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The caa3 terminal oxidase of bacillus stearothermophilus: Transient spectroscopy of electron transfer and ligand binding (Articolo in rivista)
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- The caa3 terminal oxidase of bacillus stearothermophilus: Transient spectroscopy of electron transfer and ligand binding (Articolo in rivista) (literal)
- Anno
- 1996-01-01T00:00:00+01:00 (literal)
- Alternative label
Giuffrè A, D'Itri E, Giannini S, Brunori M, Ubbink-Kok T, Konings WN, Antonini G (1996)
The caa3 terminal oxidase of bacillus stearothermophilus: Transient spectroscopy of electron transfer and ligand binding
in The Journal of biological chemistry (Print)
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- Giuffrè A, D'Itri E, Giannini S, Brunori M, Ubbink-Kok T, Konings WN, Antonini G (literal)
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- cited By (since 1996)4 (literal)
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- Department of Biochemical Sciences, CNR Center of Molecular Biology, University of Rome La Sapienza, 00185 Rome, Italy; Department of Microbiology, Groningen Biomol. Sci./Biotech. I., University of Groningen, 9750 AA Haren, Netherlands; Department of Pure Biology, University of L'Aquila, 67010 L'Aquila, Italy. (literal)
- Titolo
- The caa3 terminal oxidase of bacillus stearothermophilus: Transient spectroscopy of electron transfer and ligand binding (literal)
- Abstract
- The thermophilic bacterium Bacillus stearothermophilus possesses a caa3-type terminal oxidase, which was previously purified (De Vrij, W., Heyne, R. I. R., and Konings, W. N. (1989) Eur. J. Biochem. 178, 763-770). We have carried out extensive kinetic experiments on the purified enzyme by stopped-flow time-resolved optical spectroscopy combined with singular value decomposition analysis. The results indicate a striking similarity of behavior between this enzyme and the electrostatic complex between mammalian cytochrome c and cytochrome c oxidase. CO binding to fully reduced caa3 occurs with a second order rate constant (k = 7.8 × 104 M-1 s-1) and an activation energy (E* = 6.1 kcal mol-1) similar to those reported for beef heart cytochrome c oxidase. Dithionite reduces cytochrome a with bimolecular kinetics, while cytochrome a3 (and CuB) is reduced via intramolecular electron transfer. When the fully reduced enzyme is mixed with O2, cytochrome a3, and cytochrome c are rapidly oxidized, whereas cytochrome a remains largely reduced in the first few milliseconds. When cyanide-bound caa3 is mixed with ascorbate plus TMPD, cytochrome c and cytochrome a are synchronously reduced; the value of the second order rate constant (k = 3 × 105 M-1 s-1 at 30°C) suggests that cytochrome c is the electron entry site. Steady-state experiments indicate that cytochrome a has a redox potential higher than cytochrome c. The data from the reaction with O2 reveal a remarkable similarity in the kinetic, equilibrium, and optical properties of caa3 and the electrostatic complex cytochrome c/cytochrome c oxidase. (literal)
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