in the heme a 3 ͞Cu B binuclear center and the structure of a key intermediate at the peroxy level are poorly understood. In one model, a heme-peroxy adduct [Fe a3 III OOOO(H)] is uniquely stable (2,3,(5)(6)(7)(8). This model contrasts with peroxidases (9) and catalases (10), in which the peroxy OOO bond is spontaneously cleaved to yield an oxoferryl (Fe IV AO) product and a radical. Recent Raman work on the reaction of CcO with H 2 O 2 provided an alternati...

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Section: Discussionmentioning

confidence: 99%

Dioxygen activation and bond cleavage by mixed-valence cytochrome c oxidase

Proshlyakov

Pressler

Babcock

1998

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

323

374

View full text Add to dashboard Cite

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“…The observation of the 805 cm Ϫ1 mode in the cytochrome bo 3 /H 2 O 2 reaction (60), however, argues against this possibility since the heme O lacks a strong electron-withdrawing peripheral substituent (61). On the other hand, the occurrence of Cu 3ϩ has been demonstrated in model compounds, but supporting evidence in Cu-containing enzymes has not been reported so far (62,63). Given that a small percentage of radical species has been detected when the 607-nm form was produced, we cannot exclude that a radical species is located in the protein nor the possibility that Cu The vibrational properties of oxygenated intermediates in histidine-containing peroxidase catalysis have been explained by the push-pull reaction mechanism (64,65) in which the distal histidine acts as a base to accelerate the binding of H 2 O 2 by deprotonating the substrate to give a Fe 3ϩ -O-O-R species.…”

Section: Discussionmentioning

confidence: 99%

Direct Detection of Fe(IV)=O Intermediates in the Cytochrome aa3 Oxidase from Paracoccus denitrificans/H2O2 Reaction

Pinakoulaki

Pfitzner

Ludwig

et al. 2003

Journal of Biological Chemistry

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We report the first evidence for the formation of the "607-and 580-nm forms" in the cytochrome oxidase aa 3 / H 2 O 2 reaction without the involvement of tyrosine 280. The pK a of the 607-580-nm transition is 7.5. The 607-nm form is also formed in the mixed valence cytochrome oxidase/O 2 reaction in the absence of tyrosine 280. Steady-state resonance Raman characterization of the reaction products of both the wild-type and Y280H cytochrome aa 3 from Paracoccus denitrificans indicate the formation of six-coordinate low spin species, and do not support, in contrast to previous reports, the formation of a porphyrin -cation radical. We observe three oxygen isotope-sensitive Raman bands in the oxidized wildtype aa 3 /H 2 O 2 reaction at 804, 790, and 358 cm ؊1 . The former two are assigned to the Fe(IV)‫؍‬O stretching mode of the 607-and 580-nm forms, respectively. The 14 cm ؊1 frequency difference between the oxoferryl species is attributed to variations in the basicity of the proximal to heme a 3 His-411, induced by the oxoferryl conformations of the heme a 3 -Cu B pocket during the 607-580-nm transition. We suggest that the 804 -790 cm ؊1 oxoferryl transition triggers distal conformational changes that are subsequently communicated to the proximal His-411 heme a 3 site. The 358 cm ؊1 mode has been found for the first time to accumulate with the 804 cm ؊1 mode in the peroxide reaction. These results indicate that the mechanism of oxygen reduction must be reexamined.

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“…Above pH 8.5, [Ni III (H Ϫ2 Gly 2 Hm)] ϩ more closely mimics the reactivity of [Ni III (H Ϫ2 Gly 2 HisGly)] by forming an oxo-bridged Ni(III) dimer intermediate that reacts to form a cross-linked peptide product. The peptidepeptide cross-linking Ni(III) species is not found in the Cu(III) analogs [211], as the square planar geometry of Cu(III) precludes the formation of an oxo bridge between two Cu(III) species.…”

Section: Methodsmentioning

confidence: 99%